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The secondary
electrons (SEs) are known to be emitted with a cosine polar distribution normal to
the emitting surface. Therefore, the initial SE (secondary electrons) angular-distribution as SEs leave the emitting
surface is predicted to follow a cosine distribution [1]
----------------------------------------------- [4832]
where,
δ0 -- the SE yield at α = 0°.
α -- the angle from the normal of
the emitting surface.
Figure 4832a shows the SE
angular-distribution for our polycrystalline gold sample at electron beam energy of 1.5 keV.
Figure 4832a. SE angle-resolved yield data for
polycrystalline Au with electron beam energy of 1.5 keV.
The
curve fits the data using the cosine distribution of Equation [4832]. [2]
Figure 4832b shows the radial spread of emission of secondary electrons from a point source. Here, it shows cartesian coordinates on the sample surface.
Figure 4832b. Radial spread of emission of secondary electrons from a point source. Here, cartesian coordinates is used on the sample surface.
SE angular-distributions can be measured with a rotatable Faraday cup retarding field analyzer for a range of fixed emission angles between -18° and +73° with respect to the sample normal [2].
[1] J. H. L. Jonker, The angular-distribution of the secondary electrons of
nickel, Philips Res. Rep., 6, 372-387,1951.
[2] N. Nickles, R. E. Davies and J. R. Dennison, Applications of Secondary Electron Energy- and Angular-Distributions to Spacecraft Charging, 6th Spacecraft Charging Technology Conference, AFRL-VS-TR-20001578, 1 September 2000.
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