SECONDARY-ELECTRON EMISSION FROM VARIOUS METALS AND CSI BOMBARDED BY HEAVY MOLECULAR-IONS

Authors
Citation
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
Citations number
31
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Instument & Instrumentation","Nuclear Sciences & Tecnology","Physics, Atomic, Molecular & Chemical","Physics, Nuclear
ISSN journal
0168-583X
Volume
145
Issue
3
Year of publication
1998
Pages
332 - 345
Database
ISI
SICI code
0168-583X(1998)145:3<332:SEFVMA>2.0.ZU;2-4
Abstract
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 B.V. All rights reserved.