Plasma diagnostic with inductive probes in the discharge channel of a pulsed plasma thruster

• We measured the magnetic field in the discharge channel of pulsed plasma thruster.
• Two designs for miniaturized inductive probes are introduced and calibrated.
• The current density shows existence of an intermittent plasma creation region.
• The plasma creation region is distinct from moving light emitting regions.
• No accelerated current sheet is observed in the discharge channel at any time.

Research of magnetoplasmadynamic Pulsed Plasma Thrusters (PPTs), or iMPDs, at the Stuttgart Institute of Space Systems (IRS), led to the thruster design ADD SIMP-LEX. For optimization of the thruster's discharge behavior and of the plasma acceleration, the magnetic self-field is measured. Inductive miniaturized probes are introduced and used to acquire data at points of the volume inside of the thruster's discharge channel. The results are used for analysis to identify the extend of the discharge zone along the discharge channel of the PPT. Measured magnetic field signals along the centerline of the discharge channel are presented. The underlying distribution of the dynamic discharge current is deduced from Amperes circuital law and interpreted in a two-dimensional plot against camera images for the current-plasma-interaction, current motion and validity of today's discharge models. The evaluation of the calculated integral discharge current in a plane of the discharge channel against the recorded thruster discharge current is presented and discussed.