Showing papers in "Physical Review Letters in 1962"
3,567 citations
TL;DR: In this paper, the authors show that the mechanism of flux creep is thermally activated motion of bundles of flux lines, aided by the Lorentz force, over free energy barriers coming from the pinning effect of inhomogeneities, strains, dislocations, or other physical defects.
Abstract: Previous investigations of the critical state of the hard superconductor have defined it in terms of constants alpha and B/sub O/; alpha (T) = J/sub cr/ (B/sub cr/ + B/sub 0/). If the current density J or the field B is increased beyond the critical values, a process called flux creep'' sets in, and flux leaks through the material and returns it to the critical state. alpha (T) is a structure-sensitive constant of the material. A theory is presented to show that this behavior of alpha can be explained by assuming that the mechanism of flux creep is thermally activated motion of bundles of flux lines, aided by the Lorentz force, over free energy barriers coming from the pinning effect of inhomogeneities, strains, dislocations, or other physical defects. The theory also explains B/sub 0/, and predicts time relaxation behavior similar to those of magnetic aftereffect and some forms of plastic creep. (H.D.R.)
1,403 citations
TL;DR: In this paper, an examination of some recent reports dealing with the extremely high critical fields in certain hard superconductors was presented, and it was concluded that the critical fields for these BETA -wolfran compounds are so high that they may be effectively limited at low temperatures by the normal-state paramagnetism.
Abstract: An examination is presented of some recent reports dealing with the extremely high critical fields in certain hard superconductors. Observations of nuclear magnetic resonance in V/sub 3/Si and V/sub 3/Ga are shown to set a severe upper limit on the attainable critical field because of a reduction in the spin susceptibility of these materials in the superconducting state. Equations are derived for the maximum critical field using this limiting criterion. A table of maximum and estimated critical fields is presented for V/sub 2.95/ Ga, Nb/sub 3/ Sn, V/sub 3/Si, and V/sub 1.95/ Ga. It is concluded that the critical fields for these BETA -wolfran compounds are so high that they may be effectively limited at low temperatures by the normal-state paramagnetism. If this is the case, critical fields higher than about 300 kilogauss will not be realized unless materials can be discovered with high transition temperatures. (H.D.R.)
1,321 citations
1,089 citations
TL;DR: In this paper, the authors investigated persistent currents induced in hard superconductors (HSC) by measuring the resulting magnetic effects and found that the Lorentz force plays a crucial role in determining the critical current density and the critical persistent currents in decay with a measurable rate.
Abstract: Persistent currents induced in hard superconductors (HSC) were investigated by measuring the resulting magnetic effects. The tubular HSC examined were Nb powder, Nb/sub 3/Sn, and 3Nb- Zr samples of uniform wall thickness and length large compared to the diameter. Experimental evidence is presented that in HSC the Lorentz force plays a crucial role in determining the critical current density and the critical persistent currents in decay with a measurable rate. (H.D.R.)
973 citations
928 citations
TL;DR: In this article, data from an Aerobee rocket carrying three large-area geiger counters have revealed a considerable flux of radiation in the night sky and the bulk of the radiation is soft x rays from sources outside the solar system.
Abstract: Data from an Aerobee rocket carrying three large-area geiger counters have revealed a considerable flux of radiation in the night sky. Analysis of these data indicates the bulk of the radiation is soft x rays from sources outside the solar system. Synchrotron radiation by cosmic electrons is a possible mechanism for the production of these x rays. Ordinary stellar sources could also contribute a considerable fraction of the observed radiation. (H.D.R.)
715 citations
TL;DR: In this paper, it was shown that the neutrinos produce mu mesons but not electrons, and are likely to be different from the Neutrinos involved in beta decay.
Abstract: From the reaction pi /sup plus or minus / yields mu /sup plus or minus / + ( nu / nu /sup -/), it is dem onstrated that the neutrinos produce mu mesons but not electrons and are likely to be different from the neutrinos involved in beta decay. Approximate cross sections are determined. (L.N.N.)
691 citations
TL;DR: Deaver and Fairbank as mentioned in this paper showed that the free energy of the superconducting state is periodic in this unit of the flux if the electrons are paired in the manner described by the Bardeen-Cooper-Schrieffer (BCS) theory.
Abstract: Deaver and Fairbank1 and Doll and Nabauer2 have shown experimentally that the flax which is trapped in a superconducting cylinder is an integral multiple of the unit hc/2e. It has been pointed out3’4 that this result follows because the free energy of the superconducting state is periodic in this unit of the flux if the electrons are paired in the manner described by the Bardeen-Cooper-Schrieffer (BCS) theory.5 The free energy of the normal state, on the other hand, is virtually independent of the flux. Consequently, the transition temperature T c , which is the temperature at which the free energy of the normal and superconducting states are equal, must also be a periodic function of the enclosed flux Φ. The magnitude of the change in T c was calculated for a thin cylindrical sample using the BCS model in which the possible pairing of particles with net momentum was included.
