Very high brightness and power LCLS-II hard X-ray pulses

The feasibility of generating X-ray pulses in the 4 – 8   keV fundamental photon energy range with 0.65   TW peak power, 15   fs pulse duration and 9 × 10 − 5 bandwidth using the LCLS-II copper linac and hard X-ray (HXR) undulator is shown. In addition, third-harmonic pulses with 8 – 12   GW peak power and narrow bandwidth are also generated. High-power and small-bandwidth X-rays are obtained using two electron bunches separated by about 1   ns, one to generate a high-power seed signal, the other to amplify it through the process of the HXR undulator tapering. The bunch delay is compensated by delaying the seed pulse with a four-crystal monochromator. The high-power seed leads to higher output power and better spectral properties, with more than 94% of the X-ray power within the near-transform-limited bandwidth. Some of the experiments made possible by X-ray pulses with these characteristics are discussed, such as single-particle imaging and high-field physics.

Source: Journal of Synchrotron Radiation - April 3, 2019 Category: Physics Authors: Halavanau, A. Decker, F.-J. Emma, C. Sheppard, J. Pellegrini, C. Tags: FEL fresh-bunch FEL terawatt FEL research papers Source Type: research