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The Compton polarimeter can be used to non-invasively monitor the beam polarization. It has three major components: an optics table with a laser that can lock to a Fabry-Perot cavity; an electron detector to count scattered electrons; and a photon detector to count scattered photons. At present, the electron detector is in commissioning, so only the photon detector is fully functional.

Hall A Compton polarimeter Wiki page

Hall A compton webpage

Standard Compton



Compton Upgrade

Photon detector

The new photon detector crystal is a cylinder of GSO with a diameter of 6 cm and a length of 15 cm. It was installed in Hall A in December 2008.

In October 2008, the crystal was tested at incident photon energies of 20 MeV, 22 MeV, 25 MeV, 30 MeV, and 40 MeV. We are working on extracting the response function.

PREx requires an integrating DAQ system, which will run on a Struck FADC. We are currently commissioning this DAQ with a prototype FADC.

Electron detector

Webcams address

Webcams were added to monitor the :

APC : hareboot4

*plug 2 webcam
*plug 3 EPICS Edet
*plug 4 trigger
*plug 7 FADC crate

Compton Edet DAQ