The effect of geometry dependent Chamber Spatial Response Function in small field profile measurements

Area of Science:

• Medical Physics
• Radiation Detection
• Beam Metrology

Background:

• Accurate beam profile measurements are crucial for radiation therapy and dosimetry.
• The Chamber-Spatial Response Function (CSRF) influences the accuracy of ionization chamber-based measurements.
• Understanding CSRF is essential for optimizing radiation field analysis.

Purpose of the Study:

• To investigate the effect of Chamber-Spatial Response Function (CSRF) on beam profile measurements.
• To parameterize CSRF using chamber geometry and analyze factors influencing its width.
• To validate simulation results against experimental measurements.

Main Methods:

• Developed a Chamber-Spatial Response Function (CSRF) model based on Gaussian distribution and projected chamber geometry.
• Measured CSRF widths by correlating chamber diameter with Full Width at Half Maximum (FWHM).
• Utilized Geant4 simulations with chamber geometry derived from CT scans for analysis.

Main Results:

• Achieved excellent agreement between experimental measurements and Geant4 simulations.
• Identified Compton current as a significant factor contributing to CSRF broadening.
• Demonstrated that spherical chamber geometries result in more compact CSRF.

Conclusions:

• The study successfully modeled and analyzed the Chamber-Spatial Response Function (CSRF) in ionization chamber measurements.
• Compton current plays a critical role in the spatial response of ionization chambers.
• Spherical chamber designs are recommended for improved beam profile measurement accuracy.