arXiv subjects

Paul Emma

Publications and source records attributed to Paul Emma.

3 recordsLinked to original sources

arXiv2015

Tapering studies for Terawatt level X-ray FELs with a superconducting undulator

We study the tapering optimization scheme for a short period, less than two cm, superconducting undulator, and show that it can generate 4 keV X-ray pulses with peak power in excess of 1 terawatt, using LCLS electron beam parameters. We study the effect of undulator module length relative to the FEL gain length for continous and step-wise taper profiles. For the optimal section length of 1.5m we study the evolution of the FEL process for two different superconducting technologies NbTi and Nb3Sn. We discuss the major factors limiting the maximum output power, particle detrapping around the saturation location and time dependent detrapping due to generation and amplification of sideband modes.

physics.acc-ph↗

arXiv2010

Toward a single mode Free Electron Laser for coherent hard x-ray experiments

The fluctuations of the longitudinal coherence length expected from the world's first hard X-ray Free Electron Laser, the Linac Coherent Light Source, are investigated. We analyze, on a shot-to-shot basis, series of power spectra generated from 1D-FEL simulations. We evaluate how the intrinsic noise in the spectral profile of the X-ray beam reflects on its longitudinal coherence length. We show that the spectral stability of the LCLS beam will allow coherent X-ray experiments with a reasonable acquisition time. We also propose a scheme to deliver single-mode X-ray radiation using a narrow bandpass monochromator.

physics.ins-det↗

arXiv2006

Optical Klystron Enhancement to SASE X-ray FELs

The optical klystron enhancement to self-amplified spontaneous emission (SASE) free electron lasers (FELs) is studied in theory and in simulations. In contrast to a seeded FEL, the optical klystron gain in a SASE FEL is not sensitive to any phase mismatch between the radiation and the microbunched electron beam. The FEL performance with the addition of four optical klystrons located at the undulator long breaks in the Linac Coherent Light Source (LCLS) shows significant improvement if the uncorrelated energy spread at the undulator entrance can be controlled to a very small level. In addition, FEL saturation at shorter x-ray wavelengths (around 1.0 Å) within the LCLS undulator length becomes possible. We also discuss the application of the optical klystron in a compact x-ray FEL design that employs relatively low electron beam energy together with a short-period undulator.

physics.acc-ph↗