When beam was started in mid-April, it was observed by Operations Group that with the beam centered vertically within the protect monitor, the profile monitor showed the beam spot to be approximately 6mm high.  The protect monitor was changed during the shut-down due to a failure in November 2013, so it was suspected that the new protect monitor was not aligned properly.  The beam spot appeared to be dangerously close to the top weld of the target window so it was decided the target assembly would be removed for inspection to visually confirm the suspected misalignment before increasing beam current.  Since start-up, a maximum beam current of approximately 30 micro-amps had been used on the 10cm beryllium target in position 4 which previously had not seen beam.

On Monday April 28th, the T2-MK2 target was transported from the beam line to the hot cell.   The target assembly was measured to be 298mSv/hr at 0.5m.  A clear beam spot was visible on the entrance and exit windows of the target approximately 6mm high of vertical center (photos attached).  Target and profile monitor elevation measurements were conducted, and confirmed those previously taken on the target by Tom Lyth.  This exercise confirmed that the position 4 target and profile monitor were aligned properly, and that misalignment of the protect monitor was the cause of the beam being high on the target.  It was then decided that the protect monitor assembly would be removed and a new monitor cassette installed to remedy the problem.

On Wednesday April 30th the T2-MK2 target was returned to the beam line and the protect monitor assembly was transported to the hot cell.  A maximum field of 15mSv/hr at 0.5m from the protect monitor was measured.  Elevation of the monitor cassette was checked, and was found to be 6.8mm above the elevation of the position 4 target.  The monitor cassette was removed from the assembly.  The cassette was approximately 100μSv/hr at 0.5m and 2mSv/hr on contact, with 200cpm measured from a swipe of the outside surfaces (not the inside plates).  The cassette was returned to Probes Group for possible use in the future.  A new monitor assembly was supplied by Scott Kellog on Friday morning with the 6.8mm adjustment.   The monitor was installed on the protect monitor assembly.  Elevation was checked and found to be within 0.5mm of the target elevation.  After installation an electrical check was performed by Dave Cameron and Mike Russel.

The protect monitor assembly is ready for installation in the beam line on Monday morning.