29 research outputs found

### A theoretical study of photovoltaic converters

Mathematical models for the photovoltaic conversion of laser power were developed. These models simulate the operation of planar and vertical junction photovoltaic converters and are described in detail

### A theoretical study of photovoltaic converters

The final phase of research was performed in the model simulation for the solar simulator pumped atomic iodine laser. The geometry for the steady state laser operation with axial lasant flow is illustrated. The chemical kinetics for this laser are described

### Three-dimensional models of conventional and vertical junction laser-photovoltaic energy converters

Three-dimensional models of both conventional planar junction and vertical junction photovoltaic energy converters have been constructed. The models are a set of linear partial differential equations and take into account many photoconverter design parameters. The model is applied to Si photoconverters; however, the model may be used with other semiconductors. When used with a Nd laser, the conversion efficiency of the Si vertical junction photoconverter is 47 percent, whereas the efficiency for the conventional planar Si photoconverter is only 17 percent. A parametric study of the Si vertical junction photoconverter is then done in order to describe the optimum converter for use with the 1.06-micron Nd laser. The efficiency of this optimized vertical junction converter is 44 percent at 1 kW/sq cm

### Photovoltaic conversion of laser power to electrical power

Photovoltaic laser to electric converters are attractive for use with a space-based laser power station. The results of modeling studies for a silicon vertical junction converter used with a Nd laser are given. A computer code was developed for the model and this code was used to conduct a parametric study for a Si vertical junction converter consisting of one p-n junction irradiated with a Nd laser. These calculations predict an efficiency over 50 percent for an optimized converter

### Mathematical modeling of a photovoltaic-laser energy converter for iodine laser radiation

Space-based laser power systems will require converters to change laser radiation into electricity. Vertical junction photovoltaic converters are promising devices for this use. A promising laser for the laser power station is the t-C4F9I laser which emits radiation at a wavelength of 1.315 microns. This paper describes the results of mathematical modeling of a photovoltaic-laser energy converter for use with this laser. The material for this photovoltaic converter is Ga(53)In(47)As which has a bandgap energy of 0.94 eV, slightly below the energy of the laser photons (0.943 eV). Results of a study optimizing the converter parameters are presented. Calculated efficiency for a 1000 vertical junction converter is 42.5 percent at a power density of 1 x 10 to the 3d power w/sq cm

### Theoretical studies of lasers and converters

Discussed here is Doppler broadening and its effects upon the stimulated emission cross-section connecting an upper level with a lower level in an iodine laser. The stimulated emission cross section is given. The level transitions for the iodine laser are illustrated as are the relative intensities of these transitions. Also discussed is the Voigt profile, which considers the effect of both Doppler broadening and collision broadening upon the absorption line shape. The equations describing the Voigt profile were added to the continuous flow laser model laser simulation program. The results were compared with the standard absorption profile reported in an earlier study. There seems to be no advantage to using the Voigt profile as the laser power output is relatively insensitive to changes in the absorption cross section at the pressures being considered for a space laser. One disadvantage of using the Voigt profile is the excessive numerical computations required by the additional equations

### Comparison of laser models

Progress on the comparison of laser models is reported. Equations for an oscillatory model and a nonoscillatory model for the simulation of iodine laser operation are solved. Reaction rate coefficients used in both models are listed. Currently there are four models for the simulation of iodine laser operation are solved. Reaction rate coefficients used in both models are listed. Currently there are four models for the simulation of an iodine laser. They are: (1) a time dependent model; (2) a quasi-steady state model; (3) a noncompressible model; and (4) a compressible flow laser model. Current research is being directed toward: (1) parameter studies using the compressible flow laser model; (2) development of a two-pass amplifier model; and (3) solving a system of equations describing operation of the high powered iodine MOPA (master oscillator power amplifier)

### Theoretical studies of a molecular beam generator

We consider the problem of modeling a high temperature diatomic gas N2 flowing through a converging-diverging high expansion nozzle. The problem is modeled in two ways. The first model uses a single temperature with variable specific heats as functions of this temperature. For the second model we assume that the various degrees of freedom all have a Boltzmann population distribution which means that each degree of freedom has its own temperature and consequently each system state can be characterized by these temperatures. This suggests the formulation of a second model with a vibrational degree of freedom as having its own temperature along with a rotational-translational degree of freedom with its own temperature. Initially the vibrational degree of freedom is excited by heating the gas to a high temperature. As the high temperature gas expands through the nozzle throat there is a sudden drop in the rotational-translational temperature along with a finite relaxation time for the vibrational degree of freedom to achieve equilibrium with the rotational-translational degree of freedom. That is, the temperature change that occurs when the N2 gas passes through the nozzle throat is so great that the changes in the vibrational degree of freedom lags behind the rotational-translational energy changes. The resulting relaxation time is finite. It is in this context that the term nonequilibrium is used. That is, the term nonequilibrium denotes the fact that the energy content of the various degrees of freedom are characterized by two temperatures. We neglect any chemical reactions resulting from the high temperatures which could also add nonequilibrium effects. We develop the basic equations for the two models in various forms in order to check the derivations with other sources. The final form which is solved numerically consists of the scaled equations in a conservative dimensionless form

### Theoretical studies of solar lasers and converters

A second computer program was developed for the simulation of an n - C3F7I iodine laser. The computer program is given in Appendix A and a typical output from the computer program is illustrated in Appendix B

### Theoretical studies of solar lasers and converters

The research described consisted of developing and refining the continuous flow laser model program including the creation of a working model. The mathematical development of a two pass amplifier for an iodine laser is summarized. A computer program for the amplifier's simulation is included with output from the simulation model