Influence of linear elastic stresses on dynamic magnetostriction of cold-rolled transformer steel

The anisotropy of dynamic magnetostriction is investigated without external stresses, in extension, and in compression. Results are obtained expressing the (B) dependence for constant elastic stresses and also — () for certain induction values. Oscillograph traces are taken of the (H) and B(H) hysteresis loops with the specimens under investigation in extension and compression.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 110–115, May, 1977.     

A high flux,liquid-helium cooled source of metastable rare gas atoms

We have developed a novel, high flux source of metastable rare gas atoms (helium, neon and argon) that uses liquid helium cooling to reduce the initial atomic velocity. Fluxes exceeding 10¹⁴ atoms/ster/s with He and Ne were obtained. With average velocities of 600 m/s for He and 300 m/s for Ne and Ar, this source will enable simpler, more compact beam lines for loading magneto-optical traps. PACS 34.80.Dp; 39.10.+j; 39.25.+k     

A model of Piron's preparation-question structures in Ludwig's selection structures

We give a model of the basic Jauch-Piron (JP) approach to quantum physics, i.e., of preparation-question structure (with four basic axioms and without axioms C, P, A), in terms of Ludwig's selection structure; in the latter structure the primitive notion of individual sample of a physical entity is formally described (without making reference to any probability concept). Once we interpret Piron's concept of question in Ludwig's context of a selection structure, we find that there is no difficulty in formalizing notions such as performable together questions; moreover, results such as = or ()= can be formally proved. We develop the theory along the lines of the JP approach; the set of JP propositions is derived and it turns out to be a complete lattice, as happens in Piron's theory, but with a different physical interpretation of the lattice operations. Finally, we study some connections between the standard Ludwig foundation and our approach.     

Damage created by high-current-density implants of phosphorus into 〈100〉 and 〈111〉 silicon wafers

The damage left by high-current-density, 9 A/cm², implants of 120 keV phosphorus into 100 and 111 silicon oriented substrates was investigated as a function of the fluence in the range 4×10¹⁵–1.5×10¹⁶/cm². The samples were analyzed by 2 MeV He⁺ channeling and transmission electron microscopy. Initially a buried amorphous layer forms at low fluences until the wafer temperature saturates at 450 °C at a fluence of 4.5×10¹⁵/cm². As the fluence is further increased ion-assisted regrowth of this initial buried amorphous layer takes place and is 2 to 2.5 times faster (with respect to ion fluence) for 100 substrates than for 111 substrates. At higher fluences, most of the residual damage is located at a depth equal to the sum of the projected range and of the straggling. In the regrown layers twins are found in both orientations, and in some cases a hexagonal silicon phase is present at high fluences. The results are compared with the ion assisted regrowth of amorphous layers at well defined temperatures in the 250°–400 °C range.     

Luminescence of AgCl excited by u.v. laser light

The spectral distribution and decay of the blue-green luminescence of AgCl has been measured at very low temperatures, using u.v. laser excitation. A structure was observed in the emission band at 77°K. The decay consists of three processes: a) a very fast process which follows the laser pulse (10^–8 sec), b) a fast exponential process which is also observed with low intensity u.v. excitation,(10^–4–10^–5 sec) and, finally, c) a slow exponential process (seconds).     

The critical point indices of ferroelectric and ferromagnetic phase transitions

Magnetic transitions are described by the critical indices0,1/3,4/3 while some ferroelectric transitions appear to give0,R~1/2,1. It is pointed out that these two sets of values for the critical indices are allowed by the scaling laws and stability conditions near the phase transitions.The authors thank Prof. R. S. Krishnan for his encouragement and Mr. B. Viswanathan for some discussions. The financial assistance from DAE and CSIR is also acknowledged.     

