Showing papers on "Marx generator published in 2002"

Marx generator design and performance

Abstract: This paper presents a broad overview of Marx generators, ranging from the traditional Marx generator to the wave erection generator. It is specifically written as a brief introduction to key concepts with references tied to each area. Key topics include operating techniques, triggering techniques, switches, repetition rates, jitter, and applications.

Capillary discharge soft X-ray lasing in Ne-like Ar pumped by long current pulses

Abstract: A capillary discharge soft X-ray laser operating at 46.9 rim on the transition 3p–3s (J=0−1) of the Ne-like Ar has been realized by exciting the active medium with a long half-cycle duration current pulse of 140 ns. The current is produced by discharging a 10 nF water dielectric capacitor, initially charged to voltages lower than 200 kV by a six stage Marx generator, through a 15-cm long capillary channels. The laser amplification has been obtained by properly adjusting all the other experimental parameters. Utilizing a 3-mm in diameter AI2O3 capillary channel initially filled with 0.3 torr of Ar pressure, a laser beam, which has a 4-mrad divergence and a time duration of 1.3 ns, is characterized by a gain of 0.6 ± 0.1 cm−1. The stability of the plasma compression followed by the laser emission is verified.

Characterization of a high-intensity bipolar-mode pulsed ion source for surface modification of materials

Abstract: A high-intensity pulsed ion source of TEMP-type series, operating in bipolar mode, has been developed as a unique pulsed energy source to produce a high-intensity pulsed ion beam (HIPIB) for surface modification of materials. To generate the ion beam, a specially shaped bipolar pulse, consisting of a first negative pulse and a second delayed positive pulse both of nanosecond width, is formed by a double coaxial pulse-forming line (PFL) powered with a Marx generator and supplied to a magnetically insulated ion diode (MID) by a self-magnetic field. It is found that the efficient generation of a HIPIB is mainly dependent on the delay time of the bipolar pulse, adjusted by pressure ratio in the two gas switches of a PFL, and the anode–cathode (A–K) gap distance in the self-magnetic field MID. The delay time determines the effective area on the anode surface for plasma generation and the A–K gap distance ensures the stability of the process. A proper delay time and a proper A–K gap distance are obtained by a s...

The ZR refurbishment project

Abstract: ZR is a refurbished (R) version of Z aiming to improve its overall performance, reliability, precision, pulse shape tailoring and reproducibility. Z, the largest pulsed power machine at Sandia, began in December 1985 as the Particle Beam Fusion Accelerator II (PBFA II). PBFAII was modified in 1996 to a z-pinch driver by incorporating a high-current (20-MA, 2.5-MV) configuration in the inner ∼ 4.5 meter section. Following its remarkable success as z-pinch driver, PBFA II was renamed Z in 1997. Currently Z fires 170 to 180 shots a year with a peak load current of the order of 18–20 MA. The maximum z-pinch output achieved to date is 1.6-MJ, 170-TW radiated energy and power from a single 4-cm diameter, 2-cm tall array, and 215 eV temperature from a dynamic hohlraum. ZR in turn will, operating in double shift, enable 400 shots per year, deliver a peak current of 26 MA into a standard 4cm × 2cm Z-pinch load, and should provide a total radiated x-ray energy and power of 3 MJ and 350 TW, respectively, achieve a maximum hohlraum temperature of 260 eV, and include a pulse-shaping flexibility extending from 100ns to 300ns for equation of state and isentropic compression studies. To achieve this performance ZR will incorporate substantial modifications and upgrades to Marx generator, intermediate store capacitors, gas and water switches, water transmission lines and the laser triggering system. Test beds are already in place, and the new pulsed power components are undergoing extensive evaluation. The Z refurbishment (ZR) will be operational by 2006 and will cost approximately $60M.

