Aberration corrected emittance exchange

Abstract

Full exploitation of emittance exchange (EEX) requires aberration-free performance of a complex imaging system including active radio-frequency (rf) elements which can add temporal distortions. We investigate the performance of an EEX line where the exchange occurs between two dimensions with normalized emittances which differ by multiple orders of magnitude. The transverse emittance is exchanged into the longitudinal dimension using a double dogleg emittance exchange setup with a five cell rf deflector cavity. Aberration correction is performed on the four most dominant aberrations. These include temporal aberrations that are corrected with higher order magnetic optical elements located where longitudinal and transverse emittance are coupled. We demonstrate aberration-free performance of an EEX line with emittances differing by four orders of magnitude, i.e., an initial transverse emittance of 1 pm-rad is exchanged with a longitudinal emittance of 10 nm-rad.

Tailoring of an electron-bunch current distribution via space-to-time mapping of a transversely shaped, photoemission-laser pulse

“…Additionally, the formation of smaller, e.g. sub-optical-scale, structures is ultimately limited by optical aberrations in the TLEX beamline 21 . It should however be pointed out that the spectral content achieved in the presented simple proof-of-principle experiment could be of interest, with minor improvements, to produce prebunched beams necessary for the generation of tunable coherent THz undulator radiation such as foreseen in pump-probe experiments planned at X-ray user facilities 22 .…”

Nanomodulated electron beams via electron diffraction and emittance exchange for coherent x-ray generation

“…In [34] an aberration corrected geometry for the EEX line was found to have a transfer matrix with aberration-free performance with emittances differing by four orders of magnitude between the beamlet produced by each grating period and the longitudinal bunch. The aberration corrected geometry required the addition of only three sextupoles and one octupole.…”

“…The transverse modulation of either beam undergoes demagnification which can be varied and then is imaged into the longitudinal dimension via EEX. We have recently shown [34] that emittances with ratios as high as 10 4 between longitudinal and transverse dimensions can be fully exchanged. If both beams are imaged without aberrations the modulation would disappear.…”

“…where ζ is the longitudinal dispersion, η is the horizontal dispersion, and L is the drift length [34]. This transfer matrix will transfer the modulation from the transverse dimension into the longitudinal dimension.…”

“…After interacting with the Si grating the forward scattered beam is accelerated in a short x-band linac from 7 MeV to 22.5 MeV. The accelerator is described in [35] and the arrangement of the EEX line is given in [34,36]. The imaging quadrupole lenses are set up as a telescope that demagnifies the beam by a factor of 1=14, and then the EEX line further demagnifies by a factor of 1=6.…”