VQLUMK $4, NUMBER j.2 PHYSICAI. RXVIZW I. ZTYZRS 24 MARCH 1/75 W. P. Halperin, C. N. Archie, F. B. Rasmussen, R. A. Buhrman, and R. C. Richardson, . Phys. Rev. Lett. 32 927 (1974) H. van Dijk and M. Durieux, in Progress in I. os@ Tempemtuwe Physics, edited by C. J. Gorter (North- Holland, Amsterdam, 1957), Vol. 2; T. R. Roberts, R. H. Sherman, S. D. Sydoriak, and F. G. Brickwedde, in Progress in I. -o~ Tempemtl~e Physics, edited by C. J. Gorter (North-Holland, Amsterdam, 1964), Vol. 7R, A, Webb, R. P. Giffard, and J. C. Wheatley, J, Low Temp. Phys. 13, 383 (1973). R. A. Fisher, E. %'. Hornung, G. E. Broda]. e, and W. F. Giauque, J. Chem. Phys. 58, 5584 (1973). W. P. Halperin, C. N. Archie, F. B. Rasmussen, and R. C. Richardson, to be published; W. P. Halperin, thesis, Cornell University (unpublished). ' A similar pressure controller was employed by G. G. Ihas and F. Pobell, Phys. Rev. A 9, 1278 (1974). "S. B. Trickey, W. P. Kirk, and E. D. Adams, Rev. Mod. Phys. 44, 668 (1972). J. C. Wheatley, Physica (Utrecht) 69, 218 (1973). "A. I. Ahonen, M. T. Haikala, M. Krusius, and O. V. Lounasmaa, Phys. Rev. Lett. 33, 628 (1974). ' T. K. Alvesalo, H. K. Collan, M. T. Loponen, O. V. Lounasmaa, and M. C. Veuro, to be published. Further discussion is given by H. K. Collan, Phys. Lett. 50A, 305 (1974). '5E. R. Grilly, J. Low Temp. Phys. 4, 615 (1971). ' J. R. Thompson and H. Meyer, Cryogenics 7, 296 (1967). ' L. Goldstein, J. Low Temp. Phys. 15, 583 (1974). Indications of Strongly Flux-Limited Electron Thermal Conduction in Laser-Target Experiments* R. C. Malone, R. L. McCrory, and R. L. Morse Theoretical LNoision, University of California, Los A/amos Scientific Laboratory, I os A/amos, New Mexico 8T544 (Received 9 December 1974) It is shown by comparison with calculations that anomalies in the results of intense la- ser irradiation of solid targets, including two-humped ion distributions, indicate a reduc- tion of electron thermal conduction to considerably below classical values. This reduc- tion is interpreted as a flux limit and appears to be sufficiently restrictive to modify sig- nificantly the design of laser fusion targets. Most of the recent interest in laser-produced plasmas has focused on conditions under which electron thermal conduction is expected to play a central role in the transport of energy in the plasma. In particular, in laser fusion applica- tions, the ablation-driven compression and ther- mal heating of the target core are strongly in- fluenced by the manner in which the laser energy deposited near the critical density (n, = 10" cm ' for Nd-glass and n, = 10" cm ' for CO, lasers) is transported into the target interior. It is the pur- pose of this Letter to point out that certain anom- alies seen recently in high-power-density laser- plasma experiments indicate that electron ther- mal fluxes near critical density are limited to much less than the classical or mildly flux-limit- ed values that have previously been assumed. This more stringent flux limiting would constitute an energy decoupling mechanism which would sig- nificantly modify design of fusion targets. Previous predictions of experimental results were based on calculations of coupled hydrody- namics and heat flow in which the electron ther- mal flux was given by E), E) (E„ F~=-K, vT, Ei= fn, kT, (kT, /tn, ) I, where K, is the classical conductivity of Lands- hoff and Spitzer' and I", is an upper limit im- posed to approximate the free-streaming, high- flux failure of the perturbation derivation of K,. ' Here m„n„and T, are the electron mass, num- ber density, and temperature, respectively, and f is a dimensionless number which is calculated to be between 0.5 and 1. 0, depending on assump- tions about collisionless processes, but is com- monly taken to be about 0.6. 3' Here we show, by detailed experimental-calculational compari- sons, that f =0.6 is highly inconsistent with ex- perimental results, but that the discrepancies are largely removed and certain new experimen- tally observed effects are given a plausible phys- ical explanation by using the same form, Ecl. (1),