Position, Energy, and Transit Time Distributions in a Hemispherical Deflector Analyzer with Position Sensitive Detector

Abstract

Practical analytic equations, for the ideal field, and numerical results from SIMION simulations, for the fringing field, are presented for the exit radiusrπand transit timetπof electrons in a hemispherical deflector analyzer (HDA) over a wide range of analyzer parameters. Results are presented for a typically dimensioned HDA with mean radiusR-=101.6 mm and interradial separationΔR=R2-R1=58.4 mm able to accommodate a 40 mm diameter position sensitive detector (PSD). Results for three different entry positionsR0are compared:R0=R-(the conventional central entry) and two displaced (paracentric) entries:R0=82.55 mm andR0=116 mm. Exit spreadsΔrπ,Δtπand base energy resolutionΔEBare computed for HDA pass energiesE0=10, 100, 500, and 1000 eV, entry aperture sizesΔr0≤1.5 mm, entry angular spreads|αmax|≤5°, and an electron beam with relative energy spreadδE/E0≤0.4%. Overall, under realistic conditions,bothparacentric entries demonstratenear idealfield behavior and clear superiority over the conventional entry atR0=R-. TheR0=82.55 mm entry has betterabsoluteenergy and time spread resolutions, while theR0=116 mm has betterrelativeenergy resolutions, both offering attractive alternatives for time-of-flight and coincidence applications where both energy and timing resolutions are important.