Minutes of the Background remediation weekly meeting held Dec 11.
(In red, open questions from the presentations that will need to be rediscussed. In Brown,
action items from the meeting)
1/ Introduction (GW)
-reminder of goals, milestones, tools
-agenda for Dec 18 meeting
-agenda for Jan 8 meeting
-January 13-15 workshop
2/ Detector operation from the various subdetectors
2.1 Online (Mike Huffer)
-Weakest spot in the chain : Feature Extraction the ROM. Need input from subdetectors
-SEVERE manpower shortage to tackle the 'backpressure' problem : measure and monitor dead time
2.2 SVT (C. Hast)
-No operationnal issues in case of steady background, even high
-SEVERE operationnal issues in case of spikes : need to be turned off during injection (is the protection mechanism in place?), dataflow hang-ups. Present recovery is to start a new
run. Set up a small task
force to see how to improve on this. Try to measure the probability of a spike using the present commissioning data.
-background monitoring thru PIN diodes (beware: they are also subject to the same hang ups) and some epics readout (available only when BABAR DAQ is running).
2.3 Drift Chamber (D. Coupal)
-For an unfortunately realistic background prediction of 20xTDR in layer 1, UNCONFORTABLY close to the maximum current that can be delivered by the power supply (26 uA
expected vs 40 uA max). Check the situations in the other layers 1. . Prepare a plan for improving HV segmentation at least in layer 1
-background monitoring: current from the chamber (can be corrected for low voltage during injection). Possibly using trigger infor. But not available at lower voltages.
2.4 DIRC (B. Wilson/ G. Wormser)
-The maximum input rate per PMT is 2 MHz (10% inefficiency per channel in the analog chip at that rate, 5% gain loss in the tube, inefficiency probably similar in the digital chip under study.
(Note: the TDR rate was 3 kHz per tube! From present mSOB data, the
extrapolated rate at full current is 280 kHz. Using the same present data, the track rate as measured by the minitpc is close to 1 GHz and the dose in the SVT of 3 Mrad/month)
-Implementation of a trip mechanism if above a certain rate threshold.
-background monitor : counting rate in 1 tube per sector
2.5 Trigger (T. Liu)
No real operational issues: quantity of information to treat independant of background. Need to reassess the trigger rate with new MonteCarlo: Key quantity in the occupancy in the Drift chamber outer layers. Background monitor could be
provided by the power consumption in the trigger crate. Trigger jitter as function of background rate?
2.6 The EMC (A. McKemey) and IFR (H. Band) talks have been postponed to Dec 18 (no time left at the end). My apologies.