• L. Faillace, R.B. Agustsson, P. Frigola, A.Y. Murokh
  RadiaBeam, Santa Monica
• D. Alesini
  INFN/LNF, Frascati (Roma)
• J.B. Rosenzweig
  UCLA, Los Angeles, California
• V. Yakimenko
  BNL, Upton, Long Island, New York

The quest for detailed information concerning ultra-fast beam configurations, phase spaces and high energy operation is a critical task in the world of linear colliders and X-ray FELs. Huge enhancements in diagnostic resolutions are represented by RF deflectors. In this scenario, Radiabeam Technologies has developed an X-band Travelling wave Deflector (XTD) in order to perform longitudinal characterization of the subpicosecond ultra-relativistic electron beams. The device is optimized to obtain a single digit femtosecond resolution using 100 MeV electron beam parameters at the Accelerator Test Facility (ATF) at Brookhaven National Laboratory; however, the design can be easily extended to be utilized for diagnostics of GeV-class beams. The XTD design fabrication and tuning results will be discussed, as well as installation and commissioning plans at ATF.

* J. England et al., "X-Band Dipole Mode Deflecting Cavity for the UCLA Neptune Beamline".
** D. Alesini, "RF deflector-based sub-ps beam diagnostics: application to FELs and advanced accelerators".

• I. Pogorelsky, M. Babzien, M.N. Polyanskiy, V. Yakimenko
  BNL, Upton, Long Island, New York
• N. Dover, Z. Najmudin, C.A.J. Palmer, J. Schreiber
  Imperial College of Science and Technology, Department of Physics, London
• G. Dudnikova
  UMD, College Park, Maryland
• M. Ispiryan, P. Shkolnikov
  Stony Brook University, StonyBrook

Recent theoretical and experimental studies point to better efficiency of laser-driven ion acceleration when approaching the critical plasma density regime. Simultaneously, this is the condition for observing solitons: "bubble"-like quasi-stationary plasma formations with laser radiation trapped inside. Exploring this regime with ultra-intense solid state lasers is problematic due to the lack of plasma sources and imaging methods at ~10²¹/cc electron density. The terawatt picosecond CO₂ laser operated at Brookhaven's Accelerator Test Facility offers a solution to this problem. At 10 μm laser wavelength, the CO₂ laser shifts the critical plasma density to 10¹⁹/cc which is attainable with gas jets and can be optically probed with visible light. Capitalizing on this approach, we focused a circular-polarized CO₂ laser beam with a₀=0.5 onto a hydrogen gas jet and observed monoenergetic proton beams in the 1 MeV range. Simultaneously, the laser/plasma interaction region has been optically probed with a 2nd harmonic picosecond Nd:YAG laser to reveal stationary soliton-like plasma formations. 2D PIC simulations agree with experimental results and aid in their interpretation.