Analysis of infrared beamline noise reduction by moving mirrors

Synchrotron oscillations are a major noise source for an infrared (IR) beamline on an electron storage ring. At frequencies below ∼1 kHz, the noise may be reduced by using movable mirrors to stabilize the transverse position and propagation direction of the radiation, but this does not compensate for oscillations of the electron beam current or the radiation opening angle. For the edge-radiation beamline at the Aladdin electron storage ring, the calculated noise contributions from oscillations of the beam current and the emitted radiation's opening angle, horizontal position and horizontal direction of propagation are in the ratio 1:-200:8000:14,000. The estimated noise due to vertical oscillations is an order of magnitude smaller than the contribution from horizontal oscillations. Since transverse oscillations dominate, feedback-controlled mirrors are expected to greatly reduce the beamline's low-frequency noise.