ECRIS2010 - Table of Session: THCOAK (Ions Production & Beam Study)

Paper

Title

Page

A Correction Scheme for the Hexapolar Error of an Ion Beam Extracted from an ECRIS

191

P. Spädtke, R. Lang, J. Mäder, F. Maimone, J. Roßbach, K. Tinschert
GSI, Darmstadt, Germany

The extraction of any ion beam from ECRIS is determined by the good confinement of such ion sources. It has been shown earlier, that the ions are coming from these places, where the confinement is weakest. The assumption that the low energy ions are strongly bound to the magnetic field lines require furthermore, that only these ions which start on a magnetic field line which go through the extraction aperture can be extracted. Depending on the setting of the magnetic field, these field lines may come from the loss lines at plasma chamber radius. Because the longitudinal position of these field lines depends on the azimuthal position at the extraction electrode, the ions are extracted from different magnetic flux densities. Whereas the solenoidal component is not curable, the hexapolar component can be compensated by an additional hexapole after the first beam line focusing solenoid. The hexapole has to be rotatable in azimuthal direction and moveable in longitudinal direction. For a good correction the beam needs to have such a radial phase space distribution, that the force given by this hexapole act on the aberrated beam exactly in such a way to create a linear distribution after that corrector.

Slides THCOAK01 [1.115 MB]

THCOAK02

Kinetic Plasma Simulation of Ion Beam Extraction from an ECR Ion Source

194

S.M. Elliott, E.K. White
Thin Film Consulting, Longmont, Colorado, USA
J. Simkin
Vector Fields Ltd., Oxford, United Kingdom

Designing optimized ECR ion beam sources can be streamlined by the accurate simulation of beam optical properties in order to predict ion extraction behavior. The complexity of these models, however, can make PIC-based simulations time-consuming. In this paper, we first describe a simple kinetic plasma finite element simulation of extraction of a proton beam from a permanent magnet hexapole electron cyclotron resonance (ECR) ion source. Second, we analyze the influence of secondary electrons generated by ion collisions in the residual gas on the space charge of a proton beam of a dual-solenoid ECR ion source. The finite element method (FEM) offers a fast modeling environment, allowing analysis of ion beam behavior under conditions of varying current density, electrode potential, and gas pressure.

Slides THCOAK02 [0.821 MB]

THCOAK03

Dipole Magnet Optimization for High Efficiency Low Energy Beam Transport

197

S. Saminathan, J.P.M. Beijers, S. Brandenburg, V. Mironov, J. Mulder
KVI, Groningen, The Netherlands

Losses in the low-energy beam transport line from KVI-AECRIS to AGOR cyclotron are estimated to be around 50%. Numerical simulations of the beam transport were performed using the tracing code LORENTZ-3D. It was found that most of the losses are due to second order optical aberrations in the 110-degree analyzing magnet. These aberrations result in an increase of the effective emittance in both horizontal and vertical directions. We will show that by suitably modifying the magnet pole surfaces the second-order aberrations can be compensated to a large extent resulting in a substantially lower effective emittance of the transported beam.

Slides THCOAK03 [1.102 MB]

THCOAK04

Modeling ECRIS Using a 1D Multifluid Code

200

M. Stalder
IEAP, Kiel, Germany

We developed a one-dimensional (1D) multifluid code to simulate the production and the transport of multiple ion species in an electron cyclotron ion source (ECRIS). The ion species are assumed to be highly collisionally coupled. Each ion species is treated as a independent fluid. This allows us to study the influence of the ion temperature. The temperature is assumed to be equal for all charge states and in the whole ECRIS. As starting parameters we choose a hot magnetically trapped electron distribution, a cold electron distribution trapped by the plasma potential an the neutral density. Modeling the interaction of the different fluids led to a new understanding of the influence of the electrostatic potential that balances the pressure gradient of the ions species in the ECRIS. The highest charge states are not confined strongest as in the over barrier model but expelled in comparison to lower charge states. It can be shown that the relative velocity v of the treated fluids scales as v ~ T^5/3 with the ion temperature. First results of the simulations are presented together with a discussion of the modeling approach for the multifluid case and its theoretical predictions. As a baseline for our simulations we mainly used the results of the 1D GEM ECRIS fluid simulations.

