Passive, Low Cost Neutron Detectors for Neutron Diagnostics at the National Ignition Facility

Author

Nathaniel C. Loyd

Date of Award

3-21-2013

Document Type

Thesis

Degree Name

Master of Science

Department

Department of Engineering Physics

First Advisor

John W. McClory, PhD.

Abstract

Experimental validation of neutron fluence models of fusion events at the National Ignition Facility is necessary to predict radiation damage to measurement electronics. Due to programmatic and facility limitations, traditional neutron measurement techniques are not well suited for this application. Notably, a low cost and passive measurement technique that provides a permanent record is preferred. A detector was designed using gadolinium oxide contained within an aluminum reservoir. The reservoir is secured by a thin layer of Mylar and x-ray film, and vacuum sealed in a light tight package. In the presence of a thermal neutron flux, the gadolinium atoms absorb incident neutrons and partially de-excite by conversion electron emission. The conversion electrons exit the gadolinium oxide layer, penetrate the Mylar, and expose the x-ray film. After developing the film, the film exposure is quantified and directly related to the neutron fluence. The configuration was sensitive to thermal neutron fluences between 1.43 x 10⁷ and 1.43 x 10⁹ n/cm², and could distinguish between fluences differing by more than a tenth of a decade.

AFIT Designator

AFIT-ENP-13-M-23

DTIC Accession Number

ADA583234

Recommended Citation

Loyd, Nathaniel C., "Passive, Low Cost Neutron Detectors for Neutron Diagnostics at the National Ignition Facility" (2013). Theses and Dissertations. 939.
https://scholar.afit.edu/etd/939