No description available.

Thesis--Wisconsin. / Vita. Includes bibliographical references (leaves 66-67).

The X-ray emission from a plasma focus has been studied using time integrated and streak photography. The plasma focus, a small volume of very dense and hot plasma was created in a coaxial plasma gun driven by a fast current pulse of period T ~ 2 μsec which was produced by discharging a condensor bank of V = 12-15 kV, and C = 84 μf. Measurements have shown that a diffuse X-ray emitting plasma column is formed in the 'early' pinch stage, which extends a few centimeters in the axial direction, has expansion velocities of between 2-6 x 10⁷ cm/sec. and lasts for 30-60 nsec. In the following 10-30 nsec. X-ray emission occurs from small plasma regions which have little or no axial velocity. The distance between these "hot" spots are of the order of half a centimeter. These measurements and observations of the X-ray emitting regions are consistent with results obtained by Peacock and Mather. By comparing their results with those of this experiment it is concluded that the appearance of the isolated X-ray sources is associated with the m = 0 instability. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

A dense plasma focus device (DPF) is a pulsed power device that generates high energy particles, neutrons and X-rays through rapid compression of the plasma. The presented research investigates the modification of the DPF and use of numerical modelling to predict the neutron yield. The DPF is a 1 kJ device that uses a 1.3 uF capacitor and operated at 40 kV pulse. Spark gap switch SG181-C is integrated into the driver circuit to handle high current operations. Bus work is designed and modeled to predict the current waveform generated by the modified DPF. The control system is designed to be suitable for automation using DAQ and LabVIEW. Radial trajectories during pinch formation are analyzed using a numerical model. Two numerical models are used to investigate how neutron yield varies with pressure, pinch current and pinch duration. The modified DPF showed the neutron scaling to be fourth power of the pinch current. / Master of Science / Nuclear fusion has been researched widely for decades as a solution to meet the demand of increasing energy needs. Controlled fusion reactions has been the main challenge to achieve this and various approaches have been explored using different confinement methods. All the approaches have advantages with different challenges. One approach being explored is the dense plasma focus (DPF) device, which uses electrical discharges to create a dense 'pinch' of plasma where fusion reactions occur when operated in deuterium fuel gas. Recent DPF experiments have shown that kJ range devices are capable of generating neutrons and intense radiation. This research gives an overview of the DPF with energy of 1 kJ range. The DPF is modelled to predict the pinch formation parameters. The model also predicts how neutron yield varies with operating pressure, pinch current and duration.

Doctor of Philosophy / Department of Mechanical and Nuclear Engineering / William L. Dunn / Dense Plasma Focus (DPF) devices are multi-radiation sources of X rays, neutrons (when working with deuterium), ions, and electrons in pulses typically of a few tens of nanoseconds. The Kansas State University device (KSU-DPF) was commissioned to be used as a radiation source with the Mechanical and Nuclear Engineering Department. The device is operated by a 12.5 µF capacitor which can be charged up to 40 kV storing an energy of 10 kJ. The static inductance and resistance of the device L[subscript]0 and r[subscript]0 were measured to be 91±2 nH and 13±3 mΩ. Experiments have shown that the KSU-DPF device produces 2.45 MeV neutrons with a neutron yield of ~2 × 10^7 and 1.05 × 10^7 n/shots in both axial and radial directions. Ions up to 130 keV were measured using a Faraday Cup. The measured hard X-ray spectrum shows an X-ray emission in the range from 20 to 120 keV with a peak at 50 keV while the average effective energy was estimated, using a step filter method, to be 59±3 keV. The KSU-DPF device was used as a pulsed hard X-ray source for material interrogation studies using the signature-based radiation-scanning (SBRS) technique. The SBRS technique uses template matching to differentiate targets that contain certain types of materials, such as chemical explosives or drugs, from those that do not. Experiments were performed with different materials in cans of three sizes. Nitrogen-rich fertilizers and ammonium nitrate were used as explosive surrogates. Experiments showed 100% sensitivity for all sizes of used samples while 50% specificity for 5 and 1- gallon and 28.57% for quart samples. Simulations using MCNP-5 gave results in good agreement with the experimental results. In the simulations, a larger number of materials, including real explosives were tested. To ensure the feasibility of using the DPF devices for this purpose a second device was simulated and the results were encouraging. Experimental and simulation results indicate that use of DPF devices with simple, room-temperature detectors may provide a way to perform rapid screening for threat materials, especially for places where large number of packages need to be investigated.

