INDICO-FNAL (Indico)



DPPD Baseline Design and Installation PlanThe basic unit of installation/operation is called a sector. One DPPD sector is 6 m x 6 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 in bundles at the cryostat floor to either 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 g/m. The HV cable length will be identical for all sectors.The design is illustrated in Figs. 1 and 2. The cable length at the cryostat floor will be 9 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 25 m. This corresponds to approximately 2 kg/m load on the cable trays on the side walls (a total of 32 kg assuming a cable density of 50 g/m) per sector, also including the 6 calibration fibers. 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 (8 shown here). The locations of the feedthroughs 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 sector, 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.Transportation, Storage and ITF OperationsThe transportation of the PMTs 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. 3. 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 3. 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. 4. Two coating stations of 1.5 m x 1.5 m are envisaged. Figure 5 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. 4). Vacuum pumps will be placed in the immediate vicinity of the evaporators. Control electronics will also be placed next to the evaporator chambers. The PMTs will be taken out of their individual carton boxes when they arrive at the ITF. The PMTs will be tested for basic functionality to validate the safe transport from the remote sites. The PMT windows will be cleaned with acetone and isopropanol before the evaporation. This will be performed in the flow device/fume hood shown as a green box along the 10 m wall. Figure 6 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. It will be used to remove the vessel lid and support it during the installation of the PMT for coating. Following the evaporation procedure, an acrylic protective plate will be installed covering the coated PMT windows, and the PMTs will be placed in individual dark plastic protective bags. The PMTs will go through another round of basic functionality test before being transported to the underground areas.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. The structure will allow easy access to the short HV cables so that performance and functionality tests can be performed easily. Three of these structures will be placed inside the boxes with the crane in three rows.The work area will also be utilized as the storage area for the large PMT boxes before being sent to SURF. 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 4. The layout of the ITF work area. Figure 5. Pictures of a single TPB coating station (courtesy of Wil Vollenberg, CERN-TE Department). Figure 6. 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. 7. 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 7. 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 50 kg (25 m) per sector with an average mass/length of 2 kg/m. 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 both sides of the cryostat. 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. Once the plastic wrap is taken off, the DPPD PMT box and its entire content can be transported to the clean room. The PMTs will undergo functionality tests inside the custom design dark box which can cover the entire structure for 4 x 3 PMTs. The dark box will have high voltage patch panel and will allow consecutive tests of all 12 PMTs in one testing session. 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. 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 sector1Total number of feedthrough flanges20Number of HV racks per sector1Frequency of transportations to SURF from ITF2 loads of 1 DPPD box per month (2 loads of 2 + 1 boxes in the first delivery) Rate of installation2 sectors/month (18 PMTs/week) ................
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