chiller carrier Electronics parti 3

chiller carrier 
parti 3
carrier Electronics
The 450V to the PDBs is provided by a single CAEN SY1527LC Universal Multichannel Power Supply System using nine A1520P floating 12-channel cards.  Each of the 12 channels of the A1520P is individually programmable from 0-500V, and provides a maximum of 15mA of current.  A cable harness takes the 12 HV channels from each A1520P card to a nearby patch panel, and RG59 cables with BNC connectors go from the patch panel to the PDBs.  Each CAEN HV channel feeds two PDBs, whose high voltage inputs are daisy-chained together.
    The low voltages (3.3V and 24V) needed by the FEBs, DCMs, and TE coolers, are provided by the Wiener PL508 Power Supply System.  Each Wiener PL508 chassis has six floating individually programmable power supply modules: three 2-7V channels, each rated to 115A and 550W, and three 12-30V channels, each rated to 23A and 550W.   Hence each PL508 crate feeds power to three adjacent PDBs:  the 3.3V via 2AWG cables and the 24V via 10AWG cables.  The cables can safely carry the maximum rated current of the Wiener supplies without the need for fuses.  The Wiener low voltage supplies have a remote sensing feature which allows the voltages at the PDBs to be set to their desired values.  This feature is needed because the different cable lengths from the Wieners to the PDBs produce non-negligible differences in the voltage drops.  The longest cable runs are about 16 m, corresponding to one-way voltage drops of 0.51V and 0.56 V, respectively for the 3.3V and 24V lines.  Voltage drops on the 18AWG cables running from the PDBs to the FEBs are much smaller, resulting in a voltage range at the FEBs between 3.41-3.30V, well within the allowed range of the FEB voltage regulators, which protect
the FEBs from inadvertent application of the highest voltage (7V) the Wiener supplies can provide.  A total of 122 kW of power is consumed by the FEBs, DCMs, and TE coolers (the APDs consume no appreciable power); 19 kW is lost in the cables and 3 kW is lost in the PDBs to heat.  To provide the power the Wiener supplies, which have an average efficiency of 72%, need 215 kW
Both the Wiener and the CAEN power supplies are remotely controllable with Ethernet interfaces.  They have programmable trip levels and their noise and ripple specifications meet the requirements of the FEBs, APDs, and TE coolers. 
  Fig. 14.24:  Isometric view of a power distribution box.  Four of the cards carrying power to the FEBs are shown in the right-hand slots.  The card at the left provides power to the DCM (and has two spare outputs for FEB power).

The 24V, 1A power to the Time Distribution Units (TDUs) is provided by the National Instruments field point power modules used for the Detector Control System (DCS).
A total of 198 far detector and 10 near detector power distribution boxes are needed (not including spares).  To fit within the tight space constraints of both detectors the power distribution boxes employ a standard DIN 3U subrack with a custom backplane that feeds 3.3V, 24V, and 450V to 16 individual cards.  Each card provides power to 4 FEBs, allowing a maximum of 64 FEBs to be powered through one PDB.  Each 3.3V and 24V output is individually fused and has LED indicators.  Crate-level switches power the 3.3V, 24V, and 450V lines.  Transient voltage suppressors on the 3.3V lines protect the FEBs from over voltage due to an out of regulation power supply.  A special card feeds 24V power to the associated DCM, and has two spare FEB power outlets.  This power can be switched on and off irrespective of the status of the 24V power to the FEBs, allowing the DCM to be powered on while the 24V to the TE coolers is off.
Fig. 14.25:  The left photo shows a PDB card that powers 4 FEBs; the right photo the PDB card that provides power to a DCM (with two spare FEB power channels).

The fundamental unit for the power distribution system for the far detector is the 62-plane di-block.  The channel counts for the far detector super-blocks, di-blocks, blocks and planes are given in Figure 14.26.  There are 16 di-blocks, which come in two varieties: 13 consist of AB block pairs, and have 31 horizontal and 31 vertical planes.  These AB di-blocks are serviced by PDBs which provide power to 62 FEBs each.   The second type of di-block, which spans the boundary between superblocks, consists of AA block pairs, and has 32 vertical planes and 30 horizontal planes.  These AA di-blocks are serviced by PDBs which each provide power to 64 FEBs on the top (vertical modules) and 60 FEBs on the side (horizontal modules).  At the rear of the detector is a partial di-block consisting of 6 vertical and 5 horizontal planes; each PDB feeds 24 (20) top (side) FEBs. 

Fig. 14.26: Channel counts for the far detector super-blocks, di-blocks, and blocks.  The power distribution system is laid out on a di-block by di-block basis.  Normal di-blocks, consisting of an
AB block pair, have 31 vertical and 31 horizontal planes.  Di-blocks spanning the superblock boundaries, consist of a AA block pair, and have 32 vertical planes and 30 horizontal planes.  The last “di-block” only has 6 vertical and 5 horizontal planes.

