Plume Control of a Cusped Field Thruster
The cusped field thruster uses several permanent ring magnets of alternating polarity to create a multistage cusp magnetic topology. It has demonstrated a long lifetime because of reduced plasma losses to the discharge channel surface. However, the high beam divergence problem has not been solved in this type of thruster. The purpose of this technical note is to describe a plume control method to reduce its plume angle. The results show that the magnetic field intensity in the plume region and the shape of the last separatrix have great influence on plume divergence.
Operation and Plume Measurements of Miniaturized Cylindrical Hall Thrusters with Permanent Magnets
*§ ** § Two permanent magnet versions of the miniaturized cylindrical Hall thruster (CHT) with different channel outer diameters, 1.5 cm and 2.6 cm, were operated in the power range of 50W-300 W. With twice smaller total power consumption, the 2.6 cm CHT is twice lighter than its electromagnet counterpart. Results of the discharge and plasma plume measurements suggest that the CHT with permanent magnets and electromagnet coils operate rather differently. In particular, the plasma flow from the permanent magnet thrusters has an unusual halo shape of the angular ion current density distribution with a majority of high energy ions flowing at the angles of 50°-70° with respect to the thruster centerline. This divergence of the energetic ion flow leads to the reduced efficiency of the thrust production in these thrusters.
Failure analysis for poor solderability of Au surface of PCB
Nonwetting is one of the common problems and is always rejected in electronic assemblies. ENIG pads of a PCBA exhibited nonwetting after lead-free reflow soldering. With the aid of stereomicroscope, SEM&EDS and XRF, a series of analysis was performed. And after visual inspection, surface and cross section analysis, thickness measurement and solderability test, it can be inferred that oxidation of plating surface was the main reason for nonwetting, and corrosion in Ni plating caused an adverse impact on solderalibity.