Experiment on Suppression of Spontaneous Undulator Radiation at Atf

There are several advantages in strongly suppressing shot noise in the electron beam, and the corresponding spontaneous radiation. The self-amplified spontaneous (SASE) emission originating from shot noise in the electron beam is the main source of noise in high-gain FEL amplifiers. It may negatively affect several HG FEL applications ranging from singleto multi-stage HGHG FELs [1]. SASE saturation also imposes a fundamental hard limit on the gain of an FEL amplifier in a coherent electron-cooling scheme [2]. A novel active method for suppressing shot noise in relativistic electron beams by many orders-of-magnitude was recently proposed [3]. While theoretically such strong suppression appears feasible, the performance and applicability of this novel method must be evaluated experimentally. Several practical questions about the proposed noise suppressor, such as 3D effects and/or sensitivity to the e-beam parameters also require experimental clarification. To do this, we propose here a proof-of-principle experiment using elements of the VISA FEL at BNL’s Accelerator Test Facility. SHOT-NOISE SUPPRESSOR