Secondary-electron yields from thin foils: A possible probe for the electronic stopping power of heavy ions

Journal Article · Thu Mar 01 00:00:00 EST 1990 · Physical Review, A (General Physics); (USA)

DOI:https://doi.org/10.1103/PhysRevA.41.2521· OSTI ID:6847516

Rothard, H; Kroneberger, K; Clouvas, A; Veje, E; Lorenzen, P; Keller, N; Kemmler, J; Meckbach, W; Groeneveld, K ^[1]

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1. Institut fuer Kernphysik der Johann-Wolfgang-Goethe-Universitaet, August-Euler-Strasse 6, D-6000 Frankfurt am Main 90, Federal Republic of Germany (DE)

We have measured heavy-ion-induced {ital Z}{sub {ital P}}=2,10,18,36,54; 15 keV/u{le}{ital E}{sub {ital P}}/M{sub P}{le}600 keV/u secondary-electron (SE) yields from sputter-cleaned entrance ({gamma}{sub {ital B}}) and exit surfaces ({gamma}{sub {ital F}}) of thin solid foils (C, Al, Ti, Ni, and Cu; {ital d}{approx}1000 A) in ultrahigh vacuum ({ital p}=10{sup {minus}7} Pa). A pronounced increase of the forward to backward SE yield ratio {ital R}={gamma}{sub {ital F}}/{gamma}{sub B} with increasing {ital Z}{sub {ital P}} is observed. The SE yield to energy-loss ratio {Lambda}{sup *}={gamma}/S{sub e} has been found to be smaller for heavy ions (HI) than for light ions (H and He); i.e., {Lambda}{sup *}(HI){lt}{Lambda}{sup *}(He){lt}{Lambda}{sup *}(H). Also, at low projectile velocities ({ital v}{sub {ital P}}{sup 2}{lt}50 keV/u), the value of {Lambda}{sup *} increases with decreasing {ital v}{sub {ital P}}. The velocity and projectile dependence of both {ital R} and {Lambda}{sup *} can be described within simple extensions of Schou's SE emission transport theory and a semiempirical Sternglass-type model introduced by Koschar and co-workers as caused by nonequilibrium projectile energy losses {ital S}{sub {ital e}}{sup *} near the surfaces. The near-surface energy losses are reduced compared to tabulated bulk energy loss values {ital S}{sub {ital e}} both for forward and backward emission under the assumption of a proportionality between SE yields and {ital dE}/{ital dx}. The {ital Z}{sub {ital P}}-dependent reduction factors, i.e., the ratios {ital S}{sub {ital e}}{sup *}/S{sub e}, as well as material parameters {Lambda}={gamma}/{ital S}{sub {ital e}}{sup *}, are deduced from the SE yield measurements.

• OSTI ID: 6847516
• Journal Information: Physical Review, A (General Physics); (USA), Vol. 41:5; ISSN 0556-2791
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALUMINIUM
CHARGED-PARTICLE TRANSPORT
CARBON
COPPER
HEAVY IONS
STOPPING POWER
NICKEL
TITANIUM
ENERGY LOSSES
FOILS
MEV RANGE
SECONDARY EMISSION
CHARGED PARTICLES
ELEMENTS
EMISSION
ENERGY RANGE
IONS
LOSSES
METALS
NONMETALS
RADIATION TRANSPORT
TRANSITION ELEMENTS
654001* - Radiation & Shielding Physics- Radiation Physics
Shielding Calculations & Experiments
656003 - Condensed Matter Physics- Interactions between Beams & Condensed Matter- (1987-)