Etude de la faisabilité d'une source de positrons polarisée basée sur ...
Etude de la faisabilité d'une source de positrons polarisée basée sur ...
Etude de la faisabilité d'une source de positrons polarisée basée sur ...
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tel-00647307, version 1 - 1 Dec 2011<br />
• Transfer Compton transmission po<strong>la</strong>rimeter from LPSC to JLab.<br />
• Prepare for experiment instal<strong>la</strong>tion.<br />
May - October 2011 (Perform Experiment)<br />
• 1 month to install segmentation, experimental apparatus and commission<br />
segmentation.<br />
• 3 months to commission and perform experiment.<br />
• 1 month to un-install segmentation, remove and return experimental apparatus<br />
to DESY and Princeton University.<br />
• 1 month advance recovery in preparation of CEBAF operations.<br />
November - December 2011 (Nuclear Physics Program)<br />
• Experiment and analysis are completed.<br />
• Jonathan Dumas to <strong>de</strong>fend Ph.D. Thesis and publish results.<br />
8 Summary<br />
Thisletterproposes an experimentat theCEBAFinjectorto <strong>de</strong>monstrateand<br />
mea<strong>sur</strong>e the longitudinal po<strong>la</strong>rization transfer from a highly spin po<strong>la</strong>rized<br />
electron beam to <strong>positrons</strong> via the po<strong>la</strong>rized bremsstrahlung and subsequent<br />
pair-creation processes in radiator and pair production targets, respectively.<br />
It requires a new <strong>de</strong>dicated injector beam line and experimental apparatus. A<br />
strategywhichimpliesthesegmentationoftheMeVregionoftheinjectorfrom<br />
the remainingCEBAF complexhas been proposed to perform this experiment<br />
during the 6-month shutdown (May-October, 2011) of the 12 GeV Upgra<strong>de</strong>.<br />
This experiment is <strong>de</strong>signed to have a small physical and radiation footprint.<br />
By using a 1-10 µA electron beam low power targets and minimal shielding<br />
is inten<strong>de</strong>d. The positron (and electron beam) po<strong>la</strong>rization will be mea<strong>sur</strong>ed<br />
via the Compton transmission method. The expected positron yield is low<br />
∼pA but yet<strong>de</strong>manding in terms of data acquisition performances. We should<br />
benefit from the current <strong>de</strong>velopments for Hall A and Hall D to guarantee a<br />
powerfull operation of this <strong>de</strong>vice.<br />
In addition to this unique proof-of-principle experiment, this represents the<br />
first accelerator physics experiment at Jefferson Lab aimed at a production<br />
mechanism for <strong>positrons</strong> in the CEBAF accelerator. This R&D issue has been<br />
discussed for many years and through two workshops, most recently at the<br />
InternationalWorkshop onPositrons atJefferson Lab inMarch,2009 [21]. The<br />
results of thisexperimentwould provi<strong>de</strong>valuable information for thepotential<br />
<strong>de</strong>velopment of a higher intensity po<strong>la</strong>rized positron <strong>source</strong> for CEBAF, and<br />
may prove useful for opportunities in the context of the ILC.<br />
14
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