Orbit Compensation for the Time-Varying Elliptically Polarized Wiggler Operating at 100 Hz

The time-varying elliptically polarized wiggler, installed in the X13 straight section of the NSLS X-ray ring, generates circularly polarized photons in the energy range of 0.1–10keV, with AC modulation of polarization helicity. The DC vertical magnetic field is produced by a hybrid permanent magnet structure, and the AC horizontal magnetic field is generated by an electromagnet capable of switching at frequencies up to 100Hz. Here, we discuss the compensation of the residual vertical and horizontal orbit motion utilizing a time-domain algorithm employing a function generator to drive trim coils at the wiggler ends, and the wideband, high precision orbit measurement system of the X-ray ring. The residual orbit motion at 100Hz has been reduced to a level below 1μm, and the device has been run in regular operations with no negative effect on other users.