CAT Chat Minutes
March 25, 2002
Information and Follow-up Items
1. During a recent injector fault, beam current was decaying but beam was still usable, however shutter permit was removed and beam was not dumped for another two hours. Why did this occur?
In the past, we knew that beam stability was lost when the beam current dropped below ~45 mA. All of the improvements to the beam position measurement system had improved the system response at lower currents, but we did not have a reliable measure of how low we could go before we lost control of the beam. At the same time, we had another problem that needed to be solved. Over the last weeks, we had experienced several rf trips which caused stored beam to be lost. The rf group needed to conduct a test with stored beam to see if the reason for those faults could be identified and since the consequences of the test were uncertain, the shutters were closed to conduct the test. We will identify the stored current stability threshold so that there is no uncertainty in the future.
2. The cyro-coolers on the floor are aging and are likely to fail more often. The cryo-cooler for sector 20 has a leak and may not last for another month. Thus far, weve had excellent APS support to keep units working smoothly, however, machines will fail in the future. What kind of commitment has APS made for the support of this activity?
Oxford has been making changes to each new unit they make. For example, the coupling between the pump and hose has resulted in some incompatability from unit to unit. We are working with Oxford to resolve this and will continue to support these units. As part of the APS reorganization, the plan is to position the organization into providing even more support in this area.
3. DND-CAT has a problem with staging space. Our sector is in need of staging area for moving experimental equipment in and out for all of our users. Has any location been found at this point?
The area at sector 30 is being cleaned up to provide CATS with a limited space, temporary (maximum of one week) staging area for moving beamline equipment in and out. Announcement will be made at CAT CHAT when this area is available (approximately two weeks). Kevin Beyer will be the point of contact for use of this space when it becomes available.
4. We noticed that after the extented downtime on March 24th, when the shutter permit was given the ID gaps were at 60 mm and not at our previous gap. What happened?
The IDs will open to 60mm if left below 25mm with a shutter closed for 2 hours. This is done primarily to preserve the lifetime of vacuum pumps. Sunday night, the MCR closed all shutters with beam still in the storage ring (see question #1 above). After 2 hours, all IDs which had been closed below 25mm automatically opened to 60mm. Some time later, beam in the storage ring was dumped, triggering a "global open" of ID gaps. When this occurs, each previously commanded gap is saved as the return gap for the next "global close" of ID gaps. When that global close next occurred, all IDs that users had left below 25mm were returned to 60mm.
The correct sequence should have been to open all gaps when shutter permit was removed. If that had happened, the ID would have gone back to the users previous gaps. We will fix this issue to make sure this mistake is not repeated.
CY Yao reviewed the past week's operation. For the week, there were five faults primarily due to rf cavities. Beam availability was 95.1%. For the run, beam availability is 96.81% with a MTBF of 29.8 hours.
Next week Tuesday, 16 hours of studies have been scheduled. During that time, high current operation at 130mA with singlets will be studied. The specific operating details for the user studies at high current will be determined and cat net will be sent with further details.
If anyone has a seminar they would like posted, please call Linda Carlson at x-5089 and she will place the information on the web. This information will be displayed on the TVs around the ring.