Operator: hasell
At start of shift CCR was able to inject 100 mA which we felt was enough to start taking data. No need to try for 150 mA now. Tune was not as good as before shutdown. BQM's and WC scalers about twice previous values (top BQM around 200).
Also the valve to the target on the unpolarised system was not open so this tune was done with no gas in the target. Opened valve, buffer pressure 2 torr, ligit rose from 8x10**-8 to 1x10^-7. Gave CCR some more time to tune the beam and optimise the slits with gas in the target. They found new settings for the beam with gas in the target but BQMs and WC scalers still factor of 2 higher than before shutdown.
Around 02:00 tried to operate the detector. WC would not hold voltage. Typically 3 boxes in the left sector and 3 in the right would repeatedly trip. Not worth trying to take data. Even after dumping the beam WCs would not hold operating voltage.
Accessed the south hall floor and added water to the WC gas supply. Not sure if this was the problem but it did need water. This will take several hours to show an effect. Tried running again but WCs still tripping.
Dumped beam and turned off WCs for 1 hour. After this turned on WCs and they would hold volatage with no beam. However, as soon as beam re-injected several boxes in both sector would start to trip.
Unable to take data in this manner. Turned off all detectors except BQMs and let CCR have control to see if the tune can be improved.
At 07:00 CCR called. BQM rates were improved (150 top). WCs were better but still tripped frequently. Now only 1 box in each sector would be off at a time and at the bottom half of a fill the chambers would stay on for a minute or two. Still too unreliable to try taking data though.
CCR shift changed at 08:00 so they are going to try improving things further.
If the probloem with the WCs is the lack of water that will improve gradually and should be ready by this afternoon.
If the problem is with the beam tune then that's up to CCR.
If the beam tune problem is related to the new collimator then we may have to think about removing it. Before removing it though we should take some data even if we have to turn some WC boxes off to see whether or not the rate due to positrons is the same or less or worse with the new collimator. Then we can decide to remove the collimator completely or simply enlargen it.
Bill is coming on at 09:00 and will work on tuning things with Compton as well.
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