@misc{oai:repo.qst.go.jp:00072721,
 author = {Takase, Nobuhiko and Sakata, Suoh and Endo, Masahiro and Narita, Katsuhisa and Yamasita, Wataru and Hoteida, Masahiro and Sasaki, Yosuke and Usiroda, Tota and Mizuno, Hideyuki and Fukumura, Akifumi and 佐方 周防 and 水野 秀之 and 福村 明史},
 month = {Sep},
 note = {Purpose: Since 2004, Association for Nuclear Technology in Medicine (ANTM) has been carrying out a calibration service for radiotherapy dosimeters, as the unique secondary standard dosimeter laboratory in Japanese external radiotherapy field. The service provides an absorbed dose to water calibration factor to a set of chamber and electrometer, at a single electrometer range.
Recently, the authors have established a charge calibration system for electrometer to provide calibration factor at each electrometer range. The new system allows chamber calibration without customer's own electrometers.
Method: We assembled a reference standard measurement device of charge with capacitors and a DC voltmeter. Those are traceable to the corresponding national measurement standard. A customer’s reference class chamber can be calibrated with the best relative expanded uncertainty of 1% (k=2) with the new system. 
Result: We compared the results of electrometer with the calibration factors given in the ADCL’s certificate with A2LA accredited symbol. The calibration factors obtained be the authors and ADCL agreed within the relative expanded uncertainties. The results of ionization chambers also were compared with the calibration factors given in the NMIJ test report. Both factors agreed within relative expanded uncertainties.
Conclusion: New calibration system established by the authors has been verified by the two experiments. The individual calibration system for electrometer and chamber would simplify the quality control method of reference dosimeters at radiotherapy facilities., 8th Japan-Korea Joint Meeting on Medical Physics (114th Scientific Meeting of JSMP)},
 title = {An individual calibration system for electrometer and ionization chamber of radiotherapy dosimeters},
 year = {2017}
}