Vol. 29, No. 11 (1980)
1980-06-05
CONTENT
1980, 29 (11): 1357-1366.
doi: 10.7498/aps.29.1357
Abstract +
In this paper, the effect of stochastic magnetic field (s. m. f.) on the eigen-modes of low frequency drift wave is analysed. We show that the existence of s. m. f. can affect the response of electrons to the wave, so that the electron dispersion function varies. In the vicinity of the rational magnetic surface (where k‖≈0), the variation is particularly significant. The s. m. f. can make the electron dispersion function considerably smoother, and the change in electron dispersion function may greatly affect the stability of the eigen-modes of drift wave. It is shown that if the s. m. f. is strong enough (but still within the region achievable experimentally), the so-called universal modes of drift wave may become absolutly unstable.
1980, 29 (11): 1367-1377.
doi: 10.7498/aps.29.1367
Abstract +
Kink instabilities of a sharp boundary plasma column with elliptical cross-section are studied. A general form of dispersion relation expressed in terms of elliptical eigenfunctions and analytical results for single-mode and double-mode perturbation (to second order in ellipticity ε) are given. For an arbitrary ellipticity, numerical calculations are carried out.Numerical results show that the coupling among modes has a destabilizing effect. qΣ required for stability increases rapidly with e. Accordingly, the number of coupled modes to be taken into account will also increase. When the coupled modes for a given e increases to a certain number, qΣ approaches a limit. With a/b > 2 and in the absence of a conductive shell, we obtain approximately: qΣ-l∝(a/b)2. For a system of finite length, perturbations having wavelength equal to the system length are the most dangerous ones. In the case of small ellipticity, as the system length shortens (i.e. the aspect ratio decreases) the value of qΣ required for those perturbations increases only slightly. A conductive shell close to the plasma has a stabilizing effect to some extent. However, if a/b is large enough, either perturbation with finite wavelength or any conductive shell has hardly any effect on the value of qΣ. In addition, in the presence of a conductive shell, qΣ changes abruptly at certain values of a/b. The stability condition is more stringent in the high-β system than in low-β system.
1980, 29 (11): 1378-1384.
doi: 10.7498/aps.29.1378
Abstract +
In this paper the effects of anomalous dissipative effects on the dissipative-trapped-particle modes are discussed. The results show that the dissipative-trapped-electron mode and the dissipative-trapped-ion mode can be stabilized by the anomalous dissipative effects.
1980, 29 (11): 1385-1394.
doi: 10.7498/aps.29.1385
Abstract +
The Ziman-type theory of the electrical resistivity of liquid metals is extended to disordered crystalline alloys by means of a prescription given by Baym. The formulae for calculating the resistivity of these systems are presented and the temperature dependence of the resistivity in both low and high temperature range is discussed in some detail. By using the Debye model for lattice vibration, we can express the resisti-vity of a disordered system as ρ=ρ0+ρd(T/Θ)2+ρi(T/Θ)5 at temperatures well below Debye temperature,Θ , this behavior is compatible with experiments. On account of the Debye-Waller factor and multi-phonon effects, the resistivity approaches saturation at high temperature instead of the exhibiting a linear T-dependence predicted by onephonon approximation. A comparison between experimental data and a simple expression derived on the basis of the approximation of independent vibration of atom shows that the deviation from linearity of the high temperature resistivity similar to that of Nb can be understood with the present model.
1980, 29 (11): 1395-1404.
doi: 10.7498/aps.29.1395
Abstract +
The Ziman-type resistivity theory developed in reference [1] for disordered crystalline alloys is extended to the systems in which the long range order exists, so that it can be applied to the crystalline pure metals and ordered and disordered substitutional alloys. On the basis of this theory, we have investigated the temperature dependence of the resistivity in these systems within the one-phonon approximation. It is emphasized that the superstructure peaks in the structure factors of alloys would give a significant contribution to their phonon-induced electrical resistivity. On account of its T2 behavior and its being much larger than that due to electron-electron scattering, the electron-phonon resistivity contributed by superstructure peaks would play an important role in the temperature dependence of resistivity in alloys, which behaves as ρ≈ρ0+ρa(T/Θ)2+ρi(T/Θ)5 in a relatively low temperature range. Therefore the anomaly in low temperature resistivity of some A-15 compounds can easily be explained with our model. As an example, the low temperature expression for resistivity of alloys is fitted to the V3Si data of Milewits, the theory is found to be in good agreement with experimental results.
