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

If high-energy beta particles are required for the efficiency determination of surface contamination monitors, wide area filtered (90)Sr/(90)Y sources are commonly used instead of short-lived pure (90)Y sources. In this work we show how the instrument efficiencies are dependent on filtering. Significant difference in the instrument efficiencies between filtered (90)Sr/(90)Y and pure (90)Y 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.