University of the Witwatersrand, Johannesburg
University of the Witwatersrand, Johannesburg
SCHONLAND RESEARCH CENTRE FOR NUCLEAR SCIENCES
Annual Report
1998-9
Diamond Bending Device (see page 41)
Introduction 3
Applied and Environmental Physics Research Group 4
Ion Implantation and Surface Studies Research Programme 19
Nuclear Physics Programme 28
Wits-Northern Accelerator Research Centre 32
Health Physics Service 69
Introduction
This Report covers the first full year (1998) of the implementation of the new Schonland proposals, plus part of 1999, being based on the reports prepared by the various Groups for their Annual General
Meetings at different times in 1999. In accordance with the Physics Department's plan, the Schonland Research Centre for Nuclear Sciences is now in effect a federation of four Research Programmes, each with its own Group Leader, sharing a common support infrastructure. In addition the University's Health Physics Service has its home at the Schonland. Some of the Groups are subdivided internally along the lines of individual research interests, as will become apparent in this Report.
Matters of common interest are overseen by a Schonland Co-ordinating Committee with a rotating
(2-year) chairmanship, chosen from the Group Leaders. The Chairman for most of the period under review was Prof. Vladimir Hnizdo, but since his resignation in the middle of 1999 to take up a post in America, Prof. Trevor Derry has taken over the job.
The four recognized Research Entities are:
- Applied and Environmental Physics Research Programme (Prof. J.I.W. Watterson);
- Ion Implantation and Surface Studies Research Programme (Prof. T.E. Derry);
- Nuclear Physics Research Programme (Prof. V. Hnizdo then Dr. J.M. Carter);
- Wits Northern Accelerator Centre (Dr. S.H. Connell).
To these must be added the Health Physics Service (Dr. T.L. Nam).
The current membership of the Schonland Co-ordinating Committee is:
Prof. T.E. Derry (chair), Dr. S.H. Connell (deputy chair), Prof. J.I.W. Watterson, Dr. J.M. Carter, Mr. A.H. Andeweg (Technical rep.), Mr. D.B. Rebuli (Postgraduate rep.), Prof. B.J. Cole (Head of Physics Dept.) and Prof. W.U. Reimold (Geology Dept.); other representatives attend meetings from time to time.
The Schonland Research Centre's mission is to pursue a vigorous programme of both pure and applied nuclear research for the African context, including overseas collaborations where appropriate, integrated with the training of our higher degree students.
The University's recognition of separate Research Entities under the Schonland umbrella has been very successful. Attention and effort has now been freed for the business of research and teaching, and several major projects have blossomed, as detailed in this Report. Notable has been the implementation under International Atomic Energy Agency auspices of an annual five-month Radiation Protection Course serving the whole of Africa, which necessitated major structural changes to the Schonland buildings to accommodate some 20 students plus donated equipment.
Trevor Derry.
February 2000
Applied and Environmental Physics Research Group
August 1999
J.I.W. Watterson
and
B. Th. Verhagen
Introduction
The philosophy of this group is to carry out intrinsically interesting research in physics in an academic way and apply it to areas that are of interest in and practical importance to a developing country like South Africa. It is a fact that much of the research, particularly in physics, in most developing countries is not of direct relevance to that country. It does contribute to the development of humankind and it is certainly of cultural importance, but it does not contribute to the economic, environmental or social well-being of that particular country.
Jeffrey Sachs, Professor of International Trade at Harvard and Director for the Centre of International Development has made this point particularly well in a recent article in the Economist. He points out that the vast majority of scientific research is undertaken in areas that are mostly only of direct relevance to developed economies. He presents a chart which shows the overwhelming dominance of the rich countries in publications (90% of the total) and patents (95% of the total). He also points out that rich countries even benefit from the scientific talent of the poor countries and that many of the scientific and technological breakthroughs are made by poor-country scientists working on rich-country problems in rich-country laboratories. This could be further extended by observing that t even research in the laboratories and universities of the developing countries uses scarce local human resources and equipment to contribute to the solution of problems mainly of relevance to rich country science and hence to the economies of the richer nations.
Two South African examples that spring to mind are those of computed tomography discovered by Cormack in South Africa in the 1960’s and radical heart surgery associated with the name of Chris Barnard. In spite of the fact that these originated in this country, today CT scanners are all manufactured in the United States or Europe and artificial heart valves are manufactured in the United States and sold throughout the world. The economic benefits of these world class advances have been negligible in the country of their origin.
The Applied Physics Research Group pursues lines of research established by us in the Schonland Centre over many years, applying the techniques of Physics to the understanding of problems of economic and social importance in the context of Africa. This programme has three main themes: the application of isotope measurements in the understanding of water systems, the application of nuclear-based methods to mining and the understanding and measurement of radiation in the environment. All of these fields include elements of pure science and academic research as well as the development of direct economic and social benefits.
The application of isotope measurements in the understanding of geohydrology has been pursued at the Schonland, since its founding as the Nuclear Physics Research Unit in 1960, in the Environmental Isotope Research Group. Under the leadership of Prof B. Th Verhagen, the Environmental Isotopes Laboratory has been established as probably the foremost laboratory in Africa for the measurement of light isotopes in this field.
The development of nuclear techniques in mining had its origin in the National Institute for Metallurgy’s Activation Analysis Research Group, which was later broadened to include the development of techniques for on-line measurement.
It is important to realise that these activities, together with air pollution studies and many programmes on diamond physics, and geology always were the core research programme of the Schonland Centre. Other activities such as the neutrino collaboration with Frederick Reines of Case Western University in the 1970’s and various experiments on Nuclear Physics were peripheral.
There are thus three main programmes in the Group, the Environmental Isotope Programme, the Applied Nuclear Physics Programme and the Programme on Radiation in the Environment.
Environmental Isotopes Programme
1 Historical
The Group had its beginnings in the late 50's as the tritium laboratory, the initiative in the Department of Physics actually pre-dating the establishment of the Nuclear Physics Research Unit, which was to be renamed the Schonland Research Centre (SRC) in the mid-eighties.
The initial aim was the development of methods to enrich environmental tritium. The practical applications of tritium to hydrological problems were made in the late 60's. In the early seventies, the requirement of studying deep ground water with high residence times in the Kalahari prompted the development of radiocarbon analysis. A Water Research Commission contract to study ground water in the northern Cape and Sishen mine allowed for the expansion to stable isotope analysis which added mass spectrometry to the facility, re-named the Environmental Isotope Laboratory, in the mid-seventies.
Numerous studies, mainly of ground water systems but also of other environmental concerns followed, using the largely home-built low level counting facilities. During this period, the Environmental Isotope Group (EIG) became internationally acknowledged, generating many cooperative studies and research contracts. These were conducted with this and other universities, local and international research bodies, government agencies, and the private sector. The Group Leader spent several extended periods abroad being invited to participate in projects in this context.
By the mid-nineties, the Group became more actively engaged with the International Atomic Energy Agency (IAEA) in cooperative research programmes (CRP's) and a Regional Model Project for northern Africa, involving seven countries. The Group rendered expert services to this project in the course of which a similar endeavour for southern and eastern Africa was proposed. This new model project, which had its inception on 1 January 1999, is centered on the EIG as a regional facility responsible for training, scientific input and analytical services. To facilitate the latter, the EIG stands to receive an infusion of state of the art analytical equipment for a total of some R 2 million from the IAEA.
With the re-structuring of the SRC in 1997, the EIG became part of the Applied and Environmental Physics Group (AEPG).
The EIG is at present largely self-supporting and is led by Prof B Th Verhagen, retired in 1997, at present Honorary Research Fellow. Active steps are being taken towards leadership succession for the EIG.
2 Some past achievements
Research at the EIG has revolutionised the hydrology of the Kalahari and other arid and semi-arid environments. This work demonstrated for the time that ground water renewal is an ongoing process in such environments and that resources are not "fossil", or the remnants of earlier "pluvial" periods as believed previously.
The most rewarding of these studies has been producing a conceptual model for the aquifer feeding the northern wellfield of Jwaneng diamond mine in SE Botswana. This has led to an understanding of previously puzzling aspects of the well field's performance; estimates of recharge, later confirmed by water balance studies and information on the potential vulnerability of the system to pollution with changing land use.
The Group has been invited by governments and the private sector to participate in numerous major ground water development projects with considerable success in contributing to conceptual and numerical modelling and thus to the overall resource assessment. This framework of operation could be recommended to the IAEA in their endeavours to propagate the technique especially in developing states.
The final report on a Water Research Commission project and subsequent publication (Verhagen et al. 1999) showed for the time that estimates of ground water recharge in several studies based on isotope "snapshot" data could be corroborated by independent methods which required sometimes many years of observations.
The Group's work on ground water pollution using a wide spectrum of environmental isotopic tracers has been ground-breaking. In various studies using stable isotopes of water and of nitrogen, sources of pollution could unequivocally be established. The Group discovered the distinct isotopic signal on Gauteng mains water as a means of tracing such water in the environment; discovered artificial tritium in landfill leachate as a means of tracing such leachate in the environment; produced the concept of incipient pollution - at concentrations which may not yet be chemically evident but can be identified by their isotopic association.
Using stable isotopes and tritium the Group developed an approach to urban hydrology almost unique to South Africa: using the numerous private boreholes as sampling points for pin-pointing leakages. In the process, interesting small-scale features of ground water recharge were discovered.
The Group contributed to a number of studies by other Departments within this university, notably Geology, Archaeology and Botany as well as at other universities. The Group leader made a major contribution to a wide ranging set of isotope hydrology investigations in the arid zone undertaken by the Federal Geoscience Institute, Hanover, FRG.
3 Aims and nature of the EIG
The aims of the EIG are the application of both radioactive and stable isotopes of mainly the light elements (H,C,N,O,S) to the study of processes in the environment. The fields of mostly interdisciplinary research have been hydrology, archaeology, geology, and the life sciences.
The staff of the Group at present consists of the Leader, Prof B Th Verhagen, Mr M J Butler, Research Officer, and two laboratory technicians, Messrs O H T Malinga and B Kumalo.
