- 25 Feb 2009
Beam Alignment and Stability Study 2/18/2009 -
sbp, eff, dr, pr, st, dhr
Reports from work since the first meeting:
Dana - talked with Jim, made jigs for looking over dipoles. Ready to start but need to schedule time.
EF - C line moved recently - should be first? can't see most of line from present setup. Focus on water-cooled components. Will look at relationship of internal structures.
Peter - presentation at BNL on xbpms
partly-intercepting monitor - photo-electron bpm with pickups - hb contamination, mounted on jacks for calibration. Significant horizontal contamination.
blade monitors better - pick up low energy photons.
Gas luminescence monitor has absolute center reference, no interception.
Bench test of camera and test LED gives 0.2 um resolution.
H20 kills He luminescence quickly, diamond 50 u, brighter, very uniform. sbp - can use as vacuum window? might but don't want to keep in beam - vs Be. Diamond may be better for surface coherence.
review locations of bpms.
G line PE vs VBPM show cyclic motion through run. motion is amplified, distorted by optics.
Numbers from bpm's somewhat arbitrary. Need to reset with "golden orbit."
Do not have too much problem with radiation damage to cameras - displace to safer position.
EF - 2-D images useful to scientists and beam line techs. Immediate feedback to staff.
PR - moved away from feedback a few years ago - bpms more for diagnostics.
During startup is headache to restore beams to desired positions, but stability is ok for most users once lines are settled.
EF - long term drift after access is important. G line instability may be long term drift in X-ray optics.
ST - see 100u beam drift from beginning to end of run (PR slide) - is problem? EF - depends on experiment.
Sasha - how often read out new bpms - no option now. Experts busy, need additional help. Can read big buffer every 10-15 seconds. Need low-level programming to read out faster than ~4/minute.
DHR - wait until system is closer to operation - getting changes will be easier.
Sources of motion - Heating from quad excitation - 60C temp of iron, net motion 0.3 mm.
DHR - just from tunnel air temperature can account for ~150 um
Stu - SYNRADV program calculates ellipses of photon beam cross sections for specific optics and sets of steering correction magnets. It can fit the steering magnets to a given orbit.
Next meeting - tentatively 9 AM Wednesday, 4 March.
Agenda (please add your topics)
Pick up where we left off.
Survey data for A,B,C lines?
More discussion on sources of unstable beams