Raster Update Aug 9, 2016 R. Michaels with Chris Cuevas, Bill Gunning, Michael Johnson Problem Notes Solutions Over-heating Dec 2015 incident Thought to have weakened some supplies Improve the cooling system. Jessie Butler, et al. 8 power supplies failed during Spring 2016 Operations Notes on reasons incomplete, but thought to be radiation related. Mainly 24-volt supplies failed, but some FETs, too. Mostly affected power supplies located nearest beam. 24-V supply draws only 2.2 A (rating 20 A). Added radiation shielding (Jessie Butler, et al.) Long-term test this summer to verify no failures without beam. 26 days total. Improve record-keeping on failures and repairs Build up spares Cancellation due to 1800 phase Occurred during start-ups. Degraded amplitude when rasters were imbalanced (10% current mismatch); total cancellation when balanced. Use a pickoff-loop to verify 00 phase as a routine check after start-up. Spikes in output New in 12 GeV. Affects ability to measure target flatness None yet. Considering adding snubber capacitors.

Raster Magnets Power Supplies Synchronize X with X to double the kick. (same with Y and Y) Anecdotally more failures near the top of the stack Compared to 6 GeV running, the location of the power supplies is more directly under the beamline

Raster Power Supply No design change since 2003, except for synching two supplies to double kick, and longer cables. Investigations by Chris Cuevas and Bill Gunning Failing component: 24 Volt supply

Raster Test at Operating Current summer 2016 Steady operation with no power supply failures for 26 days total June 24 -- July 13 19 days at 30 A July 13 IOC event resets magnets, not noticed until July 27 July 27 -- Aug 3 7 days at 20 A

Spikes in raster current Holey C12 target run Spikes in raster current Current used to check beam position Also used to check target uniformity. (Here looking for a hole.) But much less “spikey” prior to 12 GeV horizontal vertical A run taken during PREX-I in Spring 2010

Wiggles in Output Current No solution yet, but possibly add “snubber capacitors” to smooth the current in the magnet.