Plasma Wakefield Experiments at ANL and FNAL

A history of significant plasma experiments performed by PBPL personnel

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Proof-of-Principle PWFA

"Experimental Observation of Plasma Wake-field Acceleration'', J.B. Rosenzweig, et al., Phys. Rev. Letters 61, 98 (1988).

• Performed in 1987 at ANL at AATF
• Drive and witness beam configuration
• 1.6 MeV/m acceleration fields
• Transverse deflection of witness beam by driver wake also observed

Witness beam centroid as a function of delay time in proof-of-principle PWFA measurement

First Observation of Nonlinear Plasma Wakefields

"Experimental Measurement of Nonlinear Plasma Wake-fields", J. B. Rosenzweig, et al., Phys. Rev. A - Rapid Comm. 39, 1586 (1989).

• Measurements at AATF
• Wave steepening into sawtooth form
• Wakes persist for 10’s of wavelengths
• Harmonics also observed in transverse deflection wakes

Witness beam centroid as a function of delay time in nonlinear PWFA measurement

Overdense beam self-focusing

"Demonstration of Electron Beam Self-focusing in Plasma Wake-fields'', J.B. Rosenzweig, et al,, Phys. Fluids B 2, 1376 (1990).

• Measurements at AATF
• Thick, overdense lens (n_b<<n_p)
• Bennett equilibrium developed in beam core through nonlinear phase mixing

Time resolved image of beam core showing formation of a Bennnett-like profile in an overdense plasma (top); no plasma case (bottom)

Underdense beam guiding

"Propagation of Short Electron Pulses in a Plasma Ion Chanel" N. Barov, M.E. Conde, W. Gai, and J.B. Rosenzweig, Physical Review Letters. 80, 81 (1998).

• Measurement at ANL AWA facility in 1997
• Underdense plasma (n_b>n_p)
• Guiding shown over 12 times β*
• First step to blow-out regime of PWFA

Time resolved focusing of beam using streak camera at end of plasma, showing guiding in beam core

First measurement of PWFA in the “blowout regime”

N. Barov, J. B. Rosenzweig, M. E. Conde, W. Gai, and J. G. Power “Observation of plasma wakefield acceleration in the underdense regime” Physical Review Special Topics Accelerators and Beams 3 011301 (2000).

• Measurement at ANL AWA facility in 1999
• First creation of witness and drive beams in RF photogun
• Average acceleration of 25 MV/m in 12 cm of 10¹³ cm^-3 plasma, with n_b>2.5n_p

Streak camera trace of drive and witness beams

Image of electron beam after plasma in spectrometer

High gradient PWFA deceleration with compressed beam

• First use of compressed beam in PWFA experiment at FNAL A0 photoinjector (2001)
• Deceleration observed at 150 MeV/m, with beam nearly stopped in plasma

  

  Spectrometer image of beam after 8 cm of plasma

High gradient PWFA acceleration with compressed beam

• Acceleration recently observed at 132 MeV/m
• New experiments with witness beam present

  

  No plasma present, beam

  

  Plasma on, acceleration to 24.3 MeV

Transition trapping injection

M. C. Thompson, J. B. Rosenzweig, H. Suk, “Plasma density transition trapping as a possible high-brightness electron beam source”, Phys. Rev. ST. – Accel. Beams, 7, 011301 (2004)

• Trapping of plasma electrons based on density transition; phase mixing near boundary
• Density tailored to produce very low energy spread injected beam
• Plasma now installed on beamline at FNAL A0

Simulation of beam captured in UCLA/FNAL transition trapping expt.

Plasma source UCLA/FNAL transition trapping expt. (side view)