also, you may notice noise problems with the Wch by the looking at the
size of coda events (do CTRL+W on the coda window to access the statistics).
Typically, expect an event size of ca 1-2 kB when things are good.
The event size will grow very quickly if we are digitizing wch noise
(typically 8 or more kB) since the Wch have multi-hit tdcs.
On Fri, 23 May 2003, Douglas Hasell wrote:
> 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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