Star-tpc-l mailing list

["Van Buren, Gene" <gene AT bnl.gov>]

Hi, TPC-ers

I propose some calibration runs for the upcoming Run 23, in order to ensure 
that we're not seeing any difference in distortions (or anything else anyone 
wants to look at?) between running the gating grid at ~2 kHz vs. 4 or 5 kHz 
(e.g. we aren't expecting ion backflow through the gating grid). We've raised 
the gating grid rate before, but I think it's well worth doing a test under 
the conditions we'll have for Run 23.

The proposed test set would consist of runs of only 50k minimum bias events 
each, enough to measure distortions, which really only takes a few seconds to 
acquire.

For a given beam condition, I would take either 3 or 5 runs in immediate 
succession, all with the same mibias trigger modulo the GG rate limitation:
0 ) 5 kHz GG, if it's available
1) 4 kHz GG
2) 2 kHz GG
3) 4 kHz GG
4) 5 kHz GG, if it's available

My understanding from what Tonko has told us is that we may not have 5 kHz 
readout available at the very start of Run 23, so I'd like to at least do the 
4-2-4 as early as possible though and get that measured quickly.

Further, I want to see these at different luminosities, and I expect the 
luminosity may not be maximum at the beginning of Run 23 either. So here's a 
more concrete proposal:

- Calibration Set A, taken in the first week with Run 23 beam:
  i) a 4-2-4 set at whatever the maximum available luminosity is (perhaps 
40-50 kHz ZDC rate?)
  ii) a 4-2-4 set at about 75% of the maximum available luminosity
  iii) a 4-2-4 set at about 50% of the maximum available luminosity

- Calibration Set B, taken a few weeks into Run 23:
  i) a 5-4-2-4-5 set at whatever the maximum available luminosity is (perhaps 
40-50 kHz ZDC rate?)
  ii) a 5-4-2-4-5 set at about 75% of the maximum available luminosity
  iii) a 5-4-2-4-5 set at about 50% of the maximum available luminosity

....and then at some point the luminosities will be raised to allow for rare 
(e.g. high pT) triggers, which should then allow a repeat with even higher 
luminosities

- Calibration Set C, taken a couple months into Run 23:
  i) a 5-4-2-4-5 set at whatever the maximum available luminosity is (perhaps 
100 kHz ZDC rate?)
  ii) a 5-4-2-4-5 set at about 75% of the maximum available luminosity
  iii) a 5-4-2-4-5 set at about 50% of the maximum available luminosity

I would attempt to rapidly get results on each of these calibration sets to 
inform our operations during Run 23.

Comments/feedback welcome,
-Gene