Summary of Working Sessions by guym13


									Summary of Working
Portovenere Laser and Plasma
    Accelerator Workshop
       October 3, 2003
      Session I -- GUIDING
• 1. Kitagawa Capillary Experiment
  – Observed 100 MeV in empty 60m capillary @ 20
  – Key differences from LOA (no acceleration):
     • Narrower capillary
     • Cone for coupling
  – Suggestions:
     • Diagnose pre-pulse (Zulf)-- Mach-Zender interferometry
       w/ a probe laser (Dino) may show density at edges but
       too low for a fringe shift in center (1016cm-3 x 1cm) at
       visible; THz below cutoff; 10m may be best (from an
     • Try ASE w/o oscillator to study plasma formation (no
       main pulse)
     • Add pre-pulse to PW (some poor or reversed mirror)
        Session I -- GUIDING
• 2. Hollow Channel Production for Afterburner (Dino)
   – Need 70 microns x 7m @ 2e16 cm-3
   – Suggestions:
       • Positron tunnel ionization + laser heating and hydro expansion
         (demonstration idea)
       • Acoustic oscillator in gas prior to ionization -- needs analysis
• 3. Shape of Channels
   – Discussed flat bottom vs. parabolic -- (Kitagawa vs. Silva)
       • either works though some breathing with parabolic-not
         impeding wake
   – Tapering of an ionized capillary input
       • Hybrid of Kitagawa cone --overcomes problems of damage
         from pointing jitter -- simulations needed
      Session I -- GUIDING
• 4. Discharge Channels-- how to reach
  densities below 3e18 cm-3?
  – H desorbed from walls is too much even w/ hi
     • Suggests: new wall materials, He gas, double discharge
  – Longer channels and higher voltages to strike the
    discharge (Nelson)
      Session II -- SOURCES
• 1. Injection in front of laser pulse idea for
  compressing long bunches (Albert)
   – Pondermotive force of laser negligible (Pukhov simulation)
   – Allows at least 10x longer bunch (1 lp long to be accelerated
   – Big question-- beams slips thru defocusing region --
     emittance blowup? needs 2d sim!!
      Session II -- SOURCES
• 2. Matching beams from or into plasma (Luca) --
   – Proton modeling looks like sp. charge is not a problem (e
   – Marnix’ 100fs (DC+RF photo-gun) pulses -- expand over dist
     of 20 cm
   – 50 MeV SMLWF beams -- space charge blows up emittance
     after a cm-- focusing doesn’t save you due to inability to
     match to all slices; energy spread makes it worse.
     Conclusion: need higher energy at plasma exit to preserve
     low (< 3 mm-mrad) e for other uses.
   – 3 Suggestions
       1. Quote #/% rather than #/MeV
       2. Quote emittance after transport rather than at plasma
     exit               3. Quote bunch length after expansion in
     the drift

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