Browsing by Subject "Pulse circuits"
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Item Item A new mathematical design of electromechanical pulsers.(Texas Tech University, 1975-05) Ching, Shin-hwaThis work is concerned with certain mathematical aspects of the design of electromechanical pulsers which will theoretically give a simple square pulse output of low duty cycle. The problem is stated in terms of the solution of two sets of equations in number theory. Under certain assumptions, this solution is shown to be a perfect Legendre sequence, the members of which have certain group symmetric Properties.Item Alternator analysis for pulsating loads(Texas Tech University, 1978-05) Lee, Chung-ShingNot availableItem An electron beam controlled diffuse discharge switch(Texas Tech University, 1985-05) Harjes, Henry CharlesIn recent years there has been an increasing interest in the development of fast, repetitive, opening switches which would allow the use of inductive energy storage in repetitively operated pulsed power systems. An opening switch concept that shows promise for such operation is the electron beam controlled diffuse discarge switch (EBCS). An analysis of this switch that demonstrates the importance of the switch gas composition is presented and several desirable gas properties are identified. An experimental facility for the study of promising gases in a repetitively operated EBCS is also described. It includes an e-beam generating tetrode that is able to deliver an e-beam with a maximum energy of 250 keV, a risetime of 10 ns, a maximum pulse duration of lus, and a variable repetition frequency up to 25 MHz in a lys burst. Results of experiments in various switch gas mixtures are presented. Current gains of approximately 10 and opening times < 100 ns have been observed.Item Analysis of high repetition rate thyratrons(Texas Tech University, 1978-12) Hill, Gregory AlanNot availableItem Arc current, voltage, and resistance in a high energy, gas-filled spark gap(Texas Tech University, 1985-05) Maas, Brian LaneA spark gap was designed and constructed to measure the time dependent arc resistance. The arc current was measured and the arc resistance calculated using the current and the other circuit parameters. Typical operating parameters were: unipolar pulse, 35 kV breakdown voltage, 30 kA peak current, and 1.15 kJ total energy per shot. The dissipated arc energy was calculated from the arc current and resistance and found to be between 4.5% and 10.5% of the total energy. Arc resistance vs time curves were obtained for all possible combinations of three electrode materials (304 Stainless Steel, ACF-IOQ Graphite, and 3w3 Copper-Tungsten), three gases (Air, N2, and SF6), and three gas pressures ( 1 , 2, and 3 atmospheres). Statistical analysis was performed on the resultant data. Essential results are: within the statistical and measurement errors, the resistance is independent of the electrode material. For each gas, R is approximately proportional to pd (pressure and gap distance). The constants of proportionality are (31 ± 7) mΩ/(cm bar) for air, (47 + 15) mΩ/(cm bar) for N2, and (76 ± 17) mΩ/(cm bar) for SF6.Item Effects of gate current on conduction modulation in pulsed power thyristors(Texas Tech University, 2001-05) Brito, Efren LujanTexas Tech, in conjunction with PTS Company, has studied some of the device parameters of PTS's Pulse Power Thyristors(PPT), especially thePPT5325. The objective of this work was to establish the di/dt, turn-on, and reverse recovery characteristics of the PPT with varying gate drive current and anode voltage and are more specifically stated below: 1. Determine if varying gate current will improve turn-on times, 2. Determine if pulling charge from the gate will improve turn-off times and lower reverse voltages, 3. Determine the reverse recovery times, 4. Determine if the reverse recovery times can be improved by removing excess charge carriers, or plasma, from the gate with varying gate voltage, 5. Compare the PPT5325 with other pulsed power thyristors. The PPT was tested using a constant current gate drive circuit having a rise time of approximately 250ns, pulse width of lOus, and a maximum of 500A. A capacitive discharge circuit was used with anode-cathode voltages varying from OV to 1.2kV. The anode circuit is also capable of reapplying a reverse anode voltage at a specified time. This paper describes the necessary methods in designing these test circuits to obtain the device characteristics just explained.Item Erosion phenomena of arcing electrodes(Texas Tech University, 1980-05) Petr, Rodney AlanNot availableItem Fast transient behavior of thyristor switches(Texas Tech University, 1985-12) Hudgins, Jerry LynnThe fast pulse switching behavior of center-fired and interdigitated thyristors was studied by switching 10 us, 1000 A (at 800 V) pulses. Single-shot switching was performed up to 10,000 A/us, and repetitive switching at 500 Hz and 800 Hz up to 10,000 A/us for various lengths of time. No damage to the devices resulted from the switching stresses.Item Fast transient switching in bipolar junction transistors and metal-oxide-semiconductor field effect transistors(Texas Tech University, 1985-12) Menhart, SteveNot availableItem Item Magnetic flux compression for high voltage pulse applications(Texas Tech University, 2004-08) Hernandez Llambes, Juan CarlosHelical Magnetic Flux Compression Generators (MFCG) are the most promising energy sources with respect to their current amplification and compactness. However, their intrinsic flux loss limits severely their performance and it is not yet well understood. All flux losses have a differing degree of impact, depending on the generator's volume, current and energy amplification, size of the driven load, and angular frequency of armature-helix contact point. Although several computer models have been developed, none of them truly quantify the ohmic and intrinsic flux losses. This dissertation describes a novel method that provides a separate calculation of intrinsic flux losses (flux that is left behind in the conductors and lost for compression) and ohmic losses. It also provides a second method that uses simple flux quantification, making a mathematical connection between the intrinsic flux losses, quantified