Fermilab, Batavia, Illinois, USA
Northern Illinois Univerity, DeKalb, Illinois, USA
Northern Illinois University, DeKalb, Illinois, USA
Sokendai, Ibaraki, Japan
BYU-I, Rexburg, USA
KU, Lawrence, Kansas, USA
The low-energy section of the photoinjector-based electron linear accelerator at the Fermilab Accelerator Science & Technology (FAST) facility was recently commissioned to an energy of 50 MeV. This linear accelerator relies primarily upon pulsed SRF acceleration and an optional bunch compressor to produce a stable beam within a large operational regime in terms of bunch charge, total average charge, bunch length, and beam energy. Various instrumentation was used to characterize fundamental properties of the electron beam including the intensity, stability, emittance, and bunch length. While much of this instrumentation was commissioned in a 20 MeV running period prior, some (including a new Martin-Puplett interferometer) was in development or pending installation at that time. All instrumentation has since been recommissioned over the wide operational range of beam energies up to 50 MeV, intensities up to 4 nC/pulse, and bunch structures from ~1 ps to more than 50 ps in length.
Northern Illinois University, DeKalb, Illinois, USA
Fermilab, Batavia, Illinois, USA
Northern Illinois Univerity, DeKalb, Illinois, USA
Masking a dispersive beamline such as a dogleg or a chicane [1, 2] is a simple way to shape a beam in the longitudinal and transverse space. This technique is often employed to generate arbitrary bunch profiles for beam/laser-driven accelerators and FEL undulators or even to reduce a background noise from dark currents in electron linacs. We have been investigating a beam-modulation of a slit-masked chicane, which was deployed for crystal-channeling experiments at the injector beamline of the Fermilab Accelerator Science and Technology (FAST) facility. With a nominal beam of 3 ps bunch length, Elegant simulations showed that a slit-mask with slit period 900 um and aperture width 300 um induces a modulation with bunch-to-bunch space of about 187 um (0.25 nC), 270 um (1 nC) and 325 um (3.2 nC) with 3 ~ 6% correlated energy spread: An initial energy modulation pattern has been observed in the electron spectrometer downstream of the masked chicane using a micropulse charge of 260 pC and 40 micropulses. Investigations of the beam longitudinal modulation are planned with a Martin-Puplett interferometer and a synchro-scan streak camera at a station between the chicane and spectrometer.
[1] D.C.Nguyen, B.E.Carlsten, NIMA 375, 597 (1996)
[2] P.Muggli, V.Yakimeno, M.Babzien, et al., PRL 101, 054801 (2008)