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Minutes of the March 19 Background Remediation video meeting

0/ Training week

Tom Mattison has kindly accepted to replace J. Seeman and Witold to take

care of the introduction sessions on Monday 29

1/ EPICS readiness

1.1 Overview (Adrian McKemey)

-EMC pursuing PIn diodes implementation. 1.5 cm Csi will be

put in front of the diode to bring it to the required sensitivity.(x15)

-DCH the question was raised whether an integrated of C int he wires will

be kept. To do this correctly, injection dose must be included, ie teh

integration time of the current measurement should be ~1 sec.

Aaron will look at the CAEN hardware features.

-For monitoring BABAR quantities, it is important to be able to accumulate histograms or look at event displays for specific triggers, and especially random triggers.

Check with DHP and event display people if this is foreseen. (Guy)

1.2 SVT/Pin diodes readiness (D. Kirby)

The SVT/PIN diodes EPICs software is well advanced, benefiting from the expereince with PEP-II commissioning.

The other subdetectors talks were postponed, due to lack of time.

2/BABAR-PEP-II communications

Ron Chestnut gave an overview of the various communications channels between BABAR and PEP-II. The most reliable is the BIC<->BIP path, used for the BABAR-PEP-II various handshakes. A complete list of the BABAR EPICS channels to be sent this way (<=100) will be collected by Terry Geld and transmitted to Ron before March 31.

Other points mentioned in the discussion :

-BABAR channels sent the Channel server will need to be updated.

-For a good management of our radiation budget, it will necessary to split up the received dose in the 4 categories : Physics running, Tuning, Injection, Machine development. Some of these flags do not exist yet on BABAR side and/or on PEP-II side. For instance in the Tuning state (the period after injection where PEP-II and BABAR are preparing for physics) , BABAR will often be in a mode , not foreseen at the beginning, where data are taken , not necessary logged, with the detector usually not in the final running configuration. On the machine side, this Tuning state can be inferred from Coasting_beams and No_physics.

-Witold pointed out the importance for the fast machine scans to get response delays less than 1 second or so for these EPICS measurements. For the channels passing thru BIC-BIP path, it should not be a problem.

3/ Global page summary

GW showed a sketch of a page summary regrouping most of the BABAR and PEP-II informations relevant for backgrounds on a single page. The page contains in addition to te well known e+ and e- currents and lifetimes,

  1. the luminosity and lumi lifetime strip chart. This work is in progress
  2. The main BABAR signals strip charts : the BABAR Beam Abort signals and the BABAR background Figure of Merit (all these signals normalized ). This work is also in progress
  3. Thermometer displays of the various BABAR signals. It was suggested to indicate clearly what are the permanent signals and those that depend upon BABAR being running in normal mode.
  4. The integrated diplay (lumi, amp-hours, dose,..)
  5. Some numerical information

It was stressed that in order to converge quickly towards the optimum global display and to find what could make the best BABAR figure-of-merit, the essential tool was a easy and versatile way to make strip charts and ther mometers of user selected variables.

Check with Michael Stanek, Jim Olsen et al. availability of such tools (Guy)

4/First results from PRV0

It was realized during the presentations that in PRV0, the LER background is heavily suppressed due to the high level collimation in IR4 which is used. Since the real effect of such a collimation has not been measured yet, caution must be taken in making a correspondence between the level of background in PRV0 and the machine currents at which it will correspond. Also, the precise characteristics of the backgrounds such as azimuthal distributions will depend of the actual LER/HER ratio which might turn out to be different from what is in PRV0. However, it is still quite worthwile to investigate whethe meaniungful results can be extracted from PRV0.

Recheck the validity of the IR4collimator suppression (Witold)

4.1 SVT (Natalia Kuznestova)

The max occupancy in layer 1 is 3 % in phi strips and 6% in z strips. The track finding occupancy remains high, around 93%. One concern is the CPU time to reconstruct 1 event, 3 seconds for the SVT alone.

4.2 DCH (Tom Schietinger and Aaron Roodman)

10-15%occupancy in first layers, dominated by HER. Strange peak at time =0 reported. When data are stored into the database, the background flat time distribution appears to be truncated : loss of thits somewhere ? Quantitative results from tracking in progress

4.3 DIRC (M. Zito)

Long time to mix the background frames and e+e- ->gamma-gamma : 40 seconds per event

Mean occupancy in DIRC 8 % with 1 microsecond window : not a problem

Ratio Quartz/water 3/1