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Title: SUPPRESSION OF THE EFFECTIVE SECONDARY EMISSION YIELD FOR A GROOVED METAL SURFACE (LCC-0145)

Abstract

We show that a grooved surface can have an effective secondary emission yield (SEY) smaller than a flat one. Two different geometries of grooves--triangular and rectangular--are studied. The effect of strong magnetic field on SEY suppression is also considered.

Authors:
Publication Date:
Research Org.:
Stanford Linear Accelerator Center, Menlo Park, CA (US)
Sponsoring Org.:
USDOE Office of Science (US)
OSTI Identifier:
827020
Report Number(s):
SLAC-TN-04-045
TRN: US200428%%1580
DOE Contract Number:
AC03-76SF00515
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 7 Jun 2004
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; MAGNETIC FIELDS; SECONDARY EMISSION; METALS; SURFACE PROPERTIES

Citation Formats

Stupakov, G. SUPPRESSION OF THE EFFECTIVE SECONDARY EMISSION YIELD FOR A GROOVED METAL SURFACE (LCC-0145). United States: N. p., 2004. Web. doi:10.2172/827020.
Stupakov, G. SUPPRESSION OF THE EFFECTIVE SECONDARY EMISSION YIELD FOR A GROOVED METAL SURFACE (LCC-0145). United States. doi:10.2172/827020.
Stupakov, G. Mon . "SUPPRESSION OF THE EFFECTIVE SECONDARY EMISSION YIELD FOR A GROOVED METAL SURFACE (LCC-0145)". United States. doi:10.2172/827020. https://www.osti.gov/servlets/purl/827020.
@article{osti_827020,
title = {SUPPRESSION OF THE EFFECTIVE SECONDARY EMISSION YIELD FOR A GROOVED METAL SURFACE (LCC-0145)},
author = {Stupakov, G},
abstractNote = {We show that a grooved surface can have an effective secondary emission yield (SEY) smaller than a flat one. Two different geometries of grooves--triangular and rectangular--are studied. The effect of strong magnetic field on SEY suppression is also considered.},
doi = {10.2172/827020},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jun 07 00:00:00 EDT 2004},
month = {Mon Jun 07 00:00:00 EDT 2004}
}

Technical Report:

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  • The development of an electron cloud in the vacuum chambers of high intensity positron and proton storage rings may limit machine performance. The suppression of electrons in a magnet is a challenge for the positron damping ring of the International Linear Collider (ILC) as well as the Large Hadron Collider. Simulation show that grooved surfaces can significantly reduce the electron yield in a magnet. Some of the secondary electrons emitted from the grooved surface return to the surface within a few gyrations, resulting in a low effective secondary electron yield (SEY) of below 1.0 A triangular surface is an effective,more » technologically attractive mitigation with a low SEY and a weak dependence on the scale of the corrugations and the external magnetic field. A chamber with triangular grooved surface is proposed for the dipole and wiggler sections of the ILC and will be tested in KEKB in 2007. The strategy of electron cloud control in ILC and the optimization of the grooved chamber such as the SEY, impedance as well as the manufacturing of the chamber, are also discussed.« less
  • In the beam pipe of the positron Main Damping Ring (MDR) of the Next Linear Collider (NLC), ionization of residual gases and secondary electron emission give rise to an electron cloud which can cause the loss of the circulating beam. One path to avoid the electron cloud is to ensure that the vacuum wall has low secondary emission yield and, therefore, we need to know the secondary emission yield (SEY) for candidate wall coatings. We report on SEY measurements at SLAC on titanium nitride (TiN) and titanium-zirconium-vanadium (TiZrV) thin sputter deposited films, as well as describe our experimental setup.
  • Complex structures on a material surface can significantly reduce total secondary electron emission from that surface. A velvet is a surface that consists of an array of vertically standing whiskers. The reduction occurs due to the capture of low-energy, true secondary electrons emitted at the bottom of the structure and on the sides of the velvet whiskers. We performed numerical simulations and developed an approximate analytical model that calculates the net secondary electron emission yield from a velvet surface as a function of the velvet whisker length and packing density, and the angle of incidence of primary electrons. We foundmore » that to suppress secondary electrons, the following condition on dimensionless parameters must be met: (π/2) DΑ tan θ >> 1, where theta is the angle of incidence of the primary electron from the normal, D is the fraction of surface area taken up by the velvet whisker bases, and A is the aspect ratio, A = h/r, the ratio of height to radius of the velvet whiskers. We find that velvets available today can reduce the secondary electron yield by 90% from the value of a flat surface. As a result, the values of optimal velvet whisker packing density that maximally suppresses the secondary electron emission yield are determined as a function of velvet aspect ratio and the electron angle of incidence.« less
  • The effect of an artificially-enhanced rough surface on the secondary electron emission yield (SEY) was investigated both theoretically and experimentally. Analytical studies on triangular and rectangular grooved surfaces show the connection between the characteristic parameters of a given geometry to the SEY reduction. The effect of a strong magnetic field is also discussed. SEY of grooved samples have been measured and the results agree with Monte-Carlo simulations.
  • Measurement of secondary electron yields and electron energy distributions appears straightforward--simple equipment, simple electronics, easy-to-acquire data, at least in a laboratory setting. Unfortunately, the low secondary electron energy (2-5 eV) and the extreme sensitivity of the yield to surface condition and surrounding environment make the measurement details anything but simple. These problems affect the accuracy and interpretation of the experimental results, often in a subtle way. Most troublesome is the production of unwanted (and unexpected) secondary electrons from within the electron sources and detectors, and tertiary electrons from the surrounding vacuum chamber environment. In addition, the sample surface condition canmore » change during measurement, for example, through electron damage or enhanced oxidation/carburization. Electron source, analyzer, and sample effects will be discussed with examples for oxidized Al, niobium, graphite, gold and, also, TiN coatings.« less