Massimo presented in 20 minutes his ideas about SiC based quadrant xBPMs for SLS 2.0. The very new idea is a central hole to make them applicable for white beam applications and soft x-rays. Massimo presented these monitors as good candidates to replace the blade xBPMs in the front ends of SLS in the transition to SLS 2.0.
Side mark: In preparation of the meeting, we discussed with some beamline scientists possible test scenarios and I suggested to replace the downstream xBPM head at X07MA with Massimo's SiC monitor. Why: a) the X07MA monitor is regularely used - one can compare benefits/drawbacks, b) it is not mission critical- if it breaks one can live without monitor for a while c) X07MA is in my opinion the most challenging test case for such a monitor at SLS (soft X-rays, polarization control, high harmonics) if the monitor works there it will likely also work at other beamlines.
Massimo presented a comparison of different monitor types, the main advantages of SiC monitors: high signal, high spatial resolution.
He showed also new results from tests with pink beam at X06SA which were not as good as expected. There seem to be still a couple of open issues: vacuum, baking, outgassing under beam load...
There was a long (30 minutes) discussion with several people involved whether, where, how to put such a monitor. No common agreement- my summary:
- The monitor seems to be not yet in a status to justify reasonable test in a SLS front end as a production environment. The front ends are good for ultimate testing but not a good place to make R&D.
- In particular vacuum and cooling issues must be clarified. In the front ends there is no vacuum window- strong outgassing under beam load may close the beamline valves or even dump the ring
- it needs more R&D before we install the monitor in a front end. The feasibility should be demonstrated in the pink beam path of a hard x-ray beamline, i.e. in a section downstream of a vacuum window inside the optics hutch for risk control and to have better access