Re: [BLAST_SHIFTS] zero field test

From: Michael Kohl (kohlm@MIT.EDU)
Date: Mon Feb 28 2005 - 14:18:30 EST


Against previous claim, the prescale factor for singles trigger type 7 was
really unchanged, i.e. 3. Sorry to say so, but setting the correct link to
the readout list object and runnning the coda configure confused me in this
point.

In the operations meeting this morning, it also was stated that a more
selective trigger may change the picture.

The other severe problem, however, was that the wire chambers would not
hold the voltage, even at a lowered beam current of 75mA. The only
workaround would then be to either turn them off (i.e. lose tracking
completely and rely on the angle resolution provided by 16 TOF channels),
or alternatively to find a way to turn only the innermost layer off in
order to at least enhance the redundancy in event selection.
The second-level trigger was effectively ineffective as for each event,
every wire chamber layer saw a hit.

It was criticized that in view of the many issues that need to be resolved
the plan to use the ion polarimeter is evolving into an R&D project. Given
the limited remaining time, it was thus questioned wether it is possible
to achieve the goals.

The question wether the polarization can be maintained at low holding
field amplitude had to be postponed until the observed low polarization at
regular holding field amplitude is understood.

Regards,

    Michael

On Mon, 28 Feb 2005, Chi Zhang wrote:

>
> Hi
>
> the 0-field runs last night as far as I can tell are miserable failures.
> live time is low. runs 13846-13849 accumulated gated charge of only 7
> Coulumbs despite the 70mA current in the ring. out of 7 coulumbs, I am
> expecting 3-4 ed elastive events.
>
> trigger 7, despite being prescaled by 1000, dominates. trigger 7
> dominate even among events where both sector contain tracks. so the
> background is really really really bad. 10% of the tracked
> events have LADS/NC hits even though the HV on them were turned off.
>
> So it is not clear still whether we can do any physics runs without Blast
> Field, may it ep elastic or ed elastic or anything. background is a
> major problem even though CCR spent quite a while tuning the beam.
>
> If we ever want to do this excercise again, I think we should do it with
> better preparation. a new trigger file must be written to take out
> anything but trigger type 1. type 1 trigger should be modified to take
> only events arround the elastic kinematics. One must make sure that all
> irrelevant HV are turned off.
>
> Chi
>
> On Sun, 27 Feb 2005, Michael Kohl wrote:
>
> > We are going to take data with zero BLAST field with ABS D2 (32deg).
> > After end of run 13842, Larry Longcoy starts to tune the beam with BLAST
> > off, at first with BQMs only. When BQMs are low, the Wch are turned on and
> > the tune is refined with help of the Wch scalers. We will start at
> > currents 50-100mA and see gradually how high we can get with regard to
> > Wch tripping, Wch S/N and overall rates.
> >
> > Plan is to take zero-field data with ABS-D2 until Monday morning.
> >
> > Regards,
> >
> > Michael
> >
> >
> >
> >
> > --
> >
> > +-------------------------------------+--------------------------+
> > | 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. | |
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> > | Fax: +1-617-253-9599 | Mobile: +1-978-580-4190 |
> > | http://blast.lns.mit.edu | |
> > +-------------------------------------+--------------------------+
> >
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> >
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> >
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> >
> >
> >
>

-- 

+-------------------------------------+--------------------------+ | 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 | | +-------------------------------------+--------------------------+



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