Model of secondary electron yields from atomic and polyatomic ion impacts on copper and tungsten surfaces based upon stopping-power calculations
The calculation of the velocity dependence and magnitude of the kinetic secondary electron yield for atomic and polyatomic ions, denoted by gamma-bar/sub a/ and gamma-bar/sub m/, respectively, is modeled on stopping-power equations and compared to experimental results from the dynode materials copper and tungsten. From the experimental data, the relationship gamma-bar/sub m/=..sigma..gamma-bar/sub a/ is verified, which is necessary to the model calculation of gamma-bar/sub m/. The fundamental assumption of this model is that gamma-bar/sub a/ is proportional (even at low ion velocities) to the electronic stopping power (dE/dx)/sub e/ of that projectile in the target. Example calculations are performed for the velocity dependence of gamma-bar/sub a/ for hydrogen, carbon, and fluorine striking copper, and from these results the predicted gamma-bar/sub m/ curves for polyatomic ions are in close agreement with experiment. Analogous calculations for a tungsten surface are outlined and the final results are compared with experiment. The utility of the model is shown by illustrating that the measurement of gamma-bar can provide, not only a relative measurement of (dE/dx)/sub e/ for different ion atomic numbers on the same target, but can also provide a means of determining the nuclear stopping power (dE/dx)/sub n/ at low ion velocities where range measurements are difficult to perform. Values of (dE/dx)/sub n/ derived from measurements for fluorine and carbon striking copper are the same as values predicted by Lindhard and Scharff; for a tungsten target the experimental (dE/dx)/sub n/ values are a factor of 2 larger than theoretical. The relationship of the stopping power values derived from gamma-bar measurements with this model are compared to the values derived from ion range measurements.
- Research Organization:
- Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973
- OSTI ID:
- 7219670
- Journal Information:
- J. Appl. Phys.; (United States), Vol. 48:9
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
CARBON IONS
COLLISIONS
COPPER
ION COLLISIONS
FLUORINE IONS
HYDROGEN IONS
TUNGSTEN
CHARGED-PARTICLE TRANSPORT
ELECTRON EMISSION
ENERGY ABSORPTION
ENERGY DEPENDENCE
ENERGY LOSSES
ENERGY SPECTRA
ION BEAMS
MASS SPECTROSCOPY
MEASURING METHODS
RANGE
SECONDARY EMISSION
SENSITIVITY
STOPPING POWER
SURFACES
VELOCITY
ABSORPTION
ATOMIC IONS
BEAMS
CHARGED PARTICLES
ELEMENTS
EMISSION
IONS
METALS
RADIATION TRANSPORT
REFRACTORY METALS
SPECTRA
SPECTROSCOPY
TRANSITION ELEMENTS
640301* - Atomic
Molecular & Chemical Physics- Beams & their Reactions
654001 - Radiation & Shielding Physics- Radiation Physics
Shielding Calculations & Experiments