Its analytical facilities consist of the following:
* two isotope ratio mass spectrometers (IRMS), one purchased in 1975, the second of about the same vintage, recently donated by the CSIRO in Australia. These are amongst the very few of these instruments world-wide still being kept operational
* two state of the art low level liquid scintillation spectrometers, the purchased from EIG funds with supplementation by the University three years ago; the second was commissioned two weeks ago and is part of the upgrading package financed by the IAEA under the regional model project. The home-built gas counting system was scrapped recently.
* various vacuum lines for sample preparation and handling and general laboratory facilities
Tenders have recently been called by the IAEA for a state of the art mass spectrometer, which is expected to be delivered and installed within the next few months.
4 Summary of activities during 1998-99
1 Activities: 1998
B Th Verhagen travels on expert missions to Uganda and Ethiopia to assist counterparts in IAEA projects to complete their final reports (January). Further investigation with Dr C J Barnes of Australia of the Lake Beseka problem in Ethiopia (January/February)
B Th Verhagen presents invited paper at ICARID international conference in Mumbai, India (February).
The EIG hosts a planning meeting on the project Sustainable Water Resources in Johannesburg attended by representatives of seven southern and eastern African countries. The EIG obtains unanimous support for being appointed Regional Centre for this project (March).
B Th Verhagen presents paper at the International Conference on the Role of a National Geological Survey in Sustainable Development, Gaborone, Botswana (May)
B Th Verhagen presents paper at Geocongress, Pretoria (July)
B Th Verhagen initiates Taaibosch Fault project, South Africa's contribution to the regional model project Sustainable Groundwater Resources (October)
M J Butler attends a research ordination meeting in Sfax, Tunisia on the CRP on Anthropogenic Influences on Groundwater Renewal and presents the Wits progress report (November).
B Th Verhagen travels to Madagascar on an expert mission under the project Sustainable Water Resources (November)
O H T Malinga and J A Geyer of the EIG attend a training course on laboratory techniques in Vienna (November)
Scientific visit to EIG by Messrs Dribidu and J Karundu, Entebbe, Uganda (November)
Delivery of second-hand mass spectrometer donated by CSIRO, Australia (December)
2 Activities 1999
B Th Verhagen attends RCM on the project Sustainable Water Resources and presents reports on the South African and Madagascar projects (February)
B Th Verhagen travels to Namibia on a joint mission with Dr K Froehlich of the IAEA to investigate the feasibility of that country's proposed project in the regional Sustainable Water Resources programme (April)
B Th Verhagen and M J Butler attend international Isotope Hydrology Symposium in Vienna and present paper and poster (May)
The IAEA accepts an EIG project proposal: Long-term isotope data series and the hydrological model of Jwaneng mine northern well field as part of the new IAEA CRP: Isotope response of hydrological systems to long term exploitation (June)
B Th Verhagen presents a paper to the International Conference of the Geological Society of Africa in Cape Town (July)
Delivery and commissioning of liquid scintillation spectrometer purchased by the IAEA under the regional model project (July/August).
sampling by M J Butler and B Th Verhagen of all Jwaneng production boreholes (July/August). This project is a continuation of a long-term investigation of the Jwaneng well field aquifer which shed much light on the geohydrology of the Kalahari.
B Th Verhagen visits Namibia to jointly initiate that country's programme under model project Sustainable Water Resources (August)
Following modifications, donated second mass spectrometer brought into operation (August)
During the past few years, considerable contributions have been made to problems of ground water pollution. Numerous smaller projects were completed with the private sector in 1998/99.
A tritium - oxygen-18 diagram of ground water and surface water from the Wurno irrigation area, NW Nigeria. The various components (upwelling deep ground water, irrigation and seasonal floods) of recharge to shallow ground water could be separated in order to predict vulnerability to ground water pollution.
5 Some Ongoing Projects
Isotope studies of thick unsaturated zones in semi-arid areas of southern Africa in the IAEA CRP on Isotope-based assessment of groundwater renewal and related anthropogenic effects in water scarce areas. Third project year.
IAEA projects RAF/8/022 in Nigeria and UG/8/002 in Uganda nearing completion. Assist Uganda in preparing final report.
Work has started on the project: Long-term isotope data series and the hydrological model of Jwaneng mine northern well field as part of the new IAEA CRP: Isotope response of hydrological systems to long term exploitation.
Little Karoo fractured aquifer study. This is a joint study with the Department of Water Affairs, under contract to the Water Research Commission and partially under an IAEA technical operation contract.
Various smaller ad hoc projects, mainly on local water resource assessment and pollution issues with the private sector.
Ground water resources assessment in the Taaibosch fault zone, N Province. This is South Africa's component in the IAEA RAF/8/029 regional model project.
A recently initiated investigation of ground water resources in the south-east artesian basin, Namibia under RAF/8/029 IAEA regional model project
Five other projects, in Uganda, Tanzania, Kenya, Zimbabwe and Madagascar under RAF/8/029 are to be initiated within the immediate future.
The EIG has for some 15 years contributed tritium, deuterium and oxygen-18 data on monthly rain water samples collected from four southern African stations under the IAEA/WMO Global Network for Isotopes in Precipitation (GNIP) as a national service free of charge.
6 Students and Teaching
I Mahomed, M Sc. Registration to be revised
J Kotze, PhD Joint supervision with the University of the Free State
M J Butler, MSc (1998) PhD to be registered when project proposal finalised.
The EIG has assisted in several Geology Honours projects
B Th Verhagen assists in teaching geohydrology to Geology Honours, part-time MSc and GDE classes
7 Future of the EIG
Activities in the immediate future of the EIG are likely to be dominated by the regional model project, which will involve training, scientific support and isotopic analyses in pursuance of the project. This endeavour is establishing research partnerships with six southern and eastern African states and strengthens operation with the Department of Water Affairs in South Africa.
Once the present re-organisation and rationalisation of the Environmental Isotope Laboratory is completed, active endeavours will be made to attract more post-graduate students.
With the passing of the new water act in South Africa the State has to assume greater responsibilities in the management of water resources. Isotope hydrology has been identified as an important tool in providing basic data on e.g. ground water systems and the EIG is seen as an important national asset. Following the drawing up of a Country Programme Framework (CPF) for IAEA support under its Technical Cooperation Programme, sustainable water resources and isotope hydrology as a key initiative in support of this goal is high on the agenda for research proposals recently called for by the NRF. Various proposals will be submitted by the EIG, including developing approaches to fractured rock aquifer studies, isotopic studies of the origins of nitrates; the role of radon as a ground water tracer; refining recharge estimates using environmental isotopes; national ground water vulnerability mapping - an extension of an initiative recently initiated with the Department of Water Affairs; ground water pollution studies using a variety of isotopes including tritium in landfill leachate; extending the national data base on isotopes in precipitation, surface water and ground water.
The EIG, with its modern low-level counting capacity, two operational isotope ratio mass spectrometers and a third state of the art instrument expected shortly, along with the Hugh Alsopp isotope laboratory and facilities in the Department of Geology, will place the University in a very favourable position to compete for housing the proposed National Isotope Facility. This may in time be further complemented by the development of accelerator mass spectrometry at the Schonland Research Centre.
Applied Nuclear Physics Programme
This programme concentrates on the detailed understanding of nuclear interactions with a view to their application to practical problems. In view of the over-all philosophy of the group and its aims these have primarily been in the mining industry. The most active project at present is that of Resonance Neutron Radiography.
1 Resonance Neutron Radiography
This project is a collaboration between the University, the Mineral Processing Division of De Beers, the Department of Nuclear Engineering at MIT, the South African Atomic Energy Corporation and Brookhaven National Laboratory. There are many different facets to it. It is based on the development of element sensitive neutron radiography based on resonances in the neutron cross-section plotted as a function of neutron energy.
The imaging process depends on the ration between the macroscopic cross-sections for the feature of interest and for the material in which the feature occurs.
There are two major regions of interest. One is at the oxygen “hole” around 2.3 MeV and the other is in the region of the resonance between 7.4 and 8.3 MeV. It turns out that the physics of neutron production favours the high energy resonance using the reaction 2H(d,n)3He with 5 MeV deuterons produced by an accelerator. This could be a cyclotron or an RFQ accelerator.
This project has gone through a number of different phases. In the initial phase (started effectively in 1993) use was made of the accelerators at the National Accelerator Centre, the Schonland Centre and the AEC. In 1994 the Group Leader spent a short sabbatical at MIT (sponsored by De Beers). After his return, a 2MeV RFQ accelerator was installed in the Neutron Source Laboratory at the Schonland as part of this ‘proof of principle” phase. De Beers contributed some R500 000 to the University in full support of the temporary acquisition of this accelerator.
The Group has continued its active involvement through a collaboration with MIT on an intermittent gas target, and research on the physics of the imaging process. This research is still continuing.
This programme involves three PhD students, two full time and one part-time (R. Ambrosi, H. Rahmanian and J. Guzek). The part time student has successfully submitted his thesis and should graduate later this year. The other two students should submit next year.
The work by Richard Ambrosi is particularly interesting, involving the use of an amorphous silicon imaging panel of a type that is being developed for medical x-ray diagnostic applications. This panel has been characterised by the candidate and it should prove extremely useful in the future. This puts the University at the forefront of research into imaging with the purchase of this panel. Some R400 000 was raised from De Beers for this purchase.
The thesis of J. Guzek has concentrated on the investigation of the physics of neutron production and the optimisation of this aspect of the project. In addition he has been concerned with the integration of the techniques into a practical system.
This work has lead to many research papers in international journals or reviewed conference proceedings, and a number of presentations at local and international conferences including five invited papers.
It has also lead to a number of patents held jointly with De Beers and owned by De Beers. Through this programme this group has achieved recognition as one of the world leaders in fast neutron radiography.
The programme has brought considerable financial resource into the University. This includes the provision of an accelerator for a year and running expenses as well as student support. This year we had about R330 00 of support from the THRIP programme and this money will be used to purchase a new camera for imaging purposes. It is estimated that the total value of this support over the last six years is in the region of R3m.
