By any chance, was the south hall floor light on while taking data?
We find that illuminated light increases the background, too.
Another reason to put shield on.
-T
Douglas Hasell wrote:
>
> 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
-- Frederick Tong-Uk Lee Senior Research Associate Laboratory of Nuclear Science at MIT tong@lns.mit.edu 26-402 tel: (617) 258-5437 77 Massachusetts fax: (617) 258-5440 Cambridge, MA 02139
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