The rigorous expression for the classical high-frequency conductivity of a fully ionized plasma was obtained earlier through a joint solution, in the plasma limit, of the first two members of the B-B-G-K-Y hierarchy when both are able to change on the same time scale. [C. Oberman, A. Ron, and J. Dawson, Phys. Fluids 5, 1514 (1962)]. That treatment is now extended to include the presence of a uniform magnetic field. Through the use of a Fourier-Bessel transformation, the equation for the pair correlation function is rendered formally identical to that of the no magnetic field case.

Abstiact-An analysis of the space and energy dependence of neutron fluctuations is presented, and applied to the results of reactor fluctuation experiments. Two experiments, measurements of Power Spectral Density and Variance to Mean, are singled out for special attention. These are of special interest, since previously published experimental results seem to be interpretable by space and energyindependent theories of neutron fluctuations. Both infinite and finite-geometry reactor models are treated, and calculations are presented to illustrate the effects of detector size, shape and location, and delayed neutrons. In any event, agreement with actual experimental results is achieved only when the effect of fast diffusion is included through a two-energy group model. It is seen that when the migration length is sufficiently large by comparison with a typical reactor dimension, the results of the space-energy independent theory appear as a first approximation. Thus it is argued that experiments on larger reactors would yield results not in agreement with the space-energy independent theory. * A.E.C. pre-doctoral fellow. * The role of delayed neutrons in noise analysis experiments has received such extensive attention, that we have referenced only three papers, each representing a different approach. t Of course a given experiment measures only an approximate value for 4(t).

A normal mode treatment is proposed for the solution of boundary value problems in plasma oscillations. The plasma distribution function and electric field are expanded in terms of the solutions of the coupled Vlasov and Maxwell equations. These normal mode solutions are somewhat unusual in that they are singular functions of the velocity variable, and, in fact, the expansion theorem is proved by means of a direct solution of an associated singular integral equation. As an application of the method we obtain the impedance of a plasma-filled parallel plate condenser. 1. INTRODUCTION 1 1 * In problems involving propagation of transverse waves, the full set of Maxwell's equations is required. However, the treatment is identical in its essentials.

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Orthogonality relations for the eigenfunctions of the one-speed transport equation are used to derive the corresponding closure relations. These express in a concise form the completeness properties previously proved by Case.