Wire chamber low voltage was indeed off. You can see this of shift either
by the high rates in the wire chambers regardless of beam. Basically the
electronics is off so the TDC's are firing on noise. You can also see this
in the electronics temperature which are just room temperature rather than
40-50.
--On Friday, May 23, 2003 9:56 AM -0400 Karen Dow <kdow@MIT.EDU> wrote:
>
> The problem with the event rate is due to a "feature" of the Trigger
> Supervisor that we discovered last summer. If the TS is in Common
> Strobe mode (which it is, for physrun), AND a trigger input is enabled
> (we enable the first 4), AND an enabled trigger input is disconnected --
> THE CS WILL FIRE THE EVENT TRIGGER. Evidently one of the chips inside
> the TS does not operate as advertised; with no input connected, floats
> true.
>
> This morning, I found that one of the 2-pin ribbon headers (PHYS0) was
> almost disconnected at the level adapter before the TS. So the CS (the
> OR of TOF meantimes) was triggering events; rate limited by a lot of
> junk in the wire chambers. That's why Runcontrol trigger rate was
> independent of selected trigger, or even beam (OR of all TOFs runs at
> 600+Hz on cosmics).
>
> You can see this on a scope, by looking at PHYS0 (or 1,2,3) and CS
> before the TS, and L1A from the TS. L1A should only be present if
> PHYS0 is. L1A<=PHYS0<=CS.
>
> Doug suspects the wire chamber junk is because the low-voltage supply
> for the thresholds is off; will check with hall access soon.
>
> Karen
> Michael Kohl wrote:
>>
>> Dear colleagues.
>>
>> this night's shift was a debugging shift, unfortunateley again with no
>> useful data.
>>
>> CCR provides improved beam with BQM TBLR=180,50,120,90, with slits at
>> LRTB=-8,8,2,-8. Max. injection 100mA, lifetime 15-20 min.
>>
>> /scratch/dblast07 appeared to be full, runs pro2003-01...99.dat removed
>> after checking that they are all identically present on spuds (see
>> md5sum-* on ~blast/ ).
>>
>> Again like last night, a lot of noise showed up in the wire chamber when
>> displaying events with nsed.
>>
>> Noticed that the Coda event rate was constantly about 170 Hz, independent
>> of ring current (!). Also, the coda event rate differed very much from
>> the PHYS* and BPHYS* rates shown in visual_scal. Further analysis showed
>> that 170 Hz event rate was also stable against change of trigger settings
>> (varied between elastic_only, elastic_coinc, elastic_een and physics, and
>> with a highly biased craptrigger.settings.
>>
>> At 3am, CCR optimized beam quality a little more, resulting in
>> BQM TBLR=140,40,100,70, with slits at LRTB=-6,8,1,-8. Max. injection
>> 100mA, lifetime 15-20 min.
>>
>> Still, nsed shows Xmas trees. Noticed that in most triggered events less
>> than two Tofs have fired (either one or none).
>> Doubting if a poor beam quality is really the reason for the noise
>> events. Requesting to switch off the beam, we find that still we have
>> 170 Hz event rate and Xmas trees (run #481). This is also the case after
>> switching off the Wch HV's (run #483).
>>
>> Assuming we have a problem with the Trigger Supervisor (TS), we
>> power-cycle the VME crate in rack 4 (didn't help)
>>
>> Noticing that there are Camac problems (cnaf 1 23 0 0 etc.), we reset
>> and power-cycle also the camac crates and the VME crate in rack 3.
>>
>> Still, Coda takes data without beam and Wch off at 170 Hz, nsed showing
>> Xmas trees. We have no further idea and wait for Karen and Doug to come
>> in.
>>
>> Hall not yet open, not until technicians are ready to work on ion
>> polarimeter.
>>
>>
>> Regards,
>>
>> Michael and Aaron
>>
>> --
>>
>> +-------------------------------------+--------------------------+
>> | Office: | Home: |
>> | -------------------------------------|--------------------------|
>> | Dr. Michael Kohl | Michael Kohl |
>> | Laboratory for Nuclear Science | 5 Ibbetson Street |
>> | MIT-Bates Linear Accelerator Center | Somerville, MA 02143 |
>> | Middleton, MA 01949 | U.S.A. |
>> | U.S.A. | |
>> | - - - - - - - - - - - - | - - - - - - - - -|
>> | Email: kohlm@mit.edu | K.Michael.Kohl@gmx.de |
>> | Work: +1-617-253-9207 | Home: +1-617-629-3147 |
>> | Fax: +1-617-253-9599 | Mobile: +1-978-580-4190 |
>> | http://blast.lns.mit.edu | |
>> +-------------------------------------+--------------------------+
>>
>>
Cheers,
Douglas
26-415 M.I.T. Tel: +1 617 258 7199
77 Massachusetts Avenue Fax: +1 617 258 5440
Cambridge, MA 02139, USA E-mail: hasell@mit.edu
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