Calibration of a Small Volume Ionization Chamber for Co-60 Gamma Beams with Low and High Activity Sources

This paper describes the measurement for calibrating a PinPoint 3D chamber type of PTW 31016 serial number 004507 with volume of 0.016 cc in term of absorbed dose to water for 60Co gamma beams using low and high activity sources. Measurement has been carried out using a Substitution Methods at the reference condition. A 0.6 cc ionization chamber type of TW 30013 serial number 6367 was used as a standard chamber connected to Farmer type of NE
2570/1B serial number 1182 and Webline type of T 10022 serial number 268 electrometers with traceability to the Bureau International des poids measures (BIPM) France. Testing on the calibration result were also described based on the determination of the absorbed dose to water at the reference conditions for a 10 MV photon beam and 60Co gamma
beams.The results obtained show that the absorbed dose to water calibration factor for the PinPoint3D chamber connected to a Farmer electrometer were ND,w= 2803.2 mGy/nC and ND,w= 2533.2 mGy/nC each for low and high activity sources,while connected to Webline were ND,w = 2534.64 mGy/nC dan ND,w = 2516.0 mGy/nC each for low and high activity sources. The test results for the absorbed dose to water determination for a 10 MV photon beam and Co-60 gamma beams show good agreement by 0.95% and 1.68%. As Summary, the calibration of the PinPoint 3D chamber for 60Co gamma beams using low and high activity sources obtained good results, except for a low activity source, if the PinPoint 3D chamber connected to a Farmer electrometer.