2 On-line Analysis and Sorting
This programme has supported a number of projects aimed at investigating the fundamental nuclear interactions and detection methods that can be used for on-line analysis and sorting. These include inelastic scattering reactions with carbon for the analysis of the energy content of coal and the gold content of gold ore. This last reaction: 197Au(n,n’γ)197mAu was the subject of research leading to the award of an MSc degree to T. Magagula in 1998. He investigated this reaction using neutrons produced through 7Li(p,n)7Be on the Schonland tandem accelerator with a lithium target. He investigated how the neutron spectrum from this reaction could be used to excite the gold without exciting reactions with silicon and aluminium and so achieve the optimum limit of detection for gold in rock. The results were presented at the ECART Conference in the Netherlands in 1997.
With the new developments in accelerator technology being pioneered on the previous project, this idea could become practically feasible and a low energy high current accelerator with a gas target should be investigated. The correct energy could be found by varying the angle of emission of the neutrons. An idea that is being developed is to do this as a project with De Beers with support from the DACST Innovation Fund.
Projects on on-line analysis of coal and other systems will also be pursued under this heading. Another idea that is being developed is that of applying a variant of the resonance neutron radiography technique that has been developed to the determination of explosives and other contraband such as drugs. This depends on the use of the fact that the energy of the neutrons varies with the angle of emission. Therefore images of the different elements, nitrogen, carbon and oxygen could be obtained as the specimen moves around the source. Once again this is being pursued in a collaboration with DeBeers.
Programme on Radiation in the Environment
The importance of the environmental effects of radiation is increasing. This applies to the products and results of mining and of power generation as well as the natural background. For a number of years the group has been involved in the use of gamma-ray spectroscopy to measure radioactivity (principally from radium, the daughter of uranium) in mining products; mainly in zircons from beach sands.
As a result of this work and new analytical ideas that were developed, the Group was commissioned to design and build a gamma-spectroscopy system to measure the amounts of uranium and thorium in these products. This system was delivered to Richard’s Bay Minerals in 1997 and the money raised in this way has been used as a source of funding for the group’s research.
In addition the International Atomic Energy Agency sponsored programme on post-graduate education in Radiation Protection is associated with the Group. In this endeavour there is a close collaboration with the Health Physics Service of the University under Dr T. L. Nam and with the South African Council for Nuclear Safety. The Head of the Group is also the Director of the Centre for Post-Graduate Education in Radiation Protection. This Centre has been equipped with about R1.5m worth of equipment over the past few years by.
There are a number of post-graduate programmes associated with this initiative.
1 Projects on Radon in the Environment
A PhD candidate Alex Tsela has submitted a thesis on the measurement and evaluation of the emanation coefficient of radon from zircons. In this project an original way was developed for measuring the radon emitted from very small samples of well characterised mineral grains. This work has lead to a greater understanding of the emanation process in zircons and to the identification of anomalies in this behaviour. This work is being carried out in collaboration with Anders Damkjaer of the Risø Research Institute in Denmark and for some time it was part of the focus of a collaboration with the University of Swaziland..
A second PhD programme has been started on radon with David Maina from the Institute for Nuclear Research at the University of Nairobi. He spends some four months each year with the Group. His project is concerned with the health effects of smoke from cooking fires in rural dwellings combined with radon in the air. There is recognised epidemiological evidence that people who smoke cigarettes and are exposed to radon have significantly higher incidences of lung cancer. The objective of this project is to investigate whether there is a similar effect from indoor cooking fires in rural dwellings in Kenya and South Africa.
Many people in Africa live in dwellings with earth floors. The radon emission is therefore expected to be higher relative to dwellings with concrete slab floors. In addition if people sleep on the floor or close to it, thoron might be an issue. Some areas where there are beach sands for example have regions where the heavy minerals are concentrated. These regions could have high concentrations of radon, and thoron close to the ground. This project is very interesting and could be of great importance to the respiratory health of rural communities.
An allied project is being undertaken together with the Environmental Isotopes Laboratory in order to measure radon in ground water using the technique of liquid scintillation counting.
2 Gamma-ray Spectroscopy for Environmental Samples
The Schonland Centre should be a centre of excellence for the measurement of radiation. A sensitive method of gamma-ray spectroscopy was developed in the Group that can be used to monitor radium daughters (214Pb and 214Bi in the uranium chain) and 208Tl in the thorium chain. This method makes use of Marinelli beakers and a 5” x 5” NaI(Tl) detector. The detector is stabilised using a method developed by Hugo Andeweg at the Schonland and works well giving very accurate results.
The method has been used over a number of years to monitor the uranium and thorium in mineral products for export (mainly zircon). As was mentioned above, a semi-commercial instrument based on this principle was also supplied to Richard’s Bay Minerals. At present the software for this instrument is being revised.
This technique is being used for the measurement of radium in effluent from slimes dams, in an honours project with the department of Geology. This research is being inhibited by the need for the stabiliser on this instrument in the same way as the one supplied to RBM.
3 Post-graduate Centre for Radiation Protection
The new Centre for Post-Graduate Education in Radiation Protection has been developed at the Schonland Centre in association with the AEPRG and the University’s Health Physics Service as well as the Council for Nuclear Safety.
The equipment for this Centre, worth about R1.5m, was provided by the IAEA. The course is being given at present to 19 students from all over Africa (including three from South Africa). The fees for the overseas students are being paid by the Centre in a complicated arrangement with the IAEA. Some 12 of the students have registered for the Post-Graduate Diploma in the Sciences.
This Centre will form the focus for post-graduate research in the field of environmental radiation. The students who successfully complete the diploma can proceed to an M.Sc by examination and research report. It is expected that a great deal of this research will be carried out in association with the AEPRG as well as with the Health Physics Service and the CNS.
So far one application has been received from a student who wishes to undertake an MSc by research as part of this programme and there have been a number of other enquiries. With the decision to proceed with the initial stages of evaluation of the Pebble Bed Power Reactor concept, there will be an increasing demand for trained personnel in this field.
Publications 1998-1999
B TH VERHAGEN, Environmental Isotope Hydrology, Hydrogeology of the Main Karoo Basin: Current Knowledge and Future Research Needs. Water Research Commission, Pretoria (1998).
NL INGRAHAM, A E CALDWELL and B TH VERHAGEN Isotope tracers in catchment hydrology. Chapter in book: Arid zone catchments. Elsevier Science Publishers, Amsterdam, (1998) 839 pp.
BTH VERHAGEN, MJ BUTLER, Environmental isotope studies of urban and waste disposal impact on groundwater resources in South Africa, In: Isotope Techniques in the study of Environmental Change. IAEA, Vienna, (1998) 411 - 422.
BTH VERHAGEN, Isotope Hydrology: applications to mining, urban, and pollution problems in southern Africa., Procs ICARID International Conference, NAARI, Mumbai, 4 - 7 February 1998, 307 - 324.
BTH VERHAGEN, Isotope Hydrology: a success story in the application of nuclear techniques to environmental problems, Nuclear Technology Conference, Mmabatho, October 1998.
A FOURIE, BTH VERHAGEN, M LEVIN, HD ROBINSON, Tritium as an indicator of contamination from landfill leachate,Wastecon '98 Conference, Kempton Park, October 1998.
BTH VERHAGEN, M LEVIN, AB FOURIE, High level tritium in leachate from landfill sites in the Republic of South Africa with emphasis on its distribution and value as an environmental tracer,Water Institute of South Africa Conference, WISA'98, Cape Town, May 1998, 10pp.
BTH VERHAGEN, Environmental isotope hydrology: past, present and future impacts on ground water studies in mining, the urban environment and understanding hydrochemistry, Procs Geocongress '98, Geological Society of South Africa, (1998) 285 - 288.
BTH VERHAGEN, Arid Zone Isotope Hydrology - Cooperation with the Geological Survey, Botswana, International Conference on the Role of a National Geological Survey in Sustainable Development, Lobatse (1998) p37.
BTH VERHAGEN, Case studies on isotope hydrology in the Kalahari,UNESCO/IHP Regional Workshop: Water Resources of the Kalahari Desert, Lobatse, Botswana, 3 - 5 November 1998.
MJ BUTLER, BTH VERHAGEN,Isotope studies of thick unsaturated zones in semi-arid areas of southern Africa,Progress Report on: International Atomic Energy Agency Research Contract Number: 335.F3.30.08 to Research Coordination Meeting, Sfax,Tunisia, 9 - 13. 12. (1998) 21pp. SRCNS 98/08.
BTH VERHAGEN,Investigation of leakages from the Aonob Dam, Namibia. ,Report on project RAF/08/026 mission (15 - 19 December 1997) to the International Atomic Agency (1998) 5pp. SRCNS 98/09.
BTH VERHAGEN, Isotopes for groundwater development, Uganda ,End of Mission Report to the International Atomic Energy Agency. Project: UGA/8/002 - 01, 10 - 18 January 1998, SRCNS 98/10, 7pp.
BTH VERHAGEN, Isotopes for groundwater development, Ethiopia,End of Mission Report to the International Atomic Energy Agency, Project: RAF/8/022 15 01, 19 - 28 Jauary 1998, SRCNS 98/11, 8pp.
BTH VERHAGEN (1999) Environmental Isotope Hydrology. Chapter in book: Hydrogeology of the Main Karoo Basin: Current Knowledge and Future Research Needs. Water Research Commission, Pretoria. In press.
B TH VERHAGEN, M LEVIN and A FOURIE (1998) High level tritium in leachate from landfill sites in the Republic of South Africa with emphasis on its distribution and value as an environmental tracer. WISA ‘98, Water Institute of Southern Africa, Biennial Conference, 4-7 May, Baxter Theatre Centre, Cape Town.
A FOURIE, B TH VERHAGEN, M LEVIN and H D ROBINSON (1998) Tritium as an indicator of contamination from landfill leachate. Wastecon í98, 13-15 October, Kempton Park.
