Speaker
Description
The KEDR detector at the VEPP-4M accelerator complex plans to measure the mass
of the Y(1S) meson with an accuracy better than 50 keV. This experiment
requires precision measurement of the beam energy. The most accurate method of
measuring beam energy is the resonance depolarization method. The method is
based on the connection of the particle energy with the spin precession
frequency, which is determined by the destruction of the beam polarization in
the presence of an alternating electromagnetic field. The polarization of the
beam is measured by the asymmetry of the Compton backscattering of
circularly polarized photons on transversely polarized electrons. The report is
devoted to the description of the "Laser Polarimeter" facility and the
features of beam energy measurement. An Nd:YLF laser with a wavelength of 527
nm and an average power of 2 watts is used as a photon source. The
backscattered gamma quanta are detected using a two-coordinate detector based
on triple GEM. The laser polarimeter allows measuring the energy of the VEPP-4M beam
with an accuracy of about 15 keV in 30 minutes directly during the data collecting by the KEDR detector.
