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GeV Wakefield Acceleration

 

History of Project

Plasma-based acceleration of particle beams has been demonstrated in several experiments around the world. These have demonstrated proof-of-principle of high-gradient acceleration in laser-driven plasma wakefields, with electrons accelerated to 100 MeV energies over millimeter distances. Experiment E-157 Conventional accelerator technique reached its limitation in cost and size to pull up to higher energies. In order to design future multi-GeV accelerator applications, it is essential to demonstrate an acceleration in an extended plasma. To meet this purpose, Plasma Wakefield Accelerator (PWFA) experiment E-157 was proposed in 1997 to Department of Energy (DOE) with collaboration of LBNL, SLAC, UCLA and USC. Experiment started from June 1999 and is continuing.

1.4 meter long Lithium Plasma oven was built and tested in UCLA. And this oven is placed in SLAC FFTB beam line to accelerate a 30 GeV SLC beam up to 1 GeV.

 

Relevant Theory

As an electron beam propagates through plasmas, electrons of plasma are rushed out by the space charge of an electron beam. Especially, in underdense regime when beam density is much higher than plasma density, the head of the beam blows out all of the plasma electrons in the beam path leaving heavier ions. This uniform ion column exerts focusing force to the beam. These plasma electrons are relaxed back after a plasma period. This density compression/rarefaction of plasma electrons exerts wake field which can be used to accelerate the particles.

 

Simulation Results

 

Recent Results

E-157: A Plasma Wakefield Acceleration Experiment

 

Work in Progress

Experiment started in May 1999. Each run of experiment usually goes for about one month.
Run 1: June 1999
Run 2: July 1999
Run 3: August-September 1999
Run 4: October 1999
Run 5: May 2000

As we started the experiment, we could explore the rich physics. While the beam is propagating in the 1.4 meter-long plasma oven, the beam undergoes betatron oscillation by large focusing forces. To understand and demonstrate longitudinal acceleration of particles, transverse beam dynamics need to be studied in detail. Results from Run 1 through 4 lead us to explore transverse beam behavior.

In addition to this plasma lensing effect, we've observed that the particle beam could be steered or bent by an asymmetric focusing force when the beam is misaligned from the plasma central axis.

After runs of 1999, we studied and analyzed data and now we are ready both in experimental and theoretical respects for May 2000 run 5! Progress and results will be announced soon!!

 

Future Work

A proposal has been submitted to the SLAC Physics Advisory Counsel. The proposal is to investigate beam propagation, wakefield excitation, and acceleration of positrons. If approved, the experiment will be known as E-162 and performed in 2001.

 

PowerPoint Presentations

On the Possibility of a 100 GeV+100 GeV Collider Based on Plasma Afterburners (2.86 MB)

 

References

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