• A.S. Johnson, H.T. Edwards, T.W. Koeth, A.H. Lumpkin, P. Piot, J. Ruan, J.K. Santucci, Y.-E. Sun, R. Thurman-Keup
  Fermilab, Batavia

Phase space manipulation techniques within two degrees of freedom are foreseen to enhance the performances of next generation accelerators such as high-energy physics colliders and accelerator based light sources. At the Fermilab A0 photoinjector, a proof-of-principle experiment to demonstrate the exchange of the transverse and longitudinal emittances is ongoing. The emittance exchange beamline consists of a 3.9 GHz normal conducting deflecting mode cavity flanked by two doglegs. Electron bunches with charges of 250 pC and energy of 14.3 MeV are routinely sent through the exchanger. In this paper, we report our latest results on the demonstration of emittance exchange obtained with significantly improved beam diagnostics. We also compare our experimental results with a simple numerical model.

• C.R. Prokop, P. Piot
  Northern Illinois University, DeKalb, Illinois
• M.C. Lin, P. Stoltz
  Tech-X, Boulder, Colorado

Terahertz (THz) radiation has generated much recent interest due to its ability to penetrate deep into many organic materials without the damage associated with ionizing radiations. The generation of copious amounts of narrow-band THz radiation using a Smith-Purcell FEL operating as a backward wave oscillator is being pursued by several groups. In this paper we present start-to-end simulations of a Smith-Purcell FEL operating in the superradiant regime. Our concept incorporates a double grating configuration to efficiently bunch the electron beam, followed by a single grating to produce Smith-Purcell radiation. We demonstrate the capabilities and performances of the device, including initial beam properties (emittance and energy spread), with the help of numerical simulations using the conformal finite-difference time-domain electromagnetic solver VORPAL.

• Y.-E. Sun, A.S. Johnson, A.H. Lumpkin, J. Ruan, R. Thurman-Keup
  Fermilab, Batavia
• P. Piot
  Northern Illinois University, DeKalb, Illinois

We report our experimental demonstration of longitudinal phase space modulation using transverse-to-longitudinal emittance exchange technique. The experiment is carried out at the A0 photoinjector at Fermi National Accelerator Lab. A vertical multi-slit plate is inserted into the beamline prior to the emittance exchange, thus introducing beam horizontal profile modulation. After the emittance exchange, the longitudinal phase space coordinates (energy and time structures) of the beam are modulated accordingly. This is a clear demonstration of the transverse-to-longitudinal phase space exchange. In this paper, we present our experimental results on the measurement of energy and time profile of the electron beam, as well as numerical simulations of the experiment.

• Y.-E. Sun, M.D. Church
  Fermilab, Batavia
• P. Piot
  Northern Illinois University, DeKalb, Illinois

Fermilab is currently constructing a superconducting RF (SRF) test linear accelerator at the New Muon Lab (NML). Besides testing SRF accelerating modules for ILC and Project-X, NML will also eventually support a variety of advanced accelerator R&D experiments. The NML incorporates a 40 MeV photoinjector capable of providing electron bunches with variable parameters. The photoinjector is based on the 1+1/2 cell DESY-type gun followed by two superconducting cavities. It also includes a magnetic bunch compressor, a round-to-flat beam transformer and a low-energy experimental area for beam physics experiments and beam diagnostics R&D. In this paper, we explore, via beam dynamics simulations, the performance of the photoinjector for different operating scenarios.