Performance of the Cygnus x-ray source

Abstract: Cygnus is a radiographic x-ray source developed for support of the Sub-Critical Experiments Program at the Nevada Test Site. Major requirements for this application are: a dramatically reduced spot size as compared to both Government Laboratory and existing commercial alternatives, layout flexibility, and reliability. Cygnus incorporates proven pulsed power technology (Marx Generator, Pulse Forming Line, Water Transmission Line, and Inductive Voltage Adder sub-components) to drive a high voltage vacuum diode. In the case of Cygnus, a relatively new approach (the rod pinch diode [1]) is employed to achieve a small source diameter. Design specifications are: 2.25 MeV endpoint energy, < 1 mm source diameter, and >3 rads dose at 1 meter. The pulsed power and system architecture design plan has been previously presented [2]. The first set of Cygnus shots were geared to verification of electrical parameters and, therefore, used a large area diode configuration offering increased shot rate as compared to that of the rod pinch diode. In this paper we present results of initial rod pinch operation in terms of electrical and radiation parameters.

Performance of the Cygnus X-ray source

Abstract: Summary form only given. Cygnus is a radiographic X-ray source developed for support of the Sub-Critical Experiments Program at the Nevada Test Site. Major requirements for this application are: a dramatically reduced spot size as compared to both Government Laboratory and existing commercial alternatives, layout flexibility, and reliability. Cygnus incorporates proven pulsed power technology (Marx Generator, Pulse Forming Line, Water Transmission Line, and Inductive Voltage Adder sub-components) to drive a high voltage vacuum diode. In the case of Cygnus, a relatively new approach (the rod pinch diode) is employed to achieve a small source diameter. Design specifications are: 2.25 MeV peak energy, < 1 min source diameter, and 5-10 rads dose at 1 meter. The pulsed power and system architecture design plan has been previously presented (Weidenheimer et al., 2001). The first set of Cygnus shots are now underway and are geared to verification of electrical parameters and, therefore, use a large area diode configuration offering increased shot rate as compared to that of the rod pinch diode. Later tests incorporate the rod pinch diode and will concentrate on X-ray production with time resolved measurements of X-ray dose and spot size. In this work we present results of initial operation in terms of electrical and radiation parameters. In addition, the issues associated with static and time resolved radiographs may be included. Performance of the pulse power system is being evaluated by comparison of measured to design output parameters. This is accomplished by comparison of multiple voltage and current measurements throughout the system with various circuit model codes such as MicroCAP and T-Line.

The ZR refurbishment project

Abstract: ZR is a refurbished (R) version of Z aiming to improve its overall performance, reliability, precision, pulse shape tailoring and reproducibility. Z, the largest pulsed power machine at Sandia, began in December 1985 as the Particle Beam Fusion Accelerator II (PBFA II). PBFA II was modified in 1996 to a z-pinch driver by incorporating a high-current (20 MA, 2.5 MV) configuration in the inner /spl sim/ 4.5 meter section. Following its remarkable success as a z-pinch driver, PBFA II was renamed Z in 1997. Currently Z fires 170 to 180 shots a year with a peak load current of the order of 18-20 MA. The maximum z-pinch output achieved to date is 1.6 MJ, 170 TW radiated energy and power from a single 4 cm diameter, 2 cm tall array, and 215 eV temperature from a dynamic hohlraum. ZR in turn will, operating in double shift, enable 400 shots per year, deliver a peak current of 26 MA into a standard 4 m /spl times/ 2 m Z-pinch load, and should provide a total radiated X-ray energy and power of 3 MJ and 350 TW, respectively, achieve a maximum hohlraum temperature of 260 eV, and include a pulse-shaping flexibility extending from 100 s to 300 s for equation of state and isentropic compression studies. To achieve this performance ZR will incorporate substantial modifications and upgrades to Marx generator, intermediate store capacitors, gas and water switches, water transmission lines and the laser triggering system. Test beds are already in place, and the new pulsed power components are undergoing extensive evaluation. The Z refurbishment (ZR) will be operational by 2006 and cost approximately $60M.