M LEVIN and B TH VERHAGEN (1999) A unique approach to evaluate the utility of landfill monitoring boreholes. ISSMGE, 12th African Regional Conference, Geotechnics for developing Africa. 25-27 October, Durban.
B TH VERHAGEN, D B BREDENKAMP, H JANSE VAN RENSBURG and J L FARR (1999) Recaharge quantification with radiocarbon: independent corroboration in three Karoo aquifer studies in Botswana. In: Procs International Symposium on Isotope Techniques in Water Resources Development and Management. IAEA, Vienna
B TH VERHAGEN (1999) Isotope hydrology in Africa. In: Procs 11th International Conference of the Geological Society of Africa. Cape Town, South Africa.
M J BUTLER (1998) Ground water pollution at sanitarylandfill sites: Geohydrological, environmental isotope and hydrochemical studies. MSc Dissertation (Geology) University of the Witwatersrand, Johannesburg.
M J BUTLER and B TH VERHAGEN (1999) Trutium in waste as a tracer of landfill leachate in surface and ground water in South Africa. Poster presentation in: Procs International Symposium on Isotope Techniques in Water Resources Development and Management. IAEA, Vienna
Papers at International Conferences. 1998-1999
1. Fifteenth Int. Conference on the Application of Accelerators in Research and Industry, University of North Texas, Denton, Texas, November 1998, J. I. W. Watterson, R. M. Ambrosi, H. Rahmanian, J. Guzek, U. A. S. Tapper and R.C. Lanza, Accelerators and non-destructive measurement in the minerals industry (Invited paper).
2. Fifteenth Int. Conference on the Application of Accelerators in Research and Industry, University of North Texas, Denton, Texas, November 1998, J. I. W. Watterson, R. M. Ambrosi,. H. Rahmanian and J. Guzek,, Experimental verification of computer image formation in accelerator fast neutron radiography (Invited paper).
3. Fifteenth Int. Conference on the Application of Accelerators in Research and Industry, University of North Texas, Denton, Texas, November 1998, R. M. Ambrosi and J. I. W. Watterson, The relationship between contrast, resolution and detectability in fast neutron radiography.
4. Fifteenth Int. Conference on the Application of Accelerators in Research and Industry, University of North Texas, Denton, Texas, November 1998, H. Rahmanian and J. I. W. Watterson, Neutron energy discrimination using a proton radiator and a phosphor layer.
Publications in Refereed Journals and Conference Proceedings
(Recognised by the S. African Department of National Education)
1. J. Guzek, K. Richardson, C.B. Franklyn, A. Waites, W. R. McMurray, J. I. W. Watterson and U. A. S. Tapper Development of a high pressure deuterium gas target for the generation of intense mono-energetic fast neutron beams. Nucl. Instr. and Methods in Phys. Res. ? (1998) ?-?
2. J. I. W. Watterson, R. M. Ambrosi, H. Rahmanian, J. Guzek, U. A. S. Tapper and R.C. Lanza, Accelerators and non-destructive measurement in the minerals industry. Applications of Accelerators in Research and Industry, Proceedings of the Fifteenth International Conference, Denton, Texas, November 1998, J.L. Duggan and I. L. Morgan eds, AIP Conference Proceedings, In Press.
3. J. I. W. Watterson, R. M. Ambrosi, H. Rahmanian and J. Guzek, Experimental verification of computer image formation in accelerator fast neutron radiography. Applications of Accelerators in Research and Industry, Proceedings of the Fifteenth International Conference, Denton, Texas, November 1998, J.L. Duggan and I. L. Morgan eds, AIP Conference Proceedings, In Press.
4. R. M. Ambrosi and J. I. W. Watterson, The relationship between contrast, resolution and detectability in fast neutron radiography. Applications of Accelerators in Research and Industry, Proceedings of the Fifteenth International Conference, Denton, Texas, November 1998, J.L. Duggan and I. L. Morgan eds, AIP Conference Proceedings, (1999) 1078 - 1083.
5. R.M. Ambrosi, J.I.W. Watterson, The effect of air cavities on the dose delivered to the lung during high-dose brachytherapy. Biological Trace Element Research vols 71 – 72 (1999) 499-507
6. H. Rahmanian and J. I. W. Watterson, Neutron energy discrimination using a proton radiator and a phosphor layer. Applications of Accelerators in Research and Industry, Proceedings of the Fifteenth International Conference, Denton, Texas, November 1998, J.L. Duggan and I. L. Morgan eds, AIP Conference Proceedings, In Press.
Patents
1. U. A. S. Tapper, G.W. Over, J Guzek, H. Rahmanian and J. I. W. Watterson, Scintillation detector, S.A. Patent 95/5218.
2. U. A. S. Tapper, J Guzek and J. I. W. Watterson, Neutron beam generator, S.A. Patent 95/7686.
3. K. Richardson, U. A. S. Tapper, J Guzek and J. I. W. Watterson, Neutron radiography gas target, S.A. Provisional Patent H0613.224.
ION IMPLANTATION AND SURFACE STUDIES RESEARCH PROGRAMME
Leader: Prof. T.E. Derry, Reader in Ion-Crystal Interactions, Physics Department.
Participating academics:
________________________________________________
name |department | time spent
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
(Prof) T.E. Derry |Physics | 50 %
(Prof) J.F. Prins* |Schonland (sec) | 90 %
(Prof) J.D. Comins |Physics | 5 %
(Dr) G. Hearne |Physics | 5 %
(Prof) A.T. Davidson |Zululand Univ. |
(Prof) V. Hoffmann |Tübingen Univ. |
---------------------------------------------------------------------
* note -- Prof. Prins is seconded from De Beers, whose Diamond Electronics Programme he manages, and although attached to the Ion Implantation & Surface Studies Research Programme, he directs his research independently, making use of our facilities.
|Objectives & Rationale: |
| |
| |
|(1) To promote research which is already well-established at the SRCNS, on ion-beam modification and/or ion beam analysis (supplemented by other |
|spectroscopies) of the (near) surface of technologically important and fundamental solids -- diamond, metals, ionic crystals, catalysts, and other |
|materials. The principal research instruments are an ion implanter, small accelerator and UHV surface-science chamber, interconnectable. |
| |
|(2) To foster the existing collaborations with industries, other institutions (including HBU's) and internationally. The Schonland ion-implantation|
|group provides a centre of both equipment and expertise for the research of others, as well as its own. The research provides a springboard for |
|overseas collaborations, via both overseas visits and visitors from overseas. |
| |
|(3) To continue to train postgraduate students, who find our combination of pure and applied physics stimulating, and to provide a variety of |
|undergraduate projects for students of all races. Some dozen research students have now graduated, many finding ready employment in industry. |
| |
The past year has been a successful one, with Prof. Prins publishing many research and review papers, and rapidly becoming an invited celebrity on the international conference circuit. Prof. Derry was elected to the Fellowship grade of the British Institute of Physics.
Research Projects:
1 (a) Investigation of the amount and position of oxygen atoms on diamond surfaces
Using Rutherford backscattering and resonant ion scattering, and transmission channelling.
Personnel: T.E. Derry, D.B. Rebuli (student), plus WNAC members
The research has possible implications for the chemical-vapour deposited diamond layer industry. Mr D Rebuli has obtained his M.Sc and written several papers (see publications lists).
(b) Functional form of the oxygen on diamond surfaces
Using fourier transform infra-red spectroscopy; a collaboration with Tübingen University.
Personnel: T.E. Derry, V. Hoffmann (Tübingen)
A sabbatical by T.E. Derry (February-July 1998) initiated this work, which has continued with another brief visit to Tübingen in 1999. The results so far are promising.
2 (a) Attempt to produce carbon (diamond) epitaxy on copper single crystals
Using ion implantation, Auger spectroscopy, possibly ion channelling.
Personnel: J.F. Prins, S.R. Naidoo (student)
This is an industry collaboration (De Beers); success would be the key to the diamond semiconductor industry, and would place South Africa at the forefront. Work continued in 1998 using the upgraded Auger hardware and software.
(b) Improvement of diamond doping
Using ion implantation and electrical measurements, plus development of the theory.
Personnel: J.F. Prins, S.R. Naidoo (student), H. van Heerden
A further industry collaboration (De Beers) with a view to developing the next millennium’s diamond semiconductors. Both p- and n-type doping (using B and P respectively) continue to be improved, and good n-type doping using oxygen implants has recently been patented. Prof. Prins will seek further improvement using high-energy implants in the U.K.
(c) Electron-injection junctions and blue luminescence in diamond
Using implantation, electrical measurements.
Personnel: J.F. Prins, S.R. Naidoo (student)
Industry collaboration (De Beers); part of the diamond semiconductors studies. Some of the work has been published during the review period.
(d) Metal-insulator transition in heavily doped diamond
Using ion implantation and electrical measurements
Personnel: M.J.R. Hoch, J.F. Prins, T.S. Tshepe (student)
A collaboration with members of the Physics Dept. Results have been published in papers and at conferences.
3 (a) Radiation damage in other substances: ionic oxides
Using ion implantation and optical spectroscopy.
Personnel: A.T. Davidson (Zululand) + students, T.E. Derry, J.D. Comins
This represents our continuing University of Zululand collaboration.
(b) Radiation damage in silicon
Using ion implantation, surface Brillouin scattering.
Personnel: J.D. Comins and other members of Physics Dept, T.E. Derry, X. Zhang (student)
This collaboration with the Physics Dept has produced both journal and conference papers.
(c) Implantation and radiation damage in InSnO4
Using both low and high energy implantations (the latter with the 1,4 MeV accelerator).
Personnel: J.D. Comins, T.E. Derry, G. Amolo (student)
This Physics Dept collaboration is relatively new.
4 (a) Attempt to synthesize the postulated ultrahard material C3N4
Proposed method: ion implantation, surface Brillouin scattering analysis of the layers.
Personnel: S.B. Luyckx, J.D. Comins, T.E. Derry, J.F. Prins
The original collaboration with the Physics Dept has been on a back-burner, but some promising results have been obtained by Prof. Prins.
(b) High pressure diamond anvil cell studies
Assisted by ion implantation of electrical contacts into the cell.
