Proton ring trapping in a gated magnetic mirror

Abstract

An axis-encircling proton ring has been trapped for times (≊4 μs) much longer than the ion cyclotron period (≊80 ns). The rings, with mean radius 10 cm and with particle energies ≤430 keV, made eight passes through the 1.5-m-long magnetic mirror well with static and puffed hydrogen used for space-charge neutralization. The measured proton inventory was typically 2 × 1015 protons during the first pass and 2 × 1013 protons during the eighth and final pass. With a central solenoidal field of 0.8 T, the peak diamagnetism and azimuthal current density of the injected ring were typically 10 mT (100 G) and 10 A/cm2, respectively.