Undulator Spin Polarimetry for the precursor storage ring eEDM experiment Page: 3 of 8
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Undulator Spin Polarimetry for the "precursor" storage ring
Alfredo U. Luccio
guest, Brookhaven National Laboratory, Upton, New York e-mail: firstname.lastname@example.org
Abstract. In a precursor eEDM experiment to the proton EDM, spin polarimetry based
on undulator radiation is proposed.
1 The EDM storage ring experiment(s)
We plan a storage ring based experiment (100 M$) to measure with an accuracy of 10-29 e-cm the
electric dipole moment (EDM) of the proton. In a second "precursor" storage ring experiment we
propose to measure the electric dipole moment of the electron. The eEDM ring will be smaller and
much less expensive than the pEDM ring and might be constructed first.
The e-ring will also be useful as a model to test the not-so-well known accelerator physics of an
electric storage ring.
In the pEDM we will use polarized protons at the "magic" (see next) momentum of 0.7 Gev/c. In
the precursor eEDM, polarized electrons at the "magic" momentum of 15 MeV/c. The EDM will be
measured by spin polarimetry.
The rings will be strictly electrostatic (no magnets). At the magic momentum, in absence of
magnetic fields, the spin direction will remain "frozen" in its direction at injection (longitudinal) and
the EDM will be measured as proportional to a small vertical component of the spin that will gradually
appear. Interested people may check another parallel talk to this Conference[? ].
1.1 Synchrotron radiation and spin polarimetry
It was suggested[? ] that synchrotron radiation by polarized particles in an accelerator will show
an extra tail. This effect was finally measured on electrons [? ]. SR is due to the radiation by an
accelerated charged particle (in particular, oscillating.) The tail is due to the radiation of an oscillating
momentum. It is a second order radiation field. This component of SR goes with the inverse square
of the mass of the particle, so it is much weaker for protons than for electrons.
It seems already promising to do spin polarimetry by ordinary wide-spectrum SR, however there
are better news. If one enhances synchrotron radiation using an undulator in the ring (say electrostatic
to preserve the magic condition), SR becomes more intense, more coherent and, very important, shows
a line spectrum. It turns out that the monopole and the dipole spectral lines have opposite polarization.
1We acknowledge the support of the U.S. Department of Energy
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U., Luccio A. Undulator Spin Polarimetry for the precursor storage ring eEDM experiment, article, August 28, 2013; United States. (digital.library.unt.edu/ark:/67531/metadc867383/m1/3/: accessed November 12, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.