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How to tune the beam

^3.1Tuning the beam to optimize its position and size is the preliminary step in performing any $\beta$ NMR or $\beta$ NQR experiment. A stable, well-centered beam that does not ``wander'' if the field (or high voltage on the platform side) are changed is pivotal. Moreover, if experiments are planned to be performed in ``fast-switching mode'', a good tune at both stations is essential. The degree of tuning at the stations depends highly on how the beam is behaving upstream of the spectrometers; adjustments of elements will vary from beam period to beam period. Tuning is best performed in the ISAC Control Room, as it is the Operators who are permitted to change settings of elements along the beam-line (some are better at this than others). In a perfect world, this procedure would be automated; by saving and re-loading beam-line element settings a good tune for both stations could be quickly achieved. In practice however, tuning takes some time. There is no clear step-by-step procedure for tuning the beam [2].

The following must be prepared before beginning to tune:
1. Sapphire scintillators must be in place at both stations; the CCD camera program must be opened [on a terminal in the ISAC Control Room (ssh to bnmrpc) and outside in the hall].
2. Strip tool utility should be running and the counter (ILE2) scalers plotted:

Channel	Counter
S4	b-NMR backward
S5	b-NMR forward
S9	polarimeter left
S10	polarimeter right
S11	neutral beam monitor (nbm) forward
S12	nbm backward

3. The Laser Optics page of Epics should be opened showing the $\beta$ NMR asymmetry (should also be plotted on the strip tool).
4. Set the high field side magnet to 0, and the high voltage to 0, and EL3 to 0.

Page last modified: 07/23/09 02:45 by Andrew MacFarlane.