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Published on: December 21, 2017
Ultrasonic absorption in polymer gel dosimeters.
Melissa L Mather1, Anthony F Collings, Nick Bajenov
1Centre for Medical, Health and Environmental Physics, Queensland University of Technology, GPO Box 2434, Brisbane, QLD 4001, Australia.
Ultrasonics
|August 16, 2003
Summary
Ultrasonic absorption in polyacrylamide gel (PAG) dosimeters reveals complex relaxation mechanisms, not ideal fluid behavior. Formulation and pH significantly alter ultrasonic dose response, impacting radiation yield and polymerization.
Area of Science:
- Materials Science
- Polymer Chemistry
- Medical Physics
Background:
- Polymer gel dosimeters are crucial for accurate radiation dose measurement.
- Understanding the physical properties of these dosimeters is essential for optimizing their performance.
- Ultrasonic absorption is a key property that can be influenced by material composition and structure.
Purpose of the Study:
- To investigate ultrasonic absorption in polymer gel dosimeters.
- To determine the frequency dependence of ultrasonic absorption in polyacrylamide gel (PAG).
- To explore the influence of absorbed dose, pH, and chemical composition on ultrasonic absorption and dose response.
Main Methods:
- Utilized an ultrasonic interferometer to measure absorption coefficient (alpha) and ultrasonic velocity.
- Studied the frequency dependence of ultrasonic absorption in PAG from 5-20 MHz.
- Analyzed the relationship between ultrasonic absorption, absorbed dose, pH, and chemical composition.
Main Results:
- Ultrasonic absorption in PAG deviated from ideal viscous fluid behavior, indicating relaxation mechanisms.
- Frequency dependence of alpha/f(2) and dispersion in ultrasonic velocity confirmed the presence of relaxation processes.
- Changes in dosimeter pH and chemical composition significantly altered ultrasonic dose response curves.
Conclusions:
- Ultrasonic absorption in polymer gel dosimeters is attributed to multiple relaxation processes, including polymer-solvent interactions and side-group motion.
- pH-induced modifications in radiation yield and polymerization kinetics due to chemical composition affect ultrasonic dose response.
- These findings provide insights into the physical basis of ultrasonic absorption in polymer gels for dosimetry applications.
