Preliminary Plume Characterization of a Low-Power Hall Thruster Cluster

In an effort to understand the technical issues related to running multiple Hall effect thrusters in close proximity to each other, testing of a cluster of four Busek BHT-200-X3 devices has begun in Chamber 6 at the Air Force Research Laboratory. Preliminary measurements have shown that the variations in the discharge currents of the four thrusters are synchronized, possibly due to cross talk through the thruster plumes. Measurements of plasma density, electron temperature, and plasma potential in the thruster plumes obtained using a triple Langmuir probe are presented. Anomalously high electron temperatures were recorded along the centerline of each thruster. Collisionless, magnetosonic shock waves induced by the ion-ion two-stream instability are proposed as a possible cause of the high temperatures. The unperturbed ion velocity distribution along the centerline of a Hall thruster is shown to be unstable and a simple geometric model is presented to illustrate the qualitative changes in plasma properties expected across the proposed shock. Estimates using this model show that relatively large changes in electron temperature are consistent with small changes in electron number density across a shock. Qualitative arguments are presented indicating that collisionless shocks are unlikely to form as a result of clustering multiple thrusters.

[1]  C. McKee SIMULATION OF COUNTERSTREAMING PLASMAS WITH APPLICATION TO COLLISIONLESS ELECTROSTATIC SHOCKS. , 1970 .

[2]  George J. Williams,et al.  Correlating Laser Induced Fluorescence and Molecular Beam Mass Spectrometry Ion Energy Distributions , 2002 .

[3]  Michelle F. Thomsen,et al.  Electron heating and the potential jump across fast mode shocks. [in interplanetary space , 1988 .

[4]  K. Miles,et al.  Formulary. , 2018, Occasional paper.

[5]  Sin‐Li Chen,et al.  Instantaneous Direct‐Display System of Plasma Parameters by Means of Triple Probe , 1965 .

[6]  J. Sanderson Jump conditions across a collisionless, perpendicular shock , 1976 .

[7]  Bruce Pote,et al.  Development of low power Hall thrusters , 1999 .

[8]  William Hargus,et al.  The Air Force Clustered Hall Thruster Program , 2002 .

[9]  Derek A. Tidman,et al.  Shock waves in collisionless plasmas , 1971 .

[10]  D. Morse Electrostatic potential rise across perpendicular shocks , 1973 .

[11]  R. P. Drake,et al.  Deconvolution of Axial Velocity Distributions from Hall Thruster LIF Spectra , 2001 .

[12]  M. Balikhin,et al.  Electron heating in quasiperpendicular shocks , 1995 .

[13]  George J. Williams,et al.  Laser induced fluorescence measurement of ion velocities in the plume of a hall effect thruster , 1999 .

[14]  Gregory G. Spanjers,et al.  Performance characteristics of a 5 kW laboratory hall thruster , 1998 .

[15]  H. Krier,et al.  Application of multiple electrostatic probes to a low power arcjet , 1994 .

[16]  H. Ikezi,et al.  Observation of Collisionless Electrostatic Shocks , 1970 .

[17]  T. Stringer Electrostatic instabilities in current-carrying and counterstreaming plasmas , 1964 .

[18]  Gregory G. Spanjers,et al.  Overview of the USAF Electric Propulsion Program , 2001 .

[19]  C. Goodrich,et al.  The adiabatic energy change of plasma electrons and the frame dependence of the cross‐shock potential at collisionless magnetosonic shock waves , 1984 .

[20]  Gregory G. Spanjers,et al.  The USAF Electric Propulsion Research Program , 2001 .

[21]  N. A. Krall,et al.  Heating of Counterstreaming Ion Beams in an External Magnetic Field , 1971 .

[22]  A. J. Kelly,et al.  The application of the triple probe method to MPD thruster plumes , 1990 .

[23]  D. R. Nicholson Introduction to Plasma Theory , 1983 .

[24]  John M. Sankovic,et al.  NASA's electric propulsion program , 1998 .

[25]  J. Scudder A review of the physics of electron heating at collisionless shocks , 1995 .

[26]  A. Kantrowitz,et al.  MHD CHARACTERISTICS AND SHOCK WAVES. , 1964 .

[27]  F. Gratton,et al.  Two-stream instability in convergent geometry , 1987 .

[28]  A. Gallimore,et al.  Hall Thruster Discharge Chamber Plasma Characterization Using a High-Speed Axial Reciprocating Electrostatic Probe , 1999 .