1. NazlI TURAN, Ugur KOKAL, Murat CELIK
EXPERIMENTAL INVESTIGATION OF THE EFFECTS OF CATHODE CURRENT ON HK40 HALL THRUSTER OPERATION  
NazlI TURAN, Ugur KOKAL, Murat CELIK
BogazIcI UnIversIty
Istanbul, Turkey
Speaker: NazlI TURAN
5th International Conference on Space Propulsion, Space Propulsion 2016,
2nd to 6th May 2016, Roma, Italy

2. Outline Introduction The current schematic
Cathode with continuous heating
Cathode without heating
Cathode with HK40 Hall thruster
Magnetic field structure
Efficiency analysis
Conclusion
References

3. Introduction
electrons are extracted from LaB6 insert surface by thermionic emission
the ionization of the propellant and the neutralization of the ion beam
electric and magnetic fields to extract ions

4. Planar, 0.5 mm diameter wire inside an alumina tube
Introduction
HK40 Hall effect thruster
Vd = 220 V Id = 1.2 A
flow rate = 18 sccm
BUSTLab hollow cathode
flow rate = 1.5 sccm
Langmuir probe
Planar, 0.5 mm diameter wire inside an alumina tube

5. Introduction Cathode voltage (Vcg) Discharge voltage (Vd)
Plasma potential (Vp)
Cathode coupling voltage (Vc)
Beam voltage (Vb)
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.

6. The current schematic
The source of the electrons that leave the cathode, thus providing the cathode current, is the LaB6 insert located inside the cathode tube.

7. The current schematic Icathode = Iec + Ieb Icathode = Iec + Ieb
Id = Iec + Iei
Id = Iib + Iec
Icathode = Iec + Ieb
Iib = Ieb
Iground = Ikeeper + Icathode
Ref: Goebel, D. M. and Katz, I.(2008), Fundamentals of Electric Propulsion: Hall Thrusters, JPL Space Science and Technology Series, New York, USA, 2008.

8. The current schematic
Rb magnetic field topology in the discharge channel
Rc the placement of the cathode as well as the external magnetic field of the thruster
Rk the resistance between the cathode insert and the keeper

9. Cathode with continous heating
Higher temperature increased thermionic emission increases the magnitude of cathode voltage
keeper voltage arranges itself to a lower value to attract the same keeper current

10. Cathode without heating
Vkeeper sheath shields the keeper voltage, keeper voltage increases.
If keeper current is increased, electrons in sheath layer contribute to the keeper current.
The cathode voltage becomes more negative.

11. Cathode with HK40 Hall thruster

12. Cathode with HK40 Hall thruster
B increases anode voltage increases
more electrons from ionization constant discharge current ground current decreases
plasma potential increases
ion beam current (Iib) > the electron current in the plume (Ieb)
full neutralization is not achieved

13. Cathode with HK40 Hall thruster
Id = Iib + Iec
Pb = Ib (Va – Vp)

14. Magnetic field structure
The neutralizing electron current is small.
divergent plume
magnetic contour lines taken from COMSOL modelling of the thruster magnetic topology
magnetization of the electrons near the cathode

15. Magnetic field structure
electron magnetization near the anode
electrons fail to reach the anode
accumulate on magnetic lines
the discharge channel of HK40 would not be long enough for electrons
magnetic field lines cross the anode

16. Efficiency analysis

17. Conclusion Measuring ground current
Investigating cathode operation with heater and keeper characteristics
Explaining the current schematic
Using resistance analogy for the thruster-cathode system
Operating HK40 with different magnetic coil currents
Discussing the magnetic field topology of HK40
Calculating efficiency analytically

18. References
Goebel, D. M. and Katz, I., Fundamentals of Electric Propulsion: Hall Thrusters, JPL Space Science and Technology Series, New York, USA, 2008.
Jameson, K., 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.
Guerrini, G., Michaut, C., Dudeck, M., Vesselovzorov, A., and Bacal, M., Characterization of Plasma Inside the SPT-50 Channel by Electrostatic Probes, Proceedings of the 25th International Electric Propulsion Conference, 1997, pp
Courtney, D.G., “Development and Characterization of a Diverging Cusped Field Thruster and a Lanthanum Hexaboride Hollow Cathode,” M.S. Thesis, Massachusetts Institute of Technology, Cambridge, MA, USA, May 2008.
Kunning G Xu and Mitchell LR Walker. Effect of External Cathode Azimuthal Position on Hall-effect Thruster Plume and Diagnostics. Journal of Propulsion and Power, Vol.30, No.2, 2014.
Martinez-Sanchez, M. and Pollard, J.E., Spacecraft Electric Propulsion-An Overview, Journal of Propulsion and Power, Vol. 14, No. 5, 1998, pp
E. Ahedo and J.M. Gallardo. Low Power Hall Thrusters: Physics, Technical Limitations and Design. Micro-Propulsion Workshop, Lerici, Italy, May 2002.
Jameson, K. K., Goebel, D. M., Hofer, R. R. and Watkins, R. M., Cathode Coupling in Hall Thrusters. 30th International Electric Propulsion Conference, Florence, Italy September IEPC

19. THANKS FOR LISTENING

20. BUSTLab Vacuum Chamber

21. HK40 Hall Effect Thruster

22. LaB6 Hollow Cathode

23. Experimental Measurements

24. Experimental Measurements

25. Experimental Measurements