Marx-stacked IGBT modulators for high voltage, high power applications

Abstract: A number of applications that require <1 /spl mu/sec risetimes at high voltage and current cannot be easily satisfied with standard designs employing low voltage solid-state components driving a large step-up turns ratio transformer North Star Research reports on the development of several products that employ the topological erection of voltages using a Marx generator stacking arrangement of lower voltage IGBT devices The configuration does not place the semiconductors in a series arrangement, thereby eliminating a failure mode wherein the loss of a single device would over-stress the stack of IGBT parts A plasma source ion implantation (PSII) modulator has been built using this technology development and provides 30 kV, 400 A, 1-50 /spl mu/sec variable pulse widths, and operates at 75 kW of average power Peak powers as high as 24 MW have been demonstrated

Rapid capacitor charger

Abstract: The increased interest in radio-frequency (RF) weapons for electronic warfare has increased the demand for rapid capacitor chargers. In most cases these charger have to operate from a DC power source and typically have to charge a capacitor bank (Marx bank) at a rate of about 10 Hz. Besides the requirements for energy delivery, the space constraints are crucial. In order to fulfill both, major components have to be operated above their specifications. However, they only need to perform for a short burst with enough time between events to enable use of thermal inertia.

Impulse generator and method for perforating a cased wellbore

Abstract: An impulse generator ( 76 ) and method for using an impulse generator ( 76 ) to initiate a detonation in a shaped charge perforating apparatus ( 60 ) is disclosed. The shaped charge perforating apparatus ( 60 ) is adapted for use in a wellbore ( 62 ) and includes a plurality of shaped charges ( 86 ). A detonation cord ( 98 ) is operably coupled to each of the shaped charges ( 86 ). An initiator ( 78 ) is operable to detonate the detonation cord ( 98 ) upon receiving a triggering impulse. A Marx generator within the impulse generator ( 76 ) provides the triggering impulse to the initiator ( 78 ).

Pulse power for future and past X-ray simulators

Abstract: Studies were made of pulse-power designs to drive 100-ns and 250-ns Z-pinches that are predicted to produce 400kJ of 13-keV krypton K-shell radiation. A radiating Z-pinch model and a simplified circuit model were used to optimize the Z-pinch and general driver parameters. Four 250-ns driver architectures are described that were developed into point designs; we used present Syllac-capacitor style Marx generators and then progressively lower inductance ("fast") Marxes or pulser stages connected in series in "linear transformer" drivers. The point designs are compared with each other and with very low inductance pulser technology developed by the U.S. Department of Defense in the 1970s and 1980s, which is described. Initial aims of a fast Marx component development program, to build on previous experience and make to available the advantages of the more advanced point designs, are presented.

Design and setup of a short pulse simulator for susceptibility investigations

Abstract: In this paper, the setup of a short pulse simulator for susceptibility investigations is presented. This simulator consists of a compact ultrawide-band source and a half impulse radiating antenna. First measurements of the simulator are compared with calculated fields. The application of interest is the generation of an ultrashort pulse with a high electromagnetic field strength.

Solid-state pulsed power systems for the Next Linear Collider

Abstract: The Next Generation Linear Collider (NLC) represents a significant challenge for high voltage modulator technology. It will require pulse modulators capable of driving over 1600 NLC klystrons at 500 kV, approximately 265 A apiece, with 3.2 microsecond pulses at 180 Hz. These pulses also have strict tolerances for flattop and voltage regulation. Average klystron input power for the complete NLC system is approximately 120 MW-representing $6-12M or more per operating hour. All losses in the power systems between the utility and the klystron must be added to this power cost, making efficiency of these systems paramount. Given the large number of modulators required and the total cost of power for the NLC, overall life cycle costs, not just the initial equipment cost, will be a significant factor in the affordability of the NLC. DTI's efforts are focused on three modulator configurations: a "hybrid modulator", using a solid-state switch and a pulse transformer, and two transformerless designs, one based on a 500 kV hard switch, and a second based on solid-state Marx bank. Each of these is discussed in this paper.