by the first method, and the intrinsic flux losses observed in the generators. This second method can also be used with the first method to a priori estimate the MFCG performance. Simple MFCG with a single helix produce high output energy only into low inductance loads, thus producing several 100 kA of current at a voltage level of less than l0kV. Many pulsed power devices require less current but a considerably higher voltage level. For effectively driving a high inductance load of several µH, a multistage MFCG design has also been successfully tested with a total length of 250 mm, a helix inner diameter of 51 mm, achieving an energy gain of ~13 into a 3 µH load. Further power conditioning utilizing an exploding wire fuse enables driving an electron beam device. Typical load parameters of electron beam devices are several 100 kV operating voltage with an impedance of a few tens of Ohms. Utilizing a multi-stage FCG as primary source for inductive energy storage with opening switch enables the production of voltages in excess of 100's kV. We built an exploding wire fuse with a length of 140mm and 100mm in diameter (including the storage inductor), conditioned to the MFCG described above. We achieved a voltage of ~ 42kV directly across the 3µH inductor, and more than 130kV with the fuse opening switch operating into a ~12-15 Ù load.Item Photodetachment as a discharge control mechanism in gases containing oxygen(Texas Tech University, 1985-05) Thurmond, Leo ErasmusInterest in high voltage switches for pulsed power applications has increased significantly in the last several years. Inductive energy storage has space and weight advantages over capacitive energy storage, but requires the use of a high power opening switch. Opening switch technology has only recently started to be developed, and several concepts for opening switches are being studied. One of these concepts is the diffuse discharge switch, which shows several advantages over other types of opening switches. One major advantage of the diffuse discharge switch is that it may be controlled externally by an electron beam or by optical means. There are several processes possible for optical control of a diffuse discharge, one of which is photodetachment. In this paper, three experiments are presented which study the possibility of using photodetachment as a discharge control mechanism in gases containing 02 are presented. The first experiment shows the effect of photodetachment outside the discharge and the dependence of the effect on laser energy flux density. The second experiment demonstrates the feedback effect of photodetachment on a glow discharge. Operating conditions for the largest effect are presented. The last experiment simulates the conditions in a high power switching device, and the preliminary results of this study are given.Item Pulse forming network investigation.(Texas Tech University, 1975-08) Cook, Edward GuyNot available.Item Pulsed magnetic field effects on dielectric surface flashover in vacuum(Texas Tech University, 1990-08) Lehr, F. MarkThe influence of pulsed magnetic fields on dielectric surface flashover in vacuum is investigated under non-uniform field conditions. The magnetic field is applied parallel to the dielectric surface and perpendicular to the electric field, which is derived from a pulsed test voltage. Predictions from computer simulations of the saturated surface avalanche process, using non-uniform fields, point to the importance of conditions at the cathode in producing magnetic insulation effects, i.e., an increase in the surface flashover voltage with an applied magnetic field. Experimentally, substantial increases in the surface flashover voltage are observed with the vector ExB pointing away from the surface. The maximum relative increase in the surface flashover voltage occurs with the maximum magnetic field or the minimum electric field applied at the cathode. Breakdown over long paths, induced by the magnetic field when ExB points into the surface, is investigated experimentally. Experiments conducted with a low density background plasma indicate that the magnetic field successfully shields the insulator surface from the plasma electrons when ExB points away from the insulator surface.Item Pulser design and performance for an electron beam gun(Texas Tech University, 1977-05) Wilson, Dale GNot availableItem Synthesis of Pulse Forming Networks for General Resistive Loads(Texas Tech University, 1979-05) Roark, Ricki MorrisNot Available.Item Turnoff transients in power switching transistors(Texas Tech University, 1986-08) Katsaras, Michael ENot availableItem Voltage recovery studies for a high energy spark gap(Texas Tech University, 1984-08) Yeh, Chung HsiungAn investigation of the voltage recovery vs time for a high energy spark gap has been performed with N2, air , SF5 , and mixtures of these as filler gases and with copper-tungsten, stainless steel, and graphite electrodes. The goal of the work was to determine the main parameters affecting the free recovery (no gas flow) of the spark gap. The percentage voltage recovery of a spark gap was measured by applying two (1 - coswt) or two ( 1 -exp(-t/RC)) successive pulses with varying parameters. The important factors that determine the percentage voltage recovery include the charging rate, the gas pressure, the energy deposited in the spark gap, the statistical delay time, and the attachment coefficient of the gas. The time to 90% voltage recovery, at a gap pressure of 1 atm, is about 1.5 ms in SF5 and SFs-No gas mixtures, 2 ms in a i r , and 3 ms in N2. The i n i t i al temperature after spark gap breakdown was measured spectroscopically by a two-line intensity ratio method. The gas density variation (or the temperature variation) was examined by Mach-Zehnder interferometry. The thermal expansion velocity evaluated from the interferograms is about 10^ to 10^ cm/s. The spatial position of the pulse pair with different delay times has been observed for plane electrodes. The results show that the breakdown position is determined by the density variations between electrodes and Paschen's Law, as expected. The Edels voltage recovery model was used to predict the theoretical voltage recovery. It is in quantitative agreement with the experimental data.