<br><br>---------- Forwarded message ----------<br>From: <b>Jay Benesch</b> <br>Date: Friday, May 24, 2013<br>Subject: PR12-13-011<br>To: Karl Slifer <<a href="mailto:karl.slifer@unh.edu">karl.slifer@unh.edu</a>><br>
Cc: <a href="mailto:marcy@jlab.org">marcy@jlab.org</a>, <a href="mailto:hansknec@jlab.org">hansknec@jlab.org</a><br><br><br>Karl,<br>
<br>
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.<br>
<br>
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.<br>
<br>
Jay<br>
<br><br><br>-- <br><div><div><div>---<br><div>Karl J. Slifer<div>Assistant Professor</div><div>University of New Hampshire<br><div>Telephone : <a>603-722-0695</a></div></div></div></div></div></div><br>