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Hall B Tests of Coherent Bremstrahlung




HI Richard,

This weekend a few days of machine development time were devoted to tests
of the Hall B goniometer and a very first look at a coherent photon beam.
Overall, the time was very productive. Here are a few pointers to log book
entries that you may find useful:

http://db6.jlab.org/cgi-bin/clas-online/logbook.cgi?-k&8422

http://db6.jlab.org/cgi-bin/clas-online/logbook.cgi?-k&8409


Also, Ken Livingston (k.livingston@physics.gla.ac.uk) from Glasgow was at
Jlab over the weekend to participate in the goniometer tests for Hall B
coherent bremstrahlung source. They were able to see a coherent peak and
thereby demonstrate that the goniometer is working, although there are
still details to be worked out.

1. high energies puts additional constraints on precision of alignment
2. software used at Mainz is available and already working at some level.
Could be ported and improved for Hall D.
3. Diamond radiators used: synthetic (100 microns) and natural (50
microns). 
4. Synthetic diamonds are going to be checked for quality, and the company
will polish the crystals down to 10-20 microns. They hope to have thin
crystals available for Hall B during the g8 run period next spring.

Ken expressed and interest in joining Hall D. Their contribution would be
software required for goniometer alignment, help with crystal selection,
and generally work on beam/tagger alignment issues. I told him that we
generally welcome collaborators and told him I would pass this information
on to Richard Jones.

A side issue came up related to obtaining collimated coherent spectra.
Fast coincidences between scalers and a detector trigger is something we
have not thought of carefully. Pipeline electronics solves delay cables,
perhaps. But tight timing might be a problem in this case. Additional
thought will need to go into this.

Cheers, Elton.




Elton Smith
Jefferson Lab
elton@jlab.org
(757) 269-7625