• J.G. Power, M.E. Conde, W. Gai, W. Liu
  ANL, Argonne
• P. Piot
  Northern Illinois University, DeKalb, Illinois

Funding: The work is supported by the U.S. Department of Energy under Contract No. DE-AC02-06CH11357 with Argonne National Laboratory.

Phase space measurements of RF photoinjectors have usually been done with multislit masks or scanning slits. These systems implicitly ignore the correlations between the X and Y planes and thus yield measurements of the projected 2D phase space distributions. In contrast, a grid-patterned pepper-pot is capable of measuring the full 4D transverse phase space distribution, f(x,x',y,y'). 4D measurements allow precise tuning of electron beams with large canonical angular momentum, important for electron cooling and flat beam transformation, as well as zeroing the magnetic field on the photocathode is zero for ultra low emittance applications (e.g. SASE FEL, ERL FEL). In this talk, we report on a parametric set of measurements to characterize the 4D transverse phase space of the 1 nC electron beam from the Argonne Wakefield Accelerator (AWA) RF photoinjector. The diagnostic is simulated with TStep, including the passage of the electron beam trough the mask and tracking of the beamlets to the imaging screen. The phase space retrieval algorithm is then bench marked against simulations and measurements.

• M.M. Rihaoui, P. Piot
  Northern Illinois University, DeKalb, Illinois
• W. Gai, J.G. Power
  ANL, Argonne

Funding: M.R. and P.P. was supported by the US DOE under Contracts No. DE-FG02-08ER41532 with NIU. W.G. and J.P are supported by the U.S. DOE under Contract No. DE-AC02-06CH11357 with ANL.

Transverse to longitudinal phase space manipulation hold great promises, e.g., as a potential technique for repartitioning the emittances of a beam. A proof-of-principle experiment to demonstrate the exchange of a low longitudinal emittance with a larger transverse emittance is in preparation at the Argonne Wakefield Accelerator using a 15 MeV electron beam. In this paper we explore the limiting effects of this phase space manipulation method associated to high order optics and collective effects. A realistic start-to-end simulation of the planned proof-of-principle experiment including jitter studies is also presented.

• T.J. Maxwell, P. Piot
  Northern Illinois University, DeKalb, Illinois
• T.J. Maxwell
  Fermilab, Batavia

Funding: Supported by U.S. Department of Energy, under Contract DE-FG02-06ER41435 with Northern Illinois University and by the Fermi Research Alliance, LLC under Contract DE-AC02-07CH11359 with the U.S. D.O.E.

Designs for developing TeV-range electron-positron linear colliders include a non-zero crossing angle colliding scheme at the interaction point to mitigate instabilities and possible background. Maximizing the luminosity when operating with non-zero crossing angles requires the use of "crab" cavities to impart a well-defined spatio-temporal correlation. In this paper we propose a novel non-interceptive diagnostic capable of measuring and monitoring the spatio-temporal correlation, i.e. the transverse position of sub-picosecond time slices, within bunch. An analysis of the proposed scheme, its spatio-temporal resolution and its limitations are quantified. Finally, the design of a proof-of-principle experiment in preparation for the Fermilab's A0 photoinjector is presented.

• P. Piot, A. Bracke, V. Demir, T.J. Maxwell, M.M. Rihaoui
  Northern Illinois University, DeKalb, Illinois
• C.-J. Jing
  Euclid TechLabs, LLC, Solon, Ohio
• J.G. Power
  ANL, Argonne

Funding: This work is supported by the U.S. Department of Energy under contract no. DE-FG02-06ER41435 with Northern Illinois University.

We present a diagnostics suite and analyze techniques for setting up the longitudinal beam dynamics in ILC e^- injectors and e⁺ and e^- bunch compressors. Techniques to measure the first order moments and recover the first order longitudinal transfer map of the injector's intricate bunching scheme are presented. Coherent transition radiation diagnostics needed to measure and monitor the bunch length downstream of the ~5 GeV bunch compressor are investigated using a vector diffraction model.

• M.M. Rihaoui, D. Mihalcea, P. Piot
  Northern Illinois University, DeKalb, Illinois
• W. Gai, J.G. Power
  ANL, Argonne

A transverse-to-longitudinal emittance exchange experiment is in preparation at the Argonne Wakefield Accelerator (AWA). The experiment aims at exchanging a low (< 5 mm-mrad) longitudinal emittance with a large (>15 mm-mrad) transverse horizontal emittance for a bunch charge of 100 pC. Achieving such emittance partitioning, though demonstrated via numerical simulations, is a challenging task and need to be experimentally verified. In this paper, we report emittance measurements of the beam in the transverse and longitudinal planes performed at 12 MeV. The measurements are compared with numerical simulations using Impact-T.

• M.M. Rihaoui, P. Piot
  Northern Illinois University, DeKalb, Illinois
• W. Gai, J.G. Power, Z.M. Yusof
  ANL, Argonne

Funding: M.R. and P.P. was supported by the US DOE under Contracts No. DE-FG02-08ER41532 with NIU. W.G., J.P., and Z.Y. are supported by the U.S. DOE under Contract No. DE-AC02-06CH11357 with ANL.

We report on a new experimental study of the space charge effect in a space-charge-dominated multi-beam electron bunch. A 5 MeV electron bunch, consisting of a variable number of beamlets separated transversely, was generated in a photoinjector and propagated in a drift space. The collective interaction of these beamlets was studied for different experimental conditions. The experiment allowed the exploration of space charge effects and its comparison with three-dimensional particle-in-cell simulations. Our observations also suggest the possible use of a multi-beam configuration to tailor the transverse distribution of an electron beam.