Investigation of a Magnetically Stabilized Helium Arc

For verifying some theoretical predictions of light scattering from magnetized plasmas, a stable pulsed helium arc discharge in a magnetic field up to 5 teslas has been built. The arc has been investigated at filling pressures of 2 to 5 Torr and plasma currents between 1 and 5 kA. Plasma parameters were measured at a magnetic field of 4 teslas and a pressure of 3 Torr. At these values of the magnetic field and the filling pressure the arc is steady, approximately cylindrically symmetric up to a plasma current of 2.8 kA.Time dependence and radial distribution of the electron density and temperature have been determined from spectroscopic measurements, laser interferometry, and laser scattering. The latter two techniques were used successfully for the first time on a magnetically stabilized arc to measure the electron density and temperature in the hot core of the arc. The axial electron density is 1.2 × 1016cm−3 and is approximately constant over the arc cross section in the high temperature region as predicted by theory. The axial temperature is 145 000 K. Thus the arc design and the plasma properties are suitable for scattering experiments.