Aperture method to determine the density and geometry of antiparticle plasmas

P. Oxley*, N. S. Bowden, R. Parrott, A. Speck, C. H. Storry, J. N. Tan, M. Wessels, G. Gabrielse, D. Grzonka, W. Oelert, G. Schepers, T. Sefzick, J. Walz, H. Pittner, T. W. Hänsch, E. A. Hessels

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


The density and geometry of p̄ and e+ plasmas in realistic trapping potentials are required if the rate of antihydrogen formation from them is to be understood. A new measurement technique determines these properties of trapped positron (e+) and antiproton (p̄) plasmas, the latter for the first time. The method does not require the common assumption of a spheroidal plasma geometry, which only pertains for a perfect electrostatic quadrupole trapping potential. Plasma densities, diameters, aspect ratios and angular momenta are deduced by comparing the number of particles that survive transmission through an aperture, to that obtained from self-consistent solutions of Poisson's equation. For p̄ the results differ substantially from the spheroid plasmas of an ideal Penning trap. The angular momentum of the plasma emerges as smooth function of the number of particles in the plasma, independent of the depth of the potential well that confines them.

Original languageEnglish (US)
Pages (from-to)60-67
Number of pages8
JournalPhysics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Issue number1-4
StatePublished - Aug 12 2004


  • 36.10.-k

ASJC Scopus subject areas

  • Nuclear and High Energy Physics


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