Antimatter plasmas and antihydrogen

Abstract

Measurement of the groundstate hyperfine structure of antihydrogen AIP Conf.Recent successes in confining antimatter in the form of positron and antiproton plasmas have created new scientific and technological opportunities. Plasma techniques have been the cornerstone of experimental work in this area, and this is likely to be true for the foreseeable future. Work by a number of groups on trapping antimatter plasmas is summarized, and an overview of the promises and challenges in this field is presented. Topics relating to positron plasmas include the use of positrons to study the unique properties of electron-positron plasmas, the interaction between positrons and ordinary matter, and the laboratory modeling of positron-annihilation processes in interstellar media. The availability of cold, trapped antiprotons and positrons makes possible the production of neutral antimatter in the form of antihydrogen. This is expected to enable precise comparisons of the properties of matter and antimatter, including tests of fundamental symmetries and the measurement of the interaction of antimatter with gravity. © 1997 American Institute of Physics.

The creation of high quality positron beams using traps

“…Radial confinement is by an axial magnetic field [18,19]. Positrons from a conventional positron source are trapped by collisions with a buffer gas, usually nitrogen, in the high pressure region and accumulate and cool in the low pressure region.…”

Thermally Excited Modes in a Pure Electron Plasma

“…Unneutralized plasmas are unique in that they can be trapped in a rotating near-thermal-equilibrium state by static electric and magnetic fields. Steady-state confinement of N 10 3 -10 9 electrons, ions, or antimatter particles [1,2] is routinely used in plasma experiments, atomic physics [3], and spectroscopy [4]. The thermal equilibrium characteristics become most evident with the formation of Coulomb crystals [5] when pure ion plasmas are cooled to the liquid and solid regimes at sub-Kelvin temperatures, but the higher temperature plasma regime studied here is also well described by near-equilibrium statistical mechanics [6].…”

A Laser-cooled Positron Plasma

“…The experimental work follows previous discussions and simulations of trapping and sympathetic cooling of positrons via Coulomb collisions with cold 9 Be + ions [1,2]. Cold positron plasmas are useful as a source for cold beams of high brightness [3,4,5,6]. Many of the chapters in this volume, for example Chapter 12 by Greaves and Surko and Chapter 24 by Surko, discuss applications of cold positron beams.…”

“…They used a 3 mCi positron source and a tungsten positron moderator in the experiment. The positrons were cooled by thermalization with a cryogenic Penning trap which ensured a temperature of ∼4 K. Surko and coworkers [3,5,18,19,20], using a 90 mCi positron source, report the largest number of trapped positrons (∼ 3 × 10 8 ) with a trapping rate of 3×10 8 positrons in 8 minutes and a trapping efficiency greater than 25 % of the moderated positrons. The positrons were thermalized to room temperature since the trapping was achieved through collisions with a room-temperature buffer gas of N 2 .…”

“…Many of the chapters in this volume, for example Chapter 12 by Greaves and Surko and Chapter 24 by Surko, discuss applications of cold positron beams. In addition cold positron plasmas are useful for studies of positron-normal-matter interactions, such as the study of resonances in low-energy positron annihilation on molecules [3], for production of a plasma whose modes must be treated quantum mechanically [1,7,8], and for formation of antihydrogen by passing cold antiprotons through a reservoir of cold positrons [9,10,11].…”