1980, 29 (11): 1405-1415.
doi: 10.7498/aps.29.1405
Abstract +
In this paper, we obtain a general equation for determining the resonant frequencies of all the modes in an open resonator in the form of waveguide with slow-varied cross section, which has any shape of longitudinal profile. The method to solve the field longitudinal distribution function in the resonators is investigated. As examples, we derived formulas for determining the resonant frequencies of all the modes for two kinds of resonators that have drum shape and dual-cone shape intersurfaces.A good agreement between the theoretical analysis and the experimental results has been demonstrated.
1980, 29 (11): 1416-1426.
doi: 10.7498/aps.29.1416
Abstract +
This paper deals with the generalization of the third order aberrations of magnetic deflection to the situation when the electron beam is originally immersed in a magnetic field. The formulae of third order magnetic deflection aberration coefficients in an arbitrary plane have been derived. The formulae are simplified and hence easy for calculation. These aberration coefficients have been applied to analyse the raster patterns produced by the in-line guns.
1980, 29 (11): 1427-1436.
doi: 10.7498/aps.29.1427
Abstract +
Calculations in Gaussian approximation and mean-field approximation are performed with the Landau-deGennes model of first order phase transitions. Some "critical exponents" are obtained. For example, in the Gaussian approximation, α = 0.5 ≠ α＇,γ= 1 ≠ γ＇, ν = 0.5 ≠ν＇, etc. Specific heat is calculated and compared with experimental results of liquid crystal MBBA. The nematic-isotropic phase transition is discussed in relation to tricritical points. In this paper, the similarities and differences of the critical properties between first and second order phase transitions are emphasized and discussed. In our opinion, results from scaling laws of second order transitions cannot be simply applied to the case of first order transitions.
1980, 29 (11): 1437-1444.
doi: 10.7498/aps.29.1437
Abstract +
The pressure effects which induce by sound wave propagation in liquid crystal near N-SA phase transition when T → Tc+ has been considered.We have calculated the ultrasonic attenuation coefficient and the dispersion by use of mode-mode coupling theory. It is found that for high frequency the behaviour of attenuation has anomalous divergence, in low frequency limit it's critical exponent is 2.5.When T→Tc+, the theoretical curves are nearly in agreement with experiment results.
1980, 29 (11): 1445-1451.
doi: 10.7498/aps.29.1445
Abstract +
The pyroelectric response of the bulk-absorbing and free-bearing pyroelectric detectors with edge electrodes is deduced by using the one-dimensional diffusion theory. The pyroelectric response and NEP of the detectors are calculated as functions of detector thickness and working frequency. It is found that the detectors have optimum thickness of response and NEP. If the absorption coefficient of material can be increased beyond 5×104cm-1, the performance of the bulk-absorbing thin film detectors approach that of surface absorbing ones.
1980, 29 (11): 1452-1461.
doi: 10.7498/aps.29.1452
Abstract +
Based on Thomas-Fermi potential, we derived an analytical expression of the total range R=2/a[E1/2-A1(arctg(2E1/2-f)/△1/2+arctg f/△1/2)+B1ln((E1/2-f)2)/(E-fE1/2+d)·d/f2], where A1, B1, a,f, d, and △ are constants related to mass and atomic number of the ion and the target. Combined with the derived hyperbolic relation η=Rp/△(Rp) =F(μ)·[A2(μ)+(B2(μ))/(ε1/2+C)], and linear function ω=Rp/△Rp=A3(μ)ε1/21/2+B3(μ), R,Rp and △Rp can be calculated easily and accurately. Here, Rp and △Bp are project range and standard deviation respectively, C is an empirical constant, and F(μ), A2(μ), B2(μ), A3(μ) and B3(μ) are all algebric functions of μ, the mass ratio of the ion and the target. By Comparing with numerical solutions of Gibbons et al. and experimental results published in literature, we conclude that our expressions can be used to both light or heavy ion implantation into Si, GaAs or SiO2 target. The physical significance of our expression was discussed also.
1980, 29 (11): 1462-1470.
doi: 10.7498/aps.29.1462
Abstract +
A rotating single crystal thermal neutron time of flight spectrometer was constructed in IAB for the study of various dynamic process in condensed matter. The surplus reflections from undesired crystallographic planes in the rotating monochromator (Ge) is eliminated by carefully choosing a proper orientation of the rotating axis in the (Ⅲ) plane. The range of incident initial neutron energy is from 10 meV to 100 meV; The corresponding energy resolution is 2.5 to 7.2% with intensities adequate for inelastic scattering studies. Based on the work of Brockhouse et al., we have calculated a theoretical value of the resolution for neutrons scattered from the sample and compared it with measured results. Inelastic neutron scattering spectra from vanadium sample is presented and comparison with other spectrometers of similar type is given.
