Sophia Gershman

Unstable behavior of anodic arc discharge for synthesis of nanomaterials

A short carbon arc operating with a high ablation rate of the graphite anode exhibits a combined motion of the arc and the arc attachment to the anode. A characteristic time scale of this motion is in a 10 -3 sec range. The arc exhibits a negative differential resistance before the arc motion occurs. Thermal processes in the arc plasma region interacting with the ablating anode are considered as possible causes of this unstable arc behavior. It is also hypothesized that the arc motion could potentially cause mixing of the various nanoparticles synthesized in the arc in the high ablation regime.

The suitability of 3D printed plastic parts for laboratory use

3D printing has become popular for a variety of users, from home hobbyists to scientists and engineers interested in producing their own laboratory equipment. In order to determine the suitability of 3D printed parts for our plasma physics laboratory, we measured the accuracy, strength, vacuum compatibility, and electrical properties of pieces printed in plastic. The flexibility of rapidly creating custom parts has led to the 3D printer becoming an invaluable resource in our laboratory. The 3D printer is also suitable for producing equipment for advanced undergraduate laboratories.

Pulsed electrical discharge in gas bubbles in water

Summary form given only. Pulsed electrical discharges in water have been investigated for water decontamination and decoloration. The optimization of the cleaning process requires detailed knowledge of the discharge process, particularly in terms of the formation of active species such as OH, O, and other radicals. Rectangular voltage pulses of 1 mus duration are applied to single Ar or oxygen bubbles in water and optical emissions from the discharge are studied as a function of applied voltage, power delivered to the discharge, and the total energy supplied or the number of pulses applied to each bubble. Average and time-resolved spectra have been recorded from Ar and oxygen bubbles in various spectral ranges from 285 nm to 880 nm. We observed increases in emission intensity with power for OH and other emissions confirming that the radical formation increases with increasing power. Ar lines and OH vibrational bands were used to determine the electron, vibrational, and rotational temperature in the discharge. Spectra were taken in 200 ns time windows during a single pulse and additional time-resolved information has been obtained using a fast photomultiplier tube with band-pass filters. This information allows us to speculate on the dynamics of the radical production and other processes in the pulsed discharge.