-- DhR - 19 Feb 2009

Beam Alignment & Stability Study 2/3/2009

EFF, SBP, PR, DER, DHR, ST

Reviewed study group objectives - improve predictability of CHESS photon beam positions, and understand primary factors determining achievable stability.
This group will meet approximately every 2 weeks and will present results to CLASSE management in about 6 months.

Draft study outline:

1. Collect survey data - relate CHESS beam line positions to CESR coordinate system
2. Collect beam position, stability data - both CESR orbit and CHESS beam positions, burns, etc.
3. Review existing software to predict CHESS beam positions from CESR orbit measurements.
4. Calculate photon positions taking into account survey data for both CHESS beam lines and CESR magnets(#1), BPM offsets etc. Check predictions against measurements. Iterate until closure. Choose "easy" beam lines first then proceed to more difficult.
5. Establish monitoring program for beam positions in CESR and CHESS.
6. Classify sources, time scales of beam instability. Prioritize by impact, likelihood of improvement.

Comments on study outline:

Stu - Intensity sensitivity of e-, photon measurements and reliability of data are high priorities. Need to know the cbpm deployment schedule in the CHESS East source region - this system has ~1/5 noise level of old relay system.

Sasha - Top-off injection studies revealed several orbit stability issues and study needs. Successive, coordinated snapshots of positions at several monitors. 10/sec update would be good though less is useful. X-ray screens on TV camera give 30/sec though averaging is necessary for decent resolution.

Dave - need to schedule a survey of the beam lines

Peter - photon position monitors have had some improvements and some degradation as they have been moved around to serve experimenters' needs. Need to focus on enumerating pm's suitable for stability analysis, and those good to correlate positions with CESR measurements. Electronic pm's give few 10's /sec, are normally read 1/sec. How do we measure current dependence
(dhr - what sampling rate can easily be supported to correlate e- and photon position measuremts?)

For next meeting (9 AM Wednesday Feb. 18) we set the following:
Dana - make list of survey points for beamlines, bpm's, apertures for the survey group to measure
Peter - list characteristics of bpm's, how to deal with movable stages, TV screens
Stu - look at MJF software, assess need for extensions
Sasha - look at bpm data acquisition (MGB), sources of beam motion in CESR
Dave - contact survey group to schedule survey