3.25.2013 Meeting

Reviewed the draft of beamline status presentation for Wednesday morning.

Power Point Presentation

Beamline 27 March 2013.ppt

Why is feedback 1 second? Answer below from Arne. 

Ken,
Nice summary/overview of the HPS beamline this morning, it was encouraging to see it all laid out in a coherent fashion.

Additional comment on feedback and the cavity beam position monitors in Hall-B. One of the main differences between SLC and CEBAF is that SLC was a pulsed machine and CEBAF is a CW. The CW nature of the beam at CEBAF means that the peak current is the same as the average current, so the peak current is really quite small. In fact Hall-B sometimes operates is less than one electron per 499MHz cycle. This low peak current means that the beam position monitors need to sample a for period of time to establish a significant signal. The cavity BPMs in the B line utilize lock-in amplifiers and report a position at a maximum rate of 10Hz, this 10Hz data is averaged and once a second (or every ten measurements) a beam position is pushed to the EPICS record. This system is 15 years old, and could be improved with an upgrade to its electronics.

The beam currents that HPS wants to run at are in the regime where the CEBAF antenna BPMs function ( ), and with new electronics that has been developed for the new Hall-D line the beam position measurement might be robust enough for a feedback system with a higher bandwidth. But this is not in the plan as far as I know. There are many antenna BPMs installed on the Hall-B line that are only used for "tune-mode" beam or high current ( ) CW operations.

Arne