The Paul Trap Simulator Experiment (PTSX) at PPPL is designed to study the propagation of intense beams in a compact laboratory setting. Studies will include: beam mismatch and envelope instabilities, collective wave excitations, chaotic particle dynamics and the production of halo particles, mechanisms for emittance growth, and the effects of the distribution function on stability properties.
The foundation of PTSX is the similarity between the equations that govern the behavior of an ion beam traveling through a spatially periodic set of quadrupole magnets and those that describe the behavior of ions in a cylindrical Paul trap under certain conditions. Varying the oscillating confining fields of the Paul trap allows us to simulate various magnetic quadrupole configurations that can include hundreds of magnet periods.
The trap consists of a 2 m long, 20 cm diameter, gold plated, stainless steel cylinder that is axially sliced into four electrodes. Applying oscillating voltages ± V0(t) to the electrodes provides radial confinement while 40 cm long biased electrodes at the ends provide axial confinement. For barium, with n = 107 cm-3 and V0 max = 400 V, the oscillation frequency will be tens of kHz. We will develop an ion source to emit barium ions to load a plasma with rp ~ 1 cm into the trap. We will measure the plasma's radial profile downstream with a moveable Faraday cup. Our plans include the eventual use of laser-induced-fluorescence (LIF) to make measurements of the full ion-distribution function. Presently, an aluminosilicate cesium source is used to produce the plasma ions.