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Experiments with short single e -bunch using preformed and beam ionized plasma. Retain ability to run short single bunch with pre-ionized plasma. Ken Marsh, Navid Vafaei , Chan Joshi. Optimized density W. Lu. Why is this important?. Can we maximize energy gain?.

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experiments with short single e bunch using preformed and beam ionized plasma

Experiments with short singlee-bunch using preformed and beam ionized plasma

Retain ability to run short single bunch with pre-ionized plasma

Ken Marsh, NavidVafaei, Chan Joshi

why is this important
Why is this important?
  • Can we maximize energy gain?
  • In theory, we should be able to reach transformer ratio > 2
  • Experiments so far TR < 2.
  • What limits TR?
    • Head erosion?
    • Trapped particles?
facet proposal for high energy gain test

Head erosion is likely the most important factor limiting energy gain.

  • Does pre-ionized plasma solve the HE problem?
  • Experimental study: using single electron bunch in the 35 cm lithium oven
  • Example: For 2x1017 cm-3
    • Ez= 110 GeV/m, total gain 40 GeV in 35 cm
    • Eloss= 45GeV/m, total loss 16 GeV in 35 cm

Facet Proposal for High Energy Gain Test

experimental requirements n b n p
Experimental Requirements nb > np
  • Lithium plasma np=2x1017 cm-3
  • 30 um bunch length, 10-30 um bunch radius
  • matched radius = 2 to 4 um
  • Charge 1.8x1010
how does pre ionization affect our most basic diagnostics
How does pre-ionization affect our most basic diagnostics?

Diagnostics

  • Energy spectrometer
    • Can FACET spectrometer measure 60 GeV?
    • Can we see drive beam energy go down to 4 GeV.
  • Energy gain has only a weak dependence on emittance
  • Participating charge? Should strongly increase.
  • X-ray level should increase because more participating charge and longer propagation distance.
concluding remarks
Concluding Remarks
  • We will need
    • High density 30x30x30 electron beam
    • Pre-ionized and beam ionized lithium plasma
    • 200 mj to preionize
example of high tr simulation with ionization trapping
Example of High TR Simulationwith “Ionization Trapping”

Generation of fully loaded transformer ratio wakes of 3 using the FACET II beam. Drive Beam Parameters: Q = 4 nC, σr = 5 μm, σz = 20 μm, εN = 5 mm mrad, E = 10.0 GeV. Trailing Beam Parameters: Q = 0.288 nC, σr = 2 μm, σz = 2 μm, εN = 1.0 mm mrad, E = 100 MeV. Distance between two beams: 93.5 μm. Plasma Density np = 2.0 x 1017 cm-3 (the beam propagates in a pre-ionized plasma). (Courtesy Weiming An)

localized self trapping experiment
Localized Self-Trapping Experiment
  • No Trapping with lithium oven using helium buffer gas
  • Add argon impurity to create a large number of self trapped electrons in a controlled way
  • What bounds the Ar impurity ratio is reduction of TR due to beam loading
  • This experiment needs
    • High density electron beam to ionize Lithium
    • Argon or Neon impurity mixing
mixed gas results in lwfa
Mixed Gas Results in LWFA
  • 4mm injector cell gas cell is compared to 8 mm two stage cell.
    • Two stage: Electron density of 3x1018 cm-3, coupled laser power of 40 TW
    • Injector only: 3.4x1018 cm-3, coupled laser power of 50 TW
    • 0.5% N2 mixed in He in both cases