Demonstration of a Novel Positron Source Based on a Plasma Wiggler

Journal Article · Mon Nov 27 04:00:00 EST 2006 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.2409122· OSTI ID:20898746

Johnson, D K; Clayton, C E; Huang, C; Joshi, C; Lu, W; Marsh, K A; Mori, W B; Zhou, M ^[1]; Blumenfeld, I; Barnes, C D; Decker, F J; Emma, P; Hogan, M J; Ischebeck, R; Iverson, R; Kirby, N; Krejcik, P; O'Connell, C L; Siemann, R H; Walz, D ^[2]

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1. University of California, Los Angeles, CA 90095 (United States)
2. Stanford Linear Accelerator Center, Stanford, CA 94309 (United States)

A new method for generating positrons has been proposed that uses betatron X-rays emitted by an electron beam in a high-K plasma wiggler. The plasma wiggler is an ion column produced by the head of the beam when the peak beam density exceeds the plasma density. The radial electric field of the beam blows out the plasma electrons transversely, creating an ion column. The focusing electric field of the ion column causes the beam electrons to execute betatron oscillations about the ion column axis. If the beam energy and the plasma density are high enough, these oscillations lead to synchrotron radiation in the 1-50 MeV range. A significant amount of electron energy can be lost to these radiated X-ray photons. These photons strike a thin (.5Xo), high-Z target and create e+/e- pairs. The experiment was performed at the Stanford Linear Accelerator Center (SLAC) where a 28.5 GeV electron beam with {sigma}r {approx_equal} 10{mu}m and {sigma}z {approx_equal} 25{mu}m was propagated through a neutral Lithium vapor (Li). The radial electric field of the dense beam was large enough to field ionize the Li vapor to form a plasma. The positron yield was measured as a function of plasma density, ion column length and electron beam pulse length. A computational model was written to match the experimental data with theory. The measured positron spectra are in excellent agreement with those expected from the calculated X-ray spectral yield from the plasma wiggler. After matching the model with the experimental results, it was used to design a more efficient positron source, giving positron yields of 0.44 e+/e-, a number that is close to the target goal of 1-2 e+/e- for future positron sources.

• OSTI ID: 20898746
• Journal Information: AIP Conference Proceedings, Journal Name: AIP Conference Proceedings Journal Issue: 1 Vol. 877; ISSN APCPCS; ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
BEAM-PLASMA SYSTEMS
BETATRON OSCILLATIONS
BETATRONS
ELECTRIC FIELDS
ELECTRON BEAMS
GEV RANGE 10-100
LITHIUM
PHOTONS
PLASMA
PLASMA DENSITY
POSITRON SOURCES
STANFORD LINEAR ACCELERATOR CENTER
SYNCHROTRON RADIATION
WIGGLER MAGNETS
X RADIATION