IAP/RAS, Nizhny Novgorod, Russia
We consider superradiance of an extended relativistic electron bunch moving over a periodically corrugated surface for the generation of multi-megawatt terahertz pulses*. To study the above process we have developed a three-dimensional, self-consistent, quasi-optical theory of Cherenkov stimulated emission which includes a description of the formation of evanescent waves near the corrugated surface and its excitation by RF current induced in the electron bunch. Results obtained in the framework of a quasi-optical model were confirmed by direct CST STUDIO PIC simulations. There is a possibility of advancement towards still shorter wavelengths (infrared and optical), which can be achieved by decreasing the period of the diffraction gratings and increasing the density and energy of the particles in the electron bunches. Increase of coupling impedance can be obtained by using inclined incidence of electron bunch on corrugated surface (clinotron configuration).
Ginzburg N.S et al. Phys. Rev. Lett. 2013. V.110, Iss.18. 184801.
LBNL, Berkeley, California, USA
SLAC, Menlo Park, California, USA
RadiaBeam, Santa Monica, California, USA
* P. Emma, et al. PRL 112, 034801
** M. Harrison, et al., NaPAc 2013, Pasadena, USA
SLAC, Menlo Park, California, USA
RadiaBeam Systems, Santa Monica, California, USA
SLAC, Menlo Park, California, USA
RadiaBeam Systems is developing a novel passive chirp removal system using corrugated plates as studied by Bane and Stupakov.* Following on from low-energy experiments at BNL-ATF,** RBS will install a much larger and powerful system for removing the chirp from the 3-GeV beams in the LTU section at LCLS. The larger plates will present new challenges in the areas of manufacturing and mechanical control. In this paper we review the requirements for the dimensions of the corrugated plates for proper operation and the infrastructure necessary for precisely placing the plates so as not to adversely disrupt the beam.
* K. Bane, et al "Corrugated Pipe as a Beam Dechirper," SLAC-PUB-14925, 2012
** Harrison, M., et al "Removal of Residual Chirp in Compressed Beams Using a Passive Wakefield Technique." NaPAC13, 2013
RadiaBeam Systems, Santa Monica, California, USA
BNL, Upton, Long Island, New York, USA
RadiaBeam Systems successfully completed testing of a proof-of-concept corrugated plate dechirper at the Brookhaven National Laboratory Accelerator Test Facility.* Such passive devices should prove indispensable for the efficient operation of future XFEL facilities. These experiments demonstrated a narrowing of the energy spectrum in chirped beam bunches at 57.6 MeV. In this paper, we compare these results with results from Elegant simulations of the BNL-ATF beam. We also compare GdfidL simulations of the wakefield with the analytic results of Bane and Stupakov.**
* Harrison, M., et al "Removal of Residual Chirp in Compressed Beams Using a Passive Wakefield Technique." NaPAC13, 2013
** K. Bane, et al "Corrugated Pipe as a Beam Dechirper," SLAC-PUB-14925, 2012
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.
