Carl A. Ventrice

Electromagnetic wave technique to determine radiation torque on micromachines driven by light

A method to determine radiation torque on a dielectric microrotor driven by a focused laser beam, while considering the wave nature of the incident light, is introduced. The method involves numerically determining the electric and magnetic field quantities of the scattered light on the surface of the rotor using the finite difference time domain method. Maxwell’s stress tensor is then employed to calculate the force over the rotor surface, enabling the determination of the rotor torque about the axis of rotation. The method is demonstrated using a simple rotor shape, with results that are in good qualitative agreement with observations reported in literature.

Static uniform magnetic fields and amoebae

Three species of potentially pathogenic amoebae were exposed to 71 and 106.5 mT from constant homogeneous magnetic fields and examined for inhibition of population growth. The number of amoebae for three species was significantly less than controls after a 72 h exposure to the magnetic fields when the temperature was 20 C or above. Axenic cultures, i.e., cultures grown without bacteria, were significantly affected after only 24 h. In 20 of 21 tests using the three species, the magnetic field significantly inhibited the growth of amoebae. In one test in which the temperature was 20 C for 48 h, exposure to the magnetic field was not inhibitory. Final numbers of magnetic field-exposed amoebae ranged from 9 to 72% lower than the final numbers of unexposed controls, depending on the species. This research may lead to disinfection strategies utilizing magnetic fields for surfaces on which pathogenic amoebae may proliferate.

High voltage DC shifted RF switch-mode power supply system design for gas lasers excitation

A prototype DC-to-high-voltage DC-shifted RF switch-mode converter was designed, fabricated, and used to excite a low-power CO/sub 2/ laser. A novel concept was used in designing the ferrite transformer which reduces the leakage inductance. A modified voltage multiplier design was used to produce the high-voltage DC-shifted RF. Converter performance analysis, laser efficiency measurements, and the effect of various converter output parameters on laser performance were obtained and are analyzed.<<ETX>>

Analytic calculation of electron transmission probability for planar-doped potential barrier devices

The electron barrier transmission probability, T, is calculated for planar‐doped potential barrier devices. The calculations are based on the analytic expression derived by Christodoulides et al. obtained from the exact solution to the Schrodinger time‐independent equation. The original Airy function solution was recast in Bessel function form for ease of computer evaluations. The barrier is assumed to be triangular with the forward slope S1, much larger than the reverse slope S2. The quantity T is calculated for values of electron energy, E, above and below the barrier peak, Um. It is found that T is a sensitive function of S1 for all values of E. The reverse slope, S2, is observed to have very little effect on T for values of (E−Um)≥10 meV, but have a large effect on T for values of (E−Um)≤0. The quantity T is observed to increase monotonically with increasing E, for practical values of device parameters. These results are in qualitative agreement with those found from the numerical solution of Chandra ...

Ambipolar Diffusion in a Weakly Ionized Unstable Plasma Afterglow

The afterglow of a weakly ionized plasma is investigated in the presence of a uniform axial magnetic field, which is varied from 0 to 900 G. Evidence of enhanced diffusion is observed and is associated with instabilities in the afterglow. In those cases for which the afterglow is quiescent, the magnetic field dependence of the transverse ambipolar diffusion coefficient is in agreement with that predicted by classical diffusion theory.

Electron density distribution in a conical laser plasma tube

The electron density distribution is determined for a low‐pressure gas in a conical plasma tube. The distribution is found to vary in the radial direction as a spherical Bessel function and in the ϑ direction as a Legendre polynomial, the order of which is proportional to L/a.

Electron‐density distribution in a laser tube with a hyperboloid of revolution boundary

The electron‐density distribution is determined in a laser tube that is formed by a hyperboloid of revolution and spherical end surfaces. Calculations are made assuming different symmetrical optical resonator configurations ranging from near‐planar to near‐confocal. The tube geometry is specified in terms of the optical resonator parameters: resonator length L, mirror radius of curvature, R, and optical spot size at the mirror surface. The active medium is assumed to be a low‐temperature, weakly ionized plasma. Schottky boundary conditions are assumed and the electron temperature is taken to be independent of position. The particle‐diffusion equation is solved using oblate spheroidal coordinates. The oblate spheroidal angular dependence (which in the cylindrical limit corresponds to the variation perpendicular to the axis of the cylinder) of the density is found to be that of a zero‐order Bessel function. The oblate spheroidal radial dependence (which in the cylindrical limit corresponds to the axial depe...

Electron density in a locally ionized plasma afterglow

An expression is derived for the electron density distribution in a weakly ionized plasma afterglow. The case for which the ionization is symmetrically localized about the center of the chamber is considered. It is shown that localization causes the existence of higher‐order modes of decay to be present in the afterglow.

Modified Schottky Boundary Condition in a Wide Plasma Column

Axial current density measurements are made in a wide argon magnetoplasma. From these measurements, a “modified Schottky” boundary condition is found to apply.

Generation of a short pulse by optical free induction decay (OFID) using the rising edge of a TEA CO/sub 2/ laser pulse for excitation

The generation of short CO/sub 2/ laser pulses is achieved in several ways such as the optical free induction decay (OFID) technique. The OFID technique is a relatively simpler mechanism of generating short pulses and easily invites further study of the technique. The present work involves the interaction of the rising edge of a pulsed CO/sub 2/ laser with ammonia and Dymel in an effort to generate an OFID pulse.