Marx generator

About: Marx generator is a research topic. Over the lifetime, 1276 publications have been published within this topic receiving 8970 citations.

Development of an X-band magnicon amplifier for the Next Linear Collider-cold cathode experiments and a thermionic design study

Abstract: Summary form only given. The Naval Research Laboratory has been studying the operation of an 11 GHz frequency-doubling magnicon amplifier driven by a -650 kV, 225 A, 5.5-mm-diam. electron beam produced by a velvet cathode driven by a single-shot Marx generator. The magnicon circuit consists of a set of 5.56 GHz TM/sub 110/ deflection cavities (a drive cavity, two gain cavities, and a two-section /spl pi/-mode penultimate cavity) containing synchronously rotating modes that spin the beam up to high transverse momentum, followed by an 11.12 GHz TM/sub 210/ output cavity that uses a synchronously rotating mode to decelerate the electrons and generate microwave radiation. In the design, the electron spin-up develops progressively Through the deflection cavities. In the experiments, a plasma saturation effect was observed that limits the circulating power in each of the gain cavities to <10 kW. In order to overcome this low field saturation, the experiment was operated near the instability point of the penultimate cavity. We have designed a new thermionic magnicon experiment, incorporating an advanced high-convergence electron gun to produce a 500 kV, 200 A, 2-mm-diam. electron beam, an improved deflection cavity design, and an improved output cavity that employs side-coupling to extract the RF power through a pair of X-band waveguides separated by 135/spl deg/ around the azimuth of the cavity without destroying the symmetry of the rotating quadrupole mode. The predicted efficiency is /spl sim/60%.

Optimization study with respect to the point of excitation in coaxial TE 11 vircator

Abstract: The vircator is a compact and robust narrow band HPM source with a simple geometry. In the most basic version of the vircator, the operating frequency depends only on the distance between the anode and cathode and the applied voltage. In a compact system the vircator is often powered by a marx generator resulting in a frequency chirp caused by the double exponential voltage pulse generated by the marx. An experimental series with a coaxial TE11 vircator has been performed in which the excitation point and the applied voltage have been varied. Experimental evidence is presented showing that the frequency shift during the pulse can be avoided by choosing the proper excitation point. The highest radiated fields were recorded when the bandwidth of the microwave radiation was narrow and only one mode was present. Both far field and waveguide measurements were in agreement with the TE11 mode. At the optimum positions the input impedance of the vircator was lower, indicating improved coupling between electron beam and microwave field. To verify the experimental findings on optimum excitation point, electromagnetic simulations were performed. Even though the simulation model was greatly simplified by replacing the electron beam with a current sheath at the position of the emitters, the results were in good agreement with experiments.

Characterization of Flash X-Ray Source From a Marx-Based Pulse Power System

Abstract: The source characterization of a Flash X-ray (FXR) device is essential in defining its utility for dynamic radiography. A Marx generator [550 kV, $50~\Omega $ , and 45 ns full-width half-maxima (FWHM)] based FXR source operating in the voltage range 200–550 kV has been characterized. The FXR electron beam diode has a cylindrical geometry with stainless steel (SS) knife-edge cathode and tapered tip Tungsten rod as anode. The FXR source is connected to the Marx generator-based pulsed power system using a flexible high-voltage cable feed through. The hard X-ray spectrum was measured using a differential absorption spectrometer (DAS). The FWHM of the spot size of FXR source was measured using a pinhole camera and was estimated to lie between 1.83 and 2.31 mm. The on-axis dose measured at 1 m matches well with the calculated dose $D \alpha V^{2.2}I\Delta t$ , where $V$ is the applied voltage and $I$ is the current, and $\Delta t$ the time duration.

6–7 MeV characteristic γ-ray source using a plasma opening switch and a Marx bank

Abstract: A 640 kV Marx bank and plasma opening switch (POS) produce an intense pulse of MeV protons that stop in a fluorine-bearing target. The 19F(p,αγ)16O reaction produces 6- to 7-MeV characteristic γ-rays that can induce fission reactions in fissionable materials, such as depleted uranium (DU). Some fission reactions are also induced by neutrons generated by proton and/or deuteron reactions in the target, indicating that this system could be used to produce a mixed source of γ-rays and neutrons. Experimental results are presented, and future options are described to improve this kind of mixed source.

Modeling Marx generators for maximum pulse repetition rate estimation

Abstract: This paper presents a generalized n stage dynamic model for unipolar semiconductor based Marx generators. The model is tailored for the capacitors charging mode to enable the estimation of the maximum pulse repetition rate of the n stage generator. The maximum pulse repetition rate for the n stage Marx generator can be calculated as a function of the number n of stages, and of the voltage decay allowed in each capacitor (usually less than 10%). Furthermore, given a needed pulse repetition rate the model can estimate the optimum number of stages (n) so that the working voltage of each stage can be selected. Simulation results for a ten-stage (n=10) positive output Marx generators are presented and discussed.