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Marcello Piccolo Napoli Dec., 1997 1 The Babar IFR High Voltage System Naples, 12/15/1997 Electronic review.

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Presentation on theme: "Marcello Piccolo Napoli Dec., 1997 1 The Babar IFR High Voltage System Naples, 12/15/1997 Electronic review."— Presentation transcript:

1 Marcello Piccolo Napoli Dec., The Babar IFR High Voltage System Naples, 12/15/1997 Electronic review

2 Marcello Piccolo Napoli Dec., Requirements oRpc’s require about 8 KV to operate (with the babar gas mixture) oNo dramatic differences in knee voltages have been experienced in testing the 800 modules needed for the IFR.    Design a system based on relatively small number of supplies and a complete monitoring system.

3 Marcello Piccolo Napoli Dec., Knee Voltage Distribution (Barrel Rpc’s) Knee voltage distribution barrel chambers

4 Marcello Piccolo Napoli Dec., Features oThe resistivity of the RPC electrodes allow the compete decoupling of the H.V. From the pulse read-out. oGround loops can be minimized and, provided that power supplies for the front end are on the detector, no connection at the ground level exists between the detector and the LEACH. oMonitoring individual current on the ground leg. oEasy decoupling of different modules

5 Marcello Piccolo Napoli Dec., Power Supply Selection  At 8 KV operating voltage the RPC dark current has been measured 5  a/m 2 at 18 o C.  The total current for the IFR would be  10 ma. oSy-127 from CAEN has been selected as H.V power supplies. oThis device consists of a mainframe which does H.V and current setting, ramping, computer interfacing for up to 10 H.V. Pods. oPods are specifically designed for different types of detector: The RPC model is the A330P/N. o One pod has two independent outputs that can deliver oThe nominal design capability of the system has been set at 36 ma,…. But everything can be easily upgraded to 80 ma.

6 Marcello Piccolo Napoli Dec., Design Philosophy oGiven the relatively small variance of the knee voltage one is led to design a system with a relatively small number of independent power supplies, and split a single (pod) output into many H.V. Feed for the RPC’s. oIn doing so one has to abide few rules: èA single RPC connection must not bring down the pod output even if is shorted out. èSome provision should be made to remotely disconnect sick//broken modules. èAn early warning system should be part of the H.V. Distribution so that potential malfunctions could be spotted and cured as soon as they develop.

7 Marcello Piccolo Napoli Dec., The Schematic Connection to the RPC’ Modules At the detector level there is a second connection between the H.V. ground and the detector ground (the black wire that carries a 10K  resistor in series

8 Marcello Piccolo Napoli Dec., Design of the H.V. box oIn order to comply with the design rules mentioned above one has to implement: èCurrent limiting on every output channel èFuse type of device (remote disconnect) in case of serious fault èExtensive monitoring of each individual counter  Bounds on the series resistor and fuse Single current monitoring to be implemented

9 Marcello Piccolo Napoli Dec., Design of the H.V. box (cont.)  A safe design ( which will handle  10 KV ) must rely on the principle: small distances  small voltage differences H.V. and ground from the power supplies separated in the box and kept at 10 cm. distance : distribution boards do not have more that few hundred V. differences between components. Use H.V. wires and connector at the joining of the wires: H.V. feed to the RPC have to use single wires as the two connection are separated in space (on opposite corners of the detectors). Dimension the H.V. series resistor so that the extra current load due to a short afterward does not knock down the relative pod output. Typical current output 400  A, so choose 20 M   400  8 KV)

10 Marcello Piccolo Napoli Dec., The H.V. box

11 Marcello Piccolo Napoli Dec., Hardware components oA330/P (the H.V. pods) use KINGS type connectors (Reynolds parts # ) H.V. coaxial cable ( Reynolds type C parts # ) does the long haul from the LEACH to the detector in the standard wire- ways. A total of 80 cables will be pulled (within January) oH.V. boxes on the detector will be housed in Al containers which are mechanically interlocked with the H.V. coax feed. oOutput of the H.V. box utilize bipolar connectors from Alden (parts # G400/G401 ) 10 KV. oConnection to the detector done with H.V. wire from Alden (parts # ) oDetector connection with adhesive copper tape glued onto Bakelite with conductive epoxy.

12 Marcello Piccolo Napoli Dec., Hardware components (H.V. boxes) oTwo single layer boards:  H.V. board contains a 20 M  alumina resistor 5 W with a 2.2 M ,.125 W resistor in series, which acts as a fuse at   Ground boards  contains the LEACH-Detector decoupling resistors, the current monitor resistors and the L-shaped connector to output the current monitoring signal.  .V. boards housed in metal container (6 of them). Half a barrel sextant or 1/3 of each half end-caps is serviced by one container. oThree H.V. cables feed one container. èNom. voltage and 2 extra voltages. oH.V. wires exit the container through small vertical slits, to prevent accidental disconnection and exposure of the H.V. pins. oContainers lined with Palusol ( fire barrier material) o One 85 o C interlocks the CAEN supplies oOne + 1/5 60 cond. Flat cable suitably split inside the container carry away monitor signals.

13 Marcello Piccolo Napoli Dec., Cabling plant The total number of long haul cables needed is 72 as the total number of Al container is 24. We plan to install 80 H.V. cables from LEACH to Detector. This number matches the total number of pods (40) that we could install. We plan to have four mainframes in LEACH: one for the barrel, one for each end-caps and a spare to feed sick/odd modules. The Cylindrical RPC could be powered by extra pods located in one of the four mainframe or have a dedicated mainframe. Long haul cables will be available within January. The (already installed) RPC’s connections will need few splicing (about 20) as the H.V. boxes have been grouped in metal containers. Assuming that all the RPC’s could be powered at the nominal voltage with one single cable per container, the current capability would be 36 mA.

14 Marcello Piccolo Napoli Dec., Installation and scheduling oPower supplies and pods: èpurchased 75%; at SLAC 50% èbalance within first quarter 1998 oH.V. boxes: è95% built; 30% at SLAC è5% special boxes for cyl. RPC to be built. oH.V. containers: èDesigned in Genoa (design approved) è24 to build: 12 in production at Frascati, 12 in Genoa and/or outside company. èReady to install by February oCables èCoax barrel : cut and ready èCoax end-caps: length not defined yet; material on hand at SLAC stores. èInstallation during January oMonitoring hardware èCables and connectors purchased èInstallation January / February

15 Marcello Piccolo Napoli Dec., Conclusions oThe components of the H.V. system of the IFR have been thoroughly tested in the quality control runs done during the RPC’s production year. oThe system seems to be quite simple and reasonably robust oThe bulk of the custom made hardware turned out to perform satisfactorily. oInstallation of the various barrel components should be completed by the end of February. oEnd-caps stuff is a bit more uncertain, as especially in the back, mechanical placement is not that easy. We expect, however, that the entire H.V. system for the IFR to be operational by the end of March.


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