Low-Level Radio Frequency (LLRF) Control


We use Low-level Radio Frequency (LLRF) to provide control over our accelerator beamlines. The high power sources that drive electromagnetic fields inside accelerating cavities must be precisely controlled against noise perturbation for best beam quality. To do this, the LLRF controller measures the magnitude and phase of a sample of the cavity field, and feeds back to the high power RF amplifier in hard real time. Typical feedback loop response times are 0.5 to 2.0 microseconds.

We are pioneers of implementing fully digital LLRF/RF controls. Achieving <0.02 degrees of stability at 2856 MHz, we have applied this technology to the timing distribution system in the latest FEL (free electron laser) facilities, synchronizing remote lasers and RF references with combined jitter and long-term drift as low as 20 femtoseconds rms.