INDICO-FNAL (Indico)



DPPD Baseline Design and Installation PlanThe basic unit of installation/operation is called a sector. One DPPD sector is 12 m x 3 m and houses 36 PMTs. A total of 20 sectors will be installed in the detector. A single HV cable per PMT will be installed in the cryostat. The cables from the PMT locations (RG303/U) will run along fixations at the cryostat floor to a single side. The short cables attached to the PMT bases will be connected to these long cables during the PMT installation at the cryostat floor. The long cables from each sector will be bundled and will run through a cable tray along the 12-m side wall to the top of the cryostat. The cable density is 45-60 kg/km. The HV cable length will be identical for all sectors.Single-Side Readout Design:The design is illustrated in Figs. 1 and 2. The cable length at the cryostat floor will be 12 m (determined by the farthest PMTs), the side wall length is 12 m, and the additional average cable length per PMT is estimated to be 4 m. Therefore, the overall cable length per PMT is 28 m and this corresponds to approximately 65 kg per sector, also including the 6 calibration fibers. The maximum load on the cable trays will be approximately 40 kg. Figure 1. Schematic view of the DUNE Dual Phase Far detector cryostat. Two neighboring sectors of DPPD are shown in orange and blue. The black lines represent the location of the cable trays.The high voltage cables and the calibration fibers will be ended through a feedthrough flange with SHV and SMA connectors respectively. One DN250 flange is envisaged per sector of DPPD. One flange will house 36 SHV and 6 SMA connections. This DPPD design will have 20 penetrations along the 60-m length of the cryostat roof, one per sector.Figure 2. A sketch of the DPPD sectors (4 shown here). The locations of the feedthrough are indicated as blue circles and the HV/signal racks with red rectangles.The high voltage and signal crates will be at a density of one per two sectors, hence resulting in a total of 10 HV/signal racks on the cryostat roof. The racks will contain the HV crates with either 3 modules of 24 channels or 2 modules of 36 channels. The HV/signal splitters will also be placed on these racks. The TCA signal crate will house the front-end electronics. The rack will also contain the calibration LED driver and the associated electronics.The design is compact, easy to construct, install, operate and maintain. The services will be provided on the single side of the cryostat roof. The cable length between the HV/signal splitter and the flange, HV modules and the front-end electronics is minimized as well as the total number of penetrations required. The disadvantages of this design are that the HV cable length inside the cryostat is maximal and will cause the largest attenuation possible; and there will be a weight imbalance on the cryostat roof.Double-Side Readout Design:The design is illustrated in Figs. 3 and 4. This design introduces the concept of the subsector corresponding to half of the sectors along the 12 m side, of which the boundaries are indicated with dashed lines. The cable length at the cryostat floor will be 6 m (determined by the farthest PMTs), the side wall length is 12 m, and the additional average cable length per PMT is estimated to be 4 m. Therefore, the overall cable length per PMT is 22 m and this corresponds to approximately 25 kg per subsector, also including the 3 calibration fibers. The maximum load on the cable trays will be approximately 20 kg. Figure 3. Schematic view of the DUNE Dual Phase Far detector cryostat. Two neighboring sectors of DPPD are shown in orange and blue. The black lines represent the location of the cable trays. Each sector is divided into two subsectors to be read out on either side.Figure 4. A sketch of the DPPD sectors (4 shown here). The locations of the feedthrough are indicated as blue circles and the HV/signal racks with red rectangles. The subsector boundaries are indicated with dashed lines.One DN160 flange can be used per subsector of DPPD. One flange will house 18 SHV and 3 SMA connections. This DPPD design will have 40 penetrations along the 60-m length of the cryostat roof, one per subsector.The high voltage and signal crates will be at a density of one per two subsectors, hence resulting in a total of 20 HV/signal racks on the cryostat roof. The racks will contain the HV crates with a single module of 36 channels. The HV/signal splitters will also be placed on these racks. The TCA signal crate will house the front-end electronics. The rack will also contain the calibration LED driver and the associated electronics.The design is favorable in terms of HV cable length inside the cryostat and weight balance on the cryostat roof.Transportation, Storage and ITF OperationsThe transportation of the PMTs in the underground halls will be on a standard EUR size pallet of dimensions 1.2 m x 1 m. The largest capacity commercially available box is exemplified in Fig. 5. The box can contain 36 PMTs in three levels of 4 x 3. Individual PMTs will be placed in carton boxes with their bases, mounting assemblies and short cables at the remote sites. 36 PMTs will then be placed in the transport boxes for shipping to ITF. Figure 5. An example transportation box envisaged to be used for all transport purposes i.e. from remote sites to the ITF and from ITF to SURF. At the ITF, DPPD will have a work area with size 10 m x 8 m and 3.6 m (12 ft) ceiling including a gantry crane. The work area will be utilized for TPB coating of the PMT windows, quality control of the PMTs, storage and preparation for the transport to SURF. The layout of the ITF work area is shown in Fig. 6. Two coating stations of 1.5 m x 1.5 m are envisaged. Figure 7 shows pictures of a station at the CERN Thin Film Facility. Between the two coating stations, an elevated platform that will be accessed with short stairs will be placed. This platform will be used to conveniently reach the top lid of the evaporator (approximately 1.5 m high from the ground level) and inside the vessel. Cooling water, nitrogen and electricity will be provided from the outlets placed along the 8 m wall (indicated as the area with wavy lines in Fig. 6). Vacuum pumps will be placed in the immediate