1. REFERENCES CONCLUSION
Department of Atomic Energy
RAJA RAMANNA CENTRE FOR ADVANCED TECHNOLOGY
Proton Linac & Superconducting Cavities Division
Simulation of Multi-cusp Magnetic Field for efficient Confinement of Hydrogen Plasma in H- Ion Source
Dr. D.V. Ghodke, *Manisha Agnihotri, *Preet Jain, Dr. V.K Senecha & S.C. Joshi
Proton Linac & Superconducting Cavity Division, Raja Ramanna Centre for Advanced Technology ,Indore, INDIA
*E & C Department, SVITS, Indore, India
ABSTRACT:This paper presents the simulation of permanent magnet multi-cusp field for hydrogen plasma confinement in H- ion source using Opera-3D. In order to increase plasma density and making it uniform along the axis of plasma chamber reduces the scattering losses, a multi-cusp magnetic field is used. For better plasma confinement, the dimensions of configurations have been optimized to increase the field free region at the center of the plasma chamber and to increase the magnetic field (B) at the plasma chamber wall. In the region of increased magnetic field, the plasma particles are reflected back into the central plasma region rather than being lost from the plasma, due to magnetic force exerted on it. A cusp magnetic field provides a way to control the shape and size of the plasma volume and slow down the loss rate of plasma particles.
Different types of multi-cusp permanent magnetic field configurations have been used for hydrogen plasma confinement in H- ion source. The proposed configuration with iron cylinder not only reduces the stray magnetic field outside the plasma chamber but also provides the return path so as to produce the Hal-bach type cusping field. Octa-pole configuration was simulated extensively using TOSCA module of Opera-3D software package. The permanent magnet used for Octa-pole configuration is NdFeB of N32SH grade having dimensions of x 10 x 14 mm3. The outer radius of iron cylinder is 54 mm, length mm & thickness is 5 mm with 2 mm gap between magnets & iron cylinder. The inner diameter of plasma chamber is 48 mm. The magnetic flux density along plasma chamber wall is ~101 mT and field free region is ~18 mm, which is sufficient to confine the plasma particles. In order to check the confinement effect, particles of 5 eV energy were simulated to understand their loss near the plasma chamber wall.
Simulated results:
The simulation of different permanent magnet multi-cusp configurations have been studied using TOSCA module of Opera-3D. The simulated results of hexapole, octapole & Hal-bach configurations is shown here. For completeness other configurations up to 18 poles are simulated and their simulation results are presented here.
3D simulated model of hexa-pole with iron cylinder showing magnetic field distribution, polar patch, histogram, contour map, particle trajectories, 2D line graphs along X, Y, Z axis & azimuthally line graph.
3D simulated model of octa-pole with iron cylinder showing magnetic field distribution, polar patch, histogram, contour map, particle trajectories, 2D line graphs along X, Y, Z axis & azimuthally line graph.
3D simulated model of hal-bach configuration showing magnetic field distribution, polar patch, histogram, contour map, particle trajectories, 2D line graphs along X, Y, Z axis & azimuthally line graph.
CONFIGURATIONS
PARTICLE TRAJECTORIES
PEAK FLUX
( in T)
FIELD FREE REGION (in mm)
FLUX AT PLASMA CHAMBER (in mT)
0.68 T
-12 TO 12
82 mT
0.7 T
-15 TO 15
63 mT
0.75 T
-18 TO 18
43 mT
0.8 T
-20 TO 20
27 mT
0.85 T
-22 TO 22
18 mT
Ten-pole magnetic configuration
REFERENCES
CONCLUSION
[1] K.N. Leung, T.K. Samec & A. Lamm, “Optimization of permanent magnet plasma confinement,” Physics Letters, Volume 51A, number 8, pp , 5 May 1975.
[2] K.N. Leung, G.R Taylor, J.M Barrick, S. L Paul & R. E Kribel, “Plasma confinement by permanent magnet boundaries,” Physics Letters, Volume 57A, number 2, pp , 31 May 1976.
[3] Anita Sengupta, “Magnetic confinement in ring-cusp ion thruster discharge plasma,” J. Appl. Phys. 105, (2009).
[4] K.N. Leung, Noah Hershkowitz, & K. R. Mackneize,“Plasma confinement by localized cusp,”The Physics of Fluids, AIP, Vol.19, No.7, July 1976.
[5] M.H. Rashid, C. Mallik and R.K. Bhandari,“Simulated new cusp field created by permanent magnet for an 18 GHz ECR IS,”in Proc. 18th International Conference on Cyclotrons and their Applications, pp ,2007.
1. The simulated results of different multi-cusp configuration is presented.
2. Among all the configurations, octa-pole configuration is suitable for the RF based H- ion source.
3. The graph between different multi-cusp magnetic configuration & their distance along X axis is also presented. This gives the information about the variation of peak flux with respect to number of poles increases.
4. The magnetic flux at plasma chamber wall with respect to different multi-cusp configuration is also presented here.
Dodeca-pole magnetic configuration
Fourteen-pole magnetic configuration
Sixteen-pole magnetic configuration
Eighteen-pole magnetic configuration
28th National Symposium on Plasma Science & Technology, KIIT University , Bhubaneshwar , Odisha, December 2013