04 December 2007

RHIC Startup:
There were big improvements in the Yellow lifetime when the Deuteron per bunch intensity was reduced below 0.6E11 per bunch.  This was discovered when collisions were turned off and the lifetime looked great.  Studies of the effect of stochastic cooling on Yellow lifetime showed it had no effect.  Currently the Yellow emittance is ~25 pi mm-mr whereas the Blue emittance is ~10.  IBS will blow up the Yellow but not the Blue.  The two beams have the same emittance at injection.

There are two approaches to improving this.  Oneis to blow up the blue emittance by adding white noise to the BBQ. This should be a simple test.  The second approach is to reduce the blue beta* from 1 to 0.8m.  This is where the IPSS lattice wants the beta* to go, although it is a bit risky.

Backgrounds in STAR appear to be due to increase pressure in the 5 and 6 OClock gauges.  It might benefit from scrubbing.  We can fire the Titanium Sublimation Pumps (TSPs) during a down ramp.  This might help, and should precede any scrubbing work. 

The study of adding 18amps to Q2 (see yesterday) did not improve the dispersion.  It made it worse.  So this was backed out.