[b1_ana] Fwd: PR12-13-011

[Karl Slifer]

---------- Forwarded message ----------
From: John Hansknecht <hansknec at jlab.org>
Date: Tue, May 28, 2013 at 8:57 AM
Subject: Re: PR12-13-011
To: Jay Benesch <benesch at jlab.org>
Cc: Karl Slifer <karl.slifer at unh.edu>, marcy at jlab.org


With plans moving forward toward 4 hall operation with 500MHz, 250MHz, and
lower rep rates, it becomes increasingly difficult to do "special" setups
for one hall.  The "average" polarization of our beam is always zero, so an
unpolarized experiment simply integrates over a long time period without
tracking the helicity signal.  At least this is what they have done in the
past.  I don't really have any other suggestions.

John


On 5/24/2013 11:08 AM, Jay Benesch wrote:

> 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
>


-- 


----------------
John Hansknecht
Jefferson Lab
757-269-7096
-------------- next part --------------
An HTML attachment was scrubbed...
URL: https://mailman.jlab.org/pipermail/b1_ana/attachments/20130528/a45314f8/attachment.html