Experimental survey of the sticking problem in muon catalyzed dt fusion

The sticking process dt + n, which constitutes the most severe limit to the number of fusions which a muon can catalyze, is reviewed. Many attempts were made to determine by calculations and measurements the probability for initial sticking _s ⁰ (immediately after dt fusion) and for final sticking _s (after the came to rest). Previous results based on neutron disappearance rates and on the observation of -X-rays were controversial and also in some disagreement with theory. New data are reported from PSI on direct observation of final sticking, using a setup with the St. Petersburg ionization chamber. These data mark a significant improvement in reliability and may clarify questions concerning previous discrepancies. The new results is _s(0.56±0.04)%, lower than the theory prediction _s=(0.65±0.03)%, at medium density.     

Infrared Texture Simulation Using Gaussian-Markov Random Fields

Infrared battlefield simulation is a most important subject today to test infrared weapons. The reality and details of simulated scenes are always relied on the infrared textures. A texture is considered to be a stochastic, possibly periodic, two-dimensional image field. A texture model can be described as a mathematical procedure. Markov random field(MRF) model is a famous model to synthesize the visible textures of various kinds. In this paper, the Gaussian-Markov random fields(GMRF) are firstly used to sample the distribution of temperature field on the surface of terrain. And the Planck's radiation law is applied to calculate the emittance in the bands of 35 m or 814 m. The emittance distribution of the terrain can be normalized and colored by the range of 0 to the gray levels decreased by 1. Then an infrared texture is generated by GMRF by given a set of certain parameters.     

Superstability estimates for anharmonic systems

We consider an anharmonic crystal described by variablesS _x ,x ^d ,S _x , with one-body interaction ¦S _x ¦ and nearest neighbor (n.n.) two body interaction ¦S _x –S _y ¦. We prove that, for ^d bounded, , where is the correlation function for the free boundary condition Gibbs state in ,>0 and are suitable constants independent of and . This generalizes previous results obtained in the case.Research partially supported by Consiglio Nazionale delle Ricerche.     

Decay of the Bethe–Salpeter Kernel and Bound States for Lattice Classical Ferromagnetic Spin Systems at High Temperature

We consider lattice classical ferromagnetic spin systems at high temperature (1) with nearest neighbor interactions and even single-spin distributions (ssd). Associated with each system is an imaginary time lattice quantum field theory. It is known that there is a particle of mass m–ln in the energy-momentum spectrum. If s ⁴–3s ²²<0, where s ^k is the kth moment of the ssd, and is sufficiently small, we show that in the two-particle subspace there is no mass spectrum up to 2m. For >0 we show that the only mass spectrum in (m, 2m) is a bound state of mass m _b=2m+ln(1–)+O(), where =(+2s ²²)^–1. A bound on the decay of the kernel of a Bethe–Salpeter equation is obtained and used to prove these results.     

Zum Problem der Exoelektronenemission

Zusammenfassung Es werden die zwei einfachsten Fälle der Exoelektronenemission untersucht und auf Grund dessen geeignete Verfahren zur Verarbeitung der Versuchsergebnisse vorgeschlagen.

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Influence of relative humidity on surface conductivity of germanium

A study was made of the influence of the relative humidity (from 0.5–90%) on the surface conductivity of bothp- andn-type germanium having differing resistivity. It was. found that the range of changes in the surface potential did not depend on the volume properties of germanium. An analysis of the experimental results shows that the surface potential has values approximately in the range from _s =–3kT/q to _s =+5kT/q for a change in humidity from 0.5 to 90%. Assuming that the Fermi level changes on the outer side of the oxide layer by approximately the same value as on the germaniumgermanium oxide boundary as a result of the increase and decrease of slow states, it follows that the levels of the slow centres are considerably distant from the Fermi level during the whole humidity range. It is also shown that on the first monomolecular layer of adsorbed water there is an increment of (7.5±0.8) x 10¹⁰ donor levels per cm². This increase in levels either decreases with the number of adsorbed monomolecular layers of water and for 90% humidity has approximately the value 2×10¹⁰ cm^–2 or remains almost unchanged with the number of layers, if it is assumed that for _s =6.0kT/q the Fermi level passes through the centres of adsorbed water.

