Characterization of a new ionization chamber in radiotherapy beams: Angular dependence and variation of response with distance

A new double faced ionization chamber was constructed at the Calibration Laboratory of IPEN. It has different collecting electrode materials: aluminum and graphite. It was irradiated in standard radiotherapy beams (60Co and X-rays). The response variation with distance and the angular dependence of this ionization chamber were evaluated. It was verified that the chamber response follows the inverse square law within a maximum variation of 11.2% in relation to the reference value. For the angular dependence it showed good agreement with international standards. - Highlights: ► The new ionization chamber was submitted to 60Co and radiotherapy X-rays beams. ► We examined the chamber response in two characterization tests. ► The chamber response variation with distance presented maximum variation of 11%. ► The angular dependence of this ionization chamber was within 1%. ► The results showed good agreement with the literature and international standards.