30 research outputs found
Annihilation-Gamma-based Diagnostic Techniques for Magnetically Confined Electron-Positron Pair Plasma
Efforts are underway to magnetically confine electron--positron pair plasmas
to study their unique behavior, which is characterized by significant changes
in plasma time and length scales, supported waves, and unstable modes. However,
use of conventional plasma diagnostics presents challenges with these
low-density and annihilating matter-antimatter plasma. To address this problem,
we propose to develop techniques based on the distinct emission provided by
annihilation. This emission exhibits two spatial correlations: the distance
attenuation of isotropic sources and the back-to-back propagation of
momentum-preserving 2- annihilation. We present the results of our
analysis of the emission rate and the spatial profile of the
annihilation in a magnetized pair plasma from direct pair collisions, from the
formation and decay of positronium, as well as from transport processes. In
order to demonstrate the effectiveness of annihilation-based techniques, we
tested them on annular emission profiles produced by a
radioisotope on a rotating turntable. Direct and positronium-mediated
annihilation result in overlapping volumetric sources, and the
2- emission from these volumetric sources can be tomographically
reconstructed from coincident counts in multiple detectors. Transport processes
result in localized annihilation where field lines intersect walls, limiters,
or internal magnets. These localized sources can be identified by the
fractional counts on spatially distributed detectors.Comment: 21 pages, 11 figures, 2 tables, contribution to the 13th
International Workshop on Non-Neutral Plasma
Injection of Positrons into a Dense Electron Cloud in a Magnetic Dipole Trap
The creation of an electron space charge in a dipole magnetic trap and the
subsequent injection of positrons has been experimentally demonstrated.
Positrons (5eV) were magnetically guided from their source and injected into
the trapping field generated by a permanent magnet (0.6T at the poles) using a
cross field E B drift, requiring tailored electrostatic and magnetic
fields. The electron cloud is created by thermionic emission from a tungsten
filament. The maximum space charge potential of the electron cloud reaches
-42V, which is consistent with an average electron density of ()
and a Debye length of () .
We demonstrate that the presence of this space potential does not hamper
efficient positron injection. Understanding the effects of the negative space
charge on the injection and confinement of positrons represents an important
intermediate step towards the production of a confined electron-positron pair
plasma
Positron orbit effects during injection and confinement in a magnetic dipole trap
Lossless injection of positrons into a magnetic dipole trap and their subsequent confinement have been demonstrated. Here, we investigate by numerical single-particle simulations how the radial distribution of positrons in the trap is affected by the measurement itself, the choice of injection parameters, the asymmetry of the electric potential, and by elastic collisions. The results are compared to experimental data. A comprehensive understanding of these effects is a milestone on the road to creating an electron–positron plasma in a trap with a levitating superconducting coil