CAT Chat Minutes
April 25, 1997
Shenoy presented an update on machine performance
The good - We could always get the orbit back during this past run resulting in beams at the same location.
The bad - We had a large number of trips during this past week. There has been a great deal of manpower devoted to diagnose the cause. We require rf2 and rf4 work simultaneously without a trip during a run. The rf trips are caused by rf2 and rarely rf4. There were a total of 38 rf trips of which 34 of them were caused by rf2. Because of the large number of trips, the average beam time is very low. It has been just under 3 hours.
Safe guarding expensive hardware on the accelerator, such as Klystrons, is very important. Hence, there are many fail-safe devices that should trip appropriate power and save such components. On the other hand, if these fail-safe mechanisms trip without a need, that only disrupts our runs. It is our estimation at this time that the majority of these trips are false. In order to understand the reason behind these occurrences, we would be increasing the diagnostics during next week. This will focus on Ignitron, cathode power, and high voltage - all of which safeguard the Klystrons. These additional diagnostics will lead to improved understanding of the false trips.
We next want to propose an alternative mode of operation during a couple of days during the next week. That is to run the machine at 6 GeV, again with the intent to provide a beam with few trips. The hope here is that, since a 6 GeV operation can be done only with rf4, the trips will be few. This will of course change the beamline operational parameters. We have attached the tunability of Undulator A and 6 GeV and compared it with 7 GeV. Indeed some of you will have to use third harmonic radiation. This will result in larger power on the first-optics.
Will anyone be in jeopardy with their studies if we did this? A follow up discussion by the CAT CHAT participants, led to a general consensus that the storage ring should only be operated at 7.0 GeV at this time. In fact, most users could use the beam in spite of the trips, profitably.
Issues that require action and/or follow-up
1. If more rf trips occur during the next ten hours, you will be able to determine what causes the false trips, is this correct?
Yes, with the new diagnostics that are being installed, we will be able to determine which signal is causing the false trip.2. Why sometimes does it take so long to recover after a trip?
It takes more time to recover from a power supply trip, but there are fewer of these. On the other hand, it takes less than an hour to recover from an rf trip, but we have a very large number of these.3. If ASD needs to do more data collection, can some be done during machine studies?
That is already being done.4. Is there any connection between the number of trips and the weekends?
No, if you have observed any connection, it was a coincidence.5. There is a rumor that you are considering adding a day to this run?
This is not a rumor. To make up for lost time during user operations, we are planning to extend the run up to Saturday (5/3) at 0800. We will inform you of this on Monday (4/28).6. How long will it take to put the rf 3 into place? Would extending the current run and losing two days from the maintenance period of this next run jeopardize the completion of this task?
We will work hard to accomplish the rf3 installation during the upcoming maintenance period.7. In last years phone book, all on-site personnel were listed. In the new book, the users are not listed. Why?
This is a mistake, and we will inform the appropriate ANL organization. Meanwhile, users are still listed in the electronic phone book and white pages.
Starting Saturday 4-26, we will go into User Operations at 0800. The ASD staff will continue these diagnostics during User Operations. We hope to be able to find the root cause of the problem.
Meanwhile, the rf3 is being made ready to install during the next maintenance period. This will replace rf2. We hope it will function as well as rf4. The rf3 and rf4 will then be used during the next User Operations period.
We are adding a week of user beam time in August. The long-term schedule with this change is not available yet.
Please contact the FC before anything under configuration management is moved.
Mini CAT CHAT held 4-28-97
It was announced that the present run will be extended to 5-May-97 at 0800.