The generation of high electric field strength RF energy using Marx generators

Abstract: The Wave Erection Marx Generator is proving to be an excellent high voltage source for the direct generation of RF energy. Unfortunately, effectively radiating the impulse energy is challenging, both in efficiency and high voltage-holdoff capability. Successful efforts have been made to generate RF energy in both the Narrow Band and Ultra Wideband realm, with field strengths in excess of I kV/m at 100 m achieved. This paper briefly describes the impulse generator and explores its use for generating Narrow Band RF energy as well as Ultra Wideband energy. Experimental results will be presented.

The direct generation of High Power Microwaves with compact Marx generators

Abstract: High Power Microwave energy may be directly generated with ultra-fast voltage pulses driving an antenna Recent efforts with the wave erection Marx generator have seen the production of voltage pulses in excess of several hundred kV, with rise times as fast as 200 ps This generator has been used to source Ultra Wideband antennas as well as Narrow Band antennas, each resulting in high electric field strengths This paper describes the Marx generator and explores its use for generating UWB and NB energy Experimental results are presented

Prototype IVA module

Abstract: A prospective module has been designed for a future large inductive voltage adder (IVA) machine that would be suitable for the most demanding radiography carried out at AWE Aldermaston, Berkshire, UK. This machine would operate at 13-15 MV. The prototype IVA module (PIM) machine has been built to test a single such module and may also provide the basis for other, lower voltage machines in the future. It consists of a single inductive cavity pulsed by a 10-/spl Omega/ water dielectric Blumlein pulse forming line which is charged by a Marx generator. The Blumlein switch initially installed was a coaxial two stage Rimfire and Trigatron switch. A laser triggering configuration utilizing two radial switches, designed by Titan PSI, is also to be tested. The Blumlein PFL and its switch were tested using a copper sulphate resistive load and achieved a peak output voltage of 1.7 MV. The inductive cavity has been added and a pulse of 1.5-MV peak voltage has been successfully applied to it.

Compact Pulsed Power Sources

Abstract: Marx generators have been traditionally relegated as pulse-charging supplies for a variety of applications including the generation of High Power Microwaves, or RF energy Compact models have served as suitable trigger generators for larger systems However, recent work has demonstrated the compact Marx generators for directly generating RF energy This paper discusses two compact Marx generators developed for RF applications General performance characteristics for each generator are discussed, as well as efforts to minimize the temporal jitter of these systems so as to make them viable sources for radar transmitters The Gatling Marx generator is presented as a multiple generator RF source for weapons and radar transmitters Finally, the generation of RF and microwave energy is discussed

Study of high energy storage Blumlein transmission lines as high power microwave drivers

Abstract: Summary form only given. The evolution of high power microwave (HIPM) sources as practical systems requires the development of compact, portable, reusable, pulsed power systems. One approach to pursuing this objective is to utilize parallel-stacked Blumlein transmission lines energized using a compact Marx generator. Such a configuration would be capable of driving low impedance HPM sources with a long pulse waveform. One of the limitations of this approach is field enhancement-induced breakdown at the edges of the line. This presentation will describe a research program that will both computationally and experimentally study electrical breakdown in such transmission line configurations for a variety of dielectric materials and substrate geometries. Calculations are being performed using the commercial code HFSSTM (Agilent/Ansoft). Results to-date of this research, and its overall relation to intense beam-driven HPM source development will be discussed.

Soft x-ray output from a pinch plasma using laser-induced Au plasma

Abstract: An experimental investigation of the characteristics of soft x-ray output emitted from a pinch plasma using a laser-induced Au plasma has been performed. The Au plasma is produced by focusing a laser pulse with a focal spot diameter of 100 μm on the tip of an Au pin anode electrode. A pulsed pinch discharge driven by a Marx generator utilizes the plasma as a discharge medium. Soft x-ray output with a pulse duration of ∼120 ns, an energy of ∼1 μJ mm−2, and an effective photon energy of ∼1 keV, has been obtained with the discharge. It is shown that the output characteristics depend strongly on the Marx charging voltage, laser pulse energy, and delay time of the discharge from the laser irradiation.

