Patent ID: 7375336

Claim:
A ZnS (Ag) scintillation detector comprising a ZnS (Ag) scintillator layer which is excited by incident α-rays and emits a scintillator light, a photomultiplier tube which converts the scintillator light into an electric pulse signal, and a counting rate meter which counts the obtained pulse signal, said detector being capable of separating α-rays from a radioactive material to be detected from α-rays from naturally occurring nuclides, wherein said ZnS (Ag) scintillator layer has a thickness which substantially coincides with a range of α-rays from the naturally occurring nuclides to be separated, and wherein a pulse height discrimination circuit which discriminates between the energy region of α-rays from the radioactive material to be detected and the energy region of α-rays from the naturally occurring nuclides, is present at a stage preceding said counting rate meter, to thereby perform pulse height discrimination of signals in an energy region of α-rays from the radioactive material to be detected and guide the discriminated signals to the counting rate meter, thereby reducing the influence of α-rays from the naturally occurring nuclides on the counting of α-rays from the radioactive material to be detected.