Non-neutral positron plasma accumulation & storage:

Non-neutral positron plasma accumulation & storage:

Non-neutral plasma traps are traditionally linear devices that use electric and magnetic fields to confine a single species of charged particles.  A common implementation is with hollow cylindrical electrodes in a uniform magnetic field.  

Buffer-gas trap (BGT) system: In order to trap and accumulate positrons from the NEPOMUC source, low-energy positrons will be magnetically guided into a buffer-gas trap.  This is the standard method to convert a low-density DC positron beam into cold, dense, tailorable pulses. The electrode structure and vacuum pumps create a pressure gradient that, along with a stepped potential profile, optimizes between competing mechanisms: annihilation on the gas and inelastic collisions with nitrogen gas that trap positrons in the electrostatic potential well. With the voltages and nitrogen flow carefully tuned, it should be possible to accumulate hundreds of millions of positrons from NEPOMUC into a non-neutral plasma, which can then be delivered to downstream experiments in a very short and intense pulse (< 10 ns).

High-field, multi-cell trap: To reach the 1010–1011 cold (∼1 eV) positrons needed to ensure plasma densities in the toroidal traps, multiple pulses from the BGT system's "accumulator" will need be transferred, combined, and stored for hundreds of seconds in another, higher-capacity trapping stage.  This consists of a nested array of several non-neutral traps in ultra-high vacuum in a 5-T magnet.  A "master cell" is used to transport plasmas into and out of the storage cells by means of controlled excitation and damping of a the m=1 diocotron mode.

Selected publications:

1.
Singer, M.; König, S.; Stoneking, M. R.; Steinbrunner, P.; Danielson, J. R.; Schweikhard, L.; Pedersen, T. S.: Non-neutral plasma manipulation techniques in development of a high-capacity positron trap. Review of Scientific Instruments 92, 123504 (2021)
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