Optical measurement of plasma densities in a large theta-pinch.

A technique is described to measure the electron density distribution of a high temperature plasma, produced in a theta-pinch, by observing the bremsstrahlung continuum radiation emitted. Streak cameras record simultaneously the visible light emitted at three axial positions. The photographic film is calibrated using ashort duration flash and a step filter, and densitometer scans give the relative intensities. The data gives the raidal intensity distribution, from which the electron density distribution may be calculated. Estimated accuracy of the density measurement is +/-25%.