[en] The optimum theory pioneered by Howard is applied to a turbulent reversed-field pinch (RFP). Energy and helicity balance equations for a steady, driven RFP are derived from magnetohydrodynamic (MHD) equations. First, an upper bound is given for the fluctuational power absorption, χ, which is the ratio of the power dissipated by fluctuations to the mean Ohmic power. The functional χ is expressed in terms of the mean magnetic field B₀ by using the energy balance constraint. Maxima of χ are then obtained from a variational principle which includes the helicity and toroidal flux constraints. In a second calculation lower bounds are given for the total energy dissipation. A variational principle is used in which energy and helicity balance, conservation of toroidal magnetic flux and the ensemble-averaged Ohm's law are imposed as constraints. The effect of the space-variation of the resistivity is also included. In all calculations of bounds, the natural boundary conditions derived from the variational principles themselves are used. It is shown that the theoretical results are consistent with observations from the Los Alamos ZT-40M experiment

[en] A scanning x-ray microscope is described including: an x-ray source capable of emitting a beam of x-rays; a collimator positioned to receive the beam of x-rays and to collimate this beam, a focusing cone means to focus the beam of x-rays, directed by the collimator, onto a focal plane, a specimen mount for supporting a specimen in the focal plane to receive the focused beam of x-rays, and x-ray beam scanning means to relatively move the specimen and the focusing cone means and collimator to scan the focused x-ray beam across the specimen. A detector is disposed adjacent the specimen to detect flourescent photons emitted by the specimen upon exposure to the focused beam of x-rays to provide an electrical output representative of this detection. Means are included for displaying and/or recording the information provided by the output from the detector, as are means for providing information to the recording and/or display means representative of the scan rate and position of the focused x-ray beam relative to the specimen whereby the recording and/or display means can correlate the information received to record and/or display quantitive and distributive information as to the quantity and distribution of elements detected in the specimen. Preferably there is provided an x-ray beam modulation means upstream, relative to the direction of emission of the xray beam, of the focusing cone means

No abstract available

[en] The phase space distribution and time structure of an electron beam have fundamental influences on synchrotron radiation properties. These influences are due to the superposition of radiation from all electrons, each following a different trajectory. When the radiation wavelength is longer than the electron bunch length, coherent superposition occurs and results in the observed coherent synchrotron radiation. Usually the wavelength we use is much shorter, so incoherent superposition occurs and the emittance effect is the dominant multi-electron effect. The Monte Carlo simulation is a straightforward and generally valid approach to compute the multi-electron effects on synchrotron radiation. In this paper, we show how the Monte Carlo method can model these multi-electron effects systematically and discuss the statistical principles governing such simulation and their implication on the computing power requirement. We also describe the implementation of an efficient algorithm to calculate a single electron radiation spectrum, which is important to make the Monte Carlo simulation practical. Some calculated results are shown to demonstrate the methods. Comments on the usefulness and limitation of the Monte Carlo method are presented

[en] Realization of the power of pulsed laser deposition (PLD) as a technique for providing desirable properties of high temperature superconductor, ferroelectric and colossal magnetoresistance thin films, gave great impetus to the field of micro-electronic device application. Integration of functional oxides into device structures will require development of understanding and technology for the integration of oxide and non-oxide materials, including epitaxial growth of oxide-metal heterostructures. A series of studies of the deposition of oxide (MgO) onto metal (Mo, Nb) on sapphire substrates was carried out to provide insight into processes concerned, in particular to see the effect of oxidation of the metal layer on the achievement of epitaxy of the MgO. These heterostructures were produced using a linked UHV deposition system. The sputtering and PLD vacuum chambers are connected by a gate valve and isolated from one another during film deposition. Such isolation avoids contamination of the sputtering process which enables very high-quality, epitaxial metal films to be produced. The oxide layer is grown on top of these metal layers, using PLD with additional pulsed oxygen jet to provide oxidation of ablation products while minimizing oxidation of the metal layer. The diffusivity of O₂ in a Nb thin film at temperatures appropriate for MgO diffusion, is sufficiently high for oxygen to penetrate through to the Nb film during MgO deposition, which caused the degradation in electric properties of the Nb film and the reduction in crystalline quality of the MgO layer. The reduction of transition temperature to the superconducting state, Tc, and the similarly systematic increase in the Nb lattice parameter were observed consistent with oxygen content data reported in the literature, as the Nb became heavily oxidized. Examination of the surface of clean and oxidized Nb by atomic force microscopy, and deposition of MgO in UHV onto a previously oxidized Nb surface, suggested that the decrease in crystalline quality of the MgO can be attributed to loss of integrity of the MgO/Nb interface as oxygen exposure during MgO growth is increased. In a separate experiment, a series of MgO layers was deposited onto Nb in an argon ambient, with no oxygen pulses. It was found that in an argon ambient of 800 Pa mm, oxidation of the Nb could be limited to such an extent that the residual resistance ratio was as high as 60 after MgO deposition. Attribution to thermalization of the ablated species, the condensation oi dissociated oxygen and the formation of molecules from atomic species in the ablation plume has been discussed. In a related but different subjects of series experiments on the correlation of infrared (IR) emissivity and sputter conditions for aluminum films at wavelength of 3.8 μm were made. This research was undertaken to establish enabling background knowledge to support the deposition of low IR emissivity Al films for the Gemini project. Al films with lowest IR emissivity are those made from the purest targets despite their having comparable roughnesses to films from lower purity targets. The lowest emissivity achieved was in the range of 1.64% to 1.72% measured at 3.8 μm for 1.5 to 1.8 μm thick films. Modifications to standard idealized Drude theory have been made which, in a phenomenological way, take account of imperfections in the sputtered Al film, oxidation state and roughness. (author)

