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In high density, high temperature plasmas, the plasma sheath that develops can result in extremely high electric fields, on the order of tens to hundreds of V/nm. Under the right conditions, these electric fields can reach magnitudes that can increase the probability of electron tunneling ionization to occur, resulting in one or more electron-ion pairs. The presence of tunneling ionization can then modify the development of the plasma sheath, as well as properties such as the ion and electron densities and plasma potential. The tunnel ionization process for hydrogen atoms is demonstrated, in this work, as implemented in a Sandia National Laboratories, particle-in-cell code Aleph. Results are presented for the application of the tunnel ionization process to a one-dimensional, undriven plasma sheath. Additional results for cases that consider warm ions and neutrals, the inclusion of electron–neutral collisions, and the injection of neutral particles, as well as the application to various plasma devices, will be discussed.

Cantilever fatigue specimens with a reduced section and rounded tensionside corners were machined from SAE 8719 steel (containing 0.19% C, 1.06% Mn, 0.52% Cr, 0.50% Ni and 0.17% Mo) bars. The specimens were plasma and gas carburized to surface carbon of 0.82% to 0.84%, surface hardness of 65 HRC, and case depths of 1.2 mm at 50 HRC. Some specimens were direct quenched from 850° C after carburizing and some were reheated to 850° C and quenched. All specimens were tempered at 150° C. Excellent high cycle bending fatigue resistance correlated with fine austenitic grain size and low retained austenite. The highest fatigue limit, 1650 MPa (240 ksi), was measured in reheated gas carburized specimens with an austenitic grain size of ASTM No. 11 and surface retained austenite content of about 22%. Reheating reduced the austenite grain size of the carburized specimens and resulted in improved fatigue resistance for both the plasma and gas carburized specimens.