Confinement and manipulation of electron plasmas in a multicell trap

Abstract

Plasma dynamics and transport are studied experimentally in a multicell Penning-Malmberg trap. The goal is to develop methods for accumulation and long-term confinement of larger numbers of charged particles (e.g., positrons) than is presently possible. In this scheme, the particles constitute non-neutral plasmas which are confined separately in a parallel array of storage cells. Experiments are presented in which pure electron plasmas are transferred from a large-diameter “master cell” trapping region into four smaller, parallel “storage cells,” three of which are offset from the magnetic symmetry axis. The physics of the transfer process, as well as the confinement properties of plasmas in the storage cells, is discussed. We show that plasmas can be transferred into the storage cells and held there for up to a day or more using the rotating wall technique, provided that the plasma radius is sufficiently small compared to that of the cell wall. Experiments regarding the confinement of plasmas with kilovolt space charge are discussed. Recommendations are provided for future efforts with high-capacity multicell traps.

Multi-cell trap developments towards the accumulation and confinement of large quantities of positrons

“…Each storage-cell stack has four set screws, used to apply individual clamping forces, to make it possible to align all the cells at once. This addresses a key issue raised by the first prototype MCT, in which simultaneous alignment of multiple storage cells proved difficult to achieve (Hurst et al 2019).…”

“…The plasma displacement using the autoresonant excitation of the diocotron mode (Baker et al 2015;Hurst et al 2015) was used to precisely address the off-axis cells. The plasma dynamics of the transfer process was determined (Hurst et al 2014), and the functionality of the MCT concept was demonstrated by transferring and confining plasmas in each of several storage cells (Hurst et al 2019).…”

A new frontier in laboratory physics: magnetized electron–positron plasmas

“…The high field magnet ensures that cyclotron cooling will maintain low temperatures and long storage times (Danielson, Weber & Surko 2006; Hurst et al. 2019). Using this multicell trap, more than positrons will be delivered in a controlled sequence of pulses to the dipole or stellarator trap.…”

“…This component employs additional techniques from the field of non-neutral plasma physics to manipulate the positron pulses coming from the accumulator, shift them off-axis and load them into one of a set of up to 21 storage cells. The high field magnet ensures that cyclotron cooling will maintain low temperatures and long storage times (Danielson, Weber & Surko 2006;Hurst et al 2019). Using this multicell trap, more than 10 10 positrons will be delivered in a controlled sequence of pulses to the dipole or stellarator trap.…”

Anomalous Beam Transport through Gabor (Plasma) Lens Prototype

“…As compact and tunable devices, active plasma lenses [51,52] are a promising solution for the extraction and transport of the witness bunch while removing the driver without loss of beam quality [53][54][55]. Finally, electron plasmas were studied in multicell traps [56,57] to develop methods by which the number of accumulated positrons could be increased compared to the present limits coming from the requirement for long-term confinement.…”