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Title: Plasma Dark Current in Self-Ionized Plasma Wakefield Accelerators

Abstract

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.

Authors:
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Stanford Linear Accelerator Center (SLAC)
Sponsoring Org.:
USDOE
OSTI Identifier:
875805
Report Number(s):
SLAC-PUB-11641
TRN: US0600795
DOE Contract Number:
AC02-76SF00515
Resource Type:
Conference
Resource Relation:
Conference: Presented at Particle Accelerator Conference (PAC 05), Knoxville, Tennessee, 16-20 May 2005
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; ACCELERATION; ACCELERATORS; AMPLITUDES; PLASMA; STANFORD LINEAR ACCELERATOR CENTER; TRAPPING; UCLA; WAKEFIELD ACCELERATORS; Accelerators,ACCPHY, ACCSYS

Citation Formats

Oz, E., Deng, S., Katsouleas, T., Muggli, P., /Southern California U., Iverson, R., Johnson, D.K., Krejcik, P., O'Connell, C., Siemann, R.H., Walz, D., /SLAC, Clayton, C.E., Huang, C., Joshi, C., Lu, W., Marsh, K.A., Mori, W.B., Zhou, M., and /UCLA. Plasma Dark Current in Self-Ionized Plasma Wakefield Accelerators. United States: N. p., 2006. Web.
Oz, E., Deng, S., Katsouleas, T., Muggli, P., /Southern California U., Iverson, R., Johnson, D.K., Krejcik, P., O'Connell, C., Siemann, R.H., Walz, D., /SLAC, Clayton, C.E., Huang, C., Joshi, C., Lu, W., Marsh, K.A., Mori, W.B., Zhou, M., & /UCLA. Plasma Dark Current in Self-Ionized Plasma Wakefield Accelerators. United States.
Oz, E., Deng, S., Katsouleas, T., Muggli, P., /Southern California U., Iverson, R., Johnson, D.K., Krejcik, P., O'Connell, C., Siemann, R.H., Walz, D., /SLAC, Clayton, C.E., Huang, C., Joshi, C., Lu, W., Marsh, K.A., Mori, W.B., Zhou, M., and /UCLA. Mon . "Plasma Dark Current in Self-Ionized Plasma Wakefield Accelerators". United States. doi:. https://www.osti.gov/servlets/purl/875805.
@article{osti_875805,
title = {Plasma Dark Current in Self-Ionized Plasma Wakefield Accelerators},
author = {Oz, E. and Deng, S. and Katsouleas, T. and Muggli, P. and /Southern California U. and Iverson, R. and Johnson, D.K. and Krejcik, P. and O'Connell, C. and Siemann, R.H. and Walz, D. and /SLAC and Clayton, C.E. and Huang, C. and Joshi, C. and Lu, W. and Marsh, K.A. and Mori, W.B. and Zhou, M. and /UCLA},
abstractNote = {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.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 30 00:00:00 EST 2006},
month = {Mon Jan 30 00:00:00 EST 2006}
}

Conference:
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  • In the recent plasma wakefield accelerator experiments at SLAC, the energy of the particles in the tail of the 42 GeV electron beam were doubled in less than one meter [1]. Simulations suggest that the acceleration length was limited by a new phenomenon--beam head erosion in self-ionized plasmas. In vacuum, a particle beam expands transversely in a distance given by {beta}*. In the blowout regime of a plasma wakefield [2], the majority of the beam is focused by the ion channel, while the beam head slowly spreads since it takes a finite time for the ion channel to form. Itmore » is observed that in self-ionized plasmas, the head spreading is exacerbated compared to that in pre-ionized plasmas, causing the ionization front to move backward (erode). A simple theoretical model is used to estimate the upper limit of the erosion rate for a bi-gaussian beam by assuming free expansion of the beam head before the ionization front. Comparison with simulations suggests that half this maximum value can serve as an estimate for the erosion rate. Critical parameters to the erosion rate are discussed.« less
  • Dark current can spoil witness bunch beam quality and acceleration efficiency in particle beam-driven plasma wakefield accelerators. In advanced schemes, hot spots generated by the drive beam or the wakefield can release electrons from higher ionization threshold levels in the plasma media. Likewise, these electrons may be trapped inside the plasma wake and will then accumulate dark current, which is generally detrimental for a clear and unspoiled plasma acceleration process. The strategies for generating clean and robust, dark current free plasma wake cavities are devised and analyzed, and crucial aspects for experimental realization of such optimized scenarios are discussed.
  • Dark current can spoil witness bunch beam quality and acceleration efficiency in particle beam-driven plasma wakefield accelerators. In advanced schemes, hot spots generated by the drive beam or the wakefield can release electrons from higher ionization threshold levels in the plasma media. Likewise, these electrons may be trapped inside the plasma wake and will then accumulate dark current, which is generally detrimental for a clear and unspoiled plasma acceleration process. The strategies for generating clean and robust, dark current free plasma wake cavities are devised and analyzed, and crucial aspects for experimental realization of such optimized scenarios are discussed.
  • Dark current can spoil witness bunch beam quality and acceleration efficiency in particle beam-driven plasma wakefield accelerators. In advanced schemes, hot spots generated by the drive beam or the wakefield can release electrons from higher ionization threshold levels in the plasma media. These electrons may be trapped inside the plasma wake and will then accumulate dark current, which is generally detrimental for a clear and unspoiled plasma acceleration process. Strategies for generating clean and robust, dark current free plasma wake cavities are devised and analyzed, and crucial aspects for experimental realization of such optimized scenarios are discussed.
  • For the parameters envisaged in possible afterburner stages[1] of a plasma wakefield accelerator (PWFA), the self-fields of the particle beam can be intense enough to tunnel ionize some neutral gases. Tunnel ionization has been investigated as a way for the beam itself to create the plasma, and the wakes generated may differ from those generated in pre-ionized plasmas[2],[3]. However, it is not practical to model the whole stage of PWFA with afterburner parameters using the models described in [2] and [3]. Here we describe the addition of a tunnel ionization package using the ADK model into QuickPIC, a highly efficientmore » quasi-static particle in cell (PIC) code which can model a PWFA with afterburner parameters. Comparison between results from OSIRIS (a full PIC code with ionization) and from QuickPIC with the ionization package shows good agreement. Preliminary results using parameters relevant to the E164X experiment and the upcoming E167 experiment at SLAC are shown.« less