INFN/LNF, Frascati (Roma)
Istituto Nazionale di Fisica Nucleare, Milano
Università di Roma II Tor Vergata, Roma
ENEA C.R. Frascati, Frascati (Roma)
INFN-Roma II, Roma
UCLA, Los Angeles, California
INFN-Roma, Roma
The optimization of the beam brightness is one of the main objectives of the research and development efforts in rf-photoinjectors devoted to short wavelength FELs. The velocity bunching experiment at SPARC has recently demonstrated the possibility of increasing the beam current via RF compression at low energies, while compensating the self-fields induced emittance degradation by means of continuous magnetic focusing. The result is an increase of the beam brightness by about one order of magnitude. Stable compression ratio up to a factor 12 has been observed. Characterization of longitudinal phase spaces an measure of projected and slice emittances, as a function of the injection phase in the first accelerating structure and for different solenoids field values are presented. Comparisons with simulations are also reported.
Diamond, Oxfordshire
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
LBNL, Berkeley, California
The New Light Source (NLS) project was launched in April 2008 by the UK Science and Technology Facilities Council (STFC) to consider the scientific case and develop a conceptual design for a possible next generation light source based on a combination of advanced conventional laser and free-electron laser sources. In this paper we present the results of the optimisation of a single pass superconducting LINAC as a driver for the the NLS FELs. The optimisation process requires the analysis of complicated electron beam dynamics in the presence of CSR, wakefields and space charge and has specifically taken into account the requirements for FEL operation in a seeded harmonic cascade scheme.
UCLA, Los Angeles, California
Recent observation of coherent optical transition radiation in FEL injectors has provoked considerable theoretical activity. As this phenomena is provoked by microbunching at or near the level of the mean interparticle spacing in the beam, any description of it should resolve the beam at the particle level. Here we present first simulations that fulfill this requirement, based on a three-dimensional code in which fields are found in the beam frame using Fourier methods. The simulations take into account acceleration, which serves to freeze relative longitudinal motion, transverse focusing, and downstream bending motion. Comparisons are made between code predictions and experimental results, as well as with theoretical models.
FZD, Dresden
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Elektronen-Speicherring BESSY II, Berlin
MBI, Berlin
More and more electron accelerator projects for FELs, ERLs or 4th generation light sources require “super” electron beam with high brightness, low emittance, and high average current. Under this background, much attention is paid on the research and development of new electron sources. Superconducting RF photoinjector was designed within a collaboration of BESSY, DESY, FZD, and MBI to improve the beam quality for ELBE IR-FEL users, and at the same time to test this kind of promising injector concept. The main design parameters of this gun are the final electron energy of 9.5 MeV, 1 mA average current, and transverse normalized emittances (rms) of 1 mm mrad at 77 pC and 2.5 mm mrad at 1 nC bunch charge. In this paper the results of the RF and beam parameter measurements with Cs2Te photo cathodes will be presented, and the experience for the gun running gained at the first experiments will be concluded, including the life time and compatibility of the normal conducting photocathode in SC cavity, the coupling of high average power into the gun, and the excitation of higher-order modes in the cavity.