Shin, Y.-M. Broemmelsiek, D.R. Crawford, D.J. Edstrom, D.R. Green, A.T. Lumpkin, A.H. Ruan, J. Santucci, J.K. Thangaraj, J.C.T. Thurman-Keup, R.M. JACoW Geneva, Switzerland 978-3-95450-180-9 10.18429/JACoW-NAPAC2016-TUPOB18 English 528-531 TUPOB18 ion simulation electron bunching controls Contribution to a conference proceedings 2017 2017-01 http://dx.doi.org/10.18429/JACoW-NAPAC2016-TUPOB18 https://jacow.org/napac2016/papers/tupob18.pdf 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.