# Micrometer-Scale Supersonic Slit Jet Nozzle Design, Simulation, and Additive Fabrication for Direct Laser Acceleration

Open Access
Author:
Morgan, Bryan William
Nuclear Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
None
Committee Members:
Millimeter- and micrometer-scale fluid and gas jets have multiple applications in research, industry, and government, such as gas duct injection, fluid flow research, materials research, and nuclear security science and technology. Manufacturing complex sub-millimeter diameter flow systems from metals presents a unique challenge. Machining methods often require milling solid metal components and joining parts with welds that can result in leakage or turbulence in the flow system. Various implementations of laser particle acceleration rely upon specially designed flow systems that can produce uniform gas density profiles of order millimeter in length and micrometer in height. The resulting gas density profiles can support acceleration of electrons using short laser pulses, a promising and rapidly developing technology for scientific, medical, industrial, and security applications. The objective of work has been to design micrometer-scale supersonic gas nozzles for this application, as well as investigate and validate novel methods for their fabrication using additive manufacturing techniques. Micrometer-scale, high-aspect-ratio supersonic gas jet nozzles were designed and fabricated by use of metal additive manufacturing to support the direct laser acceleration research. To determine the appropriate supersonic gas jet dimensions, models based on first principles were developed. The models are based on the isentropic compressible fluid dynamics. The designs were simulated using the COMSOL Multi-Physics framework with high Mach number fluid modeling. Micrometer-scale supersonic gas jet nozzles were produced at the Pennsylvania State University's Applied Research Laboratory. Titanium supersonic gas jets were manufactured with diameters as small as 600 micrometers and with asymmetric cross sections that produced a number density of $1.25 \times 10^{19}$~cm$^{-3}$ using nitrogen gas.