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Title: Wakefield accelerators

Abstract

The search for new methods to accelerate particle beams to high energy using high gradients has resulted in a number of candidate schemes. One of these, wakefield acceleration, has been the subject of considerable R D in recent years. This effort has resulted in successful proof of principle experiments and in increased understanding of many of the practical aspects of the technique. Some wakefield basics plus the status of existing and proposed experimental work is discussed, along with speculations on the future of wake field acceleration. 10 refs., 6 figs.

Authors:
Publication Date:
Research Org.:
Argonne National Lab., IL (USA)
Sponsoring Org.:
DOE/ER
OSTI Identifier:
6241351
Report Number(s):
ANL-HEP-CP-90-81; CONF-9009123-52
ON: DE91004479; TRN: 90-037550
DOE Contract Number:
W-31109-ENG-38
Resource Type:
Conference
Resource Relation:
Conference: Linear accelerator conference, Albuquerque, NM (USA), 9-14 Sep 1990
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; WAKEFIELD ACCELERATORS; DESIGN; BEAM BUNCHING; BEAM DYNAMICS; ACCELERATORS; 430100* - Particle Accelerators- Design, Development, & Operation

Citation Formats

Simpson, J.D.. Wakefield accelerators. United States: N. p., 1990. Web.
Simpson, J.D.. Wakefield accelerators. United States.
Simpson, J.D.. Mon . "Wakefield accelerators". United States. doi:. https://www.osti.gov/servlets/purl/6241351.
@article{osti_6241351,
title = {Wakefield accelerators},
author = {Simpson, J.D.},
abstractNote = {The search for new methods to accelerate particle beams to high energy using high gradients has resulted in a number of candidate schemes. One of these, wakefield acceleration, has been the subject of considerable R D in recent years. This effort has resulted in successful proof of principle experiments and in increased understanding of many of the practical aspects of the technique. Some wakefield basics plus the status of existing and proposed experimental work is discussed, along with speculations on the future of wake field acceleration. 10 refs., 6 figs.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 1990},
month = {Mon Jan 01 00:00:00 EST 1990}
}

Conference:
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  • There has recently been a study of the potential uses of multimode dielectric structures for wakefield acceleration [1]. This technique is based on adjusting the wakefield modes of the structure to constructively interfere at certain delays with respect to the drive bunch, thus providing an accelerating gradient enhancement over single mode devices. In this report we examine and attempt to clarify the issues raised by this work in the light of the present state of the art in wakefield acceleration.
  • Plasma wakefields produced by a sub-picosecond, high intensity laser pulse in a dense gas jet can accelerate plasma electrons to high energies. The acceleration is believed to be a two stage process in which plasma electrons are accelerated to moderate energies by a low phase velocity wave and then trapped and accelerated by the high phase velocity (v{sub p} {approximately} c), large amplitude wakefield. The laser wakefield accelerator (LFWA) experiment at the Naval Research Laboratory has produced up to 30 MeV electrons with no external injector when operating in the self-modulated regime. The low phase velocity wave in this casemore » could arise from the beating of the laser pump pulse with a wave arising from the backward Raman instability. This interpretation is supported by a numerical model which follows the motion of plasma electrons in analytically-prescribed fields corresponding to the laser pump pulse, the forward-going wakefield, and the Raman waves. The accelerated electrons have a large energy spread and are trapped in several bunches. Esarey, et al. have proposed a scheme which would operate in the standard LWFA regime and employs three collinear laser pulses: the large amplitude pump pulse, a lower amplitude follower pulse at the same frequency, and a counterstreaming colliding pulse at a slightly lower frequency. The interaction between the follower pulse and the colliding pulse produces the first stage of acceleration. The numerical model predicts that if the delay between the pump and follower pulses is optimized, a single short pulse bunch of accelerated plasma electrons with {approximately} 20--30% energy spread can be produced. Even if there is no guiding of the laser pulse, the model predicts that the beam energy can be tens of MeV with a bunch length of tens of femtoseconds.« less
  • We present 2-D particle-in-cell simulations of both beam-driven and laser-driven plasma wakefield accelerators, using the object-oriented code XOOPIC, which is time explicit, fully electromagnetic, and capable of running on massively parallel supercomputers. Simulations of laser-driven wakefields with low ({approximately} 10{sup 16} W/cm{sup 2}) and high ({approximately} 10{sup 18} W/cm{sup 2}) peak intensity laser pulses are conducted in slab geometry, showing agreement with theory. Simulations of the E-157 beam wakefield experiment at the Stanford Linear Accelerator Center, in which a 30 GeV electron beam passes through 1 m of preionized lithium plasma, are conducted in cylindrical geometry, obtaining good agreement withmore » previous work. We briefly describe some of the more significant modifications to XOOPIC required by this work, and summarize the issues relevant to modeling electron-neutral collisions in a particle-in-cell code.« less
  • A 10 Hz, 10 TW solid state laser system has been used to produce electron beams suitable for radio-isotope production. The laser beam was focused using a 30 cm focal length f/6 off-axis parabola on a gas plume produced by a high pressure pulsed gas jet. Electrons were trapped and accelerated by high gradient wakefields excited in the ionized gas through the self-modulated laser wakefield instability. The electron beam was measured to contain excesses of 5 nC/bunch. A composite Pb/Cu target was used to convert the electron beam into gamma rays which subsequently produced radio-isotopes through (gamma, n) reactions. Isotopemore » identification through gamma-ray spectroscopy and half-life time measurements demonstrated that Cu{sup 61} was produced which indicates that 20-25 MeV gamma rays were produced, and hence electrons with energies greater than 25-30 MeV. The production of high energy electrons was independently confirmed using a bending magnet spectrometer. The measured spectra had an exponential distribution with a 3 MeV width. The amount of activation was on the order of 2.5 uCi after 3 hours of operation at 1 Hz. Future experiments will aim at increasing this yield by post-accelerating the electron beam using a channel guided laser wakefield accelerator.« less
  • Evidence of particle trapping has been observed in a beam driven Plasma Wake Field Accelerator (PWFA) experiment, E164X, conducted at the Stanford Linear Accelerator Center by a collaboration which includes USC, UCLA and SLAC. Such trapping produces plasma dark current when the wakefield amplitude is above a threshold value and may place a limit on the maximum acceleration gradient in a PWFA. Trapping and dark current are enhanced when in an ionizing plasma, that is self-ionized by the beam. Here we present experimental results.