BLAST shifts are ON.
The ABS leak is fixed. I am now taking data on the ABS. The BQMs look
reasonable (about 140 on the top), lifetime is around 20 minutes, although
it is much lower (13 minutes) at the beginning of the fill. Dave is
filling to 160 mA.
By morning we should have a good idea of the target thickness and
polarization. Presumably the nitrogen from the leak was making the target
look thicker than expected, diluting the polarization, and blowing up the beam.
Here is some history from earlier today.
>>Ernie and Brian have indeed found a leak in the ABS above V14. Ernie says:
After doing a test over the phone with Larry L. last night, I
determined that we maybe had a sizable leak in the lower sexipole
chamber just above V14. We shut off cryos last night so that we could
work on it today.
Brian and I found a large air leak on the KF flange on V14 and a very
small one someplace else. Fixed both and ABS is discharge is on and
should be able to be run at about 3:30 to 4:00 today. Cryos started at
noon.
Ernie
>>They're fixing it, getting the cryos back on, and we should be able to
>>run the ABS by 3 pm. I'm trying to reach Genya, Vitaliy or Nik to find
>>out what has to be done to run the ABS. Hopefully we can run beam and
>>settle some of the target questions before tomorrow morning.
>>
>>Karen
>>
>>---------- Original Message ----------------------------------
>>From: "Karen Dow" <kdow@rocko.lns.mit.edu>
>>Reply-To: <kdow@rocko.lns.mit.edu>
>>Date: Sun, 13 Feb 2005 09:40:40 -0500
>>
>>
>>Last night Larry Longcoy and Fuhua Wang worked on the beam tune with the
>>empty target. When they opened the valve to the unpol system to see how
>>target gas affected the beam, they saw essentially NO effect.
>>They talked with Ernie Ihloff to check on how to tell there was actually
>>gas flowing from the unpol system. In the course of that diagnosis,
>>Ernie had them open V14. At that point, the BQMs increased dramatically,
>>and the lifetime decreased.
>>
>>Ernie suspects there is a leak in the ABS (lower sextupole chamber?).
>>He had Larry turn off the cryos last night, and is in the lab this
>>morning with a tech, looking for a leak. Perhaps the leak in the ABS is
>>feeding extra gas into the target, and that is why the thickness is so
>>high and the polarization is low. On Thursday morning while Genya was
>>tuning the ABS, Shannon tried running higher beam current than the 100 mA
>>we had limited ourselves to. He only filled a few times, but was
>>successful in filling to 140 mA or so with reasonable BQMs and
>>lifetime. Maybe the leak developed later in the day on Thursday.
>>
>>If Ernie can find a problem, we'll try running beam on the ABS target,
>>check the thickness and polarization.
>>
>>Karen
>>
>
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