Limitations from charge quantization on the parallel temperature diagnostic of nonneutral plasmas

Abstract

We develop a new algorithm to estimate the temperature of a nonneutral plasma in a Penning-Malmberg trap. The algorithm analyzes data obtained by slowly lowering a voltage that confines one end of the plasma and collecting escaping charges, and is a maximum likelihood estimator based on a physically-motivated model of the escape protocol presented in Beck [1990]. Significantly, our algorithm may be used on single-count data, allowing for improved fits with low numbers of escaping electrons. This is important for low-temperature plasmas such as those used in antihydrogen trapping. We perform a Monte Carlo simulation of our algorithm, and assess its robustness to intrinsic shot noise and external noise. Approximately 100 particle counts are needed for an accuracy of +/-10% -- this provides a lower bound for measurable plasma temperatures of approximately 3 K for plasmas of length 1 cm.