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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