Room: AAPM ePoster Library
Purpose: plane-parallel vessel was fabricated for upgrading the water calorimeter to measure the absorbed dose to water of high-energy photon beams, and further to establish absorbed dose to water primary standard of electron beams in China.
Methods: the original cylindrical calorimeter core with plane-parallel glass vessel and new thermistor probes to form the upgraded water calorimeter. The upgraded water calorimeter was used to measure the absorbed dose to water in accelerator photon beams, and compared with the results of water calorimeter previously involved in the K6 comparison organized by the Bureau International des Poids et Mesures.
Results: absorbed dose to water is absolutely measured by plane-parallel vessel water calorimeter with the combined standard uncertainty of 0.35% (10 MV). The absorbed dose to water measured at 6 MV, 10 MV and 25 MV photon beams with two different calorimeter cores are consistent within 0.3% after correcting with vessel perturbation, heat transfer and radial dose distrution.
Conclusion: results show that the new plane-parallel vessel with the new thermistor probes can be used to measure the absorbed dose to water in accelerator photon beams. Reduce the minimum measuring depth of the current calorimeter to 1.8 cm in the water. Furthermore, this upgraded water calorimeter will be applied to measure the absorbed dose to water in accelerator electron beams.
Funding Support, Disclosures, and Conflict of Interest: Supported by the National Key Technologies R&D Program of China (Grant No. 2016YFF0200804 and 2018YFF0212403).