Performance characterization of the micro-Cathode Arc Thruster and propulsion system for space applications Taisen Zhuang, Alexey Shashurin, Samudra Haque and Michael Keidar Mechanical & Aerospace Engineering, The George Washington University Washington DC 20052 This paper describes a further development and characterization of vacuum arc thruster with external magnetic field. The velocity of ions moving from the micro-Cathode Arc Thrusters ( μCAT) cathode spots was measured using a set of grid probes along the path of the plasma plume expansion. The goal was to get the ion drift velocity and determine how much, if any, change of ion drift velocity occurs in the expanded plasma propagation path. It was found the ion drift velocity was increased when magnetic field increased (from 0 up to 200mT). The average ion velocity (cathode material is Ti) increases by factor of 2-3 up to about (3-4) × 10 4 ms -1 with magnetic field strength 200mT applied. Rotation of cathode spot as a result of an applied magnetic field is demonstrated by using Langmuir probes inserted inside the source channel azimuthally. Ion current distribution outside the thruster channel was measured using a set of special assemble of concentric circles plan probe alone the plasma propagation path. It is shown that plasma generated at the cathode spot is guided along the magnetic field line. I. Introduction Micro-Cathode Arc thruster (μCAT) based on a magnetically enhanced vacuum arc has been studied and its ad- vantages for the control of nanosatellites were demonstrated 1 , 2 . In previous work 2 it is found that the magnetic field leads to cathode spot motion in the azimuthal direction, well-known as- J × B 3 , which causing uniform erosion of the cathode material. However, in order to better understand its potential, the μCAT requires detailed characterization, which is the objective of this work. In particular, ion velocity contributing to the specific impulse is measured as a function of an applied magnetic field, uniformity of the discharge contributing to the lifetime is investigated as well as plasma plume distribution contributed to plume contamination is analyzed. In this paper, μCAT ion drift velocity was measured using a set of grid probes along the path of the plasma plume expansion. It is expected that the ion velocity is affected by the gradient of a magnetic field in the plume region. In this contribution, we investigate the flow of plasma on a set of equally spaced grid probe to observe, if any, change of ion drift velocity in the expanded plasma propagation path. Further, to characterize the cathode spot motion with presence of magnetic field, 4 Langmuir probes were used to measure the plasma spot rotation speed. A special assemble of concentric circular probes were employed alone the plasma propagation path in order to measure the ion current distribution outside the thruster channel. II. Measuring principle and experimental setup A. Velocity Measurement The basic method of measuring the average ion velocity is to use a time-of-flight method. Typically, there are three types of perturbations have been investigated in the past: current oscillations 4 , current spike 5 and abrupt termination of discharge 6 . But in μCAT system thruster Power Process Unit (PPU) 7 , a special triangle shape initial plus current supply make it possible to introduce a new type of velocity measurement method. Each method has advantages and disadvantages. In present experiment, initial peak was use to mark the ion current in the velocity measurement. In other words, there is no extra wave or perturbation current was added into the thruster power supply system, thus, initial current peak method do not change the ion charge state 4 to obtain the real ion velocity. In contrast to the one probe measurement, we follow the propagation of the plasma plume using 4 grids specially distributed in the axial direction along the plume, thus allowing measurements of the ion velocitydistribution. Figure 1 shows the experimental setup. Each grid probe was biased (50V) negatively with respect to the ground. The distances of four grid probes from the cathode and isolator surface were 7.5cm 12.5cm 17.5cm and 22.5cm respectively. Each gird probe was designed with the hole of about 1cm 2 of an open space and the grids are made of the copper wires with the diameter of about 0.1mm. In this case, the size of the opening is larger than the Debye length to ensure that the plasma passes through the previous grid to the next one. The signals were recorded using one 4-channel digital oscilloscopes. The 4 circle 1 of 8 American Institute of Aeronautics and Astronautics