Investigation of ion recombination and polarity effects in high dose rate electron beams.

BACKGROUND: Accurate dosimetry is essential for enhancing the effectiveness and safety of radiotherapy treatment. High dose rate electron (HDRE) beams, a dose rate up to ten times higher at the measurement point than standard electron beam at the same Monitor Unit (MU). The increased ionization density raises concern about ion recombination effects, which may affect the reliability of ionization chamber readings. PURPOSE: ) across various dosimetry protocols in order to determine the most suitable approach for HDRE settings. METHODS: ) derived from Monte Carlo simulation and specific adjustment was applied to PPC40, where the Effective Point of Measurement was determined to be 1.39 mm from the window surface. RESULTS: values remained remarkably stable, ranging from 0.9962 to 1.0001. This study evaluated ion recombination and polarity effects in HDRE beams using plane parallel and cylindrical chambers. CONCLUSIONS: Based on data variations, we recommend elevated operating voltage (400 V) than typical voltage (300 V) to reduce ion recombination in HDRE beams. Furthermore, modified method can be alternative to measure the accuracy of charge readings for absolute dosimetry.