Production methods of radiation sensitive ultrasound contrast agents and their response to neutron irradiation

Emulsions of over expanded meta-stable halo-carbon or fluorocarbon droplets in aqueous gels or soft polymers are known as “super-heated emulsions” or “bubble detectors”. They have been used in radiation detection, dosimetry, and spectrometry since the Seventies. Their operating principle is similar to the one of bubble chambers. When enough energy is deposited inside the volume of a meta-stable liquid droplet, the phase transition of the super-heated liquid occurs and detectable bubbles are produced. Bubble formation can be caused by several external agents, including the energy deposited by charged particles produced by radiation interactions or by the sequence of compression and depression cycles of acoustic waves. Therefore, these materials can find application in the field of radiation detection as well as contrast imaging agents in ultrasound imaging. In this thesis, two methods to produce super-heated emulsions were designed, developed, and tested, including producing emulsions mechanically and chemically. A system was successfully constructed that showed the ability to combine water and gel during preliminary tests for mechanical emulsion production. Also a chemical procedure was developed to produce the visco-elastic host gel with desired parameters leading to a gel with a viscosity of 2029.40 centipoise and a density of 1.163 g/ml. In addition, we also tested a chemical procedure to produce boron loaded (PVA-BPA) emulsion droplets to be potentially used for thermal neutron detection. These emulsions’ responses to neutron irradiation from a mono-energetic 14.1 MeV source were characterized through various experimental protocols that use different sensor configurations, including optical and acoustical detection. A Monte Carlo simulation was performed to quantify the flux of neutrons irradiating the sample for both the moderated and bare source cases allowing for normalization of the interaction of the source and the emulsion. It produced a flux of 1727±4 neutrons/s/cm2 for the moderated source case and a flux of 3870±99 neutrons/s/cm2 for the bare source case. After the development of a working sensor, it was found that PVABPA emulsions exhibited a relative response to a thermalized spectrum 31±1% higher, when compared to non-boron loaded samples.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Nuclear, Plasma, Radiolgc Engr

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2022

Author dc:creator

• Carr, Michael

Contributors dc:contributor

• Di Fulvio, Angela
• Meng, Ling-Jian

• super-heated emulsions
• neutron irradiation
• thermalized

Statement dc:rights

• Copyright 2022 Michael Carr

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/115796

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F115796