WEA03
ANL, Argonne, Ilinois, USA
SLAC, Menlo Park, California, USA
An x-ray FEL oscillator (XFELO) will produce hard x-ray pulses of ultra-fine spectral resolution (~ meV) that combines FEL brightness with storage ring stability [1]. Thus, for example, the long-standing problem of high-TC superconductivity could be solved by inelastic x-ray scattering. In addition, an x-ray spectral comb can in principle be generated, vastly expanding the reach of experimental x-ray quantum optics. The accelerator for an XFELO should optimally be of the CW superconducting type. The linac for the European XFEL can be operated in CW mode without adding more cooling capacity if the energy is lowered from 14 to 7 GeV [2]. It is also possible to drive a hard x-ray XFELO at lower than 7 GeV, if a higher harmonic is chosen as the operating wavelength [3]. We have studied XFELO for 1 Å x-rays operating at the third or fifth harmonic using the 4 GeV SCRF linac planned for LCLS-II. Assuming bunch charge=50 pC, normalized rms emittance=0.2 mm-mrad, rms energy spread=500 keV, rms bunch length=190 fs, and undulator period length=2.6 cm, the gain at 1 Å as a 5th harmonic is found to be about 40%, sufficient for lasing allowing for the various losses.
[1] K.-J. Kim, Y. Shvyd’ko, and S. Reiche, Phys. Rev. Lett. 100,244802 (2008)
[2] J.K. Sekutowicz, et al., 2013 FEL Conf.(2013)
[3] J. Dai, H. Deng, and Z. Dai, Phys. Rev. Lett. 108,034802(2012)
ANL, Argonne, Ilinois, USA
Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
ANL, Argonne, Ilinois, USA
Euclid TechLabs, LLC, Solon, Ohio, USA
TUB, Beijing, People's Republic of China
LANL, Los Alamos, New Mexico, USA
A concept is presented for a multi beamline soft x-ray free-electron laser (FEL) facility where several FEL undulator lines are driven by an equal number of high repetition rate single-stage collinear wakefield accelerators (CWA). A practical design of the CWA, extending over 30 meters and embedded into a quadrupole wiggler, is considered. The wiggler’s structure of alternating focusing and defocusing quadrupoles is used to control single-bunch breakup instability. It is shown that practical restrictions on the maximum attainable quadrupole field limit the maximum attainable charge in the drive bunch whose sole purpose is to produce a high accelerating field in the CWA for the following main bunch. It is also pointed out that the distance between drive and main bunches varies along the accelerator, causing a measurable impact on the energy gain by the main bunch and on the energy spread of electrons in it. Means to mitigate these effects are proposed and results are presented for numerical simulations demonstrating the main bunch with plausible parameters for FEL application including a relatively small energy spread. Finally, results are presented for the expected FEL performance using an appropriately chosen undulator.