Personnel: G. Hearne + students, S.R. Naidoo, T.E. Derry
Another collaboration in progress with the Physics Dept.
5(a) Metal alloying and defects
Using implantation, Mössbauer, ion channelling.
Personnel: H. Pollak, T.E. Derry, J.K. Dewhurst (student), H. de Waard (Groningen)
This interesting cross-disciplinary project with overseas networking had initial success, but is now concluded with the decease of Prof. Pollak.
(b) Tungsten carbide studies
Using ion implantation or ion beam analysis.
Personnel: T.E. Derry, S.B. Luyckx.
Recent work for Boart Longyear (both here and in Ireland) has involved the ion-beam analysis of trace amounts of boron in their and others’ product.
(c) Surface engineering for industry
Using ion implantation
Personnel: T.E. Derry, H. van Heerden, S.B. Luyckx
There are industry collaboration possibilities here if the FRD/NRF were to facilitate and maintain industrial enthusiasm, but no new projects have been offered as yet.
6 Synthesis and promotion of catalysts by novel routes
Using ion implantation (including into powders), XPS.
Personnel: N.J. Coville (Chemistry), T.E. Derry, H. van Heerden
A project with cross-disciplinary networking and industry collaboration, which was very active in the past, and still of potential interest to the Chemistry Department.
7 Services to continue:
Support of other universities by provision of service implants (e.g. Pretoria, Cape Town, Durban-Westville): regularly continuing.
Availability of the UHV electron spectrometer for surface analyses by othe (paying) institutions.
Ion Implantation and Surface Studies Research Programme
plus collaborators
PUBLICATIONS FOR 1998:
WJ Huisman, M Lohmeier, HA van der Vegt, JF Peters, SA de Vries, E Vlieg, VH Etgens, TE Derry, JF van der Veen.
Evidence for Tilted Chains on the Diamond(111)-2x1 Surface Surface Science 396, pp 241-252
X Zhang, JD Comins; AG Every, PR Stoddart, W Pang, TE Derry
Surface Brillouin Scattering Study of the Surface Excitations in
Amorphous Silicon Layers Produced by Ion Bombardment
Physical Review B 58, 13677-13685
X Zhang, JD Comins, AG Every; PR Stoddart, W Pang, TE Derry
Study of the Surface Excitations in Ion-bombarded Silicon Layers by Surface Brillouin Scattering
Proceedings of the 16th International Conf on Raman Spectroscopy, September 1998, pp 884-887
JF Prins
Recombination Luminescence from Defects in Boron-ion Implantation-doped Diamond
using Low Fluences
Materials Research and Innovations 1, pp 243-253
JF Prins
Ultraviolet Cathodoluminescence from Diamond Layers after Doping
by means of Boron-ion Implantation
Applied Physics Letters 73, pp 2308-2310 (1998)
JF Prins
Ion Implantation of Diamond Below the Amorphization Threshold:
Defects, Impurities, and their Interactions
Proceedings of the 5th NIRIM International Symposium on Advanced Materials,
Tsukuba, March 1998; publ National Institute for Research in Inorganic
Materials, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan; pp 93-96
JF Prins
Recent Results on the Preparation of Doped Layers, Contacts, and Interfaces in Diamond by Means of Ion Implantation
Diamond Films and Technology 8, 181-194 (1998)
JF Prins
Doping of Diamond by the Diffusion of Interstitial Atoms into Layers Containing a Low Density of Vacancies
Diamond and Related Materials 7, 545-549 (1998)
JF Prins
Ion Implantation of Diamond Below the Amorphization Threshold:
Defects, Impurities, and their Interactions (invited paper)
5th NIRIM International Symposium on Advanced Materials, Tsukuba, March 1998
JF Prins
Recent Results on the Preparation of Doped Layers, Contacts, and Interfaces in Diamond by Means of Ion Implantation (invited paper)
Name of Journal/Book/Magazine/Report/Conference
2nd International Symposium on Diamond Electronic Devices, Osaka,
March 1998
DB Rebuli, E Sideras-Haddad, BP Doyle, RD Maclear, TE Derry, SH Connell, P Aggerholm, JPF Sellschop
Oxygen on Diamond Surfaces
SAIP Conference, Cape Town, July 1998
T Tshepe, JF Prins, MJR Hoch
Conductivity Studies in Boron-ion Implanted Type IIa Diamond
SAIP Conference, Cape Town, July 1998
SR Naidoo, JF Prins
Carbon Overgrowths on Copper by Ion Implantation
SAIP Conference, Cape Town, July 1998
WJ Huisman, JF Peters, SA de Vries, E Vlieg, JF van der Veen, TE Derry
Synchrotron Radiation Determination of Atomic Positions on the Diamond(111) Surface Before and After Reconstruction
Annual Diamond Conference, London, July 1998
JF Prins
Activation of, and Vacancy Interactions with, Large Dopant Atoms in Diamond
Annual Diamond Conference, London, July 1998
E Sideras-Haddad, D Rebuli, TE Derry, SH Connell, JPF Sellschop, BP Doyle, RD Maclear,
Oxygen on Diamond
Annual Diamond Conference, London, July 1998
DB Rebuli, E Sideras-Haddad, BP Doyle, RD Maclear, TE Derry, SH Connell, P Aggerholm, JM Butler, JPF Sellschop
Oxygen Surface Studies in Ultra-thin Diamonds using Transmission Channelled Rutherford Forward Scattering
International Microprobe Conference, Cape Town, August 1998
DB Rebuli, TE Derry, E Sideras-Haddad, BP Doyle, RD Maclear, SH Connell, JPF Sellschop,
Oxygen on Diamond Surfaces
International Conference on New Diamond Science and Technology, Pretoria, September 1998
SR Naidoo, JF Prins
Electroluminescence from Electron Injection Junctions Created by Carbon and Phosphorus Ion Implantation
International Conference on New Diamond Science and Technology, Pretoria, September 1998
T Tshepe, JF Prins, MJR Hoch
Metal-Insulator Transition in Boron-Ion Implanted Type IIa Diamond
International Conference on New Diamond Science and Technology,
Pretoria, September 1998
X Zhang, JD Comins,’ AG Every, PR Stoddart, W Pang’ TE Derry
Study of the Surface Excitations in Ion-bombarded Silicon Layers by Surface Brillouin Scattering
16th International Conference on Raman Spectroscopy, Cape Town, September 1998
PUBLICATIONS FOR 1999:
D Rebuli, P Aggerholm, JE Butler, SH Connell, TE Derry, BP Doyle, RD Maclear, JPF Sellschop, E Sideras-Haddad
Oxygen Surface Studies in Ultra-thin Diamond Using a Resonance Reaction and Transmission Channelled Rutherford Forward Scattering
Nuclear Instruments and Methods B158 (1999) 701-705
DB Rebuli, TE Derry, E Sideras-Haddad, B Doyle, RD Maclear, SH Connell, JPF Sellschop,
Oxygen on Diamond Surfaces
Diamond and Related Materials 8 (1999) 1620-1622
SR Naidoo, JF Prins
Electroluminescence from Electron Injection Junctions Created by
Carbon and Phosphorus Ion Implantation
Diamond and Related Materials 8 (1999) 1502-1507
T Tshepe, JF Prins, MJR Hoch
Metal-Insulator Transition in Boron-Ion Implanted Type IIa Diamond
Diamond and Related Materials 8 (1999) 1508-1510
SR Naidoo, JF Prins
Raman and Auger Spectroscopy Studies on Ion Implanted Diamond
SAIP Conference, Port Elizabeth, July 1999
G Amolo, JD Comins, DS McLachlan, TE Derry
Structural Damage of Tin-doped Indium Oxide (ITO) by 1MeV Protons
SAIP Conference, Port Elizabeth, July 1999
JF Prins
Metastable Dopant States in Diamond
Annual Diamond Conference, Oxford, July 1999
T Tshepe,JF Prins, MJR Hoch
The Metal-insulator Transition in Diamond
Annual Diamond Conference, Oxford, July 1999
JF Prins
Oxygen Donor States in Diamond
Annual Diamond Conference, Oxford, July 1999
JF Prins, TE Derry
Radiation Defects and their Annealing Behaviour in Ion Implanted
Diamonds (invited paper)
10th Internat Conf on Radiation Effects in Insulators, Jena, July 1999
JF Prins
Functional Materials: Physics and Chemistry of Semiconductors: Diamond
Encyclopaedia of Materials: Science and Technology (in press)
Chapter in Book
JF Prins, TE Derry
Radiation Defects and their Annealing Behaviour in Ion-implanted Diamond
Nuclear Instruments and Methods (in press)
Conferences and visits
(1) 5th NIRIM International Symposium on Advanced Materials, Tsukuba (Japan) March 1998
Attending: J.F. Prins (chairman, presenter)
(2) 2nd International Symposium on Diamond Electronic Devices, Osaka (Japan), March 1998
Attending: J.F Prins (chairman, presenter)
(3) European Materials Research Society Spring Meeting, Strasbourg (France), June 1998
Attending: T.E. Derry
(4) Annual Diamond Conference, London (UK), July 1998
Attending: J.F. Prins, T.E.Derry (both presenting)
(5) South African Institute of Physics Conference, Cape Town, July 1998
Attending: D.B. Rebuli (presenter), S.R. Naidoo.
(6) International Microprobe Conference, Cape Town, August 1998
Attending: D.B. Rebuli (presenter)
(7) International Conference on New Diamond Science and Technology, Pretoria, Sept 1998
Attending: J.F. Prins (Organizing Committee Chairman), T.E. Derry, D.B. Rebuli, S.R. Naidoo (all presented papers).
(8) South African Institute of Physics Conference, Port Elizabeth, July 1999
Attending: S.R. Naidoo, G. Amolo (presenting), T.E. Derry (chairing).
(9) Annual Diamond Conference, Oxford (UK), July 1999
Attending: J.F. Prins (presenter).
(10) 10th Internat Conf on Radiation Effects in Insulators, Jena (Germany), July 1999
Attending: T.E. Derry (presenter).
