Calibration problems, calibration procedures and reference fields for dosimetry at flight altitudes

Dosemeters used to measure the ambient dose equivalent, H*(10), usually require calibration with respect to this quantity. Under calibration conditions, the calibrated instrument will then measure H*(10) correctly, but under different irradiation conditions with respect to field composition, particle energies or other influencing quantities, deviations will most probably occur since the instruments in use do not have ideal response characteristics. The accuracy in aircrew exposure monitoring will be improved by performing the calibration in the field of interest itself or in a calibration field which has similar characteristics. Direct calibration requires a reference instrument that should be able to measure H*(10) correctly for all radiation components and energies in the field of interest. The use of reference fields produced under laboratory conditions requires similar particle composition and similar energy distributions of fluence. It is demonstrated that for radiation exposure monitoring in aircraft the tissue-equivalent proportional counter (TEPC) can, to a fair approximation, be a reference instrument for H*(10) and that the reference field facility installed at the proton synchrotron accelerator at CERN can provide reference fields of close similarity.