ILC Beam Energy Measurement Based on Synchrotron Radiation from a Magnetic Spectrometer

A magnetic spectrometer with a relative energy resolution of 5·10-5 was proposed for ILC beam energy calibration. A complementary method of beam energy measurement based on registration of synchrotron radiation (SR) from the dipole magnets of the energy spectrometer is proposed. Measuring both horizontal edge positions of the SR fan at a distance of 50-70 m downstream of spectrometer allows to determine the beam energy with high accuracy. The main principals of the SR beam energy measurement, first numerical simulations by means of GEANT and physical limitations of the detector coordinate determination are described. Two versions of novel detectors for low-energy (<20keV) photon registration are proposed. They are characterized by a high counting rate and a linear resolution of 2-3 μm