"Feasibility Of A Zero-Length Spring Gravimeter For Use In Portal Monit" by Matthew C. Stone

Date of Award

3-2024

Document Type

Thesis

Degree Name

Master of Science

Department

Department of Engineering Physics

First Advisor

Juan J. Manfredi, PhD

Abstract

In recent years, gravimeters have become sensitive enough to theoretically measure masses of interest at distances relevant for portal monitoring. Characterizing the re[1]sponse of the gravimeter to close range masses across a large solid angle is necessary before attempting to demonstrate a portal-monitoring-like measurement due to this mission being outside the scope of typical gravimeter operations. The characterization of the gravimeter focused on three primary topics. For the position-dependent bias, it is found that the models used overestimate the expected observed gravity when the test mass is closest to the gravimeter in four out of seventeen experiments and under[1]estimate the expected gravity in five out of seventeen experiments. An experiment to determine spatial resolution was able to resolve masses that are ∼ 2.7 times farther apart than the stand off distance. The mean standard deviations individually ranged from 0.92 µGal to 3.33 µGal, while a bulk analysis of eight consecutive scans revealed an average standard deviation of ∼ 8.7µGal indicating systematic effects which drive error above what any individual experiment may suggest. A measurement of a mass inside a cargo container was attempted in order to measure the difference between 421.2 ± 0.3 kilograms of lead being present or not, with an estimated observed gravity of 0.4355 µGal. A difference in observed gravity of 0.51 µGal was measured, which is different from the expected value by less than the resolution of the instrument. The standard deviations of the two measurements were ±1.13µGal for the measurement with mass loaded and ±2.72µGal for the measurement without. While the ability of the Burris ZLS Gravimeter to provide information about close range masses (e.g., spatial distribution, proximity) is thus demonstrated, the extreme sensitivity of the gravimeter stands as a challenge before being field deployable for portal monitoring

AFIT Designator

AFIT-ENP-MS-24-M-057

Comments

A 12-month embargo was observed for posting this work on AFIT Scholar.

Distribution Statement A, Approved for Public Release. PA case number on file.

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