If the magnetic field in a pure electron plasma containment device is not aligned with the axis of the conducting walls, the electrons in the device will accumulate at the ends of the plasma where the magnetic field lines come closest to the walls and the electrons bound to the field lines can be closest to their image charges. If the plasma is also offset radially from the center (as with an l=1 diocotron mode), then more density will accumulate at one end than the other. As the plasma revolves around the center, the electrons will slosh from one end to the other, creating a measurable signal. This signal has been experimentally measured and its origin verified using a three-dimensional equilibrium code. This signal can be used experimentally to align the magnetic field with the conducting walls.

Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) is often limited by space-charge effects. Previously, particle-in-cell (PIC) simulations have been used to understand these effects on FTICR-MS signals. However, none have extended fully into the space-charge dominated (plasma) regime. We use a two-dimensional (2-D) electrostatic PIC code, which facilitates work at very high number densities at modest computational cost to study FTICR-MS in the plasma regime. In our simulation, we have observed peak coalescence and the rapid loss of signal coherence, two common experimental problems. This demonstrates that a 2-D model can simulate these effects. The 2-D code can handle a larger numbers of particles and finer spatial resolution than can currently be addressed by 3-D models. The PIC method naturally takes into account image charge and space charge effects in trapped-ion mass spectrometry. We found we can quantify the relative abundances of two closely spaced (such as 7 Be ϩ and 7 Li ϩ ) species in the plasma regime even when their peaks have coalesced. We find that the frequency of the coalesced peak shifts linearly according to the relative abundances of these species. Space charge also affects more widely spaced lines. Singlyionized 7 BeH and 7 Li have two separate peaks in the plasma regime. Both the frequency and peak area vary nonlinearly with their relative abundances. Under some conditions, the signal exhibited a rapid loss of coherence. We found that this is due to a high order diocotron instability growing in the ion cloud. (J

We present an analysis of ion temperatures in laser-produced plasmas formed from solids with different initial lattice structures. We show that the equilibrium ion temperature is limited by a mismatch between the initial crystallographic configuration and the close-packed configuration of a strongly-coupled plasma, similar to experiments in ultracold neutral plasmas. We propose experiments to demonstrate and exploit this crystallographic heating in order to produce a strongly coupled plasma with a coupling parameter of several hundred.

We have observed axisymmetric Bernstein modes in an infinite-length particle-in-cell code simulation of a non-neutral plasma. The plasmas considered were in global thermal equilibrium and there were at least 50 Larmor radii within the plasma radius. The density of the plasma in the simulation is parameterized by β, the ratio of the central density to the density at the Brillouin limit. These modes have m = 0 and kz=0, where the eigenfunctions vary as ei(mθ+kzz). The modes exist both near the Coriolis-shifted (by the plasma rotation) upper-hybrid frequency, ωuh=ωc2−ωp2, and near integer multiples (2, 3, etc.) of the Coriolis-shifted cyclotron frequency (called the vortex frequency, ωv=ωc2−2ωp2). The two modes near ωuh and 2ωv are the main subject of this paper. The modes observed are clustered about these two frequencies and are separated in frequency at low plasma density roughly by δω≈10(rL/rp)2ωp2/ωc. The radial velocity field of the modes has a J1(kr) dependence in the region of the plasma where the density is nearly constant. For any given density, there are three classes of modes that exist: (1) The fundamental mode is slightly above the upper-hybrid frequency, (2) the upper branch is above the higher of ωuh and 2ωv, and (3) the lower branch is below the lower of ωuh and 2ωv, with similar values of k for both the upper and the lower frequency branches. The modes are fully kinetic and the resulting pressure tensor has significant anisotropy, including off-diagonal terms. A Vlasov analysis of these modes considering only particle resonances up to 2ωv produces a radial mode differential equation whose solution agrees well with the simulations, except at high density (β greater than about 0.9) where higher-order resonances become important.

A computer code has been developed which simulates a Thomson scattering measurement, from the counting statistics of the input channels through the mathematical analysis of the data. The scattered and background signals in each of the wavelength channels are assumed to obey Poisson statistics, and the spectral data are fitted to a Gaussian curve using a nonlinear least-squares fitting algorithm. This method goes beyond the usual calculation of the signal-to-noise ratio for the hardware and gives a quantitative measure of the effect of the noise on the final measurement. This method is applicable to Thomson scattering measurements in which the signal-to-noise ratio is low due to either low signal or high background. Thomson scattering data from the S-1 spheromak have been compared to this simulation, and they have been found to be in good agreement. This code has proven to be useful in assessing the effects of counting statistics relative to shot-to-shot variability in producing the observed spread in the data. It was also useful for designing improvements for the S-1 Thomson scattering system, and this method would be applicable to any measurement affected by counting statistics.