Hi,
I remember that back in july I noticed that the analog adders have a
settable DC offset (needs a screwdriver). It may be that if this is too
much positive the C signal may not be digitized propoerly.
I'd not expect that either the flasher or a particle event have different
offsets (since they are both coming from the sabe tube) but I would
definitely have a look at it (also, is the NIM crate on ??)
-- tancredi
________________________________________________________________________________
Tancredi Botto, phone: +1-617-253-9204 mobile: +1-978-490-4124
research scientist MIT/Bates, 21 Manning Av Middleton MA, 01949
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On Wed, 25 Sep 2002, Peter Karpius wrote:
>
>
>
> The shift began with a CODA problem as I tried to take some flasher data
> before the beam was ready for the WCs. Scaler rate was 8 Hz with flasher
> but the coda rate was 3Hz. Double checked with cosmics trigger of 50Hz -
> still only 3 Hz on scalers. Called Karen and attempted to run TS in no
> strobed mode but this led to a different problem possibly dealing with the
> non-strobed crl file. Went back to strobed mode. Checked output of
> strobe (retimingOR) with scope - it was there before the cable delay but
> not after. Check that the cable delay connections were fine and upon
> touching the cable for this action the strobe came back and coda starting
> reading events! So the strobe cables may be a bit sensitive.
>
> Re-verified that the flasher signal does not make it through the linear
> adders for the Cerenkovs without being attenuated. In fact, for a box
> with all tubes on, the flasher signal on the scope is lower than for a
> single tube of that box.
>
> Started manually gain matching tubes within Left Cerenkov Box 0. Starting
> with voltages set nominally to -2000V a target signal of -3V on teh scope
> was set. With this in mind the voltages for LCer0 were set as follows:
> top0: -2100V
> top1: -2250V
> top3: -2200V
>
> bot0: -1850V
> bot1: -2100V
> bot2: -2200V
>
> To see this effect I decided to try and get adc data for the individual
> tubes. I plugged the first four tubes listed above into the splitter
> inputs for LCer0, LCer1, LCer2, LCer3 boxes respectively. Since Doug's
> trigger rate was low (10Hz) I could not use a flasher trigger as this
> would swamp Doug with unwanted flasher data.
>
> It was noted that the scaler readout for these four tubes was not
> promising as they varied by a factor of four or so. The first run taken
> was 1852. Unfortunately for this run the adc means ranged from 200 to 387
> which is clearly pedestal.
>
> Don't know why this is.
> Got a chance to take purely flasher data for a bit as the WC folks were
> waiting for Cheever to make some adjustments. Still saw what looked like
> only pedestal for these single Cerenkov tubes. I have yet to look at the
> adc spectra for this entire box with the above voltage settings.
>
>
> Pete
>
>
> -------------------------------
> Pete Karpius
> Graduate Research Assistant
> Nuclear Physics Group
> University of New Hampshire
> phone: (603)862-1220
> FAX: (603)862-2998
> email: karpiusp@einstein.unh.edu
> http://pubpages.unh.edu/~pkarpius/homepage.htm
>
>
>
>
>
>
>
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