1. Nazli TURAN, Yavuz Emre KAMIS, Murat CELIK
STUDY OF MAGNETIC FIELD CONFIGURATION EFFECTS ON COUPLING BETWEEN HALL EFFECT THRUSTER AND HOLLOW CATHODE
Nazli TURAN, Yavuz Emre KAMIS, Murat CELIK
Bogazici University
Istanbul, Turkey
Speaker: Nazli TURAN

2. Outline Introduction The Coupling Problem between Thruster and Cathode
Numerical Results
Test Setup
Experimental Measurements
Comparison between the Results
Discussion
Future Work
References

3. Introduction
Spacecrafts moving in an orbit or in interplanetary space use propulsion system to provide thrust.
Electric propulsion systems
electrically expelling
propellant at high speed
using less propellant than
chemical rockets
providing a small thrust
for a long time
Ref:

4. Introduction
Applications: orbit maintenance, orbit raising and deep space missions
Advantages: reducing required propellant mass and resulting cost savings
Ref:

5. Introduction
Hall effect thrusters (HET): use electric and magnetic fields to extract ions from plasma discharge.
Ref:

6. Introduction
Hollow cathode: emits electrons to ionize neutral atoms in the discharge channel and prevents the spacecraft from charging.

7. Introduction
BUSTLab HK40 Hall effect thruster and LaB6 hollow cathode operation in vacuum chamber

8. The Coupling Problem between Thruster and Cathode
A large distance between the cathode and discharge plasma causes higher magnetic obstacle for the electrons to overcome.
Plasma potential increases due to magnetic field line restriction on electron motion from the cathode to ion beam and anode.

9. The Coupling Problem between Thruster and Cathode
Magnetic field separatrix: signifies the surface which forms the boundary between closed magnetic surfaces and open field lines.
Ref: Sommerville, J. D.(2009), Hall-Effect Thruster Cathode Coupling: The Effect of Cathode Position and Magnetic Field Topology, Ph.D. Thesis, Michigan Technological University, Houghton, MI,USA, 2009.

10. The Coupling Problem between Thruster and Cathode
If plasma potential (Vp) increases, cathode coupling voltage (Vcg) decreases, thus becoming more negative.
Ref: Jameson, K.(2008), Investigation of Hollow Cathode Effects on Total Thruster Efficiency in a 6 kW Hall Thruster, Ph.D. Thesis, University of California, Los Angeles, CA, USA, 2008.

11. Numerical Results
The colored contour values are vector potential and very close to zero.
The dark blue region with minimum magnetic flux density shows the separatrix region.

12. Numerical Results
The minimum magnetic flux density is detected on mm axial distance from the center of the thruster exit.

13. Test Setup to map the magnetic field topology
to determine the location of the separatrix region

14. Experimental Measurements
Magnetic flux density decreases as the probe moves away from the thruster.

15. Experimental Measurements
The region investigated starts at the center of the thruster exit. There are four outer permanent magnets those are assembled 90 degrees apart.

16. Comparison between the Results
Magnetic flux density has been measured with the Hall probe, and the experimental measurement results are compared with the COMSOL modeling.

17. Discussion
Depending on the external magnetic field topology of the thruster, there could be an optimum position for the cathode considering the separatrix region.
The location of the separatrix region could be determined as the minimum magnetic flux density region on the thruster axis away from thruster exit.
almost 10 mm difference between the numerical and experimental results while finding the separatrix region
the differences caused by actual and tabulated material properties information entered into the COMSOL model

18. Future Work
conducting experiments with different cathode positions to observe changes in cathode coupling voltage
investigating magnetic field effects on the cathode coupling process with simulation including an electron emitting cathode
comparing the results with those of the numerical simulations

19. References
Goebel, D. M. and Katz, I.(2008), Fundamentals of Electric Propulsion: Hall Thrusters, JPL Space Science and Technology Series, New York, USA, 2008.
Hutchinson, I. H. (2005), Principles of Plasma Diagnostics, Cambridge University Press, 2005.
Jameson, K.(2008), Investigation of Hollow Cathode Effects on Total Thruster Efficiency in a 6 kW Hall Thruster, Ph.D. Thesis, University of California, Los Angeles, CA, USA, 2008.
Sommerville, J. D.(2009), Hall-Effect Thruster Cathode Coupling: The Effect of Cathode Position and Magnetic Field Topology, Ph.D. Thesis, Michigan Technological University, Houghton, MI,USA, 2009.

20. THANKS FOR LISTENING

21. BUSTLab Vacuum Chamber

22. HK40 Hall Effect Thruster

23. LaB6 Hollow Cathode

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