Re: Coherent Brem, double goniometers, SOS

[Ken Livingston <k.livingston@physics.gla.ac.uk>]

Hi Franz et el,
SOS indeed at the prospect of 2 goniometers! Then I find at a glance 
through ref: hep-ex/0306028, that not only was a second goniometer 
needed, but, due to the infalated beam spot at the point where it was 
placed,  4 separate diamond crystals had to be aligned rather well with 
each other within the 2nd goniometer. This would really have to offer 
huge advantages over other polarimetry solutions to make it worth the 
effort.

I'm more interested in the prospect of channeling radiation as a source 
of polarised photons. Glasgow is leading a newly funded project called 
Eutorag, involving groups who use tagged photons. Our main contribution 
is to build a 2d photon detector to put in the beam at Mainz to 
investigate channeling radiation.

I've just heard about a relevant workshop in Frascati November:
"November 2-6 at Frascati will be planned Workshop on Charged and 
Neutral Particles Channeling Phenomena."

Cheers,
Ken

>Hi Jim,
>
>I looked into that when we "designed" the Hall-B coherent beamline.
>The 2nd goniometer/crystal must have considerably heigher quality 
>than the 1st (production goni), otherwise the analyzing power is
>too low. Yerevan used such a setup 10+ years ago (although at lower
>energies).
>The question should be: do we want/need high degrees of photon
>polarization or only high flux?
>When it comes to baryon resonances, we'll NEED as much information
>on polarization in the initial state - for meson spectroscopy this
>will also be necessary if there are many overlapping states 
>(otherwise you depend too much on "perfect" calibration/understanding
>of the detector).
>
>Greetings
>
>Franz
>
>  
>
-- 
=======================================================
Ken Livingston          

Dept. of Physics & Astronomy,        Tel: +44 141 330 6428
University of Glasgow,               Fax: +44 141 330 5889
Glasgow G12 8QQ.
Scotland. UK.
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