Experiments on PIM in support of the development of IVA technology for radiography at AWE

Abstract: The PIM machine has been designed and constructed at AWE as part of a program to investigate IVA technology for radiographic applications. PIM, as originally constructed, was a prospective single module of a 14 MV, 100 kA, ten module machine. The design of such a machine is a primary goal of the program as several are required to provide multi-axis radiography in a new Hydrodynamics Research Facility (HRF). Another goal is to design lower voltage machines (ranging from 1 to 5 MV) utilizing PIM style components. The original PIM machine consisted of a single inductive cavity pulsed by a 10 ohm water dielectric Blumlein pulse forming line (PFL) charged by a Marx generator. These components successfully achieved their design voltages and data on the prepulse was obtained showing it to be worse than expected. This information provided a basis for design work on the 14 MV HRF IVA, carried out by Titan-PSD, resulting in a proposal for a prepulse switch, a prototype of which should be installed on PIM by the end of this year. The original single, coaxial switch used to initiate the Blumlein has been replaced by a prototype laser triggered switching arrangement, also designed by Titan-PSD, which it was desired to test prior to its eventual use in the HRF. Despite problems with the laser, which will necessitate further experiments, it was determined that laser triggering with low jitter was occurring. A split oil co-ax feed has now been used to install a second cavity, in parallel with the first, on the PIM Blumlein. This two cavity configuration provides a prototype for future radiographic machines operating at up to 3 MV and a test facility for diode research.

Intense XUV emission generated by a capillary discharge based apparatus

Abstract: We present the characterization of an apparatus generating XUV radiation by a high peak value (20–40) kA and short rise time (≈ 20 ns) current pulse in a capillary discharge channel (up to 20 cm in length) filled by argon gas. The apparatus has been developed with the purpose of production of an intensive spontaneous emission in the spectral region of (2–50) nm and study of the z-pinch conditions for obtaining the laser generation in the Nelike Ar at 46.9 nm. The current pulses are generated by the direct discharge of a 7 nF water dielectric capacitor resonantly charged up to 400 kV by a six-stages Marx generator. The XUV radiation emitted during the radial compression of the plasma column is measured using calibrated PIN diodes, filters and multilayer mirrors in order to test the z-pinch plasma collapse and to measure the conversion efficiency of the electrical energy into the XUV radiation.

Solid-state pulsed power systems for the Next Linear Collider

Abstract: The Next Generation Linear Collider will require pulse modulators capable of driving over 1600 NLC klystrons at 500 kV, approximately 265 A, with 3.2 microsecond pulses at 180 Hz with strict tolerances for flattop and voltage regulation. In 1999, Diversified Technologies, Inc. (DTI) was awarded two Phase II Small Business Innovative Research (SBIR) grants from the Department of Energy to assess the application of solid state switching technology to the NLC. DTI's efforts are focused on three modulator configurations: a hybrid modulator, a transformerless design and a solid state Marx bank switch.