Slides THCOAK04 [2.268 MB]

Paper	Title	Page
THCOAK01	A Correction Scheme for the Hexapolar Error of an Ion Beam Extracted from an ECRIS	191
	P. Spädtke, R. Lang, J. Mäder, F. Maimone, J. Roßbach, K. Tinschert GSI, Darmstadt, Germany
	The extraction of any ion beam from ECRIS is determined by the good confinement of such ion sources. It has been shown earlier, that the ions are coming from these places, where the confinement is weakest. The assumption that the low energy ions are strongly bound to the magnetic field lines require furthermore, that only these ions which start on a magnetic field line which go through the extraction aperture can be extracted. Depending on the setting of the magnetic field, these field lines may come from the loss lines at plasma chamber radius. Because the longitudinal position of these field lines depends on the azimuthal position at the extraction electrode, the ions are extracted from different magnetic flux densities. Whereas the solenoidal component is not curable, the hexapolar component can be compensated by an additional hexapole after the first beam line focusing solenoid. The hexapole has to be rotatable in azimuthal direction and moveable in longitudinal direction. For a good correction the beam needs to have such a radial phase space distribution, that the force given by this hexapole act on the aberrated beam exactly in such a way to create a linear distribution after that corrector.
	Slides THCOAK01 [1.115 MB]

THCOAK02	Kinetic Plasma Simulation of Ion Beam Extraction from an ECR Ion Source	194
	S.M. Elliott, E.K. White Thin Film Consulting, Longmont, Colorado, USA J. Simkin Vector Fields Ltd., Oxford, United Kingdom
	Designing optimized ECR ion beam sources can be streamlined by the accurate simulation of beam optical properties in order to predict ion extraction behavior. The complexity of these models, however, can make PIC-based simulations time-consuming. In this paper, we first describe a simple kinetic plasma finite element simulation of extraction of a proton beam from a permanent magnet hexapole electron cyclotron resonance (ECR) ion source. Second, we analyze the influence of secondary electrons generated by ion collisions in the residual gas on the space charge of a proton beam of a dual-solenoid ECR ion source. The finite element method (FEM) offers a fast modeling environment, allowing analysis of ion beam behavior under conditions of varying current density, electrode potential, and gas pressure.
	Slides THCOAK02 [0.821 MB]

THCOAK03	Dipole Magnet Optimization for High Efficiency Low Energy Beam Transport	197
	S. Saminathan, J.P.M. Beijers, S. Brandenburg, V. Mironov, J. Mulder KVI, Groningen, The Netherlands
	Losses in the low-energy beam transport line from KVI-AECRIS to AGOR cyclotron are estimated to be around 50%. Numerical simulations of the beam transport were performed using the tracing code LORENTZ-3D. It was found that most of the losses are due to second order optical aberrations in the 110-degree analyzing magnet. These aberrations result in an increase of the effective emittance in both horizontal and vertical directions. We will show that by suitably modifying the magnet pole surfaces the second-order aberrations can be compensated to a large extent resulting in a substantially lower effective emittance of the transported beam.
	Slides THCOAK03 [1.102 MB]

THCOAK04	Modeling ECRIS Using a 1D Multifluid Code	200
	M. Stalder IEAP, Kiel, Germany
	We developed a one-dimensional (1D) multifluid code to simulate the production and the transport of multiple ion species in an electron cyclotron ion source (ECRIS). The ion species are assumed to be highly collisionally coupled. Each ion species is treated as a independent fluid. This allows us to study the influence of the ion temperature. The temperature is assumed to be equal for all charge states and in the whole ECRIS. As starting parameters we choose a hot magnetically trapped electron distribution, a cold electron distribution trapped by the plasma potential an the neutral density. Modeling the interaction of the different fluids led to a new understanding of the influence of the electrostatic potential that balances the pressure gradient of the ions species in the ECRIS. The highest charge states are not confined strongest as in the over barrier model but expelled in comparison to lower charge states. It can be shown that the relative velocity v of the treated fluids scales as v ~ T^5/3 with the ion temperature. First results of the simulations are presented together with a discussion of the modeling approach for the multifluid case and its theoretical predictions. As a baseline for our simulations we mainly used the results of the 1D GEM ECRIS fluid simulations.
	Slides THCOAK04 [2.268 MB]