T.E. Derry spent the period from February to July 1998 on study-leave at the University of Tübingen (Germany) helping to set up measurements to reveal the environment of the hydrogen and oxygen (or other) atoms on polished diamond surfaces using infra-red spectroscopy.
Post-graduate Students
0910017O S.R. Naidoo (M.Sc now converted to Ph.D), registered Jan 1995 (part-time).
Topic: Carbon overgrowths on copper by ion implantation, supervisor: J.F. Prins
9201400E D.B. Rebuli (M.Sc), registered Jan 1996, submitted and degree granted 1999.
Topic: "Ion Beam Analysis of Oxygen on Diamond Surfaces", supervisor: T.E. Derry.
Annual Report 1998-99 for Research Programme
Based at the Schonland Research Centre
1. Name of programme
2 Nuclear Physics Programme
2. Programme Leader
Professor V. Hnizdo (Reader in Nuclear Physics, Physics Department)
3. Members of the Nuclear Physics Group Pursuing the Programme
Professor V. Hnizdo (Reader in Nuclear Physics, Physics Department, Wits, resigned June 1999)
Dr J. Carter (Senior Lecturer, Physics Department, Wits, Staff number 603953, percentage time spent on research activities 35%)
Dr. R.W. Fearick (Senior Lecturer, Physics Department, UCT).
▪ Professor B. Spoelstra (Physics Department, University of Zululand).
The members of the Nuclear Physics Group have enjoyed a longstanding and ongoing collaboration which includes the corresponding groups at the National Accelerator Centre, Faure, the Florida State University, USA, the Triangle Universities Nuclear Laboratory, USA, and the Technical University, Darmstadt, Germany.
4. Research Projects
a) Professor V. Hnizdo (principal investigator)
i) Research into the implications of the so-called hidden mechanical momentum of macroscopic bodies in classical electrodynamics has continued, yielding a series of papers in the American Journal of Physics.
ii) A major calculational study of the geometric factors in the classic analysis of the masurability of the electromagnetic field of Bohr and Rosenfeld has been published. Using the calculational methods of this paper, the electromagnetic “self-force” on a spherical test body has been evaluated in closed form, which enabled us to refute the conclusions of a recent revision of the Bohr-Rosenfeld analysis that were at variance with the results of the latter work.
iii) The continuing investigation into nuclear structure effects in light heavy-ion scattering reactions was carried out at the Tandem accelerator of the Schonland Centre. This led to the award of an MSc degree to J. Madonsela in December 1998.
b) Dr J. Carter (principal investigator)
i) Data were obtained in 1997 at the Cyclotron Facility of the National Accelerator Centre in the latest of a series of experiments investigating the excitation and decay of giant resonances in nuclei. This involved the participation of colleagues from Darmstadt. Subsequent data analysis was undertaken during a sabbatical visit of three months to Darmstadt in 1998 and a another visit of one month in 1999. This work is currently being prepared for publication.
ii) An ongoing programme of light heavy-ion scattering is being pursued at the Tandem accelerator, Schonland Centre. Recently two major publications were produced, one associated with a PhD degree and one with an MSc. The present work involving the scattering of 9Be from 9Be together with existing data will lead to the third paper.
5. Publications 1998-99
• V. Hnizdo, “Covariance of the total energy-momentum four-vector of a charge and current carrying macroscopic body,” American Journal of Physics 66 (1998) 414-418.
• J. Carter, A.A. Cowley, H. Diesener, R.W. Fearick, S.V. Förtsch, M.N. Harakeh, J.J. Lawrie, S.J. Mills, P. von Neumann-Cosel, R.T. Newman, J.V. Pilcher, A. Richter, K. Schweda, F.D. Smit, G.F. Steyn, S. Strauch and D.M. Whittal, “Isoscalar quadrupole strength in 40Ca from the (p,p’(o) reaction at Ep = 100 MeV,” Nucl. Phys. A 630 (1998) 631.
• V. Hnizdo, “Radiation from circling relativistic charges, comment on a paper by Gordeyev,” Am. J. Phys. 66 (1998) 847.
• V. Hnizdo, “Comment on: An exactly solvable two-body problem with retarded interactions and radiation reaction in classical electrodynamics,” J. Math. Phys. 39 (1998) 5663.
• V. Hnizdo, “Common misrepresentation of the Einstein-Podolsky-Rosen argument,” Found. Phys. Lett. 11 (1998) 359-370.
• V. Hnizdo, “Geometric factors in the Bohr-Rosenfeld analysis of the measurability of the electromagnetic field,” J. Math. Phys. 32 (1999) 2427-2445.
• V. Hnizdo, “Comment on ‘Limits of the measurability of the local quantum electromagnetic field amplitude, ” Phys. Rev. A, in press (1999).
• V. Hnizdo, “On the Laplacian of 1/r,” Eur. J. Phys., submitted (1999).
• H. Diesener, U. Helm, H. Miska, P. von Neumann-Cosel, A. Richter, G. Schrieder, A. Stascheck, A. Stiller, H.J. Emerich, G. Fricke, T. Kroehl and J. Carter, “Giant resonance spectroscopy of 40Ca with (e,e’x) reaction (I): Experiments and overview of results,” Phys. Rev. C, submitted (1999).
• H. Diesener, U. Helm, V. Huck, P. von Neumann-Cosel, C. Rangacharyulu, A. Richter, G. Schrieder, A. Stascheck, S. Strauch, J. Ryckebusch and J. Carter, “Giant resonance spectroscopy of 40Ca with the(e,e’x) reaction (II): Multipole decomposition of 4( integrated spectra and angular correlations,” Phys. Rev. C, submitted (1999).
• H. Diesener, U. Helm, G. Herbert, P. von Neumann-Cosel, A. Richter, G. Schrieder, S. Strauch and J. Carter, “Giant resonance spectroscopy of 40Ca with the (e,e’x) reaction (III): Semidirect versus statistical decay,” Phys. Rev. C, submitted (1999).
• B.M. Nangu, J. Carter, H. Machner, B. Spelstra, J. Pilcher, E. Sideras-Haddad, S.H. Connell, J.P.F. Sellschop, A.A. Cowley, D. Aschman, D. Steyn and K. Baruth-Ram, “Energy deposition and the origin of intermediate-mass fragments in mdedium-energy proton induced reactions,” in preparation.
6. Conferences and Visits
i) V. Hnizdo: Research visit to Florida State University, Tallahassee, July 1998
ii) J. Carter: Research visits to the Nuclear Physics Institute, Technical University, Darmstadt July/August/September 1998 and June/July 1999
7. Visiting Scientists
i) Dr S.V. Förtsch, National Accelerator Centre, August 1999
8. Higher-degree students 1998-99
|Student |Name |Degree |First |Completion |Topic |Supervisor |
|number | | |Registration | | | |
|9411102A |J Madonsela |MSc |Mar 93 |Nov 98 |Nuclear |V Hnizdo |
|9213310A |B M Nangu |MSc |Feb 92 |2000 |Nuclear |J Carter/B Spoelstra |
| | |Part-time | | | | |
|MHLNCE001 |N W Mhlahlo |MSc |Jan 98 |2000 |Nuclear |R W Fearick |
|MBLGIV00X |G.K Mabala |PhD |Jan 98 |2001 |Nuclear |R W Fearick |
|MRRSEA003 |S H T Murray |MSc |Jan 98 |2000 |Nuclear |R W Fearick |
Dr J. Carter
September 1999
Report of the
WITS-Northern Accelerator Research Centre
within the
Schonland Research Centre for Nuclear Sciences
Description of the Research Centre 34
Group Membership 36
Research Projects 37
Accelerator Laboratory Facilities 51
Usage 54
Publications 56
Conferences and Visits 60
Visiting Scientists 67
Students 68
Version of 13.8.98
The WITS-Northern Accelerator Research Group
(Director : Dr SH Connell)
The WITS-Northern Accelerator Research Centre research entity provides a common home for a range of research groups spanning basic physics, applied physics, industrial physics and various interdisciplinary sciences, such as nuclear geology and nuclear techniques in industry, bio-medicine, metallurgy and the environment.
1. The Particle-Solid Interactions Research Group
(Leader : Dr SH Connell) : focuses on the phenomena associated with the interaction of accelerated beams and radiation with ordered materials. In the case that the material properties are well understood, then the basic physics aspects of the interaction are studied. In the inverse situation, the goal is materials physics. In all cases the research methodology involves accelerated beams, nuclear instrumentation, highly automated computer controlled data acquisition and processing, sophisticated engineering in the equipment construction and finally data interpretation via simulation of the experimental observables based on modern quantum mechanical models. Most of the work is carried out at the SRCNS, but where appropriate, regular use is made of CERN, TRIUMF, PSI and other major international facilities.
2. Nuclear-Interdisciplinary Science based on Ion-Beam Microscopies
(Leader : Dr E Sideras-Haddad) : applies nuclear and atomic physics phenomena in the interaction of focused beams with small samples to perform a range of novel microscopies in collaborative interdisciplinary research projects. Accelerator Mass Spectrometry capability is currently being developed
3. The Nuclear Diamond Physics Research Group
(Leader : Prof JPF Sellschop) : focuses particularly on new physics and resulting applications in specific areas at the interface of nuclear and diamond physics. Most of the work is carried out at the SRCNS, but where appropriate, regular use is made of CERN, TRIUMF, PSI, Grenoble, GSI Darmstadt and other major international facilities.
4. The Nuclear Geology Research Group
(Leader : Dr RJ Hart) : pursues global geological topics relevant to modern theories of crustal and earth forming processes. Primarily geologists, they benefit from the synergy of a close association with novel nuclear techniques for a vital part of their sample characterisation.
The synergy, mutual operation and interdependence between these research groups includes the following points:
Nuclear and particle physics knowledge is either a goal or an important tool of the research thrust.
Nuclear techniques (accelerated particle beams, radioactivity, nuclear electronics and detection systems and computer systems for data processing, visualisation and process control) are used in the research programmes.
