Laser, Particle Beam, and Plasma Technologies

A novel high-flux neutron generator based on the principle of deuteron-deuteron (D-D) fusion reaction will be used for neutron activation of samples for 40Ar/39Ar geochronology, one of the most powerful methods of radioisotope dating. This dating method has limitations related to its conventional reliance on fission reactors. The broad spectrum of energies from fission neutrons produce accuracy-limiting interfering argon isotopes from Ca, Cl, and K as well as recoil displacements that prevent dating of small particle materials and obscure the fine-structure of isotope gradients. The ideal neutron energy would be 1-3 MeV, which is closely matched by the ~2.5 MeV neutrons produced by D-D fusion reaction. Modeling indicates that most interfering reactions would be eliminated with D-D neutrons, and the recoil displacement length scale should be reduced significantly. Furthermore, D-D neutron generation intrinsically produces no radioactive waste, and the samples and container materials are radiologically safer than those irradiated in fission reactors.

Conventional focused ion beam systems utilize a
liquid metal ion source to generate gallium ions for ion milling
and ion-assisted deposition. But gallium ions can cause contamination
in many focused ion beam applications. Plasma ion sources can generate
many gaseous ion beams, which can minimize the contamination in
FIB processes. New FIB system with combined ion and electron beams will facilitate
many researches in nano-science & technology.

Compact neutron and gamma tubes are being developed for oil well logging, medical and homeland security applications. These new devices produce monoenergetic neutrons or gammas via nuclear reactions. They can replace the commonly used radiological sources such as Cs-137, Cf-252 and Co-60. Neutron tubes can also be used for boron neutron capture therapy (BNCT).
BNCT is a two-step treatment modality for cancer. 10B atoms are concentrated in tumor cells by the administration of tumor-seeking pharmaceuticals. The neutrons generated using the RF-driven ion
source is moderated to the thermal energy, and thermal neutrons are delivered to the patient. The reaction between the thermal neutron and 10B yields an alpha particle and 7Li. The range of the alpha particle in the cell is approximately 10 microns in the tissue, appropriate to destroy the tumor cells.

A realistic driver for an ICF power plant could be a particle
beam which deposits its energy into a fusion target. In order for
this scheme to be successful, appropriate beam sources and accelerators
must be developed, and the beam must be focused accurately onto
the target. UCB students are participating in this endeavor to make
beam drivers a reality. Projects have included studies of ion sources
for ICF beam drivers and design of diagnostic systems for current
ICF driver experiments.

Research of models and methods relevant to high power
sources, up to GW power levels. Current investigations include aliasing
effects of stairstepped boundaries, models for field emission of
electrons, and fluid-particle hybrid models for simulation of high
density plasmas interacting with beams and waves. Supported by the
Air Force Research Laboratory at Kirtland.

Study of computational models for plasma propulsion systems, including ion beams and electron sources. Initial research is on development of a flexible object-oriented modeling framework which is optimized for speed. Subsequent steps will include adding   physical models to the framework, initially in 1D, followed by 2D and 3D. The physical models of interest include electrostatic field solvers (Possion eq. on a mesh, gridless Coulomb’s law, gridless treecode, and others), equipotential boundary conditions, electron- and ion-neutral collisions, ion-induced secondary electron effects, and many others. This will result in a computational tool capable of modeling a broad spectrum of plasma propulsion devices, including hollow cathode ion thrusters, hall effect thrusters, and pseudospark thrusters.  This project is funded by the Air Force Research Laboratory at Edwards Air Force Base.

In this project, a computational model of a sputtering magnetron is being developed. The sputtering magnetron is a coaxial configuration, with the center comprising a series of permanent magnets surrounded by a tantalum tube. A DC voltage accelerates electrons toward the substrate (outer coaxial conductor), but they are confined by the magnetic field to a region close to the inner electrode (cathode).  The energy gained from the DC field is primarily expended in ionizing a background gas, forming new electron-ion pairs. The unmagnetized ions are accelerated into the negatively biased cathode, and impact with sufficient energy to sputter material from the target cathode.  The target is typically tantalum. The sputtered tantalum atoms then propagate across the gap and deposit on the substrate forming the outer conductor (anode). This technique can be used to coat material surfaces to improve their properties, such as hardness, resistance to heat and chemical erosion, and so forth. The present application is to improve the lifetime of tank and artillery gun barrels by replacing the currently used chromium coating with tantalum. This has the added benefit that tantalum is environmentally benign, while chromium is a controlled substance known to pose serious environmental risks. This research is supported by Benet Army Research Laboratory.