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The Brillouin flow is the dominant flow in crossed-field devices. We systematically study its stability in conventional, planar, and inverted magnetron. We find that the negative mass effect in the inverted magnetron tends to destabilize the planar flow, and that the positive mass effect in the conventional magnetron tends to stabilize the planar flow. We find that the presence of a slow-wave structure,...
The Multi-Frequency Recirculating Planar Magnetron (MFRPM) is a crossed-field oscillator capable of producing high-power microwaves (HPM). The MFRPM-6+8 is the first prototype MFRPM, which consists of a 6-cavity 1-GHz and 8-cavity 2-GHz set of planar cavity arrays coupled by cylindrical electron beam / RF recirculation bends. Recent experimental work conducted using a −300 kV, 200–300 ns voltage pulse,...
Recent experiments on the UM Recirculating Planar Magnetron (RPM), have explored the use of 3-D printed components in a HPM system. The system was driven by MELBA-C, a Marx-Abramyan system which delivers a −300 kV voltage pulse for 0.3–1.0 us, with a 0.13–0.31 T axial magnetic field applied by a pair of electromagnets. Anode blocks were printed from Water Shed XC 11122 photopolymer using a stereolithography...
The Brillouin flow is the dominant flow in crossed-field devices. We systematically study its stability in conventional, planar, and inverted magnetron. We found that the negative mass effect in the inverted magnetron tends to destabilize the planar flow, and that the positive mass effect in the conventional magnetron tends to stabilize the planar flow.
Wire z-pinch experiments at the University of Michigan are in progress to test potential spectral lines for use as a local magnetic field diagnostic in dense plasmas driven by high currents. The goal of these experiments is to determine several spectral lines that can be used to reliably characterize the magnetic field and current density profiles of high energy density plasmas. Initial feasibility...
Thin film contacts are becoming increasingly important in the miniaturization of electronic devices. This paper considers the spreading resistance of a microscopic contact of size a ("a- spot") on a thin film. The effect of the film thickness h on the spreading resistance is evaluated over a large range of the aspect ratio a/h, for both Cartesian and cylindrical geometries. In the limit...
X-pinch experiments are currently underway on the Linear Transformer Driver (LTD) at the University of Michigan. The MAIZE LTD can supply 1 MA, 100 kV pulses with 100 ns risetime into a matched load. The x-pinch consists of a single wire separated by conical electrodes1, between two current return plates. The LTD was charged to +/−70 kV resulting in approximately 0.5 MA passing through a 50 µ Mo wire...
Recent research on the 1-MA Michigan Linear Transformer Driver, MAIZE, has focused on the Magneto Rayleigh-Taylor (MRT) instability and validation of analytic theory, developed at UM [1,2]. MRT is a concern to all forms of magnetically imploding experiments, most recently with the imploding liners anticipated in the MagLIF geometry.[3] Eliminating or mitigating MRT is crucial to success of these programs.
Risky decision-making is subserved by the frontostriatal system, which includes a network of interconnected brain regions known to be dysfunctional in patients with schizophrenia. This study aimed to investigate whether and to what extent patients with schizophrenia display a different pattern of risk-taking behavior relative to matched healthy controls. The Balloon Analogue Risk Task (BART) and the...
Spectroscopic analysis has been performed on Al foil plasmas ablated by the Linear Transformer Driver (LTD) at the University of Michigan. The MAIZE LTD can supply 1-MA, 100 kV pulses with 100 ns risetime into a matched load. The plasma load used in this experiment consists of a 400 nm Al foil (cathode) placed between two, planar, current return anode posts. The LTD was charged to +−70 kV, resulting...
Linear Transformer Drivers (LTDs) represent the most compact, high-current accelerators. LTDs have numerous advantages over Marx PFL systems: a) fast risetime (100 ns) without additional pulse forming, b) high efficiency (∼70%), c) inductive voltage adder and d) repetitively pulsed operation. LTDs have been utilized in a patented Sandia design for a PW pulsed power driver for fusion.[1] MYKONOS, a...
Recent work on the 1-MA Michigan Linear Transformer Driver, MAIZE, has focused on the Magneto Rayleigh-Taylor (MRT) instability and validation of analytic theory, developed at UM (see abstract by Lau et al.). MAIZE is a nominal 1-MA, 100 ns, 100 kV driver, capable of driving 0.1 Ω matched loads. We present here the results of a series of shots using different techniques to seed the MRT instability...
Initial dynamic load experiments were performed on UM's 1-MA linear transformer driver (LTD) facility, MAIZE, to characterize magneto-Rayleigh-Taylor (MRT) instability growth and plasma dynamics on planar-foil plasmas. The MAIZE LTD is capable of delivering a 1-MA, < 100 ns risetime drive pulse into a 0.1 Ω matched load with a ±100 kV charge. For these dynamic load experiments the LTD was...
Most of the modern high-current high-voltage pulsed power generators require several stages of pulse conditioning (pulse forming) to convert the multi-microsecond pulses of the Marx generator output to the 40-300 ns pulse required by a number of applications including x-ray radiography, pulsed high current linear accelerators, Z-pinch, isentropic compression (ICE), and inertial fusion energy (IFE)...
Surface roughness plays an important role in a cavity or slow wave structure. It may cause enhanced RF power absorption. It may lead to excessive local electric field enhancement that triggers RF breakdown. In a superconducting cavity, surface roughness may also cause local magnetic field enhancement that leads to abrupt quenching, i.e., rapid loss of superconductivity. In this work, we analytically...
The UM/L-3 relativistic magnetron operates at -300 kV, 2-5 kA, for durations of 500 ns and is capable of generating microwave pulses of 100's MW output power at 1 GHz for 100's ns. Previous research at UM utilized Metal-Oxide- Junction (MOJ) cathodes to exploit triple point field enhancement to stimulate electron emission. These MOJ cathodes generated fast current turn-on, however, the lifetime of...
Summary form only given. Experiments are underway at UM on the first 1-MA LTD to be operated in the USA following its development at the Institute of High Current Electronics in Tomsk, Russia. This LTD employs 80 capacitors and 40 spark-gap switches arranged in 40 "bricks" that each generate 25 kA when charged to +-100 kV. Initial experiments at UM generated nearly 1-MA into resistive loads...
Summary form only given. While not widely used, thin foils as Z-pinch loads may soon become necessary to achieve the required mass for higher current-driven X-ray sources, and they may also offer useful options for X-ray pulse shaping (T.J. Nash et.al., 2004). This paper reports our latest design and experimental progress on the study of the dominant instability, the magneto-Rayleigh-Taylor instability...
Summary form only given. Electrical contact is an important issue for high power microwave sources, wire-array Z pinches, field emitters, and metal-insulator-vacuum junctions. Because of the surface roughness on a microscopic scale, true contact between two pieces of metal occurs only on the asperities of the two contacting surfaces. Current flows only through these asperities, which occupy a small...
Summary form only given. Post-hole convolutes are commonly used in large scale pulsed power devices to combine the current from several sources. The primary examples of convolute use are Load Current Multipliers (LCMs) and current combination from multiple Self-Magnetically Insulated Transmission Lines (MITLs). Sandia National Laboratory's Z-Machine utilizes a double post-hole convolute to combine...
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