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Title: Heavy-Ion-Induced Electronic Desorption of Gas from Metals

Abstract

During heavy-ion operation in several particle accelerators worldwide, dynamic pressure rises of orders of magnitude were triggered by lost beam ions that bombarded the vacuum chamber walls. This ion-induced molecular desorption, observed at CERN, GSI, and BNL, can seriously limit the ion beam lifetime and intensity of the accelerator. From dedicated test stand experiments we have discovered that heavy-ion-induced gas desorption scales with the electronic energy loss (dE{sub e}/dx) of the ions slowing down in matter; but it varies only little with the ion impact angle, unlike electronic sputtering.

Authors:
; ;  [1];  [2]; ; ; ;  [3];  [4]; ; ;  [1];  [2]; ;  [5];  [6];  [7]
  1. Heavy-Ion Fusion Science Virtual National Laboratory, Berkeley, California 94720 (United States)
  2. (United States)
  3. GSI, Planckstrasse 1, 64291 Darmstadt (Germany)
  4. CERN, 1211 Geneva 23 (Switzerland)
  5. Uppsala University, 751 21, Uppsala (Sweden)
  6. CCLRC Daresbury Laboratory, Warrington (United Kingdom)
  7. Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)
Publication Date:
OSTI Identifier:
20955448
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Letters; Journal Volume: 98; Journal Issue: 6; Other Information: DOI: 10.1103/PhysRevLett.98.064801; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; ACCELERATORS; BNL; CERN; DESORPTION; ENERGY LOSSES; HEAVY IONS; ION BEAMS; LIFETIME; MATTER; SLOWING-DOWN; SPUTTERING

