Showing papers on "Marx generator published in 1975"

Production of dense thermonuclear plasmas by intense ion beams

Abstract: For very high density plasmas, large energy accumulation within a small volume is required. As an alternative to laser- or relativistic electron-beams, the employment of intense non-relativistic beams of heavy ions is considered. Because of the rather low ion velocities, the beams can be axially compressed thereby shortening the duration of the beam pulse and increasing the beam power by perhaps several orders of magnitude. The low ion velocities make it possible to build up the beam rather slowly in about approximately 10-6 sec, prior to its axial compression and delivery to the target. This long build up time may permit the use of cheap inductive energy storage devices to drive the beam. In case capacitors are used one can simply pulse the beam with the upper terminal of a Marx generator.

Untriggered Water Switching

Abstract: Recent experiments indicate that synchronous untriggered multichannel switching in water will permit the development of relatively simple, ultra-low impedance, short pulse, relativistic electron beam (REB) accelerators. These experiments resulted in the delivery of a 1.5 MV, 0.75 MA, 15 ns pulse into a 2 ? line with a current risetime of 2 x 1014 A/sec. The apparatus consisted of a 3 MV Marx generator and a series of three 112 cm wide strip water lines separated by 2 edge-plane water-gap switches. The Marx generator charged the first line in < 400 ns. The first switch then formed 5 or more channels. The second line was charged in 60 ns and broke down with 10 to 25 channels at a mean field of 1.6 MV/cm. The closure time of each spark channel along both switches was measured with a streak camera and showed low jitter. The resulting fast pulse line construction is simpler and should provide considerable cost savings from previous designs. Multiples of these low impedance lines in parallel can be employed to obtain power levels in the 1014 W range for REB fusion studies.

OWL II pulsed‐electron‐beam generator

Abstract: OWL is a water‐dielectric line‐type pulse generator capable of producing ∠100‐nsec electron beams with total energies of as much as 150 kJ. In its present form, OWL II consists of an oil‐immersed, 1/3‐MJ Marx generator charging a 3.9‐Ω coaxial pulse‐forming line which is series switched into either a two‐ or three‐stage impedance transformer. The output impedance is 1.9 or 1.1 Ω, depending upon which transformer is used, and nominal beam outputs in the two cases are 1.3 MV at 0.8 MA and 0.9 MV at 1.2 MA, respectively. The pulse width can be selected at either 60 or 120 nsec (FWHM of power) by interchanging two available pulse lines. Shot‐to‐shot reproducibility in output of ±2% with a mean electron energy ∠1.0 MeV is obtained with the 1.9‐Ω final transformer. A triggered multichannel water switch minimizes the risetime of pulses injected into the transformer section.

Laser Triggered Switching of a Pulsed Charged Oil Filled Spark Gap

Abstract: A focused, Q‐spoiled laser, aligned along the interelectrode axis of a pulse charged switch assembly, was used to initiate the conduction of an overvolted transformer oil filled gap. Laser power varied between 5 and 200 MW and the voltage pulse exhibited a risetime of 500 nsec to a voltage of 700 kV. A parametric study of the factors affecting the delay between the laser pulse arrival at the gap and conduction of the gap was accomplished, in which the effects of the focal point location, laser power, switch polarity, and voltage on the gap at laser arrival were determined. Delay times as short as 12 nsec were recorded with jitter, a measure of reproducibility, in the low nanosecond region.

The VEBA Relativistic Electron Accelerator

Abstract: The VEBA high-current, relativistic electron accelerator has been designed and constructed at NRL for application in the study of high-power microwave sources. To meet the requirements of this study, the accelerator was designed for operation in either a short (60 nsec) or long (2.2 ?sec) pulse mode. The short-pulse mode has been in operation for nearly two years and has proven to be an extremely reliable design. The design of the long-pulse mode is now complete and component fabrication will soon be underway. The pulse-forming network in the short-pulse mode is an unbalanced, water Blumlein with an output impedance of 9.2? The Blumlein is pulse charged by a 17 stage Marx generator which has a series capacitance of 29.4 nF. By transmission along a tapered coaxial line, the output pulse is transformed to 20 ? and the voltage developed across a matched load increased to a maximum of 2.5 MV. The proposed conversion to the long-pulse mode will require that the Blumlein and transformer sections be removed and the diode assembly be attached directly to the oversized Marx tank. The direct coupling between the Marx and the Blumlein will then be replaced by two, nested, water capacitors which are shunted by spiral inductors. When coupled in series with the Marx, this output filter will form a three-section, voltage-fed, Guillemin (type A), pulse-forming network with a characteristic impedance of 40 ? and a maximum output voltage of 0.9 MV.

The VEBA relativistic electron accelerator

Abstract: The VEBA high-current, relativistic electron accelerator has been designed and constructed at NRL for application in the study of high-power microwave sources. To meet the requirements of this study, the accelerator was designed for operation in either a short (60 nsec) or long (2.2 ?sec) pulse mode. The short-pulse mode has been in operation for nearly two years and has proven to be an extremely reliable design. The design of the long-pulse mode is now complete and component fabrication will soon be underway. The pulse-forming network in the short-pulse mode is an unbalanced, water Blumlein with an output impedance of 9.2? The Blumlein is pulse charged by a 17 stage Marx generator which has a series capacitance of 29.4 nF. By transmission along a tapered coaxial line, the output pulse is transformed to 20 ? and the voltage developed across a matched load increased to a maximum of 2.5 MV. The proposed conversion to the long-pulse mode will require that the Blumlein and transformer sections be removed and the diode assembly be attached directly to the oversized Marx tank. The direct coupling between the Marx and the Blumlein will then be replaced by two, nested, water capacitors which are shunted by spiral inductors. When coupled in series with the Marx, this output filter will form a three-section, voltage-fed, Guillemin (type A), pulse-forming network with a characteristic impedance of 40 ? and a maximum output voltage of 0.9 MV.

Split-ring marx generator grading

Abstract: Metallic tubing bent to a shape consistent with the cross-sectional shape of a Marx generator, tubing is split into two symmetrical halves and insulated; two halves combined have an initial DC potential equal to one stage voltage, after erection of the Marx the potential collapses to zero.

Cold cathode investigation

Abstract: Experiments for the evaluation of a cold cathode electron gun are described. Different anode and cathode materials and configurations were tried. Small signal gains of 6.3 percent/cm were measured. It was found that the same small signal gains could be obtained with less energy deposition in the laser gas with the larger pre-ionizing currents from a cold cathode. Long-duration pulses were observed that were limited only by the electrical energy available in the Marx bank. (auth)

Trace I, A Transformer-Charged Electron Beam Generator

Abstract: A transformer-charged electron beam generator has been developed. The system is designed to operate with up to 500 kV on a water-dielectric pulse-forming line (PFL) and to generate a 100 kA, 30 ns electron beam. The transformer charging supply replaces a 12-stage Marx generator and reduces the size, weight, and complexity of the system. It also eliminates the need for a large insulating-oil supply. A description of the physical features of the machine is included along with a discussion of the electrical characteristics of the system.