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User name mitchell
Log entry time 04:09:49 on February 3,2000
Entry number 32183
keyword=Compton - summary
Got called in about 8:30 PM or so. Lots of problems. Could not go CW because it was not possible to check the trip levels on the Dump Ion chambers. The steering coils which are normally used in this checkout were not functioning ( plastic straps that hold the air core magnets in place on the beamline had broken, Omar was notified but it must have fallen through the cracks). Attemps to use steering coils further upstream failed because ep-chambers trip before dump. Kees was called and he authorized temporary masking of the ep chambers. Even so it was not possible to trip the dump chambers ( In a humorous side note the dump chambers tripped as soon as fast feedback was eneabled !). Next, found that the BCM's used by the beam loss accounting system were out of calibration, again preventing high current CW delivery. This delayed things till approximately midnight. There were also problems with fast feedback (presumably due to software problem in the slow locks server). Finally , steered through the compton chicane. Backgrounds started off a factor of 10 or so above last year. Quad tuning upstream of compton reduced it to a factor of 4 or so above last year. Finally, removing tails from spot at injector got background to about a factor of two above last year. We were unable to improve further. Filled the cavity and observed back-scattered gamma's (sig to noise ~ 8 to 1) at 40 micro Amps. Noise ~ 9 kHz at 40 micro Amps. Optimum beam height for crossing has changed since Happex ( cavity was removed to change mirrors !). Finally, the Compton is absolutely incompatible with OTR. When the OTR is in the PMT's on the photon calorimeter saturate. Completed about 3:15 AM. Compton used about 3 hrs of time. The rest was occupied by the problems described earlier that prevented CW delivery.