A Laser Heater Undulator for FLASH2020+

Abstract Space charge induced micro bunch instabilities, amplified in cascaded compression stages, spoil the phase space of compressed bunches and lead to unstable seeding. To “heat” up with an external laser induce uncorrelated energy spread suppresses bunching a short undulator will be installed front first chicane. The has planar hybrid magnet structure 43 mm period length, 11 full periods, 22 minimum gap deflection parameter K 1.52 (K = (eBλ u / (2 πm e c, B - max. magnetic field amplitude, λ length) match 534 nm wavelength at 146 MeV beam energy. paper describes undulator’s compact design, its control system results measurements tuning.