Log entry time 15:05:47 on September24,2009

Entry number 291435

We say the noise of the BCMs and Lumis go down dramatically in the middle of 
slug 11. I have investigated this throughly and here is what I have found.

The change happended at the very end (last couple of thousand events) of run 
12570 (9-22-09 10:28AM) and continued on run 12571 (9-22-09 11:25AM) and after.

The RMS was ~1100 and suddenly dropped to less than 900ppm. I investigated the 
HALOG and the ELOG to find what caused this. There was nothing helpful in the 
HALOG but there was an entry in the ELOG that might help explain this. 

Please refer to ELOG entry 1488553. It seems they disabled a 500keV sensor to 
improve beam stability. Attachment 2 is the log entry and plot they posted to 
show the improvement.