V. Nguyen et K. Wien, SECONDARY-ELECTRON EMISSION FROM VARIOUS METALS AND CSI BOMBARDED BY HEAVY MOLECULAR-IONS, Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms, 145(3), 1998, pp. 332-345
Secondary electron emission from metals and CsI was studied with 25, 3
0 and 40 keV organic molecular ions in the mass range 18-5335 u. The e
lectron yields were measured before and after cleaning the target surf
aces by ion-etching at a vacuum pressure of 3 x 10(-9) mbar. The inves
tigated metals were Al, Fe, stainless steel, Pb, Cu, Ag, Au, AgMgO, Cu
Co2Be and CuBe2Pb, Except for Al and CsI, ion-etching reduced the elec
tron yields. Regarding the metal targets, the most efficient converter
s were iron and stainless steel. Under the assumption that for the met
al targets an additivity relationship is valid, the functional depende
nce of the measured yields on ion mass and velocity was parameterized
using the expression gamma(m)= C x M-0.98(upsilon(x) - a(x)). Apart fr
om iron and stainless steel (x = 1.0 +/- 0.2), with beta=0.98, the yie
lds were found to be over-linear in velocity (x = 1.5 +/- 0.1 before s
putter-cleaning and x = 1.4 +/- 0.2 after). The extrapolated velocity
threshold had a value a = 27 +/- 2 km/s. The yield curves are characte
rized by a maximum at molecular masses between 1000 and 2000 u. Electr
on yields measured with CsI are distinctly higher than those observed
with metals and increase after sputter-cleaning. Corresponding yield c
urves scale with the second power of velocity. Additivity seems not to
be valid for molecular masses above 2000 u. (C) 1998 Elsevier Science
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