Detection of highly enriched uranium and tungsten surface damage studies using a pulsed inertial electrostatic confinement fusion device.

摘要

The research in this thesis examines two applications of a pulsed Inertial Electrostatic Confinement (EEC) fusion device: detection of highly enriched uranium (HEU) and tungsten surface damage studies. In order to complete this thesis, a pulsed IEC device was developed that is capable of generating converging ion pulses with widths ranging from 0.1 to 5 ms at frequencies between 1 and 50 Hz. This device operated at cathode voltages as high as 120 kV, and with D+ currents in excess of 6 A and He+ currents as high as 1 A. Pulsed D-D neutron production rates as high as 4.7x 10 9 n/s were measured during 110 gs pulses at 5 Hz, with a cathode voltage of 94 kV and pulse current of 4.8 A.; The first project used the EEC device as a pulsed D-D neutron source to detect HEU. An MCNP5 model was developed that accurately models the time-dependent behavior of pulsed IEC neutron production and the associated HEU detection hardware. This model aided in the construction of a 3He detector-based system capable of detecting delayed neutrons. Using this hardware, pulsed D-D neutron production rates as low as 4x108 n/s were used to detect the presence of a 10 gram sample of uranium-235. Delayed neutron production was found to increase linearly with fusion neutron rates.; The second project studied the effects of high energy He+ and D+ implantation on the surface morphology of high-temperature tungsten, for use as a fusion first-wall material and IEC cathodes. Irradiations were performed with 0.2--2 ms He+ pulses of up to 1 ampere at rep rates ranging from 1--25 Hz. Pulsed helium implantation of polycrystalline tungsten was performed at 1,150°C to fluences of 1x10 -8 to 1x10-9 He+/cm 2 in 1 ms pulses at 25 Hz. Micrographs of these samples revealed increased surface damage at all fluences compared to steady-state irradiation. The samples also experienced a measurable change in mass.; The pulsed IEC fusion device developed at the University of Wisconsin is a versatile piece of equipment. It has been used both to detect special nuclear material and as an irradiation facility for fusion first wall materials research.