| dc.description |
Practical analytic equations, for the ideal field, and numerical results from SIMION simulations, for the fringing field, are presented for the exit radius r(pi) and transit time t(pi) of electrons in a hemispherical deflector analyzer (HDA) over a wide range of analyzer parameters. Results are presented for a typically dimensioned HDA with mean radius (R) over bar - 101.6mm and interradial separation Delta R = R-2 - R-1 = 58.4mm able to accommodate a 40mm diameter position sensitive detector (PSD). Results for three different entry positions R-0 are compared: R-0 = (R) over bar (the conventional central entry) and two displaced (paracentric) entries: R-0 = 82.55mm and R-0 - 116 mm. Exit spreads Delta r(pi), Delta t(pi) and base energy resolution Delta E-B are computed for HDA pass energies E-0 - 10, 100, 500, and 1000 eV, entry aperture sizes Delta r(0) <= 1.5 mm, entry angular spreads vertical bar alpha(max) vertical bar <= 5 degrees, and an electron beam with relative energy spread delta E/E-0 <= 0.4%. Overall, under realistic conditions, both paracentric entries demonstrate near ideal field behavior and clear superiority over the conventional entry at R-0 = (R) over bar. The R-0 = 82.55mmentry has better absolute energy and time spread resolutions, while the R-0 = 116mmhas better relative energy resolutions, both offering attractive alternatives for time-of-flight and coincidence applications where both energy and timing resolutions are important. |
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