Ghost peaks in a sector-focusing magnetic β-ray spectrometer

Abstract

Zero-, single- and double-loop trajectories in a magnetic sector field, H = H φ ∼ 1 r , have been investigated. The focusing of single- and double-loop trajectories has been calculated for a K = 0.82 β-ray spectrometer with a symmetric entrance and exit profile shape. The trajectories are represented graphically. The counting ratio N 1/ N 0 of single-loop electrons/zero-loop electrons has been measured depending on the spectrometer entrance angle ψ s and the detector width Δz. An important decrease of N 1/ N 0 was achieved by a radial baffle S r placed in the central plane z = 0 of the spectrometer gap. The maximum length Δr max ( Δz, ψ s) of S r was found from the condition that the transmission T 0 ( Δz, ψ s) of the zero-loop electrons is unaffected by S r. Minimum obtainable values (N 1/N 0) min = ƒ min (Δz, ψ s ) are reported.