03 December 2007

RHIC Startup:

AGS Klixon tripped off the MMPS.  Probably a controls issue. 

Stochastic cooling in Yellow doesn't seem to have any effect on beam lifetime.  It appears to be reducing the bunch length, but not improving things.  It is as if closing the aperture by putting in the jaws is reducing the momentum spread, but the cooling is not taking place.  It also appears as if Blue bunch length is growing with and without cooling on in Yellow, but Yellow is not growing even when cooling is off.  Quite a puzzle.  It is possible that BBQ is not off, and so could be injecting noise into the system, heating up the beams.  This is not a tune space issue.  It is a real transverse emittance growth colliding with betatron aperture.  We need to get the IPM working.  The problem is not small aperture, but rather large beam emittance. 

Yun and Vincent applied chromaticity corrections yesterday, but it made beam losses worse.  They were hampered by ramping speed.  The chromaticity corrections reduced the chromaticity beautifully, by a factor of two or more.  But this did not improve beam lifetime.  So the chromaticity corrections are working well, but that is not the problem with the beam. 

Use the Shottkey to measure the beam emittance.   So begin by doing the 18 Amp measurement with Q2, then Todd wants 4 hours to do Orbit Response Matrix (ORM) measurements, turn on the logging of Shottkey data, verify that the BBQ is really off, verify that gap cleaning is off.