Implementation of Rogowski coil and Taylor discharge for ionospheric plasma chamber experiments in the Versatile Toroidal Facility (VTF)

Summary form only given. The VTF is a large torus used to to simulate ionospheric plasmas. Hydrogen plasmas are formed in the chamber at a base pressure of the order of 10/sup -7/ torr. Currently plasmas can be generated by electron emission from four LaB/sub 6/ cathodes, spaced around the bottom of the chamber, by electron cyclotron resonance heating (ECRH) with microwaves injected radially into the chamber from a 3 kilowatt magnetron, and by a Taylor discharge apparatus. Electron beams travel in a helical path till they reach a collector plate at the top of the chamber, and produce plasma currents from 500 to 1500 amps. Eighteen large toroidal field coils, spaced equally around the chamber, produce a toroidal magnetic field of 0.8 Tesla. A 0.01 Tesla uniform vertical field is added to the toroidal field to yield a helical magnetic field that guides the electron beams along their path. Recently, a Rogowski coil has been calibrated to quantitatively measure current in the plasma. A 4.2 meter coil of approximately 5500 turns encircles the torus vertically. As a changing current goes through the coil, a changing magnetic field is produced perpendicular to each of the coil´s turns. Each turn produces a small voltage, and the sum of all the voltages from all the turns in the coil is proportional to the change in plasma current. The voltage signal is integrated and the result is the plasma current circulating toroidally inside the chamber. Good results measuring electron beam plasma current have been obtained and are reported.