• G. Andonian, S. Boucher, A.Y. Murokh, M. Ruelas
  RadiaBeam, Marina del Rey
• D. Dooley, S. Levingston, M. Stout
  Spectrum Detector, Lake Oswego, Oregon
• U. Happek
  UGA, Athens, Georgia
• G. Travish
  UCLA, Los Angeles, California

Funding: Work supported by U.S. DOE Grant Number DE-FG02-07ER84814.

The generation of high peak current, high brightness beams routinely requires compression methods (e.g. four-bend chicane), which produce coherent radiation as a by-product. The sensing of this radiation, coupled with interferometric methods, yields crucial longitudinal bunch length and bunch profile information. This paper discusses the progress of the development of a real-time terahertz interferometer used for longitudinal beam profile diagnosis.

• R. Tikhoplav, G. Travish
  UCLA, Los Angeles, California
• G. Andonian, A.Y. Murokh, M. Ruelas
  RadiaBeam, Marina del Rey
• T.V. Shaftan, V. Solovyov
  BNL, Upton, Long Island, New York

Funding: NSF grant # IIP-0724505

We describe our effort in the development of a low cost, wide-band detector/camera for generation of spatially resolved images of radiation beams in a multi-spectral range of wavelengths, from IR (infrared) to THz (terahertz). The detector (T-camera) utilizes a TLC (thermochromic liquid crystal) film as the sensitive element in a temperature controlled chamber and a CCD detector array and can be used as a powerful diagnostic for terahertz sources such as a synchrotron or an FEL

• G. Andonian, M. Ruelas
  RadiaBeam, Marina del Rey
• S. Reiche
  UCLA, Los Angeles, California

The accelerator community has many codes that model beams and emitted radiation. Many of these codes are specialized and often, as in start-to-end simulations, multiple codes are employed in subsequent fashion. One of the most important goals of simulations is to accurately model beam parameters and compare results to those obtained from real laboratory diagnostics. This paper describes the development of a user-friendly code that models the coherent radiation of high brightness beams, with a heavy emphasis on simulation of observables via laboratory diagnostics.

• M. Ferrario, D. Alesini, M. Bellaveglia, R. Boni, M. Boscolo, M. Castellano, E. Chiadroni, L. Cultrera, G. Di Pirro, L. Ficcadenti, D. Filippetto, V. Fusco, A. Gallo, G. Gatti, C. Marrelli, M. Migliorati, A. Mostacci, E. Pace, L. Palumbo, B. Spataro, C. Vaccarezza, C. Vicario
  INFN/LNF, Frascati (Roma)
• G. Andonian, G. Marcus, J.B. Rosenzweig
  UCLA, Los Angeles, California
• A. Bacci, V. Petrillo, A.R. Rossi, L. Serafini
  Istituto Nazionale di Fisica Nucleare, Milano
• A. Cianchi, B. Marchetti
  INFN-Roma II, Roma
• L. Giannessi, M. Labat, M. Quattromini, C. Ronsivalle
  ENEA C.R. Frascati, Frascati (Roma)
• M. Rezvani Jalal
  University of Tehran, Tehran
• M. Serluca
  INFN-Roma, Roma

One of the main goals of the SPARC high brightness photoinjector is the experimental demonstration of the emittance compensation process while compressing the beam with the velocity bunching technique, also named RF compressor. For this reason, the first two S-band travelling wave accelerating structures downstream of the RF gun are embedded in a long solenoid, in order to control the space charge induced emittace oscillations during the compression process. An RF deflecting cavity placed at the exit of the third accelerating structure allows bunch length measurements with a resolution of 50 μm. During the current SPARC run a parametric experimental study of the velocity bunching technique has been performed. The beam bunch length and projected emittance have been measured at 120 MeV as a function of the injection phase in the first linac, and for different solenoid field values. In this paper we describe the experimental layout and the results obtained thus far. Comparisons with simulations are also reported.

• M.P. Dunning, G. Andonian, A.M. Cook, E. Hemsing, A.Y. Murokh, S. Reiche, J.B. Rosenzweig, D. Schiller
  UCLA, Los Angeles, California
• M. Babzien, K. Kusche, V. Yakimenko
  BNL, Upton, Long Island, New York

Coherent radiation emitted by relativistic electron bunches traversing the edge regions of dipole magnets in a chicane bunch compressor was extracted and transported for measurement, using a dedicated terahertz beamline at the Accelerator Test Facility (ATF) at Brookhaven National Laboratory (BNL). Measurements include frequency spectrum and polarization of the radiation. The measurements are compared to predictions from QUINDI, a new simulation code developed at UCLA to model radiation emitted by charged particles in bending systems. Simulations and measurements indicate that because of interference of radiation from the two magnet edges, the edge radiation is suppressed at long wavelengths. In addition to being a source of broadband terahertz radiation, the system is also used as a non-invasive, single-shot, relative bunch length diagnostic to monitor compression in the chicane.

• O. Williams, G. Andonian, E. Hemsing, J.B. Rosenzweig
  UCLA, Los Angeles, California
• M. Babzien, K. Kusche, J.H. Park, I. Pogorelsky, V. Yakimenko
  BNL, Upton, Long Island, New York

It is possible to obtain spectral and angular information of inverse Compton sources using only an x-ray imaging device and various foils with K-edges in the many keV energy range. Beam parameters are chosen such that on-axis photons are above the K-edge for a given material, where absorption is strong and there is relatively zero transmission. Photons observed off-axis are red-shifted and fall below the K-edge, therefore being transmitted and creating a “donut” pattern, or "lobes" in the ideal case for a circularly or linearly polarized laser, respectively. We present simulation and experimental results of the double differential spectrum (DDS) for angle and energy of Compton photons generated at the BNL ATF.

• G. Marcus, G. Andonian, A. Fukasawa, P. Musumeci, S. Reiche, J.B. Rosenzweig
  UCLA, Los Angeles, California
• M. Ferrario, L. Palumbo
  INFN/LNF, Frascati (Roma)
• L. Giannessi
  ENEA C.R. Frascati, Frascati (Roma)

It has been suggested that an ultra-short, very low charge beam be used to drive short wavelength single-spike operation at the SPARC FEL. This paper explores the development and construction of a longitudinal diagnostic capable of completely characterizing the radiation based on the Frequency-Resolved Optical Gating (FROG) technique. In particular, this paper explores a new geometry based on a Transient-Grating (TG) nonlinear interaction and includes studies of start to end simulations for pulses at the SPARC facility using GENESIS and reconstructed using the FROG algorithm. The experimental design, construction and initial testing of the diagnostic are also discussed.