| Paper |
Title |
Page |
| MOPLS143 |
Suppression of Secondary Emission in a Magnetic Field using Sawtooth Surface
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897 |
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- L. Wang, T.O. Raubenheimer, G.V. Stupakov
SLAC, Menlo Park, California
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The effect of surface roughness on the secondary electron emission from a sawtooth surface in a magnetic field under electron bombardment is investigated using a Monte-Carlo method. Some of the secondary electrons emitted from the sawtooth surface return to the surface within their first few gyrations, resulting in low effective secondary electron yield. A sawtooth surface in magnetic field can significantly reduce the secondary emission yield below the multipacting threshold.
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| TUPLS003 |
A Perfect Electrode to Suppress Secondary Electrons inside the Magnets
|
1489 |
| |
- L. Wang, M.T.F. Pivi
SLAC, Menlo Park, California
- H. Fukuma, S.-I. Kurokawa
KEK, Ibaraki
- G.X. Xia
DESY, Hamburg
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Electron cloud due to multipacting in the positron ring of B-factories is one of the limitations on the machine performance. Electron cloud in the drift region can be suppressed by solenoid. However, solenoid doesn't work inside a magnet. Numerical studies show that there is strong multipacting in the dipole magnet of the B-factory positron ring. Electrons also can be trapped inside quadrupole and sextupole magnets. The electron cloud from the dipole magnet and wiggler in the positron damping ring of the ILC is a critical limitation on the choice of damping ring circumference, which directly results in a choice of two 6km rings as the baseline for the positron damping ring. Various electrodes have been studied using the program CLOUDLAND. Our studies show that a wire type of electrode with a few hundred voltages works perfectly to kill the secondary electrons inside various magnets.
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| WEPCH103 |
Ion Effects in the Electron Damping Ring of the International Linear Collider
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2155 |
| |
- L. Wang, T.O. Raubenheimer
SLAC, Menlo Park, California
- A. Wolski
Liverpool University, Science Faculty, Liverpool
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Ion-induced beam instabilities and tune shifts are critical issues for the electron damping ring of the International Linear Collider (ILC). To avoid conventional ion trapping (multi-turn trapping), a long gap is introduced in the electron beam by omitting a number of successive bunches out of a long train. However, the beam can still suffer from the fast ion instability (FII), driven by ions that last only for a single passage of the electron bunches. Our study shows that the ion effects can be significantly mitigated by using multiple gaps, so that the stored beam consists of a number of relatively short bunch trains. The ion effects in the ILC damping rings are investigated using both analytical and numerical methods.
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| THPCH075 |
Simulation of the Electron Cloud for Various Configurations of a Damping Ring for the ILC
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2958 |
| |
- M.T.F. Pivi, T.O. Raubenheimer, L. Wang
SLAC, Menlo Park, California
- K. Ohmi
KEK, Ibaraki
- R. Wanzenberg
DESY, Hamburg
- A. Wolski
Liverpool University, Science Faculty, Liverpool
- F. Zimmermann
CERN, Geneva
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In the beam pipe of the Damping Ring (DR) of the International Linear Collider (ILC), an electron cloud may be first produced by photoelectrons and ionization of residual gasses and then increased by the secondary emission process. This paper reports about the work that has been done by the electron cloud assessment international task force group for the recommendation of the ILC Damping Rings baseline design, made in November 2005. We have carefully estimated the secondary electron yield (SEY) threshold for electron cloud build-up and estimated the related single- and coupled-bunch instabilities that can be caused by the presence of electron cloud as a function of beam current and surface properties, for a variety of optics designs. The result of these studies was an important consideration in the choice of a 6-km design for the ILC damping rings. On the basis of the theoretical and experimental work, the baseline configuration specifies a pair of damping rings for the positron beam to mitigate the effects of the electron cloud.
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| THPCH077 |
Resistive-wall Instability in the Damping Rings of the ILC
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2964 |
| |
- L. Wang, K.L.F. Bane, T.O. Raubenheimer, M.C. Ross
SLAC, Menlo Park, California
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In the damping rings of the International Linear Collider (ILC), the resistive-wall instability is one of the dominant transverse instabilities. This instability directly influences the choice of material and aperture of the vacuum pipe, and the parameters of the transverse feedback system. This paper investigates the resistive-wall instabilities in an ILC damping ring under various conditions of beam pipe material, aperture, and fill pattern.
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