The crystal counter : A new apparatus in nuclear physics for the investigation of β- and γ-rays. Part II

AgCl crystals were irradiated with monochromatic β-rays in a magnetic β-ray spectrograph. The results show that under suitable experimental conditions in the crystal all β-rays of a certain energy cause ionisation pulses of the same value within the errors of measurement. The magnitude of an ionisation pulse is proportional to the energy of the β-particle. This means that the amount of energy necessary for the formation of one conduction electron is independent of the energy of the β-rays. This amount was found to be 7,6 eV. The measurements of the ionization pulses caused in AgCl by α-rays showed that many of the α-particles caused an ionization pulse smaller than normal. We ascribed this effect to a thin irregular surface layer which is less effective than the crystal's interior. Many of the crystals we investigated showed a thicker surface layer. This layer also influenced the ionization by β-particles, which then showed the same effect as the α-rays. The nature and the circumstances under which this hypothetical surface layer appears or can be removed are not yet clear and still form a point of investigation