Common major facilities. The most important major equipment items here are the two Van de Graaff accelerators with their associated infrastructure.
Postgraduate student training. The research group leaders believe the open environment of a large research facility facilitates the development of students due to the points mentioned above.
Coherence. The whole is greater than the sum of the parts.
Group Membership
|Name |Department |Staff No. |Percentage Time |
|Dr SH Connell |Physics : Senior Lecturer |08800031 |40% lecturing |
| | | |25% Lab Management |
| | | |35% Research |
|Dr E Sideras-Haddad |Physics : Senior Research |00675961 |30% lecturing |
| |Officer | |25% Lab Management |
| | | |45% Research |
|Prof JPF Sellschop |Physics : Emeritus |00911272 |75% Research |
| |Professor | |25% National Advisory Committees |
|Dr RJ Hart |Secondment : Council of |09000631 |40% Research |
| |Geosciences | |15% CGS line function |
| | | |25% Lab Man |
| | | |20% International Collaboration |
Research Projects
Impurity Chemistry and Dynamics in Diamond by In-beam Molecular Complex Spectroscopy
Staff : SH Connell, JPF Sellschop, E Sideras-Haddad.
Students : MG Bossenger, BP Doyle.
Collaborators : H Appel (KFK Karlsruhe), K Bharuth-Ram (UDW), W Verwoerd (UNISA).
This work involves basic research into the behaviour of defects and impurities in insulators and wide-band gap semiconductors. Defects and impurities play an important role in determining the physical, electrical, optical and chemical properties (among others) of materials. Using the EN-Tandem Accelerator, radioactive impurities are recoil-implanted into materials to study their geometrical, chemical and dynamical relationships in the host lattice and as complexes with other defects. A unique opportunity to visualise transient and stable molecular complexes formed immediately after ion-implantation is afforded (hot-atom chemistry). The data is reconstructed using the details of the hyperfine interaction of the probe nucleus with local fields. Diamond, other carbon allotropes, as well as various carbon containing molecules have been targeted as important materials for research. During the review period, attention has focused on analysis of previous data, writing papers, design and fund-raising for development of a heavy-ion pulsing system for the EN-Tandem (THRIPP program with DeBeers) as well as organising the 11th International Conference on Hyperfine Interactions at the end of August 1998.
Impurity Chemistry and Dynamics in Diamond by Perturbed Angular Correlations
Staff : SH Connell, JPF Sellschop, E Sideras-Haddad.
Students : BP Doyle, EJ Storbeck
Collaborators : K Bharuth-Ram (UDW), H Pattyn (Leuven), W Verwoerd (UNISA), U Wahl (Leuven)
This is the off-line source based activity version of the previous measurements, enabling later time windows to be accessed, allowing solid-state reactions to occur. A PAC project on 111In in diamond is ongoing as a complementary technique to the CEEC measurements mentioned further on. A new PAC facility has been developed. Conventional systems rely on many crates of fast electronics to process the signals. Our system is novel in that buffered event-by-event acquisition (COLLECT - see later section), enables software logic to extensively replace the expensive hardware systems, while still maintaining the data-rate of the larger systems. The project has been given a large boost with access being granted to the ISOLDE facility, CERN, Switzerland for implantation of exotic radioactive species. New software for the analysis of this data is being developed. These analyses are compared to the CEEC data taken on the same systems, and with theoretical calculations that have been made in collaboration with the Physics Department. Subsequently double implant experiments will also be done with the aim of studying the dynamical behaviour of In-X complexes. The PAC technique can label various complexes and follow their behaviour through various sample treatments with particularly simple sample preparation for the measurement process. These studies illuminate processes of diffusion, decoration, complexation, dissociation, trapping and detrapping in the solid state. This information is relevant to processes which lead to doping, passivation and poisoning phenomena in semi-conductors (in our case, semi-conducting diamond). There was substantial experimental activity during the year, and the results are being presented at the conference mentioned above, as well as being prepared for more detailed exposure in journals.
Positron Spectroscopy studies of pure diamond, dilute bulk defects and surfaces.
Staff : SH Connell, JPF Sellschop.
Students : RWN Nilen, CG Fischer
Collaborators :A Alam (Bristol), W Anwand (Rosendorf), K Bharuth-Ram (UDW), G Brauer (Rossendorf), DT Britton (UCT), P Coleman (East Anglia), F Malik (East Anglia), K Maier (Bonn, J Major (MPI-Stuttgart), A Seeger (MPI-Stuttgart), E Sendezera (U Zululand), H Stoll (MPI-Stuttgart), W Verwoerd (UNISA).
Positrons implanted into solids thermalise, diffuse rapidly, and finally form well defined configurations with the host lattice or its defects. Observation of the properties of the annihilation radiation allows a reconstruction of the local microscopic configuration by means of quantum mechanical models. In this way, detailed information concerning solid state parameters is measured. Spectra taken for the diamond host matrix demonstrate severe and hitherto unexplained anomalies. This anomalous behaviour of the positron in diamond has now been resolved following our measurements, calculations, and the calculations of our collaborators. Many papers have been published or are in preparation, including a review article. Following these advances, our programme has broadened from the positron-pure-bulk-diamond interaction to the studies of positron-defect and positron-surface interactions. A detailed set of experiments probing lattice effects in extended damage transport during ion-implantation, photochromic defects and surface structures as well as near-surface defects has been performed this year. The results are currently being published and prepared for publication.
Conversion electron emission channeling spectroscopy
Staff : SH Connell, JPF Sellschop.
Students : BP Doyle, EJ Storbeck.
Collaborators :K Bharuth-Ram (UDW), H Hofsass (Konstanz), H Pattyn (Leuven), W Verwoerd (UNISA), U Wahl (Leuven).
Ion implantation in diamond of radioactive nuclides such as 111In can be exploited to provide information on the environment in which the nuclide resides. In the emission of conversion electrons from the nuclide at its characteristic lattice sites in the diamond, the electrons are sensitive to the source-lattice configuration as well as the structure of the crystal through the channeling, blocking and flux peaking effects. The CEEC research is entirely complementary to the PAC study mentioned above, and the projects will be run simultaneously. The same comments apply then with respect to future research, as in the PAC section. A two-dimensional position and energy sensitive PAD detector was developed at CERN, Switzerland, originally as a high-energy physics tool, but now available to CEEC measurements. This detector is the of its kind to be used in this way and now allows the rapid collection of 2-dimensional channeling spectra. In two dimensions one is able to see both the axial and planar effects in channeling, enabling a more complete picture of the impurity lattice site. A profitable collaboration with K.U. Leuven has enabled the ISOLDE facility at CERN to be exploited by us. This allows implantation of the radioactive probe ions to the stringent specifications required for CEEC measurements. In order to explain the experimental results it is necessary to use solutions to the quantum mechanical theory of electron channeling. This demanded the development of an analysis program that takes into account the quantum nature of electron channeling. An important recent contribution is the inclusion of molecular effects in the construction of the transverse channeling potential, using Fourier methods based on the output from self-consistent quantum chemical simulations of large diamond-like molecules. There is experimental evidence that this was necessary, particularly in the case of channeling in diamond ( direction), where the electronic structure is not well approximated by the normal methods based on atomic scattering factors. Analysis of the large data sets obtained is well advanced. Results thus far indicate new perspectives on the annealing of the implant damage and concur with recent density functional theory calculations on the stable lattice site for the implanted and annealed In. This research is entirely complementary to the PAC study mentioned above, and the projects have been run simultaneously. The same comments as with regards future research apply here, as in the PAC section.
Muon Spin Rotation/Relaxation/Resonance (MSR) spectroscopy in diamond
Staff : SH Connell, JPF Sellschop.
Students : BP Doyle, CG Fischer, IZ Machi, RD Maclear, RWN Nilen
Collaborators :JM Baker (Oxford), K Bharuth-Ram (UDW), JE Butler (NRL-Washington), SFJ Cox (Rutherford Lab), TL Estle (Rice U), T. Jestadt (Oxford). R Kiefl (TRIUMF), J Major (MPI-Stuttgart), P. Murphy (Oxford), R Scheuermann (MPI-Stuttgart), A Seeger (MPI-Stuttgart),
Muonium-defect interactions as well as muonium dynamics are being explored using Muon Spin Rotation/Relaxation/Resonance (MSR) spectroscopy. The current program takes advantage of the unique properties of the muon to probe the behaviour of the hydrogen-like atom in diamond. The importance of hydrogen as an impurity in diamond is widely appreciated. Its important catalytic role in the metastable synthesis of diamond, as well as its anticipated significance regarding the electronic properties of future diamond devices are two examples. Despite the relevance of hydrogen to diamond growth, properties and engineering, comparatively little is known about it, and it has proved to be a most difficult impurity to study using conventional techniques. On the other hand, most of the information on hydrogen in diamond has been inferred by the indirect technique of the MSR, which is sensitive, robust, accurate, and has a low background. Clear examples of muonium diffusion, trapping and detrapping, and possibly even Ionisation reactions at B acceptors in semi-conducting diamond have been both observed and modelled. The transparency of diamond and the photochromicity of certain defects was used to illuminate some of the processes involved. A new muonium site in diamond containing substantial amount of nitrogen-related defects was discovered. This has provided evidence for a new deep trap for hydrogen in diamond, as well as a new way to study one of the nitrogen related defects whose structure is much debated.
Thin diamond crystals - the doorway to new diamond physics
Staff : SH Connell, JPF Sellschop, E Sideras-Haddad.
Students : BP Doyle, IZ Machi, RD Maclear, DB Rebuli
Collaborators :P Aggerholm (Aarhus), M Rebak (DeBeers), J.E. Butler (NRL-Washington)
If thin, that is to say micron and sub-micron thickness, diamond of high quality, were to become available it would make possible a large suite of research opportunities in both atomic and nuclear physics, as we have long appreciated. Conventional polishing techniques become problematic for thicknesses below 20 microns, owing to increasing difficulties with plastic deformation of the diamond remnant. We have made substantial progress in this quest through a new approach : carbon ions are implanted into a prepared diamond at an energy selected to place the Bragg peak at a depth below surface corresponding to the thickness of the final diamond sliver required. A dose of incident ions is delivered that is adequate to amorphise the layer corresponding to the Bragg peak. The diamond is then heated to about 1200C to both make the amorphisation more complete and to restore the crystal perfection of the superficial layer of any small amount of radiation damage by annealing. This is followed by an electrochemical etch in pure water whereby the amorphous layer is removed, allowing the superficial layer to float free. Special techniques are necessary to handle the sub-micron to few-micron thick diamonds. In this manner we have successfully prepared diamond targets of 1 to 3 microns thickness.
