Current collection and ionic recombination in small cylindrical ionization chambers exposed to pulsed radiation

Area of Science:

• Medical Physics
• Radiation Detection

Background:

• Accurate dosimetry is crucial for radiation therapy and diagnostics.
• Ionization chambers are standard detectors, but recombination effects can introduce errors.
• Pulsed radiation fields present unique challenges for recombination correction.

Purpose of the Study:

• To reexamine the recombination correction for small cylindrical ionization chambers under pulsed radiation.
• To validate existing theoretical models with new experimental data.
• To introduce and demonstrate a simple two-voltage testing technique.

Main Methods:

• Experimental measurements using a small cylindrical ionization chamber.
• Exposure to pulsed radiation fields.
• Application of a novel two-voltage testing technique.
• Comparison of experimental data with the existing Boag (1950) theory.

Main Results:

• The existing theory for air-filled chambers (Boag 1950) was found to be accurate.
• Accuracy was confirmed over a range of charge densities from 0.013 p/pulse to 3.8 p/pulse.
• The two-voltage testing technique proved effective in demonstrating the theory's validity.

Conclusions:

• The Boag (1950) theory provides an accurate recombination correction for cylindrical ionization chambers under pulsed radiation.
• The simple two-voltage technique is a reliable method for verifying these corrections.
• Further validation of dosimetry models is supported by this experimental evidence.