442 citations
372 citations
TL;DR: In this paper, the partial width for the observed decay mode ω→π+π followed by p→2π was estimated by assuming that ω is a nearly stable particle and defined a coupling parameter f_(ωpπ).
Abstract: The partial width for the observed decay mode ω→π^++π^-+π^0 can be estimated by assuming, in the sense of dispersion theory, that the process is dominated by ω→p+π followed by p→2π. We treat p as a nearly stable particle and define a
coupling parameter f_(ωpπ).
TL;DR: In this article, Rosenbluth et al. showed that the cancellation of a stabilizing effect resulted from using only the scalar pressure in the ion equation of motion, and derived several additional factors using modifications to both the ion pressure tensor and Ohm's law.
Abstract: Calculations using two-fluid magnetohydrodynamic equations (B. Lehnert, Phys. Rev. Letters 7: 442(1961)) appear to show cancellation of a stabilizing effect (M. N. Rosenbluth, et. al., Conference on Plasma Physics and Controlled Nuclear Fusion Research, Salzburg (1961)). It is shown that the cancellation resulted from using only the scalar pressure in the ion equation of motion. Derivations of additional factors using modifications to both the ion pressure tensor and Ohm's law are presented. (L.N.N.)
TL;DR: In this paper, the pair distribution function for a classical fluid in thermal equilibrium is found to be more closely approximated by the Percus and Yevick (Phys. Rev., 110: 1(1958)) approximation than by the Bogoliubov-Born-Green- Kirkwood-Yvon (B.G.K.H.) approximation or the hypernetted chain approximation.
Abstract: The pair distribution function for a classical fluid in thermal equilibrium is found to be more closely approximated by the Percus and Yevick (Phys. Rev., 110: 1(1958)) approximation than by the Bogoliubov-Born-Green- Kirkwood-Yvon (B.B.G.K.Y.) approximation or the hypernettedchain approximation. It is noted that the reason for this finding lies in the fact that the Percus and Yevick approximation chooses a quite advantageous function for making a Taylor expansion of the appropriate equation for a grand canonical ensemble. (T.F.H.)
TL;DR: In this article, a discussion is presented to point out that in certain rare earth ferromagnetic metals H/sub eff/ opposes H and allows conduction electron polarization to be canceled so that if these metals also possess a predominantly attractive electron-electron interaction, the possibility arises that superconductivity will occur in the compensation region.
Abstract: In a rare earth ferromagnetic metal the effective exchange field (H/sub eff/) impressed on the conduction electrons is in general so large as to inhibit the occurrence of superconductivity in zero external field H. A discussion is presented to point out that in certain ferromagnetic metals H/sub eff/ opposes H and allows conduction electron polarization to be canceled so that, if these metals also possess a predominantly attractive electron-electron interaction, the possibility arises that superconductivity will occur in the compensation region. Since the cancellation will presumably occur for H approximates ,-H/sub eff/, critical fields may be obtained that exceed the limit derived for ordinary superconductors by an order of magnitude. (H.D.R.)
TL;DR: In this paper, the authors discussed the possibility that strong interactions saturate the unitarity condition, i.e., that they have the maximum possible strength consistent with unitarity and analyticity of the S matrix.
Abstract: In previous publications, the authors have discussed the possibility that strong interactions “saturate” the unitarity condition; i.e., that they have the maximum possible strength consistent with the unitarity and analyticity of the S matrix.(1) Our earlier discussion was confined to elastic scattering, however, and although the conjectured existence of Regge poles underlay our arguments, we did not at the time of the earlier work appreciate certain essential properties of these poles.
TL;DR: In this article, general symmetry argumeats giving selection rules and showing that anisotropies are expectcd in a majority of cases are presented, and discussion is confined to electron scattering by diatomic molecules.
Abstract: General symmetry argumeats giving selection rules and showing that anisotropies are expectcd in a majority of cases are presented. Discussion is confined to electron scattering by diatomic molecules. (L.N.N.)
TL;DR: In this article, the electron-ion three-body recombination process and its physical principles are discussed and a general method for calculating the electron temperature and the net rate of three body recombination is discussed.
Abstract: Physical principles domlnating the electron-ion threebody recombination process and forming the basis of a general method for calculating the electron temperature and the net rate of three-body recombination are discussed. Calculations and data are presented in graphical and tabular forms. (L.N.N.)