SCT Barrel System Test - Shield

(February-April 2002)

The system test bases its grounding and shielding scheme on the proposal outlined in the ATLAS SCT/Pixel Grounding and Shielding Note, ATL-IC-EN-0004. A schematic sketch of all shielding connections can be found in a picture below.

Default Shield

The following configuration is used as "standard" shielding set-up, trying to follow Ned Spencer's proposal:

Shield of conventional cables DC-connected to DGND at LV.
Chokes used at PP2; shield-line re-routed through coils.
Above shield DC-connected through to "screen" on PP2 (PIN 18 on SUB-D connector, see schematics).
All LMT's (thick and thin) wrapped in Al foil in bundles of six (ie grouped per harness).
Each "screen"-track on PP2 (PIN 18 on SUB-D connector) is DC-connected to LMT wrapping.
Both thin and thick LMT wrapping DC-connected to shield on PP1; this also provides connection between shields of thin and thick LMT's.
100um, 300x900mm² copper sheet connected to PP1 at one end and to the main support structure at the other end to simulate radial heat spreader plates. All shield parts connected to that sheet at PP1.
All default jumpers at PP1 are in (see circuit diagram for details).
Thin-LMT shields connected to their respective metal end-plate holding the sector.
"Dummy" thermal shield covering the sector at a distance of ~45mm is DC-connected to each end-plate (photo1, photo2).
Carbon-fibre sector connected to either end-plate.
Cooling pipes electrically split in the middle (ie between left and right harnesses).
Cooling pipes halves DC-connected to the respective end plate.
Shunt shields between modules and cooling pipes; connected to AGND.

Modifications

The following lists options or test-modifications to above "default" configuration; items 1-3 together make an alternative shielding scheme as suggested in ATL-IC-ER-0019:

DC-connect both halves of the cooling pipes.
DC-connect shunt shields to cooling pipe (effectively making a connection between module AGND and cooling pipe).
AC-connect shield of conventional cables to VME-crate metal at LV.
not used
Remove chokes at PP2.
Remove default jumpers at PP1 (ie no AC-connection of power lines to shield).
Auxiliary VME crate taken out of the rack; powering this through mains line P1 (near irrad, freezer). HV for all modules and LV for half of the modules going through the aux. crate. Main crate, providing LV for other modules, still powered through mains line P2.
Auxiliary VME crate taken out of the rack and put into opposit corner of the room. HV and LV for half of the modules going through the aux. crate. Main crate providing LV for other modules, HV provided through old HV crate.
Disconnect shield of conventional cables from PP2-"screen" track.
Disconnect dummy radial heat spreader plates from main metal, leave connected at PP1.
Shield of conventional power cables floating at LV's.
Replace Dgnd-shield AC connection by a DC connection at PP1.

Sketch of shielding connections

click on figure to get jpg-source

Sketch of the different paets of the shield plus the connections made between them (shown in green). The purple numbers indicate the AC-resistance of these connections measured at several 10kHz.

Page maintained by Jörn Grosse-Knetter

Last modified: 11 April 2002