CAT Chat Minutes
November 19, 2001
Information and Follow-up Items
What happens when you stop and restart top-up?
Beam motion was reported as having been observed between 0830 and 0840 on 11/15/01, coincident with top-up operation being stopped and restarted. The root cause was a loss of communication to the ioc, which is responsible for measuring the stored beam current (S35DCCT). In addition to stalling the top-up process, several orbit control processes were affected. In particular, the process that compensates for intensity dependent offset changes operated incorrectly and likely was responsible for the observed orbit shift. Once communication was reestablished, all processes were restored, along with the orbit.
During this run, after we switched to low-emittance top-up, we had problems with beam position. Will something be done in the future to avoid this happening again?
We clearly underestimated the time that it would take to set up low-emittance top-up operation in trying to schedule the transition during an eight-hour studies shift. A further complication during that shift was the need to perform some maintenance as well. In the future, we will not schedule such a transition to low-emittance operation during the short studies period.
The seven-day storage ring and beamline history was presented. The results show last week's availability of 98.5%. The mean time between failures has been 31.2 hours. Total availability since the beginning of the run has increased to 95.6%.
On November 22, at 2400 hours a 32-hour machine studies period will take place. Operations will begin at 0800 on November 23, with low emittance lattice in top up mode.
Happy Thanksgiving to all!