Download or read book Comparison of Numerical and Experimental Near Field Plasma Properties of the BHT 200 X3 Hall Thruster Preprint written by and published by . This book was released on 2006 with total page 25 pages. Available in PDF, EPUB and Kindle. Book excerpt: Near-field ion velocity distributions of a BusekBHT-200-X3 xenon Hall thruster obtained through numerical simulation are compared with laser-induced fluorescence measurements taken for one nominal operating condition. The numerical code Hybrid-PIC Hall, a 2D hybrid particle-in-cell model, is used to simulate an axisymmetric cross section of the plasma acceleration zone. A set of nine HP Hall simulations are run using three different cathode positions and Bohm electron mobility coefficients to study the effects of these parameters on ion acceleration. Six additional cases were run in an attempt to better match the simulation results to the experimental data. For model validation, agreement between the numerical and experimental results is examined. The results show that it is difficult to match both the global operational parameters (i.e, thrust, discharge current, and beam current) and the ion velocity distributions. The shape of the axial velocity distributions can be closely matched by using high Bohm electron mobility values. However, this correlation comes at the expense of peak ion velocity and discharge current agreement. Radial velocity distributions are more closely matched by the simulations, but the simulations uniformly predict lower than measured inward and higher than measured outward radial velocity components (relative to the centerline) from the annular acceleration channel.
Download or read book Experimental and Numerical Examination of the BHT 200 Hall Thruster Plume Postprint written by and published by . This book was released on 2007 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt: The plume of a Busek BHT-200 xenon Hall thruster has been characterized through measurements from various plasma electrostatic probes. Ion current flux, plasma potential, plasma density, and electron temperatures were measured in the near-field of the plume to 60 cm downstream of the exit plane. These experimentally derived measurements were compared to simulations of the thruster/vacuum chamber environment using the plasma plume code DRACO. The goals of this study were to gain understanding of the effect of the vacuum facility on the thruster plume and to determine the fidelity of the DRACO numerical simulation.
Download or read book Complementary Density Measurements for the 200W Busek Hall Thruster PREPRINT written by and published by . This book was released on 2006 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: Results of two complementary methods of measuring the near field plasma densities of a 200W Busek X3 Hall thruster are presented. Both a Faraday probe and microwave interferometry system are used to examine the density distribution of the thruster plasma at regular spatial intervals. Both experiments are performed in situ under the same conditions. The resulting density distributions obtained from both experiments are presented. Advantages and uncertainties of both methods are presented, as well as how comparison between the two data sets can account for the uncertainties of each method alone.
Download or read book Plasma Oscillations and Associated Electron Transport Within Hall Thrusters written by Aaron Kombai Knoll and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The Hall thruster is a type of plasma propulsion system for space vehicle applications. The thrust produced by this device is derived from the momentum of ions, which are accelerated to high exit velocities by the action of an electric field sustained within the plasma. The advantage of the Hall thruster compared to conventional chemical rocket propulsion is a significantly higher exhaust velocity, which leads to better utilization of propellant mass. Since the early days of Hall thruster research, experiments have suggested that the mobility of electrons along the axis of the thruster, perpendicular to an imposed magnetic field, is higher than can be explained by classical collision transfer processes alone. A lack of understanding regarding the mechanism for this enhanced mobility has proved a significant challenge toward the development of reliable simulations capable of predicting the performance of these devices. This thesis examines the role of high frequency plasma oscillations on the electron mobility using a combination of experimental studies on a laboratory Hall thruster, and numerical simulations capable of capturing these oscillations and quantifying their impact on the electron mobility. Two high frequency oscillations were consistently observed in the experiments: a 10MHz mode which appeared strongest in the vicinity of the anode, and a 4.5MHz mode which was strongest in the mid-channel region of the thruster. These were relatively low wave number (long wavelength) oscillations: approximately 6cm for the 4.5MHz oscillation and 3cm for the 10MHz oscillation. The angle of these waves varied considerably depending on the operating conditions of the thruster. They were found to be closely aligned to the axis of the thruster for experiments conducted with Xenon propellant, and were aligned with the circumference of the thruster (in the direction of electron drift) for experiments conducted with Krypton. A Hall thruster simulation, formulated in the axial-azimuthal coordinates of the thruster, was able to capture high frequency oscillations in reasonable agreement with experimental findings: 13MHz near the anode and 5MHz in the mid-channel region of the thruster for 160V discharge conditions. The simulation results demonstrated the crucial role of these oscillations in regulating the electron transport. In the vicinity of these oscillations the electron mobility was increased by a factor of five or more. The central finding of this thesis is that high frequency oscillations in the range 1 - 50MHz can account for the observed discrepancy between classical and experimental electron mobility in the Hall thruster.
Download or read book Plasma Diagnostics in the Near Field Plume of a Hall Thruster written by Kai-Mei C. Fu and published by . This book was released on 2000 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Performance Testing and Internal Probe Measurements of a High Specific Impulse Hall Thruster written by Noah Zachary Warner and published by . This book was released on 2003 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt: The BHT-1000 high specific impulse Hall thruster was used for performance testing and internal plasma measurements to support the ongoing development of computational models. The thruster was performance tested in both single and two stage anode configurations. In the single stage configuration, the specific impulse exceeded 3000s at a discharge voltage of 1000V while maintaining a thrust efficiency of 50 percent. Two stage operation produced higher thrust, specific impulse and thrust efficiency than the single stage configuration at most discharge voltages. The thruster thermal warmup was characterized using a thermocouple embedded in the outer exit ring, and the magnetic field topology was investigated using a Gaussmeter. The single stage thruster configuration was outfitted with a series of axially distributed Langmuir probes to determine plasma properties inside the discharge channel. Probe data were taken at discharge voltages between 300-900V. Axial profiles of electron temperature, electron density, and plasma potential were measured and compared to results of a previously developed two dimensional particle-in-cell simulation of the BHT-1000 thruster. The experimental data matched the simulation results well, particularly in profiles of electron temperature and plasma potential at low discharge voltages. The peak electron temperature was shown to depend on discharge voltage through a power law relationship in both the experimental and simulated data. The greatest discrepancies between experimental data and simulation results were found to be in comparisons of electron density, where it appears that the simulation may be "smearing" the plasma over too wide of an axial region. Hypotheses for this behavior were discussed along with recommendations for future work.
Download or read book Probe Measurements of Plasma Properties Inside an Experimental Hall Thruster written by Y. Raitses and published by . This book was released on 1998 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Performance Evaluation of the SPT 140 written by and published by . This book was released on 1997 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Laser Spectroscopy written by Wolfgang Demtröder and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 710 pages. Available in PDF, EPUB and Kindle. Book excerpt: The impact of lasers on spectroscopy can hardly be overestimated. Lasers re present intense light sources with spectral energy densities which may exceed those of i ncoheren t sources by severa 1 orders of magnitude. Furthermore be cause of their extremely small bandwidth, single-mode lasers allow a spectral resolution which far exceeds that of conventional spectrometers. Many experi ments which could not be done before the application of lasers because of lack of intensity or insufficient resol ution are readily performed wi th lasers. Now several thousands of laser lines are known which span the whole spec tral range from the vacuum-ultraviolet to the far-infrared region. Of parti cular interest are the continuously tunable lasers which may in many cases replace wavelength-selecting elements, such as spectrometers or interferome ters. In combination with optical frequency mixing, techniques such conti nuously tunable monochromatic coherent light sources are available at nearly any desired wavelength above 100 nm.
