On the nature of the photocurrent in secondary-emission multipliers of atomic-beam tubes

Abstract

The physical cause for origination of the photocurrent in secondary-emission multipliers (SEMs) after long-term studies in the operation mode used for stabilization of parameters of atomic-beam tubes is considered. A general expression for the spectral photon flux penetrating through the channel connecting the ionizer with the SEM due to reflections in the channel and impinging on the surface of the first dynode of the SEM is obtained. Estimates of three versions of simplification of the general expression for the spectral photon flux are performed for several δ, i.e., average values of fine irregularities (in μm) characterizing the surface roughness of the channel, including a specified class of the channel treatment quality, and radiation angles of incidence on the channel surface θ. The expression that is the closest to correct determination of the illumination function of the surface of the first SEM dynode by a absolute black body source, which is described by the Wien equation at radiation wavelengths λ ≤ 2 μm, is determined.