Among other things, the BQM read backs are archived
by the EPICS Archiver software. Simply ask the Ops
crew for the rates, for a specific time range, and
they can get you a graph in a few minutes. This
software can be made available for use on the BLAST
computer network if that would be useful.
Shannon
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
-- Shannon Krause Accelerator Operations Group Leader MIT Bates Linear Accelerator Center 21 Manning Rd. - P.O. Box 846 Middleton, MA 01949, USA617-253-9206 krause@mit.edu
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