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Title: Energy loss of 1-50 keV H, He, C, N, O, Ne, and Ar ions transmitted through thin carbon foils

Abstract

Thin foils are used extensively in space plasma spectrometers, for example, for generation of a coincidence measurement via secondary electron emission in time-of-flight mass spectrometers and charge conversion of energetic neutral atoms (ENAs) in ENA imagers. An ion or neutral atom passing through the carbon foil experiences energy loss and straggling that can degrade the energy resolution or mass resolution. These effects need to be quantified in order to permit efficient instrument development and modeling. We present measurements of energy loss and energy loss straggling for H, He, C, N, O, Ne, and Ar ions between 1 and 50 keV passing through carbon foils of different thicknesses (nominally between 0.5 and 3.0 {mu}g/cm{sup 2}). We derive empirical relationships for the energy loss and energy loss straggling as a function of foil thickness, ion species, and ion energy. In particular, below {approx}10 keV the energy loss of hydrogen seems to vary with foil thickness and the energy loss straggling seems to vary with the square root of the thickness. Our results apply equally well to ions and neutral atoms.

Authors:
; ; ; ; ; ; ; ;  [1];  [2];  [3]
  1. Southwest Research Institute, San Antonio, Texas 78228-0510 (United States)
  2. (CETP), 94100 Saint-Maur (France)
  3. (United States)
Publication Date:
OSTI Identifier:
20779206
Resource Type:
Journal Article
Resource Relation:
Journal Name: Review of Scientific Instruments; Journal Volume: 77; Journal Issue: 4; Other Information: DOI: 10.1063/1.2185490; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; ARGON; ARGON IONS; ATOMS; CARBON; ELECTRON EMISSION; ENERGY RESOLUTION; FOILS; HELIUM; HYDROGEN; KEV RANGE 10-100; MASS RESOLUTION; NEON; NITROGEN; OXYGEN; THICKNESS; TIME-OF-FLIGHT MASS SPECTROMETERS