Doctor of Philosophy / Department of Mechanical and Nuclear Engineering / William L. Dunn / Dense plasma focus (DPF) devices are pulsed power devices capable of producing short-lived, hot and dense plasmas (~10[superscript]19 cm[superscript]-3) through a fast compression of plasma sheath. A DPF device provides intense bursts of electrons and ion beams, X-rays, and 2.5 MeV neutrons when operated with deuterium through the fusion reaction [superscript]2H(d,n)[superscript]3He. The Kansas State University DPF machine was designed and constructed in early 2010. The device was characterized to determine its performance as a neutron source. The device was shown to produce 5.0x10[superscript]7 neutrons/pulse using a tungsten-copper anode. Such machines have the advantages of being non-radioactive, movable, and producing short pulses (typically tens of nanoseconds), which allows rapid interrogation. The signature-based radiation-scanning (SBRS) method has been used to distinguish targets that contain explosives or explosive surrogates from targets that contain materials called “inert,” meaning they are not explosive-like. Different targets were placed in front of the DPF source at a distance of 45 cm. Four BC-418 plastic scintillators were used to measure the direct neutron yield and the neutrons scattered from various targets; the neutron source and the detectors were shielded with layers of lead, stainless steel, and borated polyethylene to shield against the X-rays and neutrons. One of the plastic scintillators was set at 70[supercript]o and two were set at 110[superscript]o from the line of the neutron beam; a bare [superscript]3He tube was used for detecting scattered thermal neutrons. Twelve metal cans of one-gallon each containing four explosive surrogates and eight inert materials were used as targets. Nine materials in five-gallon cans including three explosive surrogates were also used. The SBRS method indicated a capability to distinguish the explosive surrogates in both experiments, although the five gallon targets gave more accurate results. The MCNP code was used to validate the experimental work and to simulate real explosives. The simulations indicated the possibility to use the time of flight (TOF) technique in future experimental work, and were able to distinguish all the real explosives from the inert materials.

<div>For decades nuclear fusion space propulsion has been studied but due to technological set backs for self-sustaining fusion, it has been repeatedly abandoned in favor of more near-term or present day solutions. While these present day solutions of chemical and electric propulsion have been able to accomplish their missions, as the human race looks to explore Mars, a near term solution utilizing nuclear fusion propulsion must be sought as the fusion powered thruster case currently does not meet the minimum 0.2 thrust-to-weight ratio requirement. The current work seeks to investigate the use of a ssion powered magnetic fusion thruster for a manned Mars mission with an emphasis on creating a very near-term propulsion system. This will be accomplished by utilizing present day readily available technology and adapting methods of nuclear electric and nuclear fusion propulsion to build this ssion assisted propulsion system. Near term solutions have been demonstrated utilizing both DT and D-He3 fuels for a ssion powered and ssion assisted Dense Plasma Focus fusion device capable of achieving thrust-to-weight ratios greater than 0.2 for V's of 20 km/s. The Dense Plasma Focus can achieve thrust-to-weight ratios of 0.34 and 0.4 for ssion assisted and ssion powered cases, respectively, however, the Gasdynamic Mirror device proved to be an infeasible design as a ssion powered thruster due to the increased weight of a ssion reactor.</div>

Thomas J. Fessenden. / Issued also as a thesis, M.I.T. Dept. of Electrical Engineering, April 29, 1961." "August 29, 1961." / Bibliography: p. 50-51. / Army Signal Corps Contract DA36-039-sc-78108. Dept. of the Army Task 3-99-20-001 and Project 3-99-00-000.