CAT Chat Minutes
August 14, 1998
APS Operational Status Update
As of this week, availability has been at about 93%. We had a few minor trips this week. On Thursday evening, we had a power glitch that lasted only a few cycles, however we lost a few of the storage ring systems. It took us about 2 hours to recover.
We have done some top-up testing with the shutters closed but are still awaiting DOE approval for top-up testing with any of the shutters open. As soon as we receive approval, we will do preliminary tests with a single SRI CAT beamline to confirm previous radiation calculations and limited measurements. After these tests are completed, we would like to do some testing in September with increased user participation during one or more of the machine studies periods.
We are still exploring various top-up scenarios and identifying any potential limitations. We will keep you informed of the developments.
We will also look into providing an EPICS Process Variable that will be set at a predetermined time interval prior to an injection.
Information on the 5-BM PSS trip
A PSS trip at 5-BM, which dumped the stored beam, occurred just prior to the CAT Chat. It was caused by a unique set of conditions. At the time, the shutters had been disabled by the storage ring ACIS. The door-open button was pushed to gain access into one of the beamline stations. Since the shutters were closed, the command was accepted by the PSS and the logic told the pneumatic system to start opening the door. At the same time, the control room operator issued an ACIS shutter enable, and, since 5-BM has a remote shutter control interface, the beamline software immediately commanded the shutter to open. Because of mechanical delays in opening the door, the door switches still indicated that the door was closed, so the PSS logic accepted the shutter-open command and began to open the shutters. As soon as the door limit switches indicated an open door and the shutter-closed limit switches indicated an open (not closed) shutter, a major fault occurred, tripping the storage ring. All of this occurred in less than 1/2 second. We are looking at ways of preventing this situation from occurring again, without further complicating the safety code.