Abstract: Flat, insulated, metallic strips ("applicators"), are fixed to the wider sides of each permanent magnet assembly in the channel array of a Magnetohydrodynamic (MHD) Vacuum Pump. Electromagnetic power from an external rf/microwave generator is delivered by an appropriate transmission line to each pair of applicators, providing an rf/microwave electric field, generally parallel to the magnetic field of the magnets, across each channel in the array. As the plasma ions and electrons formed by the rf/microwave field lose energy by collisions with the channel surfaces and by collisions with neutral molecules in the channel, the microwave electric field reheats the plasma throughout its passage through the length of the channel array, increasing plasma density and enabling the use of much longer channels, thus increasing the throughput and compression ratio in the MHD Vacuum Pump.

Abstract: This invention relates to the technology of preparing a vacuum by removing gases from an enclosed volume and to the use of magnetized plasma as the working fluid in a vacuum pump. The pumping action is created by ionizing the gas to be pumped with microwave radiation and then by exerting magnetohydrodynamic forces on the plasma to flow through a region of constricted space which impedes the backflow of neutral gas thus causing compression of the gas in the exit region. The magnetohydrodynamic forces arise as the vector product of a plasma current j and a magnetic field B, which are imposed on the plasma by a structure of electrodes and permanent magnets. The geometry of this structure is such that the magnetic force and the plasma current between electrodes are approximately perpendicular to each other and to the axis of the device. The resulting j.times.B force then creates an axial plasma flow and neutral compression.