Modeling Intense Beam Propagation in the Paul Trap Simulator Experiment (PTSX)

摘要

The Paul Trap Simulator Experiment (PTSX) is a compact laboratory facility whose purpose is to simulate the nonlinear dynamics of intense charged particle beam propagation over large distances through an alternating-gradient magnetic transport system. The PTSX device is a 200 cm long, 20 cm diameter cylindrical Paul trap in which a 400 V, 100 kHz signal confines cesium ions to an rms radius of 1 cm. The one-component cesium plasmas can be confined for hundreds of milliseconds, which would correspond to an equivalent alternating-gradient transport system many kilometers long. The normalized intensity parameter s = ω_p~2|_r=0/2ω_q~2, where ω_q is the average transverse focusing frequency, describes whether the plasma is emittance-dominated (s 1) or space-charge-dominated (s→1). By increasing the amount of charge loaded into the trap, PTSX reaches values of s = 0.8. Thus, the opportunity exists to study important physics topics such as: the conditions necessary for quiescent intense beam propagation over large distances, beam mismatch and envelope instabilities, collective mode excitations, the dynamics and production of halo particles, emittance growth, compression techniques, and the effects of the distribution function on stability properties. Results are presented that demonstrate the sustainment of the radial density profile over long times, and the ability of PTSX to reach large s. The results of initial three-dimensional particle-in-cell simulations are also presented.