Accelerator Commissioning Update

The APS storage ring commissioning has progressed well during the past few months, with typical periods of two to four weeks, for studies. The major accomplishments during these runs include record beam intensity (> 20 mA) in multiple bunches, first insertion device light from beamline 1-ID, and the demonstration of acceptable machine operation with both 12-mm and 8-mm vertical aperture insertion-device vacuum chambers installed. The machine is currently in a maintenance period during which vacuum system modifications (see related stories on pp. 11 and 13) and final bakeout will be completed, which will allow adequate beam lifetime at high beam current.

While the storage-ring modifications are being completed, advantage is being taken of the opportunity for dedicated machine studies on the injector machines. This will allow for comprehensive beam studies in the booster to incorporate the latest power supply upgrades to enhance reliability. Linac studies in support of positron operation continue, with implementation of the decision to change the magnet polarities of downstream machines expected later this year. The new high-repetition-rate septum magnet for the PAR, a critical item for positron operation, has been installed.

Machine objectives for the coming operations period are to achieve 100-mA stored beam operation with greater than 10-hour lifetime, and to investigate intensity limitations. Closed-orbit feedback systems will be implemented, which will reduce low frequency beam motion to a level well within specification. Operation at specification (+/-17 microns rms horizontal and +/- 4.5 microns rms vertical) has already been demonstrated without feedback, with good progress towards the understanding and elimination of noise sources. Operational considerations such as operator training and machine availability and reliability tracking and improvement will be addressed in more detail as regular beamline operation approaches.

-G. Decker, Accelerator Systems Division

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