Fast discharge energy storage development for improving X-ray simulators

Abstract: Over the last two years there have been design studies to investigate the impact of improvements in fast energy storage systems on the design of simulator upgrades (Double-EAGLE and Decade Quad) and on larger future simulators (40-MA to 60-MA PRS machine). The fast energy storage systems investigated in these design studies included Fast Marx Generators (FMG with √LC = 200 ns and √LC = 300 ns) and Linear Transformer Drivers (LTD). A design sketch of a compact 20-MA PRS driver and a potential upgrade of Double-EAGLE using FMG technology will be presented. The first concept that will be discussed is a 16-MA driver for PRS (plasma radiation source) loads. This generator would consist of 48 eight-stage FMG units and 13 m diameter and would drive the PRS directly without further pulse compression. The second concept that will be presented is a potential upgrade of an operational simulator, Double-EAGLE. This concept would utilize the FMG to replace the existing slower Marx generator, transfer capacitor and triggered gas switch. The basic building blocks for these future FMG driven machines are a low- inductance Marx switch and a low-inductance capacitor designed to be integrated with the new switch. These components are configured in a low-inductance FMG stage and then stacked in series to form a unit for the voltage required and a number of units in parallel for the required system inductance and stored energy. A review of the FMG component requirements and the status of the FMG component testing in a single-stage FMG configuration will also be presented. A four-stage FMG unit is being built and tested to demonstrate the required stage voltage and inductance. Results of these initial tests will be presented.

Design of a new driver for fast and ultra-powerful capillary discharge

Abstract: A new driver for fast capillary and ultra-powerful capillary discharge is designed. The designed new apparatus is capable to reach a potential transition to shorter wavelengths. A geometry of its all main parts enables axial access to both capillary ends. The "transparent" capillary distinctly simplifies adjustment, monitoring and subsequent applications of the capillary discharge experiments. As a next free parameter for the new driver the Marx generator has been added as well. The new Marx generator is designed and solved for two types of composing capacitors. Results of two models of the designed driver are presented.

The pulsed compact electron source

Abstract: Summary form only given, as follows. The pulsed compact electron source with plasma cathode is considered in the report. The source consists of high voltage pulsed Marx generator and vacuum diode with plasma cathode on the basis of explosive electron emission. The plasma emitter on the basis of vacuum discharge forming on the surface of the nanotubes of cathode is used in this electron source. The electron source has next main parameters: accelerating voltage 100-150 kV, beam current 5-200 A, pulse duration 100-400 nsec. The experimental data for forming of cathode plasma: time and energy characteristics are discussed. The comparison of forming cathode plasma for carbon fibers and carbon nanotubes is experimental results with computer simulation is presented. The given. The physical model for explanation of forming stable cathode plasma is suggested.

Raising the Efficiency of a Plasma Opening Switch by Applying an External Magnetic Field

Abstract: The influence of an external magnetic field on the performance of a high-impedance plasma opening switch is studied experimentally. A 1.5-fold increase in the output voltage of a plasma opening switch operating in the erosion mode is achieved by applying an external magnetic field. The magnetic field strength and the parameters of the plasma opening switch at which the maximum output voltage is attained are determined. It is shown experimentally that the predicted dependence of the maximum output voltage on the Marx generator voltage, UPOS [MV]=3.6 (UMG [MV])4/7, is confirmed experimentally.

Intense source of nanosecond duration 10-KeV to 250-KeV x rays

Abstract: The fabrication and the fundamental study of a repetitive nanosecond x-ray generator having a sealed field emission x-ray tube is described. A compact Marx generator storing 12 Joules directly drives a field emission tube with voltage pulses > 380 kV and with < 4 nanosecond risetime from an equivalent generator-impedance of 52 Ω. A numerical model is used in which the x-ray tube's cathode width and anode-cathode gap (AK) spacing are permitted to change with time while electron flow between the cathode and anode is space-charge-limited (SCL) and nonrelativistic. Coupling this model to an equivalent circuit representation of the Marx generator, which includes the voltage variation of the BaTiO3 Marx capacitors, an estimation of the cathode current, anode-cathode potential and the x-ray spectrum was obtained and compared with measured values.

Small compact pulsed electron source for radiation technologies

Abstract: The small compact pulsed electron source for radiation technologies is considered in the report. The electron source consists of pulsed high voltage Marx generator and vacuum diode with explosive emission cathode. The main parameters of electron source are next: kinetic energy is 100–150 keV, beam current is 5 – 200 A and pulse duration is 100 – 400 nsec. The distribution of absorbed doses in irradiated materials is considered. The physical feasibility of pulsed low energy electron beam for applications is considered.