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0,5 90% p n. . , _s =– 3kT/q _s =+ 5kT/q 0,5 90%. , - , , . , (7,5 ±0,8). 10¹⁰ cm². 90% . 2. 10¹⁰ cm^–2 , , , _s =6,0kT/q .

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In conclusion the author thanks Dr. J. Taue for instigating this work and S. Koc, C. Sc., for remarks and the interest with which he followed the work. He also thanks A.Müller for measuring the Hall constant in the samples.     

Self interstitial trapping at Hf impurities in Niobium

After electron irradiation at 15 K of Niobium doped with¹⁸¹Hf the trapping of defects at the Hf impurities was observed by means of the perturbed angular correlation method. The results are interpreted as the formation of Hf-Nb mixed dumbbells which are formed at 5 K and are stable up to 80 K.     

Attenuation of powerful ruby laser pulses in the atmosphere by resonant absorption of water vapor

The attenuation of a ruby laser pulse at the wavelength = 6943.8å is calculated under conditions of spectroscopic saturation for a parallel beam and a diverging beam with divergence angle = 10^–5 rad. It is shown that deviation from the Bouguer law may reach 45% at a path length = 2 km for an initial power level of I₀ = 0.5I_s for the parallel beam, and 20% for I₀ = 0.25I_s for the divergent beam (I_s, saturation power).Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 7–12, February, 1978.     

Discretization of the thermal excitation in highly excited matter

In this paper the thermal energy diffusion for quantum particles is described. The quantum heat transport equation is obtained. It is shown that, for a short-time thermal excitation (of the order of the relaxation time), the excited matter response is quantized on the different levels (atomic, nuclear, quark) with quantum thermal energy equalE ^atomic 9 eV,E ^nuclear 7 MeV, andE ^quark 139 MeV.     

Inelastic action of a gradient radio-frequency neutron spin flipper

The energy shift due to the inelastic interaction of the neutron with the time dependent magnetic fields of a gradient radio-frequency spin flipper was studied. A nondispersive perfect crystal spectrometer was used to measure extremly small energy changes of E0.2 eV. The gradient of the magnetic field causes a broadband action of the spin flipper which facilitates its use for new active neutron optical components.     

Development of a very low energy μ+ beam at PSI

At PSI we are investigating the technique of decelerating an existing very intense secondary beam of surface ⁺ (4 MeV) to an energy of 10 eV using appropriate moderators. These ⁺ can then be used as a source of a tertiary beam of low energy muons with tunable kinetic energy between 10 eV and 10 keV.With a 1000 A layer of solid Argon deposited on an Al substrate we obtain a moderation efficiency (with respect to the number of incoming surface ⁺) of the order of 10^–4.Results of our investigations and the present status of the project are presented together with future plans and possibilities.     

The vibration and rotation of piezoelectric particles in high frequency electric fields observed by a thermoacoustic method

We have observed, by a thermoacoustic method, the acoustic resonance vibration of small (diameter 115 m) piezoelectric particles in high frequency (15 MHz) electric fields. The frequency dependence of the thermoacoustic signal gives direct information about the size distribution of the particles.In very strong rf electric fields we also observed a rotation of the vibrating particles by large angles — as originally suggested by Melcher and Shiren [3] — orienting the initially random rf dipoles parallel to the rf electric fields.The observed strong forces acting on vibrating piezoelectric particles in rf fields can probably be used as a new method of selectively extracting particles of a given size from a broad distribution of very small particles.     

μ+SR study of Ising spin-glass Fe0.5Mn0.5TiO3

A typical Ising spin-glass Fe_0.5Mn_0.5TiO₃ has been investigated by ⁺ spin relaxation measurements. It is found that the local magnetic fields at the ⁺ stopping sites appear at a temperature twice as high asT _SG. The directional distribution of the local magnetic fields is nearly isotropic, indicating the existence of the transverse spin components. It is clearly demonstrated that the spins fluctuate belowT _SG and even at 4 K. Taking into account the results obtained by other methods, the main part of the fluctuations is inferred to be due to the transverse spin components and the fluctuation limes at 4 K are driven into a range between 10^–5 and 10^–7 s.