Space charge induced beam instability in periodic focusing channel
Abstract
The transverse evolution of the envelope of an intense, unbunched ion beam in a linear periodic transport channel can be modeled for the approximation of linear selffields by the KapchinskijVladimirskij envelope equation. The envelope mismatched modes, or the second order even mode [I. Hofmann, Phys. Rew. E 57, 4713 (1998)], are the lowest order of resonance leading to collective instability that the designer should avoid, which suggests that an accelerator system should be established in the parameter region where the zero beam current phase advance σ{sub 0} less than 90°. In this paper, we systemically studied the resonance mechanisms which result in confluent resonance in quadrupole FocusingDefocusing (FD) channel and parametric resonance in solenoid channel. We propose that the mismatch modes cannot be exactly separated in FD channel; if one mode is excited, there is always some contribution of the other. To verify the influence of the confluent resonance and parametric resonance, the 2D Poissons solver in the selfconsistent particleincell simulation code TOPOPIC is adopted to study the beam evolution in both channels. Our simulations results show that the emittance show significant growth both in the confluent resonance stop band and parametric resonance stop band. The influences of the highermore »
 Authors:
 Key Laboratory of Particle Acceleration Physics and Technology, Institute of High Energy Physics, Chinese Academy of Sciences, 19(B) Yuquan Road, Beijing 100049 (China)
 Publication Date:
 OSTI Identifier:
 22408138
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Physics of Plasmas; Journal Volume: 22; Journal Issue: 2; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ACCELERATORS; APPROXIMATIONS; BEAM CURRENTS; COMPUTERIZED SIMULATION; FOCUSING; INSTABILITY; ION BEAMS; RESONANCE; SPACE CHARGE
Citation Formats
Li, Chao, Email: lichao@ihep.ac.cn, and Qin, Qing. Space charge induced beam instability in periodic focusing channel. United States: N. p., 2015.
Web. doi:10.1063/1.4908546.
Li, Chao, Email: lichao@ihep.ac.cn, & Qin, Qing. Space charge induced beam instability in periodic focusing channel. United States. doi:10.1063/1.4908546.
Li, Chao, Email: lichao@ihep.ac.cn, and Qin, Qing. 2015.
"Space charge induced beam instability in periodic focusing channel". United States.
doi:10.1063/1.4908546.
@article{osti_22408138,
title = {Space charge induced beam instability in periodic focusing channel},
author = {Li, Chao, Email: lichao@ihep.ac.cn and Qin, Qing},
abstractNote = {The transverse evolution of the envelope of an intense, unbunched ion beam in a linear periodic transport channel can be modeled for the approximation of linear selffields by the KapchinskijVladimirskij envelope equation. The envelope mismatched modes, or the second order even mode [I. Hofmann, Phys. Rew. E 57, 4713 (1998)], are the lowest order of resonance leading to collective instability that the designer should avoid, which suggests that an accelerator system should be established in the parameter region where the zero beam current phase advance σ{sub 0} less than 90°. In this paper, we systemically studied the resonance mechanisms which result in confluent resonance in quadrupole FocusingDefocusing (FD) channel and parametric resonance in solenoid channel. We propose that the mismatch modes cannot be exactly separated in FD channel; if one mode is excited, there is always some contribution of the other. To verify the influence of the confluent resonance and parametric resonance, the 2D Poissons solver in the selfconsistent particleincell simulation code TOPOPIC is adopted to study the beam evolution in both channels. Our simulations results show that the emittance show significant growth both in the confluent resonance stop band and parametric resonance stop band. The influences of the higher order of resonance are also discussed.},
doi = {10.1063/1.4908546},
journal = {Physics of Plasmas},
number = 2,
volume = 22,
place = {United States},
year = 2015,
month = 2
}

The predictions of the smoothapproximation theory for the effective radius of a spacecharge dominated beam in a periodic solenoid focusing channel were checked experimentally over a wide range of focusing conditions. Electron beams with an energy of 5 keV and currents of 50 to 70 mA were transported through a 5mlong periodic channel and beam radii were measured by an axially moveable phosphor screen and a chargecoupled device camera. The phase advance of betatron oscillation per period without spacecharge, [sigma][sub 0], was varied from [sigma][sub 0]=45[degree] to [sigma][sub 0]=90[degree]. The tune depression due to spacecharge, [sigma]/[sigma][sub 0], was in themore »

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