Creation of finely focused particle beams from single-component plasmas

Abstract

In a recent communication ͓Danielson et al., Appl. Phys. Lett. 90, 081503 ͑2007͔͒, a nondestructive technique was described to create finely focused beams of electron-mass, charged particles ͑i.e., electrons or positrons͒ from single-component plasmas confined in a Penning-Malmberg trap. This paper amplifies and expands upon those results, providing a more complete study of this method of beam formation. A simple model for beam extraction is presented, and an expression for a Gaussian beam profile is derived when the number of extracted beam particles is small. This expression gives a minimum beam diameter of four Debye lengths ͑full width to 1 / e͒ and is verified using electron plasmas over a broad range of plasma temperatures and densities. Numerical procedures are outlined to predict the profiles of beams with large numbers of extracted particles. Measured profiles of large beams are found in fair agreement with these predictions. The extraction of over 50% of a trapped plasma into a train of nearly identical beams is demonstrated. Applications and extensions of this technique to create state-of-the-art positron beams are discussed.

Plasma and trap-based techniques for science with positrons

“…This scaling is illustrated in Fig. 30 (Danielson et al, 2007b;Weber et al, 2008Weber et al, , 2009). The favorable scaling of D with T and n indicates that further improvements are possible using colder, higher-density plasmas.…”

“…Beams with Gaussian radial profiles and diameters as small as D = 50 µm have been extracted from electron plasmas with D ≈ 2 mm before compression (Danielson et al, 2007b;Weber et al, 2008). A simple theory predicts that the beam diameter (full width to 1/e) is D = 4λ D ∝ (T /n) 1/2 , where λ D is the Debye length.…”

“…III.D), these techniques typically involve unavoidable losses of particles. A nondestructive technique was developed to produce a beam with narrow transverse width and enhanced brightness, without such losses (Danielson et al, 2007b;Greaves et al, 2002;Weber et al, 2008Weber et al, , 2009.…”

Finite-length, large-amplitude diocotron mode dynamics

“…These SCPs are useful in many research areas including particle, atomic, plasma, and condensed matter physics; fluid dynamics, and material science. Singlecomponent plasmas are used to trap and cool antiparticles [2], and to subsequently generate antiparticle beams [3,4,5,6]. Such beams are used in a variety of applications including studies of binding and annihilation of positrons with molecules [7], scattering experiments [8], the production of antihydrogen [9], the creation of electron-positron plasmas [10], efforts to create positronium Bose-Einstein condensates [11], and the study of materials [12,13].…”

The behaviour of positron clouds in the single-particle regime under the influence of rotating wall electric fields

“…These instruments are significantly cheaper and easier to operate than three-stage devices, which typically require a large electromagnet [1,8] or a superconducting solenoid [5] for their operation. They are, for instance, beginning to find applications in atomic physics [27], where they can be used to provide narrow energy width beams [28] for the new field of high-resolution positron scattering.…”