Date of Award

2022

Degree Type

Capstone Project

First Advisor

Dr. Bahram Nassersharif

Abstract

The Rad Finder team was tasked with developing an array of detectors that could locate the position of a radioactive gamma-ray source in three dimensions. Since the strength of the source was to be unknown, standard triangulation algorithms would not work. Thus, the team had to develop a method of triangulation that, to the team’s knowledge, had never been done before. This project was sponsored by Los Alamos National Laboratory (LANL) and overseen by Dr. Bahram Nassersharif from the University of Rhode Island. The detection array, the “RADFINDER”, consisted of three gamma-ray detector wands attached to three subsequent analyzers from which the readings were gathered. Each detector wand was then mounted on its respective tripod. Ergonomic tripod adapters for these wands were designed in AutoCAD and manufactured using 3D printers. Additionally, it was vital to the triangulation algorithm that the exact positions of each detector wand were known. A Leica DISTO measuring device was thus implemented to determine the exact position of each detector wand. For the DISTO’s laser to gather accurate data, targets that were to be placed around each wands’ crystals were designed and 3D printed.

The triangulation algorithm constructed by the team was initially constructed in Mathematica, but later moved to MATLAB. The functionality of MATLAB allowed for a GUI to be constructed, as well as a three-dimensional plot displaying the positions of each detector wand and the calculated source position. The algorithm consisted of a system of three spherical equations, one for each detector. The system was then solved, and the result was two sets of x, y, and z coordinates. One of these sets was a phantom point that could be eliminated using logic. However, to improve the consistency of the array, a method of mathematically eliminating the phantom point was developed and implemented. This involved gathering a fourth detector point and solving an additional system of equations. The results could then be compared and the two source points closest to one another was where the source position was calculated to be.

Using the array and triangulation software that was constructed, the team utilized the Rhode Island Nuclear Science Center (RINSC) to conduct testing of the accuracy of the RADFINDER. The RINSC provided the team with gamma-ray emitting sources of varying strengths. For each source, the team tested to find the maximum range at which the detectors could be from the source before the readings were less than 150% of the background radiation. Once this distance was found, the target volume could be calculated for. The detectors were then placed at the corners of the target volume and shot with the DISTO device to find each wand’s position. The radioactive source was then placed randomly in the target volume and shot with the DISTO device to find its true position. Readings were then gathered off the analyzers in counts per second (cps) for 60 seconds and averaged. The readings off the detectors and the position of the detectors were then entered into the MATLAB analysis program, which calculated the position of the source in three dimensions. Through all the team’s trials, the calculated source position was always within +/- 10% of the target volume, which satisfied one of the team’s design specifications. Additionally, no team member picked up a measurable dose, which also satisfied the team’s specification for ALARA (maintaining radiation doses as low as reasonably achievable).

The RADFINDER was designed to prove concepts that are integral to the team’s final design goal. If scaled up, the RADFINDER could have real-world applications in nuclear non-proliferation and the detection of orphan sources.

Comments

Team Name: Team 12, The Rad Finders

Sponsor: Los Alamos National Laboratory

Sponsor Representative: Philip Lafreniere

Document Reference: URI-MCE-402-012-2022

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