Just some comments on the runs from last night with magnet on, gas in the
target, and the wire chambers on.
First, even with a supposed ep elastic trigger the event rates were
incredibly high, hundreds of Hz. Even with no gas in the target. So I
expect the beam is hitting the target cell or else someone left a Coke can
in the beampipe. I think the slits should be run in very tight and the
beam tuned to minimize such background rates.
Looking at the runs with the event display shows lots of noise in the wire
chambers with only occasional tracks on top of the noise. Since the magnet
was on it can't be Moeller electrons but can be X-rays. So perhaps
something is needed to cover the wire chamber entrance windows again.
Looking at the wire chamber TDC distributions signal/background is almost
zero! One can see the TDC shape but barely above the background.
Background or noise levels appear worse in the right sector if that helps
anyone.
To study this properly we need a shift for wire chamber studies with the
toroid on and control of the beam.
--On Thursday, November 7, 2002 12:18 AM -0500 Bill Franklin
<wafrankl@MIT.EDU> wrote:
> On shift: Vitaly Ziskin, Bill Franklin
>
> Tancredi summarized up until about 21:30. Beam tune with BLAST field on
> and slits positions established was finished shortly thereafter. Ops had
> 125 mA stored in Ring with 27 minute lifetime, although ops had some
> concerns about closed orbit. Fuhua or Jan may have to look at this
> tomorrow.
>
> We took a few runs (logged on run sheet, starting with 2626) with no gas
> flow and last8 trigger. Event rate was fairly high. Wire chambers were
> on and Doug looked at some data from home. He saw reasonable looking
> tracks, but also a fair amount of background. We also took some short
> runs with 0.2 sccm.
>
> Gas flow was then raised to 1 sccm as specified by run plan. This created
> some problems for injection and only 90 mA was available. Lifetime was
> 13 minutes. Voltages and thresholds were loaded to start a Cerenkov
> efficiency study which will continue for the full night shift.
>
> --
> **********************************************************************
> Wilbur A. Franklin * Phone: 617-253-9518
> Bates Linear Accelerator Center * FAX: 617-253-9599
> P.O. Box 846 * Email: wafrankl@mit.edu
> Middleton, MA 01949 *
> **********************************************************************
>
>
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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