Imaging free-falling particles for multipoint measurement of plasma fluctuations

Abstract

The measurement of plasma fluctuations by insertable probes is sometimes limited by the perturbation of the probe on the plasma, and some non-invasive diagnostics such as photodiode arrays can only measure integrated values. In this paper, we introduce a new approach to plasma fluctuation measurement using small, free-falling particles imaged with a fast camera to provide simultaneous multipoint measurement of visible light emissions surrounding each particle. We find that the fluctuations measured in this manner are in agreement with existing diagnostics, and the particle signals are correlated to those measured on inserted floating potential probes. Signals from multiple particles demonstrate an application of multipoint measurement of the plasma spatial structure and coherence.

The Roles of Grain Boundaries in Thermoelectric Transports

“…The degrading of carrier mobility across grain boundaries is counted as grain boundary scattering, while the mechanism explaining how Seebeck coefficient gets enhanced at grain boundaries is usually defined as the energy filtering effect [27] . Martin et al [28] found a unique temperature dependence of carrier mobility in PbTe-based nano-composites, and proposed that charge carriers that are trapped at grain boundaries would form energy barriers that impede further electrical conduction of those low-energy charge carriers which contribute negatively to the overall Seebeck coefficient across the boundaries. A subsequent work [29] obtained a fitted value of barrier height at grain boundaries and explained the enhanced power factor in ZnSb-based thermoelectric material in a more theoretical aspect.…”