Re: [BLAST_SHIFTS] Shift summary 03/27/2004 C (8-12)

From: Mr. Shannon Krause (skrause@rocko.mit.edu)
Date: Mon Mar 29 2004 - 17:07:17 EST


The drop in beam lifetime was due to a failure of the S. Hall cooling
tower fan belt
(1 of 3 fans).

There was no spare belt, so the water temperature in the BLAST coils is
not as well
regulated. Initially the temperature dropped about 2 degrees C, and is
now about
2 degrees C warmer than when we tuned the ring. We also get periods of
instability
where the water temperature fluctuates by about 5 C peak to peak. This
in turn steers
the beam vertically by approximately +/- 0.5 mm (which is significant)
at all points around
the ring and we have not had the opportunity to retune over the weekend.

Fortunately, the holding fields gauss probes do not see these
temperature fluctuations
which indicates (as expected) that the BLAST steering comes from
downstream where
the coils are closest to the beam line.

The broken fan belt will be replaced on Tuesday and we should be able to
improve
the lifetime when we turn on after the snake fill, hopefully with some
additional steering
correctors as well.

Shannon

Electronic Log Book wrote:

>Operators: franklin ---- ----
>
>Data taking on polarized deuterium continued throughout this shift. There are a few concerns. From run sheets, the beam lifetime dropped yesterday afternoon from 18 to 15 minutes. It's not clear why (BLAST PS rampdown?) and it has not recovered. There have been a few intermittent bad fills where BQM's are very high and lifetime is short. Wire chamber signal-noise is also rather poor as noted previously in elog. A brief investigation of slit positions did not improve things. However, Vitaly has been analyzing the data remotely and says that the target retains good polarization and that the data are coming in at a good clip. Deadtime is as Tancredi documented last night. So we are pressing on.
>
>VZ advocates running full target until tomorrow night since data continue to look good. This seems like reasonable to me since the decision to run a full day of empty target was somewhat arbitrary.
>
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-- 
Shannon Krause
Accelerator Operations Group Leader
MIT Bates Linear Accelerator Center
21 Manning Rd. - P.O. Box 846
Middleton, MA 01949, USA

617-253-9206 krause@mit.edu



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