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Title: Halo Formation And Emittance Growth of Positron Beams in Plasmas

An ultrarelativistic 28.5 GeV, 700-{micro}m-long positron bunch is focused near the entrance of a 1.4-m-long plasma with a density n{sub e} between {approx}10{sup 13} and {approx}5 x 10{sup 14} cm{sup -3}. Partial neutralization of the bunch space charge by the mobile plasma electrons results in a reduction in transverse size by a factor of {approx}3 in the high emittance plane of the beam {approx}1 m downstream from the plasma exit. As n{sub e} increases, the formation of a beam halo containing {approx}40% of the total charge is observed, indicating that the plasma focusing force is nonlinear. Numerical simulations confirm these observations. The bunch with an incoming transverse size ratio of {approx}3 and emittance ratio of {approx}5 suffers emittance growth and exits the plasma with approximately equal sizes and emittances.
Authors:
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Publication Date:
OSTI Identifier:
1028122
Report Number(s):
SLAC-PUB-14657
Journal ID: ISSN 0031-9007; PRLTAO; TRN: US1105370
DOE Contract Number:
AC02-76SF00515
Resource Type:
Journal Article
Resource Relation:
Journal Name: Phys.Rev.Lett.101:055001,2008; Journal Volume: 101; Journal Issue: 5
Research Org:
SLAC National Accelerator Laboratory (SLAC)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ELECTRONS; FOCUSING; PLASMA; POSITRON BEAMS; POSITRONS; SPACE CHARGE Astrophysics,ASTRO