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Title: Transport characteristics of a Glaser magnet for an axisymmetric and non-axisymmetric space charge dominated beam

Abstract

This paper describes the dynamics of space charge dominated beam through a Glaser magnet which is often used to focus charged particle beams in the low energy section of accelerators and in many other devices. Various beam optical properties of the magnet and emittance evolution that results from the coupling between the two transverse planes are studied. We have derived ten independent first order differential equations for the beam sigma matrix elements assuming the linear space-charge force consistent with the assumption of the canonically transformed KV like distribution. In addition, the feasibility of using a Glaser magnet doublet in a low energy beam injection line to match an initial non-axisymmetric high intensity beam with net angular momentum to an axisymmetric system to suppress effective emittance growth after transition back to an uncoupled system, has also been studied.

Authors:
; ;  [1]
  1. Variable Energy Cyclotron Centre, 1/AF, Bidhannagar, Kolkata 700064 (India)
Publication Date:
OSTI Identifier:
22072660
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 19; Journal Issue: 12; Other Information: (c) 2012 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ANGULAR MOMENTUM; AXIAL SYMMETRY; BEAM INJECTION; BEAMS; CHARGED PARTICLES; DIFFERENTIAL EQUATIONS; MAGNETS; MATRIX ELEMENTS; OPTICAL PROPERTIES; SPACE CHARGE

Citation Formats

Goswami, A., Sing Babu, P., and Pandit, V. S. Transport characteristics of a Glaser magnet for an axisymmetric and non-axisymmetric space charge dominated beam. United States: N. p., 2012. Web. doi:10.1063/1.4772061.
Goswami, A., Sing Babu, P., & Pandit, V. S. Transport characteristics of a Glaser magnet for an axisymmetric and non-axisymmetric space charge dominated beam. United States. doi:10.1063/1.4772061.
Goswami, A., Sing Babu, P., and Pandit, V. S. Sat . "Transport characteristics of a Glaser magnet for an axisymmetric and non-axisymmetric space charge dominated beam". United States. doi:10.1063/1.4772061.
@article{osti_22072660,
title = {Transport characteristics of a Glaser magnet for an axisymmetric and non-axisymmetric space charge dominated beam},
author = {Goswami, A. and Sing Babu, P. and Pandit, V. S.},
abstractNote = {This paper describes the dynamics of space charge dominated beam through a Glaser magnet which is often used to focus charged particle beams in the low energy section of accelerators and in many other devices. Various beam optical properties of the magnet and emittance evolution that results from the coupling between the two transverse planes are studied. We have derived ten independent first order differential equations for the beam sigma matrix elements assuming the linear space-charge force consistent with the assumption of the canonically transformed KV like distribution. In addition, the feasibility of using a Glaser magnet doublet in a low energy beam injection line to match an initial non-axisymmetric high intensity beam with net angular momentum to an axisymmetric system to suppress effective emittance growth after transition back to an uncoupled system, has also been studied.},
doi = {10.1063/1.4772061},
journal = {Physics of Plasmas},
number = 12,
volume = 19,
place = {United States},
year = {Sat Dec 15 00:00:00 EST 2012},
month = {Sat Dec 15 00:00:00 EST 2012}
}
  • The predictions of the smooth-approximation theory for the effective radius of a space-charge 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 5-m-long periodic channel and beam radii were measured by an axially moveable phosphor screen and a charge-coupled device camera. The phase advance of betatron oscillation per period without space-charge, [sigma][sub 0], was varied from [sigma][sub 0]=45[degree] to [sigma][sub 0]=90[degree]. The tune depression due to space-charge, [sigma]/[sigma][sub 0], was in themore » range of 0.2--0.3. The theoretical results for average beam radius [ital [bar R]] over one period and the ratio [ital [bar R]]/[ital R][sub max] were found to agree with the experimental data to better than 5% when a correction due to spherical aberration was taken into account.« less
  • A self-consistent particle-in-cell (PIC) simulation is used to study the transport properties of a space-charge-dominated multispecies beam propagating through a solenoid-based low energy beam transport line. The evolution of the beam radius and emittance growth of each species arising due to the nonlinear space-charge forces has been investigated. The self-consistent PIC simulation shows the formation of hollow density profiles of subdominant unwanted species around the primary beam, downstream of the transport line. We have utilized this effect for efficient removal of unwanted species by making use of a slit at a suitable location in the beam line.
  • Possible mechanisms of beam emittance conservation in high current transport lines and in RF linacs are discussed. Invariance of beam emittance is treated as a problem of proper matching of the beam with focusing and accelerating channels. To obtain matching conditions for a beam with an arbitrary distribution function in transport channel, it is necessary to accept that the potential of the external focusing field is a highly nonlinear function of radius. The solution for external potential is obtained from the stationary Vlasov{close_quote}s equation for beam distribution function and Poisson{close_quote}s equation for electrostatic beam potential. Gradual change of nonlinear focusingmore » field results in adiabatic transformation of the beam with initial nonlinear distribution into the beam, matched with the linear focusing channel. Alternating-gradient focusing structure with higher order multipole component creates better matching of the beam with the channel than pure quadrupole structure. Beam emittance growth in linear accelerator is studied for a drift tube linac with solenoid focusing. It is shown that beam phase space distortion in RF linac can be eliminated by the appropriate choice of the value of focusing field with respect to acceleration gradient. An analytical approach is illustrated by results of a particle-in-cell simulation. {copyright} {ital 1996 American Institute of Physics.}« less
  • The homogenization of a beam with a transversely nonuniform initial density distribution is examined by masking the ouput from a Pierce electron gun into five parallel beamlets, which are then propagated down a channel of periodically spaced solenoid focusing magnets. Experimental measurements, theoretical predictions, and PIC simulations are in excellent agreement for averaged beam quantities such as rms emittance and envelope radius. In addition, the fine-structure characteristic of the nonlinear evolution of the beam, including the formation of downstream images, is reproduced in detail by the simulations.
  • It has been found for the first time in experiments with an electron beam that space-charge waves can be generated not only in pairs. A single slow wave, a single fast wave, or combinations of the two waves with different amplitude and polarity relations have been produced experimentally in a space-charge dominated beam. Analytical solutions derived from one-dimensional fluid equations show the amplitude and polarity of each space-charge wave as a function of the initial perturbation parameters. The theory provides the correct interpretation of the experimental observations.