Hi,
I have only a couple of comments. I think that the wire chamber tripping
can be divided into two cases.
1.) The the tripping is intermittant and is fixed for the most part by
reseting the voltages.
2.) The box never is able to hold voltage.
If it is determined to be solely a wire chamber problem and not a beam
tune, then I think for condition 1. it makes sense to reset the voltages.
I can add in an auto reset feature that does this and can be switched on
an off at will. If it is condition 2. then it makes sense to disable the
voltage on that box because with the daq inhibit working, you will never
be taking any data anyway.
Doug, do you think an auto reset would be useful? I can see pros and cons
to automating this.
Also I am writing and EPICS Alarm handler similiar to the one CCR uses
that will beep when there is an alarm (for example, a crate trips) along
with other features. Although it is in its infancy, it has the WC gas
system and the crate trip status. I will test it tonight and, Allah
willing, leave it running so that users will not have to keep checking on
the trip status while I expand it to include other components.
Cheers,
Adam
On Thu, 29 May 2003, Douglas Hasell wrote:
> Hi,
>
> Just a comment about the wire chamber tripping last night.
>
> During the first part of the shift there was an attempt to run
> without the BLAST magnetic field which was unsuccessful. The rates in the
> BQM were not reported but this would be useful to know. In any case I
> suspect the wire chambers charged up during this phase.
>
> Then, when the toroid was turned on some boxes continued to trip.
> Again, knowing what BQM rates were would be useful. I think the correct
> thing to do in this case is to turn the WC HV off and have no beam for
> about one hour and then try again. The shift turned off four boxes which
> were tripping regularly and then continued to run.
>
> Turning off the boxes and continuing data taking should be avoided
> if at all possible. Each box usually connects to 5 cells. The inner
> chamber has 18 or 19 cells so 5 corresponds to over 25% of the angular
> range covered by the inner chambers. The middle and outer chamber have
> 26-27 and 34-35 cells so are a bit less important. With these cells
> missing there is effectively no tracking through that region (there are
> some fixes which can track with missing super-layers but it is a reduction
> in efficiency if nothing else). So not only do we lose the data from these
> tracking regions but if we wish to use these runs in any physics analysis
> we have to run the Monte Carlo with these boxes turned off for the same
> luminosity and spin states in order to compare the data.
>
> The inconvenience of resetting the HV during a run has to be
> weighed against shutting things down for an hour or the hassle of running
> the MC with these same boxes off in order to use the data.
>
> Of course ultimately boxes tripping is a wire chamber problem which
> has to be solved. But for the past few weeks we have run the wire chambers
> with relatively few trips and without needing to turn off boxes so I think
> the BQM rates were probably high and/or the chambers had become charged
> during the period with no toroid.
>
> 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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