EURAMET supplementary comparison of ambient dose equivalent H*(10) in ¹³⁷Cs and ISO Narrow Beam Series N-60 x-ray beams at low dose rates

Comparison measurements among national standards laboratories are required to demonstrate their equivalence in the realization and transfer of the quantity ambient dose equivalent, H*(10), for photon radiation by these laboratories. The first comparison of the radiation protection quantity H*(10) with focus on the special needs for calibration of area dosemeters, low dose rates and large fields, started in January 2013 and was completed in December 2014. The comparison was piloted by the PTB as EURAMET project No. 1132 known also as EURAMET.RI(I)-S11. The operation and results of the comparison are reported here. The transfer instrument was a secondary standard ionization chamber for H*(10) with a volume of 10000 cm³. The response of this transfer instrument in various photon reference fields (N-60 and 1 mSv/h, S-Cs and 10 μSv/h, S-Cs and 1 mSv/h, radiation quality according to ISO 4037-1:1996 [1]) was compared. Measurements were made by the fourteen participants from the following countries: Germany, Austria, Greece, Norway, Sweden, Finland, Portugal, Spain, Czech Republic, Romania, the Netherlands, Slovenia, Italy and by one international organization. The results obtained by almost all of the participants are consistent with the stated uncertainties. (authors)