Uncertainty and routine use of Aerial l-alanine – Electron spin resonance dosimetry system

• Uncertainty can be determined by experimental measurement data processing.
• RMS obtained through calibration corresponds uncertainty in use of Aerial equipment.
• The dose rate affects the alanine dosimeter dose response on high absorbed doses.

Aerial l-alanine pellet dosimeter is characterized by MiniScope MS300 electron spin resonance spectrometer measurements using Aer'EDE Version 2.0.4. software for dose calculation. The measurement traceability is achieved by Aerial dosimetry laboratory where dosimeters for calibration curve were irradiated by electron beam accelerator. Dose determinations in Aerial are traceable to National Physical Laboratory (NPL). The software used for construction of calibration curve gives also the standard deviation of the residuals of measurements for calibration that is used for dose uncertainty calculation. In aim to determine whether this value can actually be taken as absorbed dose uncertainty during usage of this dosimetry system, alanine dosimeters were irradiated with doses between 5 and 32 kGy by 60Co laboratory source for internal calibration. The dose rate at the places for irradiation was (20 ± 0.5) mGy s−1 determined by Fricke dosimeter. Measurement of each irradiated dosimeter was repeated ten times in ten days. The results of measurements were analyzed to identify the sources of uncertainty, as well as their quantification in evaluation of total measurement uncertainty. In addition to statistical effects, the very low dose rate that was used for the irradiation of alanine dosimeters affects the measurements of absorbed dose, particularly for higher absorbed doses where the measured dose can be up to 3% lower than the real.