Determination of high energy β-emitters with a Ge spectrometer or Cherenkov radiation in an aerogel

Two types of coincidence measurements of β-radiation are described. In both cases a thin multiwire proportional chamber (MWPC) selects the useful events. In the first experiment a GeHP detector with a thin window is used as a β-spectrometer. Cherenkov radiation in silica aerogel with a low refractive index of 1.055 is used as an alternative method of discrimination of high energy β-emitters like 90Sr/Y in thin samples. A detection limit for 90Sr/Y of 0.1/0.5 Bq was obtained in few hours in samples containing no other high energy β-emitters. Elimination of contribution of β-γ-emitters is discussed for both experiments.