A scheme for evaluating T e/T i and Z̄ by light scattering

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Abstract
When highly ionized impurities are present in a plasma, the scattered spectrum of the major ion species can be distorted in a complicated way. A method is given by which Te/Ti and Z̄ (≡Jnjzj2/ne) can be measured which does not require any knowledge of the mass, charge state, or concentration of the impurity species. A generalization of the Salpeter approximation for the integrated cross section is proven. The result is that the total cross section is a function of α (≡ 1/KλD), Te/Ti, and Z̄ as long as the temperature of all ion species is the same and Te/Ti is not too large. Thus a measurement of the integrated ion cross section at two different scattering angles can yield Te/Ti and Z̄. This method is insensitive to magnetic fields and to moderate electron drifts. For 1≲Te/Ti, Z̄≲3 the cross section must be measured to an accuracy of about 3% to give Te/Ti to within 10% and Z̄ within 20%.