[Halld-tagger] [EXTERNAL] Re: About monitoring of the photon circular polarization

[Ken Livingston]

Hi Eugene,

It looks like they already use this method in Hall-A, or at least have 
in the past. (https://www.jlab.org/compton/Virtual_manual/index.html)
In Hall-B they have a Moeller polarimeter, which has a separate target 
(magnetized foil + solenoid) and detectors, but could probably be 
replicated (in fact Hovanes used to be the expert on that system).

Both methods would need additional hardware.

In Mainz we also measure the electron polarization using Moeller 
polarimetry, but it's part of the standard setup. We have the Moeller 
foil+solenoid in the goni chamber as an extra target on the goni 
translation axis. We also use this as the amorphous radiator most of the 
time. If the solenoid is energized we can make a moeller measurement by 
looking at coincident pairs of hits on the tagger focal plane. It might 
be possible to do something similar in HallD.

Regards,
Ken



On 14/10/2020 08:05, Eugene Chudakov wrote:
> I mentioned at the beam meeting that one can potentially 
> detect/monitore the circular polarization of a photon beam, but did 
> not remember the details. Meanwhile, I recalled it - one can use the 
> Compton scattering on longitudinally polarized electrons (in iron). I 
> attach a few plots showing the kinematics, the cross section and the 
> analyzing power. I do not know at this time whether it is practical or 
> not for the GDH project.
>
> Eugene
>
>
> _______________________________________________
> Halld-tagger mailing list
> Halld-tagger at jlab.org
> https://mailman.jlab.org/mailman/listinfo/halld-tagger

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mailman.jlab.org/pipermail/halld-tagger/attachments/20201014/df961b0b/attachment-0001.html>