BRIEF REPORT
1980, 29 (11): 1471-1478.
doi: 10.7498/aps.29.1471
Abstract +
This paper describes the behaviour and experimental results of low temperatureplasma in mirror-bar combined magnetic well. The plasma is produced by collisionionization of the electron beam, which is injected alone the magnetic axis, with neutral hydrogen molecules.
1980, 29 (11): 1479-1482.
doi: 10.7498/aps.29.1479
Abstract +
We discussed here the importance of the gravitational anomaly observation and suggested that the use of torque pendulum for the lunar esclipe observation would be a possible effective method to survey the gravitational anomaly.We used a torque pendulum which has a great improvement in precision to observe the lunar esclipe on 6 Sept. 1979 in Peking and had observed an obvious anomaly. The result was similar to that of Saxl's observation.We also suggested a method to improve the observation.
1980, 29 (11): 1483-1489.
doi: 10.7498/aps.29.1483
Abstract +
In this areticle, general formulae for the direction of the extraordinary ray are obtained in the case of light incident on uniaxial crystal, the corresponding data are plotted in three-view diagrams for Iceland spar, these make the trajectory of the extraordinary ray clear as the crystal rotates. The obtained results offer a possibility of developing new methods for determination of optical constants of crystals.
1980, 29 (11): 1490-1496.
doi: 10.7498/aps.29.1490
Abstract +
The X-ray powder diffraction patterns of mixed bismuth oxide ferroelectrics with layer type structure PbBi4Ti4O15 and SrBi4Ti4O15 were obtained with a counter diffractometer and a Guinier focusing camera using Cu Ka radiation. The detail indexed powder diffraction data of 88 and 76 diffraction lines of which d value are larger than 1.13? were given. The crystals belong to the orthorhombic system with a space group of Bb21m(C2v12). The lattice parameters and density calculated from X-ray measurements are:PbBi4Ti4O15: a = 5.431?, a = 5.459?,c = 41.36?;Z = 4;DX = 7.986g/cm3. SrBi4Ti4O15;a = 5.428?, 6 = 5.438?, c = 40.94?;Z = 4; Dx = 7.447g/cm3.
1980, 29 (11): 1497-1502.
doi: 10.7498/aps.29.1497
Abstract +
The pseudo-binary system Li4GeO4-Zn2GeO4 has been studied by means of DTA and X-ray diffraction techniques. According to the phase diagram established, Li14Zn(GeO4)4 ("LISICON") is a solid solution based on the high temperature phase of Li4GeO4 which is stabilized to room temperature by the addition of Zn2GeO4. Long period "aging" at room temperature of the ceramic specimens of "Lisicon" reduced its conductivity remarkably, for which the authors propose an additional explanation.
A NEW PHASE MAGNESIUM IODATE Mg(IO3)2 2H2O AND SOLUBILITY-TEMPERATURE DIAGRAM OF Mg(IO3)2-H2O SYSTEM
1980, 29 (11): 1503-1506.
doi: 10.7498/aps.29.1503
Abstract +
Magnesium iodate dihydrate Mg(IO3)2·2H2O was discovered in the Mg(IO3)2·H2O system as a new phase. The solubilities of Mg(IO3)2, Mg(IO3)2·2H2O and Mg(IO3)2·4H2O varying with temperature were determined by weighing method.
1980, 29 (11): 1507-1512.
doi: 10.7498/aps.29.1507
Abstract +
Under the pressure of 77 kb, double layer structure always appears in the polycrystal diamond grown with wireform catalyst. The distribution of catalyst metal nickel in specimen has been in vestigated.The appearence of partial precipitate peak of catalyst metal has been explained by means of the forced diffusion equation of phase transformation growth. The cause of the presence of metal partial precipitated zone, the relationship between the double layer structure and the P-T growth region have also been discussed.
1980, 29 (11): 1513-1516.
doi: 10.7498/aps.29.1513
Abstract +
We have started the study of low temperature acoustics recently.Here present the characteristics of the first, second and fourth sound propagating in superfluid Hell and the experimental equipment used to measure their propagating velocity employing acoustic resonator. The primary results we have got are in essential agreement with those obtained by Prof. I. Eudnick et al.
