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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.
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...
The data presented in this paper are the culmination of many experiments studying the combined effects of contact, polarity and risetime on wire array z-pinches. The data are collected on 16-wire Aluminum z-pinch arrays in both negative and positive polarity, with solder and no-solder contacts, and with 100-200 ns risetimes. Diodes and diamond detectors, inductive voltage monitor, 150 ps pulsed laser,...
Summary form only given. We are investigating the development of the axial instability that occurs on each exploding wire in wire-array Z-pinches. The axial instability is a growing modulation of the size of the coronal plasma around individual wires of the array that results in non-uniform ablation of material from the cold wire core. It has long been known that the wavelength of this modulation...
Streaked visible-light spectroscopy measurements are presented for aluminum (Al) wire-array z-pinch experiments on the 1-MA, 100-ns rise-time COBRA pulsed-power generator. For these measurements, a half-meter Czerny- Turner spectrometer was used in conjunction with the COBRA visible-light streak camera system. This allowed us to record visible-light spectra emitted from Al coronal plasma as a continuous...
Summary form only given. Wire array implosions with different current pulse rise times have been studied on the 1 MA COBRA facility at Cornell University. The flexibility of the COBRA generator allowed switching between the short (100 ns) and long (220 ns) current pulse rise time to study the implosion of nested wire array loads in these two regimes. The load design and optimization was performed...
Wire-array z-pinch experiments were performed on the 1 MA, 100 ns rise-time COBRA facility at Cornell University. Experiments utilized wire-arrays containing 2 pair of 5 to 7.5 micron diameter tungsten wires spaced ~240 nm apart. X-pinch x-ray backlighters were used to image breakup of the wire cores. Axially correlated ablation regions between paired wires were observed. These correlated regions...
Summary form only given. Wire-array Z pinches have been studied on the 1.2 MA peak current, 100 ns rise time COBRA generator at Cornell University using a wide range of diagnostics. In addition to the X-ray and electrical diagnostics, two framing cameras with 5 ns temporal resolution, a three frame laser shadowgraphy system with 170 ps temporal resolution and optical and X-ray streak cameras have...
Experimental results are presented which characterize the implosion dynamics and subsequent radiation output of wire-array Z-pinches on the 1-MA, 100-ns rise-time COBRA pulsed-power generator. Diagnostics fielded include an optical streak camera, a time-gated XUV framing camera, a laser shadowgraph system, filtered time-integrated pinhole cameras, an X-ray focusing spectrometer with spatial resolution...
Summary form only given. X pinch backlighting is a useful imaging technique whereby two or more wires are crossed at a single point and driven with a high current (300-500 kA). At the crossing point, a micron-scale sub-nanosecond X-ray source is produced that acts as a point source and can be used for point-projection imaging. Three new modes of X pinch imaging on COBRA have been implemented. One...
Summary form only given. In this experiment we examine the temporal evolution of the current distribution among individual wires and pairs of wires in wire array z-pinches using different wire materials (e.g., aluminum and tungsten). To accomplish this we electrically isolate the wires, or pairs of wires, from each other using segmented load hardware. Each segment is able to hold one or two wires...
Summary form only given. Experimental results showing wire array z-pinch implosions on the 1-MA, 100-ns rise time COBRA pulsed power generator are presented. The principal diagnostic used for these studies was an optical streak camera system, while other supporting diagnostics include a time-gated framing camera, a laser backlighting system, time-integrated pinhole cameras with various filters, and...
Summary form only given. Experiments with low-wire-number nested arrays from Al, stainless steel and brass wires have been performed on the 1 MA COBRA generator at Cornell University. Diagnostics included fast X-ray and EUV detectors, time-integrated X-ray pinhole cameras, a time-gated EUV/X-ray imaging pinhole camera, time-gated and time-integrated X-ray spectrometers, an optical streak camera and...
Summary form only given. Experimental comparison of low-wire-number nested cylindrical wire arrays (inner and outer arrays of 6 mm and 13 mm diameter, respectively) composed of one or two materials (different in outer and inner arrays) and small (6 mm) diameter single cylindrical arrays are presented. Wire materials studied include Al alloys, stainless steel, and brass. Diagnostics include filtered...
Summary form only given. Single aluminum wires, 15 μm in diameter and 2 cm in length, were driven by the Cornell LCP3 pulse generator, which nominally produced 1 kA, 200 ns current pulses with rise times ranging from 15 to 100 ns. Both positive and negative polarities were investigated. Wires with both an axially uniform radius and a periodic axial modulation of the radius were studied. The modulated...
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