Citation Formats

Allegrini, F., McComas, D.J., Young, D.T., Berthelier, J.-J., Covinhes, J., Illiano, J.-M., Riou, J.-F., Funsten, H.O., Harper, R.W., Centre D'Etude Terrestre et Planetaire, and Los Alamos National Laboratory, Los Alamos, New Mexico 87545. Energy loss of 1-50 keV H, He, C, N, O, Ne, and Ar ions transmitted through thin carbon foils. United States: N. p., 2006. Web. doi:10.1063/1.2185490.
Allegrini, F., McComas, D.J., Young, D.T., Berthelier, J.-J., Covinhes, J., Illiano, J.-M., Riou, J.-F., Funsten, H.O., Harper, R.W., Centre D'Etude Terrestre et Planetaire, & Los Alamos National Laboratory, Los Alamos, New Mexico 87545. Energy loss of 1-50 keV H, He, C, N, O, Ne, and Ar ions transmitted through thin carbon foils. United States. doi:10.1063/1.2185490.
Allegrini, F., McComas, D.J., Young, D.T., Berthelier, J.-J., Covinhes, J., Illiano, J.-M., Riou, J.-F., Funsten, H.O., Harper, R.W., Centre D'Etude Terrestre et Planetaire, and Los Alamos National Laboratory, Los Alamos, New Mexico 87545. Sat . "Energy loss of 1-50 keV H, He, C, N, O, Ne, and Ar ions transmitted through thin carbon foils". United States. doi:10.1063/1.2185490.
@article{osti_20779206,
title = {Energy loss of 1-50 keV H, He, C, N, O, Ne, and Ar ions transmitted through thin carbon foils},
author = {Allegrini, F. and McComas, D.J. and Young, D.T. and Berthelier, J.-J. and Covinhes, J. and Illiano, J.-M. and Riou, J.-F. and Funsten, H.O. and Harper, R.W. and Centre D'Etude Terrestre et Planetaire and Los Alamos National Laboratory, Los Alamos, New Mexico 87545},
abstractNote = {Thin foils are used extensively in space plasma spectrometers, for example, for generation of a coincidence measurement via secondary electron emission in time-of-flight mass spectrometers and charge conversion of energetic neutral atoms (ENAs) in ENA imagers. An ion or neutral atom passing through the carbon foil experiences energy loss and straggling that can degrade the energy resolution or mass resolution. These effects need to be quantified in order to permit efficient instrument development and modeling. We present measurements of energy loss and energy loss straggling for H, He, C, N, O, Ne, and Ar ions between 1 and 50 keV passing through carbon foils of different thicknesses (nominally between 0.5 and 3.0 {mu}g/cm{sup 2}). We derive empirical relationships for the energy loss and energy loss straggling as a function of foil thickness, ion species, and ion energy. In particular, below {approx}10 keV the energy loss of hydrogen seems to vary with foil thickness and the energy loss straggling seems to vary with the square root of the thickness. Our results apply equally well to ions and neutral atoms.},
doi = {10.1063/1.2185490},
journal = {Review of Scientific Instruments},
number = 4,
volume = 77,
place = {United States},
year = {Sat Apr 15 00:00:00 EDT 2006},
month = {Sat Apr 15 00:00:00 EDT 2006}
}
  • We have measured the electron emission yields ..gamma.. of clean aluminum under bombardment with H/sup +/, H/sub 2/ /sup +/, D/sup +/, D/sub 2/ /sup +/, He/sup +/, B/sup +/, C/sup +/, N/sup +/, N/sub 2/ /sup +/, O/sup +/, O/sub 2/ /sup +/, F/sup +/, Ne/sup +/, S/sup +/, Cl/sup +/, Ar/sup +/, Kr/sup +/, and Xe/sup +/ in the energy range 1.2--50 keV. The clean surfaces were prepared by in situ evaporation of high-purity Al under ultra-high-vacuum conditions. It is found that kinetic electron emission yields ..gamma../sub k/, obtained after subtracting from the measured ..gamma.. a contribution duemore » to potential emission, are roughly proportional to the electronic stopping powers, for projectiles lighter than Al. For heavier projectiles there is a sizable contribution to electron emission from collisions involving rapidly recoiling target atoms, which increases with the mass of the projectile, and which dominates the threshold and near-threshold behavior of kinetic emission. The results, together with recently reported data on Auger electron emission from ion-bombarded Al show that the mechanism proposed by Parilis and Kishinevskii of inner-shell excitation and subsequent Auger decay is negligible for light ions and probably small for heavy ions on Al and in our energy range. We thus conclude that kinetic electron emission under bombardment by low-energy ions results mainly from the escape of excited valence electrons.« less
  • We calculate the mean energy loss of H{sub 2}{sup +} molecular ions transmitted through carbon and aluminum foils as a function of the bombarding energy. Our results are in good agreement with available experimental data. Furthermore, inhomogeneities containing the foil are found to be essential in the energy-loss measurement of transmitted molecular ions.
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  • We present experimental results for the angular scattering of ∼1–50 keV H, He, C, O, N, Ne, and Ar ions transiting through graphene foils and compare them with scattering through nominal ∼0.5 μg cm{sup −2} carbon foils. Thin carbon foils play a critical role in time-of-flight ion mass spectrometers and energetic neutral atom sensors in space. These instruments take advantage of the charge exchange and secondary electron emission produced as ions or neutral atoms transit these foils. This interaction also produces angular scattering and energy straggling for the incident ion or neutral atom that acts to decrease the performance of amore » given instrument. Our results show that the angular scattering of ions through graphene is less pronounced than through the state-of-the-art 0.5 μg cm{sup −2} carbon foils used in space-based particle detectors. At energies less than 50 keV, the scattering angle half width at half maximum, ψ{sub 1/2}, for ∼3–5 atoms thick graphene is up to a factor of 3.5 smaller than for 0.5 μg cm{sup −2} (∼20 atoms thick) carbon foils. Thus, graphene foils have the potential to improve the performance of space-based plasma instruments for energies below ∼50 keV.« less