Beam tracking simulations for a BPM-based energy spectrometer prototype for ILC

T-474 at SLAC is a prototype BPM-based energy spectrometer for the ILC. A 4-dipole chicane is used with mid-chicane dispersion of 5-mm and magnetic fields of ~1 kGauss; these match the current ILC parameters. Better than 100 part-per-million (ppm) accuracy is needed for ILC energy measurements, requiring better than 50 ppm accuracy for magnetic field integral measurements. Code for beam tracking through the spectrometer chicane was developed. Magnetic field maps for dipole magnets obtained from the measurements at SLAC are used. Different aspects of the magnetic field influence to the beam deflection value are discussed. Results of the beam dynamics study using the measured magnetic fields for T-474 chicane to estimate magnetic effects on capabilities for the energy measurements are also reported.