The layout of a far detector di-block is shown in Figure 14.27.  In a normal di-block there are 12 x 31 = 372 vertical modules, requiring 6 PDBs, each feeding power to 62 FEBs, and 372 horizontal modules, requiring 6 PDBs, each feeding power to 62 FEBs.  For each PDB there is one DCM.   The Wiener power supplies are mounted on relay racks on the upper catwalk:  one Wiener for every three PDBs for a total of four for each di-block.  One CAEN mainframe is needed for the entire detector: it is situated at the detector midpoint.  Since each CAEN output
channel supplies power to two PDBs, 6 HV channels are needed to supply the 12 PDBs in a di-block. 
For the complete far detector, 198 PDBs are needed, 1 CAEN mainframe with a total of 9 A1520P boards, and 66 Wiener PL508 crates (Table 14.4).
 Fig. 14.27:  Layout of the power distribution system for a far detector di-block.  Each PDB powers all of the FEBs in a 2 longitudinal block by two module wide area.

The detailed layout of the PDBs, cable trays, and cables (as well as the DCMs and cooling manifolds) for the far detector has been drawn using AutoCAD.  The PDBs serving the vertical modules will be set on the flat part of the module manifolds. as can be seen in Fig. 14.28.  The DCMs are adjacent to them.  The restriction in the maximum height of the PDBs (and DCMs) to 3U (5.25”) is in order to allow the rolling access bridge to be as close as possible to the vertical module manifolds and electronic boxes for installation and repair.  The PDBs (and DCMs) serving the horizontal modules will be mounted sideways on the west side of the detector using a commercial framing system such as Unistrut
.Fig. 14.28:  Front view of the top west corner of a far detector di-block.  The PDBs fit between the module manifolds and the rolling walkway on the top, and between the manifolds and the catwalk support columns on the side.  Cable trays and cooling water manifolds are shown.  Not shown are the DCMs, which are behind the PDBs, and the power and signal cables.

The power cables will be placed in wire basket cable trays.  The layout of the cable trays for part of a top far detector AB di-block is shown in Figure 14.29.  The layout of the side cable trays is similar.  The top lateral cable trays (and cooling manifolds) are set between the vertical modules in order to allow access to the electronics boxes and the FEBs.  Cable tray and cable lengths are given in Table 14.4.  A total of 12,036 6-conductor, 18 AWG, cables are needed to carry the power from the PDBs to the FEBs for the far detector.  A total of 495 cables carry the power from the Wiener and CAEN supplies to the PDBs.

Fig. 14.29:  Top view of the west side of a far detector AB di-block, showing the locations of the PDBs and the DCMs, as well as the cable trays, and power cables. 

    The layout for the power distribution system for the near detector is shown in Fig. 14.30.  The FEBs are on the top and on one side of the detector.  Each side PDB feeds power to 45 (48) horizontal modules for type A (B) blocks and each top PDB feeds 64 (62) vertical modules for type A (B) blocks.  An additional PDB feeds the 13 planes of the muon ranger at the rear of the spectrometer.  A total of 10 PDBs, 4 Wiener supplies, and one CAEN mainframe with one A1520P card are needed for the entire near detector.  Unlike the far detector, where each HV channel serves two PDBs, each PDB crate in the near detector has its own HV channel.
The PDBs will be fabricated and tested at the University of Virginia.  A prototype PDB has been built and is in the process of being tested.  Cables will be cut, terminated, and tested at Virginia.  The CAEN and Wiener power supplies will be tested at the University of Virginia
before being shipped out to the experiment.  The University of Virginia has sufficient space to store the entire system, whose components will be shipped out to the far and near detectors as needed.

Front End Boards
Power Distribution Boxes
CAEN A1520P boards
CAEN SY1527LC mainframes
Wiener PL508 crates
Relay racks
Total power
215 kW
9 kW
3.3V, 2-conductor, 2 AWG cable: Wieners to PDBs
1,842 m
66 m
24V, 2-condcutor, 10 AWG cable: Wieners to PDBs
1,822 m
66 m
450V, RG58 cable:  CAEN patch panel to PDBs
2,975 m
66 m
2-conductor, 22 AWG sense cable: PDBs to Wieners
3,665 m
133 m
6-conductor, 18 AWG cable: PDBs to FEBs
37,407 m
1,563 m
2”x2” cable tray
155 m
4”x2” cable tray
1,657 m
43 m
8”x4” cable tray
70 m
24 m
Table 14.4  Power distribution system components

Fig. 14.30:  Layout of the power distribution system for the entire NOvA near detector
.11      Changes in the Photodetector and Electronics Design Since the CDR

Since writing the Conceptual Design Report (CDR) we have received 20 prototypes of APDs mounted on carrier boards. While this development took longer than expected to converge, test results show that the devices have performed well.
Recent development in modeling the near detector showed that there would be substantial overlapping of events in space and time since the beam spill is one single turn of the Main Injector.  In order to resolve these overlaps faster sampling, and possibly different algorithms for timing extraction are needed in the near detector.  The simple fix for this was to increase the number of outputs from the ASIC to reduce the multiplexing.  This does not change the input stage, or the available settling time of individual outputs, so the noise performance should not change. 
The water cooling scheme for removing heat from the TEC modules has evolved from a large chiller distributing process water to the entire detector to individual chillers, 1 per pair of 31 plane block.  This eliminates the need to open the water system once operation has begun, and limits the impact of any failures.

     abo bahaa eddine.


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