NOVEL COMPACT 60-KV MOTT DETECTOR FOR SPIN-POLARIZATION ELECTRON-SPECTROSCOPY

A compact 60-kV Mott polarimeter designed specially for the local anal ysis of surface and two-dimensional magnetism by spin-resolved electro n spectroscopy is developed and tested. The use of a design which comb ines a spherical accelerating field and the absence of a retarding pot ential after scattering of the electron beam ensures high stability of the measured polarization even when the potential and diameter of the beam being investigated vary. As a result of optimization of the scat tering angle (118 degrees) and the use of surface-barrier detectors wi th a large collection angle (similar to 48 degrees), the efficiency or figure of merit of the polarimeter, which determines the signal-to-no ise ratio epsilon = (I/I-0).(S-eff)(2), equals 2.5 x 10(-4). Specially developed electronic circuits and optimum positioning of the detector s provide a maximum electron counting rate as high as 5 x 10(6) counts /s. Consequently, it is possible to calibrate the polarimeter (to find the effective Sherman function S-eff) by extrapolating the measured a symmetry to a high discrimination level. This instrument can also be u sed in other areas of solid-state physics, atomic physics, and high-en ergy physics. (C) 1998 American Institute of Physics. [S1063-7842(98)0 2208-9].