[en] A method and apparatus for detecting, in a specimen, atoms, of an element having an atomic number of at least 20, comprising irradiating the specimen with monochromatic x-rays having a wavelength capable of inducing an inner shell ionization of the atoms with subsequent auger cascade and recording the emission of the auger electrons emitted by the cascade

[en] A process is described for manufacturing radiation shield structures of the type consisting of neutron absorbing boron carbide particles embedded in a copper matrix. The material comprises a multiplicity of particles comprising a core of boron carbide, a film of electroless copper bonded to the carbide, and a relatively thick electrodeposited copper layer bonded to the film. The particles are then consolidated to produce shield structures by hot rolling or hot pressing, with or without sintering

[en] The kinetic theory is developed to investigate a conditioner for a helically imported electron beam. Linear expressions for axial velocity spread are derived. Numerical simulation is used to check the theoretical results and examine nonlinear aspects of the conditioning process. The results show that in the linear regime the action of the beam conditioner on a pulsed beam mainly depends on the phase at which the beam enters the conditioner and depends only slightly on the operating wavelength. In the nonlinear regime, however, the action of the conditioner strongly depends on the operating wavelength and only slightly upon the entrance phase. For a properly chosen operating wavelength, a little less than the electron's relativistic cyclotron wavelength, the conditioner can decrease the axial velocity spread of a pulsed beam down to less than one-third of its initial value

[en] United-atom 2pσ-2pπ rotational coupling in asymmetric collisions is influenced by an avoided crossing between the 2pσ and 2sβ orbitals. This influence is studied using the HeH⁺ system as a prototype. In Σ₂-Σ₃-π₁ three-state calculations, the time-dependent Schroedinger equation in solved numerically. Substantial population of the 2sσ state is found, which disagrees with the estimates based on the Landau-Zener model. The Σ₃ level is populated directly by transitions near the avoided crossing at b = 0.4 au. The ratios of P/sub Σ₂/(b)/[P/sub Σ₃/(b) + P/sub π₁/(b)] are calculated and compared with Dr. R. Hippler's experimental data. A six-state calculation, in the basis of Σ₁, Σ₂, Σ₃, Σ₄, π₁ and π₂ molecular states, is also made. Cross sections and alignment and orientation parameters were computed from the transition amplitudes for various energies

[en] Optimization of nonlinear driving terms have become a useful tool for designing storage rings, especially modern light sources where the strong nonlinearity is dominated by the large chromatic effects of quadrupoles and strong sextupoles for chromaticity control. The Lie algebraic method is well known for computing such driving terms. However, it appears that there was a lack of explicit formulas in the public domain for such computation, resulting in uncertainty and/or inconsistency in widely used codes. This note presents explicit formulas for driving terms due to sextupoles and chromatic effects of quadrupoles, which can be considered as thin elements. The computation is accurate to the 4th-order Hamiltonian and 2nd-order in terms of magnet parameters. The results given here are the same as the APS internal note AOP-TN-2009-020. This internal nte has been revised and published here as a Light Source Note in order to get this information into the public domain, since both ELEGANT and OPA are using these formulas.