vicinity of the evaporators. Control electronics will also be placed next to the evaporator chambers (indicated as grey boxes). The PMT windows will be cleaned with chemicals before the evaporation. This will be performed in the flow device/fume hood shown as a green box along the 10 m wall. Figure 8 shows pictures of the fume hood in the CERN Thin Film Facility. The gantry crane (indicated with red bars) will be capable of moving parts between the coating stations and the work desks. Multi-shelf racks will allow temporary storage of PMTs, bases and fixtures before, during and after coating, and small parts. The desks are large enough to allow both pre- and post-coating work and quality control tests. Figure 6. The layout of the ITF work area.The work area will also be utilized as the storage area for the large PMT boxes before being sent to SURF. The PMTs in arrays of 4 x 3 will be placed in a custom structure. The structure will be assembled with metal and plastic parts so that the entire structure together with the PMTs can be moved into the clean room underground. To cover the coated window side of the PMTs, polyurethane foam is envisaged. The structure will allow easy access to the PMT electronics so that performance and functionality tests can be performed when the structure is in the transportation box. Three of these structures will be placed inside the boxes with the crane in three rows. The boxes will be stored in the single-shelf racks to the right and left of the entrance of the work area. The first set of boxes will be placed on the floor and the second set will be on the shelf which is 1.5 m higher off the ground. This area is capable of storing the entire DPPD PMT inventory of 720 PMTs in 20 boxes. The 80 spare PMTs can be placed in two boxes and the shelves, and the boxes can be stored on the floor in the available space in the work area towards the end of the DPPD ITF operations. Figure 7. Pictures of a single TPB coating station (courtesy of Wil Vollenberg, CERN-TE Department). Figure 8. Pictures of the fume hood (courtesy of Wil Vollenberg, CERN-TE Department).The transportation of the boxes in the ITF area and also within the DPPD work area can be done with compact warehouse-type forklifts. An example is shown in Fig. 9. At the beginning phases of the DPPD operations at the ITF, the storage area will be used for storing cold HV cables and calibration fiber assemblies which will then be transported underground.Figure 9. An example fork-lift to be utilized in the DPPD ITF work area.At the ITF, the PMT windows will be coated at a rate of 4 PMTs/day resulting in 20 PMTs/week and 80 PMTs/month which is compatible with the installation schedule of 2 sectors (72 PMTs) per month.Underground Transportation and InstallationThe cryostat cable/fiber installation will precede the installation of the field cage. The cables/fibers will be routed from the flanges to the bottom of the cryostat. The total cable/fiber mass (length) is approximately 25 kg (22 m) per subsector for the dual-side readout design and 65 kg (28 m) for the single-side readout design. The free ends of the cables/fibers will be temporarily mounted to the cryostat floor in such a way that they will be easily accessed during installation. The cable/fiber and tray installation will be done on a single side of the cryostat in the single-side readout design, significantly simplifying the logistics of the operation. At this stage, the HV cables will be transported in a single box from the ITF to SURF. At the same time, a separate box containing the 120 calibration fiber + fiber bundle assemblies will be transported from the ITF to SURF. The boxes will be transported to the cryostat roof for hanging the cables/fibers through the feedthroughs for installation in the cable trays. The large DPPD boxes will be wrapped with plastic foil at ITF to be opened in SAS underground. Two DPPD boxes can be stacked on top of each other in the cage making a single trip for two sectors. Therefore, the underground transportation will be performed once a month.The boxes will be transported to SAS where the plastic wrap will be taken off. Afterwards, the DPPD PMT box and its entire content can be transported to the clean room. The PMTs will undergo functionality tests while inside the transportation boxes. The test will be a simple check of healthy PMT operations. Once the operation of the PMTs is validated, the structure can be moved inside the cryostat.Inside the cryostat, the PMTs will be removed from the structure. The window protections will be kept on the PMTs. The PMTs will be mounted on the membrane floor, in the areas between the membrane corrugations, through their support structures. The attachment is done via a stainless steel supporting base that could be point-glued to the membrane. The weight of the support and PMT exceeds the buoyancy force of the system. Furthermore, these supports also ensure stability against possible lateral forces acting on the PMTs due to the liquid flow. Once the fixation is completed, the short HV cables will be connected to the cold HV cables with SHV barrel connectors. The calibration fibers will be routed and connected to the support structure. Once all the PMTs of a given DPPD sector are installed, the cables and fibers will be fixed in their final positions.The installation will be done at a rate of 2 sectors/month or 18 PMTs/week. After the installation, the empty PMT boxes and the transport structures will be transported back to ITF. This transportation can be synchronized with the other installation teams and will be once a month on average. In the clean room, at most three DPPD PMT boxes will be present at a time.Below table summarizes the quantities related to the DPPD installation.ParameterValueNumber of DPD sectors20Number of PMTs per sector36Number of calibration fibers per sector6Number of feedthrough flanges per sector1 (single-side readout) / 2 (double-side readout)Number of HV racks per sector? (single-side readout) / 1 (double-side readout)Frequency of transportations to SURF from ITF1 load of 2 DPPD boxes per month (2 loads of 2 + 1 boxes in the first delivery) Rate of installation2 sectors/month (18 PMTs/week) ................
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