Linear microbunching analysis for recirculation machines

Abstract

Microbunching instability (MBI) has been one of the most challenging issues in designs of magnetic chicanes for short-wavelength free-electron lasers or linear colliders, as well as those of transport lines for recirculating or energy-recovery-linac machines. To quantify MBI for a recirculating machine and for more systematic analyses, we have recently developed a linear Vlasov solver and incorporated relevant collective effects into the code, including the longitudinal space charge, coherent synchrotron radiation, and linac geometric impedances, with extension of the existing formulation to include beam acceleration. In our code, we semianalytically solve the linearized Vlasov equation for microbunching amplification factor for an arbitrary linear lattice. In this study we apply our code to beam line lattices of two comparative isochronous recirculation arcs and one arc lattice preceded by a linac section. The resultant microbunching gain functions and spectral responses are presented, with some results compared to particle tracking simulation by ELEGANT (M. Borland, APS Light Source Note No. LS-287, 2002). These results demonstrate clearly the impact of arc lattice design on the microbunching development. The underlying physics with inclusion of those collective effects is elucidated and the limitation of the existing formulation is also discussed.

Vlasov analysis of microbunching instability for magnetized beams

“…The only difference from those described in Ref. [43] is that the initial conditions for the beam are no longer Twiss parameters but the beam sigma matrix Σ 0 . Diagonalization of the beam sigma matrix, Eqs.…”

“…(54) for density-to-density modulation with inclusion of the above analytical impedance models is detailed in Ref. [43]. The remaining three aspects are similar and we do not repeat them here.…”

Electron Beam Shaping and Its Applications

“…Low emittance flat beams could also serve as a probe for highorder mode auxiliary couplers studies in the ILC-type cryomodule. Additionally, magnetized beams could be injected into IOTA for microbunching supression [127].…”

Mitigation of microbunching instability in x-ray free electron laser linacs

“…The microbunching instability was extensively studied in the past [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. A conventional method to control the instability is to use a laser heater to increase the electron beam uncorrelated energy spread before bunch compression to damp the instability [4,5,15].…”