Coherent Brem using SOS configurations

[Elton Smith <elton@jlab.org>]

Hi Richard and Jim,

I wanted to make sure you were aware of some recent developments in 
producing photon beams with crystal radiators.

You have probably already heard about recent work/measurements which
produce high-energy beams using a special case of coherent bremstrahlung
using the so-called String-or-Strings (SOS) configuration. Harut Avakian
has made a draft paper available to Bernhard Mecking describing recent
measurements at CERN. The draft indicates that coherent-like peaks at say
80% of the electron beam energy can be achieved with enhancements over
Bethe-Heitler of around 18. For comparison, our coherent peaks (after
collimation) show enhancements of approximately 4-5. The drawback of this
system, if it is proven is that measurements of the polarization are quite
small, i.e. less than 5%.

Let me know if you have any information and/or opinions on this work. We
should think about whether to pursue this as a collaboration. Bernhard is
interested in developing some of these ideas here at JLab. The Yerevan
Physics Institute is involved in the measurements (A. Apyan and R.O.
Avakian are authors). Richard: Are these some of the contacts you have in 
Armenia, and has any of this work been discussed for further study?

Generally, JLab clearly has an interest in developing special photon beams 
at high energy and/or polarization. Therefore, it might be useful to 
consider a workshop and/or meeting at JLab to invite some of the experts 
and pursue this further.

Any comments/suggestions?

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