Some of the new suite of research possibilities enabled by these exciting samples involves applying any of Ion Beam Analysis (IBA) measurement technologies in channeling mode. This delivers lattice structural information about defects and impurities, in addition to the normal analytical information. Channeling Rutherford Backscattering Spectroscopy is used to study the details of the thin crystal production process and to optimise it. Channelling-ERDA has been applied to identify hydrogen structures in diamond. Transmission Channeling Forward Scattering is being used to study oxygen termination structures on diamond.
A new concept in creating thin single crystal samples will shortly be explored in which the implanted ion species is helium and the superficial layer is removed by the application of heat alone, as successfully demonstrated in the case of silicon.
Hydrogen dynamics and chemistry by micro-scanned Elastic Recoil Detection Analysis
Staff : SH Connell, JPF Sellschop, E Sideras-Haddad.
Students : BP Doyle, CG Fischer, IZ Machi, RD Maclear, RWN Nilen, DB Rebuli
Collaborators :P Aggerholm (Aarhus) K Bharuth-Ram (UDW), JE Butler (NRL-Washington), E Fritsch (Institut de Matériaux de Nantes)
Diamond has many physical and chemical properties attractive to the semi-conductor industry. The presence of hydrogen in the diamond lattice influences these properties. Its presence is known to affect the hardness of the material, it passivates active dopants and changes the optical transmission of diamond. Theoretically, hydrogen is a simple example of an atom in a covalently bonded macro-molecule, and is therefore instructive to model. The unique capability to perform 3-dimensional microscopy of trace hydrogen distributions has been developed at the EN-Tandem accelerator to a level of sophistication unmatched elsewhere in the world. This has enabled a coherent program focusing on hydrogen dynamics and chemistry in diamond, supported as well by the other projects using muons, positrons and radioactive ions described above. The new method has been called (ERDA (see the title of this section for expansion). In one programme of measurements, phenomena like hydrogen stability, diffusion, trapping, detrapping, decoration, complexation and so on are studied. In another set, hydrogen distributions were evaluated to characterise natural and synthetic processes leading to hydrogen incorporation into diamond. This has relevance to metastable synthesis of diamond as well as the natural genesis environment of diamond. This program has recently been extended to include the channeling phenomenon, due to the availability of thin single crystal diamond, as described in the previous research project. Channeling-ERDA measurements will give a much improved picture of the crystallographic location of hydrogen in diamond. The possibility of measuring the exact location of the hydrogen allows measurements of other important phenomena involving hydrogen in the diamond lattice, for example, hydrogen diffusion pathways and complexation modes with other defects.
European synchrotron radiation facility (Grenoble)
Staff : JPF Sellschop, M Rebak
Collaborators :A Freund (ESRF)
Work over the past few years has continued in pursuit of using diamond in critically sensitive areas in this powerful third generation radiation source. Diamond is usually compared with silicon and germanium in its application as a monochromator for synchrotron radiation. Some of the physical constants for which diamond is greatly superior to the other two are
the linear absorption coefficient (and consequently the absorption length) for, say, 8 keV X-rays diamond is enormously transparent for these wavelengths
the Debye temperature for diamond is very high, and consequently the thermal vibration amplitude is very low indeed
the thermal expansion coefficient is very low
the heat conductivity is very high
the Darwin band width is small
The usually accepted figure of merit in such applications for diamond is some 600 times superior to silicon, and 2000 times better than germanium. With the deployment of especially-grown diamond with very small mosaic spread, tests have been carried out on the use of diamond as a high heat load monochromator. Rocking curves confirmed the high quality of the diamond materials selected. In heat load tests the rocking curve width remained constant over a wide range of beam intensities, quite unlike silicon. The highest intensity, namely 3.5 kW / mm2, tested is to put it mildly most impressive, since it corresponds to an energy density that exceeds that at the surface of the Sun !
Diamond proves to be radiation hard in this application also with very little evidence of damage over prolonged periods of beam exposure. A second research thrust has been in an attempt to bend diamond to provide saggital focusing of the monochromatised x-ray beam. A crystal bender was especially designed, a diamond of high quality was configured to dimensions 10 mm x 5 mm x 67 micrometer with the large face the {111} orientation. This diamond was successfully and repeatedly bent to a radius of curvature of 0.9 meter, giving a demagnification (focusing) factor of 20 times ! This field has proved to be a fruitful one and will be continued. Two invited papers were presented at the recent SPIE conference in San Diego (July 1998).
Coherent, correlated phenomena resulting from the Incidence of High Energy Leptons and Photons on Oriented Crystals
Staff : SH Connell, JPF Sellschop.
Students : ZZ Vilakazi
Collaborators :K Kirsebom (ISA-Århus), R. Medenwaldt (ISA-Århus), U. Mikkelsen (ISA-Århus), SP Møller (ISA-Århus), E Uggerhøj (ISA-Århus), T Worm (ISA-Århus), S Ballestrero (INFN-Florence), P Sona (INFN-Florence), K Elsener (CERN), YuV Kononets (RRC Khurtarchov Institute), A Apyan (Yerevan Physics Institute), RO Avakian (Yerevan Physics Institute), AE Avetisian (Yerevan Physics Institute), KA Ispiyran (Yerevan Physics Institute), C Biino (INFN-Turin)
The Research programme is founded predominantly in fundamental Physics, embracing both the local and the overseas capacity in a ordinated way. The scope of the research addresses all phenomena associated with lepton-photon processes resulting from the incidence of ultra-relativistic particles on highly-ordered crystalline materials. Scattering in a well aligned crystal geometry is extended to investigate coherent and correlated versions of the basic theory of electromagnetic processes viz. quantum electrodynamics (QED) at higher energies. QED is a highly developed field theory and has been investigated experimentally to very stringent detail. In recent years it has become technically possible to investigate QED processes in very strong crystalline electromagnetic fields. In short, new phenomena and physics do arise, opening up a plethora of new concepts to be explored therein inter alia Strong Field QED. This programme is undertaken at the CERN-SPS in the multi-national NA43 collaboration. The results show either very strong enhancements or losses in the cross-sections, as well as changes in the shape of the cross-sections. This in turn leads to new phenomena, which deepen an understanding of fundamental theories, as well as allowing new theoretical tests and new applications. The NA43 experiment has essentially completed its brief. The investigations which were carried out throughout the period that covered most of the period reported herein are: Establishing and studying the occurrence of a very new effect, the production of linearly polarised, partially monochromatic ultra-hard single photons by electron aligned incidence on crystals of very specific relative orientation to the beam. Studying coherent enhancements in both pair-production and brehmsstrahlung at ultra-relativistic energies. Realising and studying for the time in the laboratory under well characterised conditions the occurrence of super-critical fields and their effect on energy loss mechanisms. Studying channeling in bent crystals for super-relativistic particles. Most of these new phenomena have lead to remarkable new devices which have already found application in other High Energy Physics experiments, or are in a proposal stage which may lead to new HEP capabilities. Of special mention : One new proposal is intended to lead to the use of the ultra-high energy (polarised) photons produced as described above as a tool to study the gluon contribution to nucleon spin. Another proposal would like to extract parasitic beam from the LHC accelerator for fixed target experiments using bent diamonds.
Apart from the good physics delivered by the CERN programme, there has also been significant technology transfer. The Physics Analysis Workstation (PAW) package was ported to a graphical Linux-PC environment by S Ballestrero during a working visit of his to the SRCNS. This was the time the entire CERN Libraries became available on PC in a graphical environment. Previously, only mainframes or mini-computers could access the physics capability of this software. The port was welcomed by the international (HEP) group and the CERNLIB's on Linux-PC's became officially supported by the CERN Computer Group from then mn. S Ballestrero also developed a Data Acquisition System (DAQ) that front-ends PAW to small lab detector systems. This gave the SRCNS (and any other small lab) essentially the same data capture power as the large CERN experiments for an incredibly reduced price. This innovation has been released via a WW page, and other labs are now sharing in it. This development has allowed us to run the CERN Monte Carlo package GEANT (which simulates many physics processes from keV to TeV interaction energies) and to contribute effectively to the analysis of data taken at CERN in our own local environment, by having a local PAW capability. It also enabled us to take the lead internationally in certain of our Physics Experiments based locally at our microprobe. Part of this programme is discussed in a separate section.
The Physics foothold at CERN will be extended when the ex-PhD student ZZ Vilakazi takes up a Post Doc position on four CERN-HEP experiments later this year. An initiative to synergise our efforts with the local theoreticians and other interested groups in other Universities in the country is in progress.
Alkali Halide Materials and Super-Ionic Conductors
Staff : DJ Comins, SH Connell, TE Derry, JPF Sellschop.
Students : CG Fischer, RWN Nilen
Collaborators : EJ Sendezera (U Zululand), AT Davidson (U Zululand)
The use of positrons as a microscopic probe for the investigation of defects in crystal and amorphous systems, allows a study of the kinetics of creation and annealing out of defects. In particular, for the Super-Ionic materials, an enhanced conductivity mechanism occurs which is not yet fully understood, and is an issue of great current importance. An experiment using Positron Spectroscopy is being developed as it is believed it can provide information on the role of vacancies in this phenomenon.
Non-Stochastic Ion-Implantation - Industrial Collaborative R&D
Staff : SH Connell, JPF Sellschop.
Collaborators : W Wesch (Jena), Leonard C. Feldman (Nashville)
The aim is to develop and study non-stochastic systems for maskless implantation of dopants for situations of small feature size ( ................
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