Effects of beta-particles attenuation filter of reference sources and contribution in the calibration of surface contamination monitors

• We show how the instrument efficiencies are dependent on filtering.
• We examine the isotropy of β-particle fluences and observe the angular dependence.
• We explain discrepant instrument efficiencies of pure 90Y source and filtered 90Sr/90Y.

If high-energy beta particles are required for the efficiency determination of surface contamination monitors, wide area filtered 90Sr/90Y sources are commonly used instead of short-lived pure 90Y sources. In this work we show how the instrument efficiencies are dependent on filtering. Significant difference in the instrument efficiencies between filtered 90Sr/90Y and pure 90Y source was obtained due to spectral degradation of the beta emission spectrum. Changes in the β-particle spectra were investigated by the use of a plastic scintillation spectrometer and the anisotropy of β-particle fluences was examined to clarify the possible reason of such discrepancy.