RF-FREE CHIRP REMOVAL USING LONGITUDINAL WAKEFIELDS

In order to produce short, intense pulses of x-ray light, current- and next-generation light source facilities must compress the electron bunches that feed the free-electron laser using a magnetic chicane. Such compression often results in a residual chirp, which has a detrimental effect on the lasing capabilities of the FEL, such as lowering the output power and widening the bandwidth of the resultant light. Methods exist for removing the chirp from the bunch, either through running RF accelerating cavities off-crest, or by employing wakefields in long sections of beam pipe; however, such techniques are not always available or economical, and they lack the flexibility to adequately attend to varying input conditions. Technical Approach In response to this problem, RadiaBeam proposes to create the first versatile commercial Dechirper system, based on an adjustable-gap corrugated insertion device, ruggedized for high- average-beam-power applications. Tuning the Dechirper by adjusting the gap between the corrugated plates applies a near-linear corrective wakefield of regulated strength across the length of the beam bunch and enables not only a removal of the undesired chirp, but also an unprecedented degree of control over the longitudinal phase space. Phase II progress to date A full-scale prototype Dechirper consisting of two 2-meter long modules was designed, fabricated, and installed in the beamline at the LCLS. The Dechirper system has been commissioned and has demonstrated the dechirping approach for the first time at an active multi-GeV light source. Phase IIB plans Building on the success first prototype’s experimental success, RadiaBeam Systems will design and manufacture a commercial-grade Dechirper system tailored to the demanding needs of superconducting XFELs such as the SLAC LCLS-II. The Dechirper Phase IIB prototype will be equipped with beam position monitoring diagnostics, cost-engineered, and ruggedized for high average current operations. Commercial Applications and Other Benefits The proposed Dechirper will improve XFEL performance by maximizing the achievable X-ray brightness and enabling the generation of longitudinally tailored X-ray beams for specific needs of the Users. The Dechirper system developed in this project will be delivered to the flagship US XFEL facility, LCLS-II, and, upon acceptance, will result in commercial sales of multiple units to this and other XFEL facilities worldwide.