Measurement of the Plasma Beta in the Enormous Toroidal Plasma Device (ETPD)

Utilizing the Enormous Toroidal Plasma Device (ETPD), a large toroidal chamber (30 m in circumference) with a Lanthanum Hexaboride (LaB6) cathode, a pulsed plasma was created the plasma beta (β = nek(Te+Ti)B2/(2µ0) ) was measured for various plasma parameters. Langmuir probe measurements give electron temperatures ranging from 5 to 30 eV as well as the ion saturation current as a function of distance into the plasma. Using a microwave interferometer to scale the Langmuir measurements, average electron densities were measured between 2×1011 cm−3 to 3×1012 cm−3. Line widths of both the Helium neutral 4471 A ̊ line and the Helium ion 4685 Å line were measured using a monochromator, giving an ion temperature of approximately 13 eV. Using fast photography, the plasma was found to have a more bifurcated structure than expected; an observation that is also confirmed via fast photography of strictly the 468 nm Helium II line. The ranges of values found for electron temperature, ion temperature, and density give a range of 0.014 ≤ β ≤ 1.01. PACS numbers