This paper presents a systematized review of the research on the production of nanosecond high-power pulses using solid-state generators based on an inductive energy store and a semiconductor opening switch that have been performed in the past 25 years. This research has been underway since 1992-1993 when the nanosecond cutoff of ultrahigh-density currents in semiconductor diodes was discovered and named the SOS (Semiconductor Opening Switch) effect. The discovery of the SOS effect provided a breakthrough in the development of semiconductor generators, as their most important characteristics, such as pulse power and output voltage, were increased tens and hundreds of times compared with previously known semiconductor generators. In particular, in the nanosecond semiconductor technology, megavolt voltages combined with gigawatt peak powers have been achieved. This review considers the main physical processes that determine the mechanism of operation of a SOS based on the SOS effect. The principle of operation, design, and characteristics of SOS diodes and SOS generators is described, and prospects for their further development are discussed. Examples are given of using SOS generators in various pulsed power applications such as electron accelerators, X-ray pulse devices, high-power microwave electronics, pumping of gas lasers, and ignition of electrical discharges.

Pulsed power technology based on semiconductor opening switches: A review.

Methods and an apparatus for determining a radiation dosage received by a product being exposed to radiation in an irradiator cell through a computer simulation are provided. One exemplary method includes a computer simulation for determining radiation dosages received by a product to be passed along a radiation cell, where the product is to be stationary at a set number of locations within the cell is provided. The method initiates with a point on the product being defined. Then, pre-calculated lengths between the point on the product and the radiation source at each of the set of locations in the cell are identified. Next, a dosage of radiation to be received by the point on the product at each location is calculated using the pre-calculated lengths.

Method and apparatus for simulating a radiation dose delivered to an object

Multi-kilojoule repetitive pulsed power technology moved from a laboratory environment into its first commercial application in 1997 as a driver for ion beam surface treatment. Sandia's RHEPP II (Repetitive High energy Pulsed Power), a repetitive 2.5 kJ/pulse electron beam accelerator, has supported the development of radiation treatment processes for polymers and elastomers, food products, and high dose-rate effects testing for defense programs since early 1996. Dos Lineas, an all solid-state testbed, has demonstrated synchronization techniques for parallel magnetic modulator systems and is continuing the development of design standards for long lifetime magnetic switches and voltage adders at a shot rate capability that exceeds 5/spl times/10/sup 6/ pulses per day. This paper describes progress in multi-kilojoule class repetitive pulsed power technology development, magnetic switching technology for modulator applications, and future research and development directions.

Status of repetitive pulsed power at Sandia National Laboratories

A plasma opening switch using laser produced plasma is successfully operated at repetition rates up to 3.3 pulses per second. It is shown that the switch performance has good reproducibility without any maintenance. Reliability tests indicate that the switch lifetime is limited by the volume of the target material and the lifetime of the energy storage capacitor.

Repetitively operated plasma opening switch using laser produced plasma

The plasma opening switch (POS) is a key element producing nanosecond high-voltage pulses in many pulsed power systems using inductive energy storage. For POS experiments with microsecond conduction times described in the paper, an erosion regime is considered to be critical at the opening and power delivery phases. The technique to enhance the magnetic insulation of the POS gap and to increase the switching voltage using externally applied magnetic field is discussed. Examples of use of the applied field for microsecond sub-MA POS to achieve switching voltages up to 3 MV are reported. Further development of POS schemes at megaampere currents is discussed. A design of the new six-section POS is proposed for the 3.7 MA facility prototyping the 1/24 of the future concept of the multimegajoule Baikal generator.

Microsecond plasma opening switches in externally applied magnetic field

Operation peculiarities of the RS-20 generator based on the plasma opening switch (POS) including its repetitive operation capabilities are reviewed. They are: limited current value, gas emission, pulsed heat loads, etc. The feasibility of a POS with maximum impedance and relatively low (100 kA and lower) drive current is being investigated. The evolution of the POS design used in the repetitive X-ray generator RS-20 is presented in various schemes. The "reflecting" scheme has a variable anode transparency in the direction of the load and another scheme uses an external pulsed magnetic field. The paper describes a combined X-ray converter having a multilayer structure: a thin layer of fine-grained tungsten is placed between two layers of carbon film. The progress achieved in improvement of the RS-20 main units (Marx Generator, Plasma Opening Switch, X-ray Converter) made it possible to increase their lifetime to more than 10/sup 7/ pulses without replacement.

Plasma-opening-switch-based repetitive generator

Repetitive plasma opening switch (POS) research for X-ray and electron beam generators for commercial applications is reviewed. This research was started on the RS-20 generator in 1991 with submicrosecond conduction times, 100 kA currents, and MV voltages. In the experiments wall-plug to electron beam production efficiency was increased from 10-50%. Maximum voltage obtained at POS was 3 MV starting from 0.8 MV at the Marx generator. POS operation was improved using an applied external magnetic field for the opening phase. Diode current and total generator efficiency were increased by combining the POS and diode system in one technology unit. For the opening phase of the high-impedance, repetitive POS, a set of conditions based on early POS experiments in the Kurchatov Institute were proposed. Repetitive POS generators have obtained peak X-ray dose rates of 1 MGy/s and electron dose rates of 10 GGy/s. This may be important for applications as pulsed irradiation may cause more efficient sterilization at lower doses. An X-ray generator based on repetitive POS technology at 5 MV and 200 kW in the electron beam is proposed.

Study of repetitive plasma opening switch generator technology

Super-high-power repetitive-pulse generators with plasma opening switches (review)

The report describes possibilities to make existing repetitive plasma opening switch (RPOS) technology competitive with existing accelerator X-ray radiating systems. The use of an external magnetic field for magnetic insulation of the RPOS system allows to increase the achievable voltage in RPOS and diode and the total efficiency of the system from the wall plug to X-ray irradiation. The experiments on an RS-20 pulsed power generator with the use of an external magnetic field allows one to raise the RPOS voltage from 2-2.2 to 2.8-3 MV. Another option is to combine the RPOS and diode in one unit to avoid energy losses when switching current to the diode with a wall plug to e-beam efficiency of 50-70%. On this basis, a concept of a 5 MV RPOS X-ray generator is proposed, capable of producing 200-300 kW in an e-beam.

Efficiency study of repetitive POS-in-magnetic-field technology

The report represents the results of experimental research into the plasma opening switch (POS) in an applied longitudinal magnetic field. Applying magnetic field on an area of the POS reduced the electron component of the current through the POS on a stage of sharp increase of the resistance. The POS which has been chosen for the experiments is one of the versions which the authors used in the repetitive pulsed power X-ray generator RS-20. The parameters of the the electron accelerator are as follows: electron energy 2.5 MeV; electron beam current 10-20 kA; pulse width 100 ns; and average power 10-20 kW. The scheme of the electron diode which is represented allowed X-ray flow focusing.

L.P. Zakatov

Papers

Plasma-opening-switch-based repetitive generator

Study of repetitive plasma opening switch generator technology

Super-high-power repetitive-pulse generators with plasma opening switches (review)

Efficiency study of repetitive POS-in-magnetic-field technology

Repetitive plasma opening switch in the magnetic field