[b1_ana] Fwd: PR12-13-011

[Karl Slifer]

---------- Forwarded message ----------
From: *Jay Benesch*
Date: Friday, May 24, 2013
Subject: PR12-13-011
To: Karl Slifer <karl.slifer at unh.edu>
Cc: marcy at jlab.org, hansknec at jlab.org


Karl,

I was wrong.  I just spoke with Marcy.  Linearly polarized red light on the
existing cathode would give you unpolarized electrons.  All one would have
to do is remove the unit that turns linear to circular polarization.
 Unfortunately, this is done on all three laser beams with the same unit so
all halls would have to agree.  I couldn't reach John Hansknecht to learn
whether there's enough room to rebuild the laser table to allow the hall C
beam to bypass the unit while getting to the cathode at the right time.  I
doubt it, but John does extraordinary things.

The gun group is also working with another cathode with high QE in green
light and no polarization but there is some valid reluctance to put it in
the CEBAF production injector due to "volatility" (my word - the stuff can
move within the chamber if too much light gets to it).  It needs to stay in
vacuum so it can't be installed in the old gun.

Jay



-- 
---
Karl J. Slifer
Assistant Professor
University of New Hampshire
Telephone : 603-722-0695
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