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Title: Beam Energy Scaling of Ion-Induced Electron Yield from K+ Impact on Stainless Steel

Abstract

Electron clouds limit the performance of many major accelerators and storage rings. Significant quantities of electrons result when halo ions are lost to beam tubes, generating gas which can be ionized and ion-induced electrons that can multiply and accumulate, causing degradation or loss of the ion beam. In order to understand the physical mechanisms of ion-induced electron production, experiments studied the impact of 50 to 400 keV K{sup +} ions on stainless steel surfaces near grazing incidence, using the 500 kV Ion Source Test Stand (STS-500) at LLNL. The experimental electron yield scales with the electronic component (dE{sub e}/dx) of the stopping power and its angular dependence does not follow l/cos({theta}). A theoretical model is developed, using TRIM code to evaluate dE{sub e}/dx at several depths in the target, to estimate the electron yield, which is compared with the experimental results. The experiment extends the range of energy from previous works and the model reproduces the angular dependence and magnitude of the electron yield.

Authors:
; ; ; ; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
899118
Report Number(s):
UCRL-JRNL-219620
TRN: US0701740
DOE Contract Number:
W-7405-ENG-48
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Special Topics - Accelerator and Beams, vol. 9, no. 6, June 12, 2006, pp. 063201
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; 29 ENERGY PLANNING, POLICY AND ECONOMY; 36 MATERIALS SCIENCE; 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ACCELERATORS; CLOUDS; ELECTRONS; ION BEAMS; ION SOURCES; LAWRENCE LIVERMORE NATIONAL LABORATORY; PERFORMANCE; PRODUCTION; STAINLESS STEELS; STOPPING POWER; STORAGE RINGS

Citation Formats

Covo, M K, Molvik, A, Friedman, A, Westenskow, G, Barnard, J J, Cohen, R, Seidl, P, Kwan, J W, Logan, G, Baca, D, Bieniosek, F, Celata, C M, Vay, J, and Vujic, J L. Beam Energy Scaling of Ion-Induced Electron Yield from K+ Impact on Stainless Steel. United States: N. p., 2006. Web.
Covo, M K, Molvik, A, Friedman, A, Westenskow, G, Barnard, J J, Cohen, R, Seidl, P, Kwan, J W, Logan, G, Baca, D, Bieniosek, F, Celata, C M, Vay, J, & Vujic, J L. Beam Energy Scaling of Ion-Induced Electron Yield from K+ Impact on Stainless Steel. United States.
Covo, M K, Molvik, A, Friedman, A, Westenskow, G, Barnard, J J, Cohen, R, Seidl, P, Kwan, J W, Logan, G, Baca, D, Bieniosek, F, Celata, C M, Vay, J, and Vujic, J L. Mon . "Beam Energy Scaling of Ion-Induced Electron Yield from K+ Impact on Stainless Steel". United States. doi:. https://www.osti.gov/servlets/purl/899118.
@article{osti_899118,
title = {Beam Energy Scaling of Ion-Induced Electron Yield from K+ Impact on Stainless Steel},
author = {Covo, M K and Molvik, A and Friedman, A and Westenskow, G and Barnard, J J and Cohen, R and Seidl, P and Kwan, J W and Logan, G and Baca, D and Bieniosek, F and Celata, C M and Vay, J and Vujic, J L},
abstractNote = {Electron clouds limit the performance of many major accelerators and storage rings. Significant quantities of electrons result when halo ions are lost to beam tubes, generating gas which can be ionized and ion-induced electrons that can multiply and accumulate, causing degradation or loss of the ion beam. In order to understand the physical mechanisms of ion-induced electron production, experiments studied the impact of 50 to 400 keV K{sup +} ions on stainless steel surfaces near grazing incidence, using the 500 kV Ion Source Test Stand (STS-500) at LLNL. The experimental electron yield scales with the electronic component (dE{sub e}/dx) of the stopping power and its angular dependence does not follow l/cos({theta}). A theoretical model is developed, using TRIM code to evaluate dE{sub e}/dx at several depths in the target, to estimate the electron yield, which is compared with the experimental results. The experiment extends the range of energy from previous works and the model reproduces the angular dependence and magnitude of the electron yield.},
doi = {},
journal = {Physical Review Special Topics - Accelerator and Beams, vol. 9, no. 6, June 12, 2006, pp. 063201},
number = ,
volume = ,
place = {United States},
year = {Mon Mar 06 00:00:00 EST 2006},
month = {Mon Mar 06 00:00:00 EST 2006}
}
  • Electron clouds limit the performance of many major accelerators. Significant quantities of electrons result when halo ions are lost to beam tubes, generating gas which can be ionized and ion-induced electrons that can multiply and accumulate, causing degradation or loss of the ion beam. In order to understand the physical mechanisms of ion-induced electron production, experiments studied the impact of 50 to 400 keV K{sup +} ions on stainless steel surfaces near grazing incidence, using the 500 kilovolts Ion Source Test Stand (STS-500) at LLNL. The experimental electron yield scales with the electronic component (dE{sub e}/dx) of the stopping power.more » A theoretical model is developed, using TRIM code to evaluate dE{sub e}/dx at several depths in the target, to estimate the electron yield, which is compared with the experimental results.« less
  • For the GSI future project Facility for Antiproton and Ion Research a beam intensity of 10{sup 12} U{sup 28+}ions/s is planned to be extracted from the GSI heavy ion synchrotron SIS18. Measurements performed in 2001 showed that the beam lifetime of the ions in the synchrotron is decreasing with increasing number of injected particles due to vacuum instabilities caused by ion-induced desorption. The injection energy for the SIS18 is about 10 MeV/u and U{sup 28+} ions are accelerated to 200 MeV/u limited by the magnetic rigidity for the low charge state. The aim of this work was to measure themore » desorption yield as a function of the impact energy from injection to extraction of SIS18 at GSI. Low energy yields at 5.0, 9.7, and 17.7 MeV/u were measured at the Cyclotron of The Svedberg Laboratory in Uppsala. High energy yields at 40, 80, and 100 MeV/u were measured at SIS18 of GSI in a different setup. It was found that the desorption yield scales with the electronic energy loss (dE/dx){sub el}{sup n}, with n between 2 and 3, decreasing for increasing impact energy above the Bragg maximum.« less
  • Absolute yields of electrons and negative ions resulting from positive ions impacting stainless steel have been determined as a function of impact energy for clean and oxygen-covered surfaces. Photoelectron emission has been used to monitor the effect of oxygen coverage on the surface work function. The emission of negative ions and electrons has been described with an excitation mechanism similar to that used in the Menzel{endash}Gomer{endash}Redhead model. We illustrate the implications of the present observations for discharge modeling and diagnostics by citing a parallel-plate, rf discharge in oxygen as an example. {copyright} {ital 1999 American Institute of Physics.}
  • A 1D Lagrangian magnetohydrodynamic z-pinch simulation code is extended to include wire ablation. The plasma transport coefficients are calibrated to reproduce the K-shell yields measured on the Z generator for three stainless steel arrays of diameter 55 mm and masses ranging from 1.8 to 2.7 mg. The resulting 1D scaling model is applied to a larger SS array (65 mm and 2.5 mg) on the refurbished Z machine. Simulation results predict a maximum K-shell yield of 77 kJ for an 82 kV charging voltage. This maximum drops to 42 kJ at 75 kV charging. Neglecting the ablation precursor leads tomore » a {approx}10% change in the calculated yield.« less