ISSN:
1089-7666
Source:
AIP Digital Archive
Topics:
Physics
Notes:
A detailed study of the trapping of proton rings in a magnetic mirror both in uniform gas fillings and in localized puffed-gas fillings is presented. The trapping of about 3×1014, 400 keV protons in a 1.5 m long, 0.8 T magnetic mirror was accomplished with a static 1.23:1 downstream mirror and a fast "gate'' upstream mirror with mirror ratio 〈1.3:1. Protons were trapped for 4 μs (〉50 cyclotron periods) or longer. The proton ring mean radius, length, and annular thickness in the trap were 10 cm, 1.5 m, and 5–8 cm, respectively. Detailed study of the dynamics of the injected and trapped protons with a variety of diagnostic techniques showed that the bulk of the protons followed trajectories that could be fully explained using the ion diode voltage and the details of the applied magnetic field configuration. However, a small fraction of the injected protons had axial energy much higher than was possible from single-particle trajectories; incomplete electrostatic neutralization of the proton ring by the beam-generated plasma in the injection region is postulated to explain this observation. Ring proton lifetime in the mirror trap appeared to be determined by mirror losses upon initially encountering the downstream and then the upstream mirrors, followed by a gradual radial loss due to charge-exchange collisions with the neutral gas contained in the experiment chamber.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.859028
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