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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Development of a Marx Modulator for FNAL Linac

A Marx-topology modulator has been designed and developed at the Fermi National Accelerator Laboratory under the Proton Improvement Plan (PIP). This modulator replaces the previous triode hard-tube design, increasing reliability, lowering operational costs, and maintaining waveform accuracy. The Marx modulator supplies the anode of the 7835 VHF power triode tube with a 35 kV, 375 Amp, 460 μs pulse at 15 Hz. It consists of 54 individual Marx cells, each containing a 639 μF capacitor charged to 900 Volts, combined in series with IGBT switches to create the desired output waveform. This requires variable rise and fall times, flattening of capacitive droop, and feedforward beam loading compensation. All five 201.25 MHz RF systems have been upgraded to Marx modulators to ensure continued operation of the linear accelerator.

43 PARTICLE ACCELERATORS↗
DOE OSTI2019

Development of a Marx Modulator for FNAL Linac

A Marx-topology modulator has been designed and developed at the Fermi National Accelerator Laboratory under the Proton Improvement Plan (PIP). This modulator replaces the previous triode hard-tube design, increasing reliability, lowering operational costs, and maintaining waveform accuracy. The Marx modulator supplies the anode of the 7835 VHF power triode tube with a 35 kV, 375 Amp, 460 µs pulse at 15 Hz. It consists of 54 indi-vidual Marx cells, each containing a 639 µF capacitor charged to 900 Volts, combined in series with IGBT switches to create the desired output waveform. This requires variable rise and fall times, flattening of capaci-tive droop, and feedforward beam loading compensation. All five 201.25 MHz RF systems have been upgraded to Marx modulators to ensure continued operation of the linear accelerator.

43 PARTICLE ACCELERATORS↗
DOE OSTI2014

Design and development of a portable flash X-ray source driven by battery powered compact Marx generator

The design, construction and operational characteristics of a portable flash X-ray source driven by battery-powered compact Marx is reported. The novel configuration of compact Marx utilizes hollow capacitors in successive stages to enhance the erection reliability. The characteristic impedance of this system is ∼ 200 Ω. At discharge of ∼ 22 kV, >200 kV output pulse of 60 ns duration (FWHM) with rise time of <5 ns (10% - 90%) is produced. The pulser requires Nitrogen gas pressurization up to 3 atm for operation at maximum rating. The Marx generator assembly is fitted in to a stainless steel tube of 10 cm diameter and 1.2 m length. While using a demountable sealed X-ray tube of matched impedance, this device produces an X-ray pulse of approximately ∼ 30 ns duration and has maximum energy of ∼ 200 keV. This true tabletop device is able to produce dose up to 100 mR per shot, measured at the distance of 30 cm from output window. The focal spot size has been passively confirmed to be in the sub-millimeter (<1 mm) range. (author)

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

Gas spark switches with increased operating life for Marx generator of lightning test complex

A new design of gas spark switches with an increased operating life and stable dynamic characteristics for the Marx generator of the lightning test complex has been developed. The switches are characterized by the following parameters in the mode of operation: voltage up to 80 kV, discharge current up to 50 kA, flowing charge up to 3.5 C/pulse. An increased operating life is achieved by using torus-shaped electrodes with increased working surface area and a trigger electrode in the form of a thick disk with a hole located between them. Low breakdown delay time and high stability of breakdown voltage under dynamic conditions are provided by gas preionization in the spark gap using UV radiation of an additional corona discharge in the axial region.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Los Alamos Portable Pulser (LAPP) Marx Bank and Digitizer System Characterization

Over the duration of June 22 nd to July 15 th , I interned at Los Alamos National Laboratory within ISR-2 on the Los Alamos Portable Pulser (LAPP) Program. This program concerns a radar dish used for characterizing signal propagation through earth’s ionosphere. The bulk of my internship consisted of characterizing the delay of a Marx Bank Generator and writing hardware-interface C/C++ code for the pulse-recording Digitizer System.

47 OTHER INSTRUMENTATION↗
DOE OSTI2014

Inverse Marx modulators for self-biasing klystron depressed collectors

A novel pulsed depressed collector biasing scheme is proposed. This topology feeds forward energy recovered during one RF pulse for use on the following RF pulse. The presented ''inverse'' Marx charges biasing capacitors in series, and discharges them in parallel. Simulations are shown along with experimental demonstration on a 62kW klystron.

42 ENGINEERING↗
DOE OSTI2024

0D, 1D, 2D, and 3D simulations of an idealized coaxial impedance-matched Marx generator

We have conducted 0D, 1D, 2D, and 3D simulations of an idealized coaxial impedance-matched Marx generator (IMG) []. The 0D calculations were conducted with a four-element circuit model; the 1D, 2D, and 3D calculations were conducted with highly resolved, fully electromagnetic representations. The IMG consists of 30 stages distributed axially and connected electrically in series. Each stage is powered by two bricks separated by 180° and connected electrically in parallel. Each brick comprises two opposite-polarity capacitors in series with a single switch. The bricks drive an internal impedance-matched coaxial transmission line terminated by a resistive load. The simulations neglect effects due to the switch-triggering circuit, the capacitor-charging circuit, external conducting boundaries, and reactive components of the load. We find dimensionality does not significantly affect the electrical power delivered by the IMG to its load: peak load powers estimated by the 0D, 1D, 2D, and 3D simulations agree to within 1%. The 3D calculations demonstrate that electromagnetic power radiated by the bricks, and axial gaps between stages, reduces the peak load power by less than ∼ 1 % . Each simulation assumes the load impedance is 34% above that at which the load power is maximized. Operating an IMG with such an overmatched load offers several advantages while decreasing the peak load power by only 2%. The 0D, 1D, 2D, and 3D models outlined herein could be adapted to assess computationally competing IMG designs, and conduct a variety of numerical IMG experiments, an IMG is constructed. Published by the American Physical Society 2024

43 PARTICLE ACCELERATORS↗
DOE OSTI2015

Design of a Marx-Topology Modulator for FNAL Linac

The Fermilab Proton Improvement Plan (PIP) was formed in late 2011 to address important and necessary upgrades to the Proton Source machines (Injector line, Linac and Booster). The goal is to increase the proton flux by doubling the Booster beam cycle rate while maintaining the same intensity per cycle, the same uptime, and the same residual activation in the enclosure. For the Linac, the main focus within PIP is to address reliability. One of the main tasks is to replace the present hard-tube modulator used on the 200 MHz RF system. Plans to replace this high power system with a Marx-topology modulator, capable of providing the required waveform shaping to stabilize the accelerating gradient and compensate for beam loading, will be presented, along with development data from the prototype unit.

43 PARTICLE ACCELERATORS↗