Operator: franklin
The removal of the BLAST collimator was carried out yesterday morning. Beam
tuning commenced in the afternoon and the wider collimator
improved injection markedly. However, it took a while to establish
reasonable halo rates. At around 3:00 a ring steering solution was found
which permitted us to turn on the BLAST detectors. Background was clearly
higher than previous year, but wire chambers were staying on at 100 mA
and we were getting reasonable spectra.
However, wire chamber rates were not proportional to beam current and for 100 mA injection, substantial vacuum rise in the target region was observed in the initial stage of the storage cycle for the
present steering solution. For 50 mA fills this was not the case. In part, this was
due to fact that cell temperature had been set low enough (50 K) to highly sensitive to beam incident upon it. Beam has been given back to ops to work more on steering in the target region to optimize wire chamber
scalers and eliminate the vacuum rise. The cell temperature has also been raised
to 85 K since this is closer to the point we will run at.
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