Citation Formats

Molvik, A. W., Covo, M. Kireeff, Westenskow, G., Lawrence Livermore National Laboratory, Livermore, California 94550, Kollmus, H., Bellachioma, M. C., Bender, M., Kraemer, A., Mahner, E., Bieniosek, F. M., Kwan, J., Seidl, P. A., Lawrence Berkeley National Laboratory, Berkeley, California 94720, Hedlund, E., Westerberg, L., Malyshev, O. B., and Prost, L. Heavy-Ion-Induced Electronic Desorption of Gas from Metals. United States: N. p., 2007. Web. doi:10.1103/PHYSREVLETT.98.064801.
Molvik, A. W., Covo, M. Kireeff, Westenskow, G., Lawrence Livermore National Laboratory, Livermore, California 94550, Kollmus, H., Bellachioma, M. C., Bender, M., Kraemer, A., Mahner, E., Bieniosek, F. M., Kwan, J., Seidl, P. A., Lawrence Berkeley National Laboratory, Berkeley, California 94720, Hedlund, E., Westerberg, L., Malyshev, O. B., & Prost, L. Heavy-Ion-Induced Electronic Desorption of Gas from Metals. United States. doi:10.1103/PHYSREVLETT.98.064801.
Molvik, A. W., Covo, M. Kireeff, Westenskow, G., Lawrence Livermore National Laboratory, Livermore, California 94550, Kollmus, H., Bellachioma, M. C., Bender, M., Kraemer, A., Mahner, E., Bieniosek, F. M., Kwan, J., Seidl, P. A., Lawrence Berkeley National Laboratory, Berkeley, California 94720, Hedlund, E., Westerberg, L., Malyshev, O. B., and Prost, L. Fri . "Heavy-Ion-Induced Electronic Desorption of Gas from Metals". United States. doi:10.1103/PHYSREVLETT.98.064801.
@article{osti_20955448,
title = {Heavy-Ion-Induced Electronic Desorption of Gas from Metals},
author = {Molvik, A. W. and Covo, M. Kireeff and Westenskow, G. and Lawrence Livermore National Laboratory, Livermore, California 94550 and Kollmus, H. and Bellachioma, M. C. and Bender, M. and Kraemer, A. and Mahner, E. and Bieniosek, F. M. and Kwan, J. and Seidl, P. A. and Lawrence Berkeley National Laboratory, Berkeley, California 94720 and Hedlund, E. and Westerberg, L. and Malyshev, O. B. and Prost, L.},
abstractNote = {During heavy-ion operation in several particle accelerators worldwide, dynamic pressure rises of orders of magnitude were triggered by lost beam ions that bombarded the vacuum chamber walls. This ion-induced molecular desorption, observed at CERN, GSI, and BNL, can seriously limit the ion beam lifetime and intensity of the accelerator. From dedicated test stand experiments we have discovered that heavy-ion-induced gas desorption scales with the electronic energy loss (dE{sub e}/dx) of the ions slowing down in matter; but it varies only little with the ion impact angle, unlike electronic sputtering.},
doi = {10.1103/PHYSREVLETT.98.064801},
journal = {Physical Review Letters},
number = 6,
volume = 98,
place = {United States},
year = {Fri Feb 09 00:00:00 EST 2007},
month = {Fri Feb 09 00:00:00 EST 2007}
}
  • During heavy ion operation in several particle accelerators world-wide, dynamic pressure rises of orders of magnitude were triggered by lost beam ions that bombarded the vacuum chamber walls. This ion-induced molecular desorption, observed at CERN, GSI, and BNL, can seriously limit the ion beam lifetime and intensity of the accelerator. From dedicated test stand experiments we have discovered that heavy-ion induced gas desorption scales with the electronic energy loss (dE{sub e}/d/dx) of the ions slowing down in matter; but it varies only little with the ion impact angle, unlike electronic sputtering.
  • We report measurements of O{sup +} secondary-ion emission induced by 25--250-keV Ne{sup +}, Ar{sup +}, and Kr{sup +} bombardment of oxidized surfaces of Ti, Mo, Nb, W, and Ni, and of Ni and Pd surfaces with adsorbed CO. The yield {ital I}(O{sup +}) of O{sup +} from bombardment of oxygen adsorbed onto nickel, as well as the yields of all metal and metal-oxide ions, exhibits behavior similar to the sputtering yields as functions of incident ion energy. By contrast, the yield of O{sup +} from the other oxidized targets increases linearly with projectile velocity {ital v}, making {ital dI}(O{sup +})/dvmore » a convenient, velocity-independent parameter with which to characterize the emission. The variation of {ital dI}(O{sup +})/dv with projectile species depends on the substrate. For Ti and, to a lesser extent, Nb, {ital dI}(O{sup +})/dv is independent of projectile species, although for Mo and W {ital dI}(O{sup +})/dv varies with projectile species in a manner similar to the corresponding variation of the electronic stopping power of the projectile. However, the magnitude of the observed O{sup +} yields is not consistent with that expected if the O{sup +} emission is produced by secondary-electron-stimulated desorption. {ital I}(O{sup +}) for bombardment of Ni and Pd surfaces with adsorbed CO is not clearly related to either the sputtering yield or the O{sup +} yields from the oxidized targets.« less
  • During heavy ion operation in several particle accelerators world-wide, dynamic pressure rises of orders of magnitude were triggered by lost beam ions that bombarded the vacuum chamber walls. This ion-induced molecular desorption, observed at CERN, GSI, and BNL, can seriously limit the ion beam lifetime and intensity of the accelerator. From dedicated test stand experiments we have discovered that heavy-ion induced gas desorption scales with the electronic energy loss (dE{sub e}/dx) of the ions slowing down in matter; but it varies only little with the ion impact angle, unlike electronic sputtering.
  • Yields of molecular ions desorbed from surfaces by energetic heavy ions have been studied using a thermal spike model. A temperature profile was assumed which is appropriate for high linear energy transfer (LET) ion-solid interactions. The desorption kinetics were assumed to follow a simple Arrhenius rate law which has been found to be useful in understanding desorption due to rapid temperature jumps. With these assumptions, we have fit recent desorption experiments where the exciting ions had a LET in the range of 10--100 MeV cm/sup 2/ mg/sup -1/ and where the desorbed molecules ranged from valine to insulin. The thermalmore » spike model predicted nonlinear dependence of the yield on LET at lower LET and a nearly linear dependence of the yield on LET at high LET. These features are in good agreement with the experimental data. We also considered modified models which included a loss channel due to fragmentation. These models gave somewhat better agreement with the experimental data. The parameters obtained in these fits were analyzed using sensitivity analysis to determine their uncertainties and to determine the interdependencies between parameters. The best fit model has been used to predict desorption yields at higher and lower LET and for different initial energy densities in the ionized track.« less
  • The dependence of the secondary-ion yield {ital Y} on the energy loss {ital dE}/{ital dx} of fast (MeV/u) primary ions has been measured for organic and inorganic samples. It is found that the dependence of {ital Y} on {ital dE}/{ital dx} can be expressed in the whole {ital dE}/{ital dx} range investigated (1{le}{ital dE}/{ital dx}{le}54 keV {mu}g{sup {minus}1} cm{sup 2}) as {ital Y}{proportional to}({ital dE}/{ital dx}{minus}{ital S}){sup {ital n}}, where {ital S} is a threshold energy loss. Different exponents {ital n} exist for positive and negative secondary ions as well as ions desorbed from different samples.