1. 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 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.

2. 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

3. 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

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

5. 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

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