Generation and Implementation of Mixed Radiation from Laser Interactions on a Liquid Target

Author

• Benjamin M. Knight

Date of Award

9-2024

Document Type

Thesis

Degree Name

Master of Science in Nuclear Engineering

Department

Department of Engineering Physics

First Advisor

Anil K. Patnaik, PhD

Abstract

The simultaneous generation of different forms of radiation from the same source is highly desirable but technically challenging. We present the generation of D-D fusion neutrons and >MeV-energy x-rays from extreme intensity (∼ 10¹⁹ W/cm² ), high repetition-rate (1 kHz) laser pulses on a thin liquid target. Total neutron fluxes of ∼ 105 neutrons/s and x-ray exposure rates up to ∼ 200 R/hr at 74 cm are measured. Evidence of D-D fusion is verified with a measurement suite including three independent neutron detection systems: an EJ-309 organic scintillator, a ³He proportional counter, and a set of 36 bubble detectors. Timeof-flight analysis of the outgoing neutrons is consistent with the expected 2.45 MeV neutron energy. A prepulse is found to cut neutron yield by a factor of 36.0 while enhancing x-ray yield by a factor of 8.4. Neutron yield trended lower as chamber pressure increased, in contrast with findings in literature. This high-energy and high-flux x-ray signal was used to examine the effects of x-ray radiation on MOSFETs, with threshold voltage shifts of ∼10 mV seen after absorbed doses of only 2 rad – a shift significantly larger than reported in the literature. This high-repetition rate laser system provides a mixed radiation environment for radiation hardening applications. Further optimization of radiation yields of x-rays, neutrons, ions, and electrons will enable this low-cost, small-area facility to provide unique research and development capabilities for applications in national security, imitation of space-weather environments, and validation of radiation effects simulations.

AFIT Designator

AFIT-ENP-MS-24-S-033

Comments

An embargo was observed for posting this thesis.

The document is Distribution A: Approved for public release, Distribution Unlimited. PA Case number 88ABW-2024-0775

Recommended Citation

Knight, Benjamin M., "Generation and Implementation of Mixed Radiation from Laser Interactions on a Liquid Target" (2024). Theses and Dissertations. 8328.
https://scholar.afit.edu/etd/8328