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Once beam has been established for Physics running, the operators will do their best to continuously deliver beam. During running, the halls should notify the MCC Control Room of any configuration changes that may alter the beam orbit, such as changing the state of magnets, radiators, rasters, target cells etc. Interruption of beam delivery to a hall can be for a variety of reasons, either planned or unplanned.
Unplanned Beam Interruptions
When the beam trips off (i.e., it is not turned off deliberately), an alarm sounds in the MCC Control Room, alerting the operators to the trip (these are referred to as Fast Shutdown [FSD] trips).
- MOMENTARY FAULTS: The beam may trip because of a simple RF fault. These types of trips can be reset in a matter of seconds. RF faults become increasingly frequent as energy and current are increased.
- EXTENDED FAULTS: A more serious problem may, of course, take longer to correct. If the operators suspect that the problem will take longer than five minutes to fix, they will call each hall and provide an initial update on the problem and then provide periodic updates thereafter. Please remember that these first five minutes are crucial to the Operations Crew. During this time they are trying to determine the extent and cause of the failed beam delivery and get beam back to you as quickly as possible.
Planned Beam Interruptions
- AN INDIVIDUAL HALL REQUEST: A hall can, at any time, request that the beam to their hall be turned off. This will not affect beam delivery to the other halls.
- A "PRIORITY HALL" REQUEST: For each day, the long-term schedule identifies a specific hall as the "Priority Hall". The Priority Hall has the primary voice in decisions concerning beam quality and/or changes in the accelerator operating conditions (this does not include changes in beam energy that would affect planned running in the other halls without their consent). The "Priority Hall" has the right to do the following:
- Require an immediate retune of the accelerator when beam quality is not acceptable.
- Insist that an energy change occur as scheduled.
- For more information on Priority Hall status, please refer to the Accelerator Schedule Memorandum posted on the World Wide Web at: https://www.jlab.org/physics/experiments/schedule
- SYSTEM CHECKS: Every evening on Swing Shift (at around 1630) the operators inter- rupt beam delivery to check a standard set of accelerator parameters. These system checks are done to ensure that beam quality remains acceptable and to try to spot developing problems before they become critical. The checks normally take about 1/2 hour. There are times, however, when, based on problems found during the checks, adjustments need to be made. In these instances, the system checks may take a little longer. If this is the case, the MCC Control Room will inform the halls.
- SCHEDULED TEST PLANS: On occasion, beam time may be required to test program-critical hardware or software in the accelerator. These activities are planned in advance and executed according to written test plans. Each test plan follows a standard format and must be preapproved by the PD and MCC Operations. Every effort is made to minimize interruption to scheduled beam delivery.
- MAINTENANCE DAYS: Accelerator maintenance shift(s) generally occur on alternate Tuesdays, beginning at 0700. They are typically preceded by a shift of machine development activity and then followed by a shift of hot checkout/restore. The "Machine Development" time is used to prepare for new experiment setups such as polarized beam nonstandard energies, and three-beam operation. "Hot Checkout" is dedicated time during which all accelerator systems are recovered, exercised, and made ready for beam operation prior to actually attempting to restore beam. Finally, "Restore" is the period assigned to tune the beam to meet specifications for its next scheduled use. The accelerator schedule allots shifts as necessary for each of these activities.