Electron Temperature of Helium Plasmas Produced by Theta Pinch

The electron temperatures of the plasmas produced by the theta pinch with dB/dt=8×10 8 gauss/sec were measured spectroscopically by two different methods, one using the intensity ratio of HeI (4921A) to HeII (4686A), and the other using those of singlet lines (4921A, 4387A) to triplet line (4713A). The pairs of spectral line intensities were measured simultaneously by two photomultipliers. The temperatures obtained are 6ev in the former case and 40ev in the latter. The electron density determined from Stark broadening of 4686A is 3.5×10 15 cm 3 . The large discrepany between these electron temperatures is due to the radial inhomogeneity of plasmas and due to some decaying mechanism of charged particles more rapid than the two-body recombination. Thus, the method using ionic lines gives erroneously lower temperatures and the temperatures obtained from neutral pairs are more reliable.