Design study of a transverse-to-longitudinal emittance exchange proof-of-principle experiment
Transverse-to-longitudinal emittance exchange can be achieved through certain arrangements of dipole magnets and a dipole mode rf cavity. Theory on such schemes has been developed in the past several years. In this paper we report our numerical simulations to optimize a low energy (E sime 15 MeV) proof-of-principle experiment planned at the Argonne Wakefield Accelerator (AWA). Parametric studies of the dipole magnets and cavity strengths, as well as initial beam parameters, are presented.
A 3-cell deflecting rf cavity for emittance exchange experiment at ANL.
Abstract An RF deflecting structure has been designed and fabricated for a transverse-to-longitudinal emittance exchange experiment at Argonne National Laboratory (ANL) [Y.-E. Sun, et al., Design study of a transverse-to-longitudinal emittance exchange proof-of-principle experiment, in: Proceedings of PAC-2007, Albuquerque, NM, USA, 2007, pp. 3441–3443 [1] ]. The structure is a 1300 MHz normal conducting RF cavity consisting of three cells operating in a dipole ( TM 110 -like) mode. As high as 3.4 MV deflecting voltage is required for the experiment. In this paper, we present detailed RF design of the cavity, particle tracking simulations in the cavity and low power RF measurement results in comparison with numerical simulations. The cavity cell geometries (gaps in particular) are optimized to giving a zero orbit offset for particles crossing the cavity with zero-phase.
Beam Conditioning for Free Electron Lasers:Consequences and Methods
The consequences of beam conditioning in four example cases [VISA, a soft x-ray free-electron laser (FEL), LCLS, and a 'Greenfield' FEL] are examined. It is shown that in emittance limited cases, proper conditioning reduces sensitivity to the transverse emittance and, furthermore, allows for stronger focusing in the undulator. Simulations show higher saturation power, with gain lengths reduced by a factor of 2 or more. The beam dynamics in a general conditioning system are studied, with 'matching conditions' derived for achieving conditioning without growth in the effective emittance. Various conditioning lattices are considered, and expressions derived for the amount of conditioning provided in each case when the matching conditions are satisfied. These results show that there is no fundamental obstacle to producing beam conditioning, and that the problem can be reduced to one of proper lattice design. Nevertheless, beam conditioning will not be easy to implement in practice.