A new concept for solar energy thermal conversion

of Naval Research and the A ir Force Aerospace Research Laboratories and the Air Force Weapons Laboratory, Air Force Systems Command, United States Air Force, under Contract No. F33615-73-C-4107. tA. C. Eckbreth and J. W. Davis, IEEE J. Quantum Electron. QE-8, 139 (19n), and references cited therein. 2A.C. EckbrethandF.S. Owen, Rev. Sci. Instrum. 43,995 (1972); A.C. Eckbreth and P.F. Blaszuk, Paper No. 72-723, AIAA, New York, 1972 (unpublished). gA. E. Hill, Appl. Phys. Lett. 18, 194 (1971). 4W. L. Nighan and W.J. Wiegand, Appl. Phys. Lett. 25, 633 (1974); see also Phys. Rev. A 10, 922 (1974). 5Such reasoning has recently been applied in connection with the design of both cw and pulsed electron-beam-sustained lasers; see Yeo p. Velikhov, S.A. Golubev, Yu. K. Zemtsov, A.F. Pal, I.G. Persiantsev, V.D. Psimennyy, and A.J. Rakhimov, Zh. Eksperim. Teor. Fiz. 65, 543 (1973) [Sov. Phys. -JETP (to be published)]; and in the past in connection with analysis of the stability of magnetohydrodynamic devices, see J.K. Wright, Proc. Phys. Soc. 81, 498 (1963). 60. Biblarz and R.E. Nelson, J. Appl. Phys. 45, 633 (1974). 7H. Schlichting, Boundary Layer Theory (McGraw-Hill, New York, 1960), Chap. 16-19. 8Turbulence intensity T is defined as the ratio of the timeaveraged rms value of the oscillating velocity component to the mean flow velocity (see Ref. 7). 9G. K. Batchelor, Theory of Homogeneous Turbulence (Cambridge U.P., London, 1953); J.O. Hinze, Turbulence (McGraw-Hill, New York, 1959), Chap. 3; H. L. Grant and I. C. T. Nisbet, J. Fluid Mech. 2, 263 (1957), tOJ:l.. McLeary and W.E.K. Gibbs, IEEE J. Quantum Electron. QE-9, 828 (1973).