Photoionization mass spectrometry for the investigation of combustion generated nascent nanoparticles and their relation to laser induced incandescence

Premixed laminar flat ethylene flames were investigated for nascent nanoparticles through photoionization mass spectrometry (PIMS). Using an atmospheric McKenna burner and ethylene air flames coupled to an atmospheric sampling system, within a relatively narrow C/O range two modes of these particles were found, which can be clearly distinguished with regard to their temperature dependence, their reactivity, and their ionization behaviour. Behind a diesel engine the same particles were observed.     

Entanglement frustration for Gaussian states on symmetric graphs

We investigate the entanglement properties of multimode Gaussian states, which have some symmetry with respect to the ordering of the modes. We show how the symmetry constrains the entanglement between two modes of the system. In particular, we determine the maximal entanglement of formation that can be achieved in symmetric graphs like chains, 2D and 3D lattices, mean field models and the platonic solids. The maximal entanglement is always attained for the ground state of a particular quadratic Hamiltonian. The latter thus yields the maximal entanglement among all quadratic Hamiltonians having the considered symmetry.     

Inclusive photon and π0 production inK + p interactions at 70 GeV/c

Inclusive and semi-inclusive cross sections and distributions of γ's and π⁰'s inK ⁺ p interactions at 70 GeV/c are presented. The results are compared to other experiments and to the Lund model for low-p _T hadron collisions.     

Static characteristics of Josephson interferometers

This investigation deals with the range in operating currents for which a Josephson interferometer, sometimes also referred to as Superconducting QUantum Interference Device (SQUID), may remain in the zero-voltage Josephson condition. An interferometer consists of one or more inductive loops each of which contains two Josephson junctions or other weak links. Two types of current are considered. Gate currentI _gpasses the junctions in parallel. Control currentI _cgenerates magnetic flux via inductive coupling in the loops. Zero-voltage operation is possible within certain areas of theI _g,I _cplane. These areas are manifestations of flux-quantum states and their boundary lines are referred to as static characteristics. In view of the nonlinearity of the constituting equations, not all their formal solutions are physically realizable. A stability analysis yields criteria which permit the identification of realizable operating conditions. The static characteristics comprise operating conditions where the limit of stability is reached. To obtain the static characteristics, linearized equations may be utilized if theLI _o product, a measure for the size of an interferometer, is large compared to the flux quantumΦ ₀, whereL is the inductance per loop, andI _o the maximum Josephson current per junction. As a general method of solving system of transcendental equations, continuation is discussed. The utilization of continuation for obtaining interferometer characteristics is explained. It is shown that some changes in the gate-current feed arrangement are equivalent to shearing the characteristics in theI _g,I _cplane. Analytical results are given on extrema, inflexion points, and singularities in the shape of cusps which conceptually relate to the existence and connectivity of flux-quantum states. Experimental static characteristics are presented on two-and four-junction interferometers. They are in agreement with characteristics computed on the basis of simple lumped circuit models. Relevant circuit parameters are obtained from the experimental characteristics.     

Microscopical studies at cadmium impurities in compound semiconductors

Molecule-like defect complexes have been studied at Cd acceptors in the III–V semiconductors GaAs, GaP, InP, InAs, and InSb by PAC spectroscopy. After hydrogen plasma treatment, the formation of Cd-H complexes was observed in all these compounds. Additionally, the formation and stability of Cd-S and Cd-Se pairs in GaAs have been analyzed.     

Direct soft photon production inK + p andπ + p interactions at 250 GeV/c

Inclusive production of direct soft photons is studied inK ⁺ p andK ⁺ π interactions at 250 GeV/c. Total cross sections, Feynman-x and transverse momentum distributions of direct γ's are presented. The measured cross sections are several times larger than expected from QED inner bremsstrahlung, indicating the presence of an anomalous soft photon source. The model of Lichard and Van Hove, based on the “cold quark-gluon plasma” picture, agrees with the data.     

Measurement of lattice damage caused by ion-implantation doping of semiconductors†

Two new techniques have been used to measure the lattice damage produced in gallium arsenide by the implantation of 60 keV cadmium ions. In one of these methods, optical reflection spectra of the ion-implanted samples were measured in the wavelength range from 2000 to 4600Å. The decrease in reflectivity resulting from ion- implantation was used to determine the relative amount of lattice damage as a function of ion dose. The second technique employed the scanning electron microscope. Patterns very similar in appearance to Kikuchi electron diffraction patterns are obtained when the secondary and/or backscattered electron intensity is displayed in the scanning electron microscope as a function of the angle of incidence of the electron beam on a single crystal surface. The degradation of these ‘Coates-Kikuchi’ patterns resulting from ion implantation was used to obtain a quantitative measure of the lattice damage caused by the implantation process. The results of measurements made by both of the methods described have been compared with each other, and with data obtained by the more established method of measuring lattice damage by Rutherford scattering of 1 MeV helium ions.     

Mechanisms of edge-localized-mode mitigation by external-magnetic-field perturbations

Particle and energy transport in the tokamak edge transport barrier is analyzed in the presence of magnetic field perturbations from external resonant coils. In recent experiments such coils have been verified as an effective tool for mitigation of the edge-localized modes of type I. The observed reduction of the density in plasmas of low collisionality is explained by the generation of charged particle flows along perturbed field lines. The increase of the electron and ion temperatures in the barrier is interpreted by the reduction of perpendicular neoclassical transport with decreasing density and nonlocality of parallel heat transport. The found modification of the pressure gradient implies the stabilization of ballooning-peeling MHD modes responsible for type I ELMs.     

Gastrennung mit Hilfe des Zirkulations-Diffusions-Verfahrens Teil I : Hochanreicherung von Gasen in Trennrohren mit natürlicher Zirkulation

Auf der Grundlage des Zirkulations-Diffusions-Prinzips wurden zwei Trennrohre für die Hochanreicherung von Gasen enytwickelt. Als Modellgasmischungen dienten H₂-N₂ Kr-CH₄ und Luft. Neben Wasserdampf wurden Methanol- und Äthaanoldämpfe als Treibmittel benutzt. Gute Trennungen wurden in einem nur 20 cm langen Rohr erzielt, dessen Trennspalt horizontal durch Lamellen in kleine Sektionen und durch ein Drahtdiaphragma vertikal in zwei Ringkammern geteilt wird. Drei Rohre dieses Typs wurden in einer rechteckigen Kaskadenanordnung getestet. Die Theorie des Transportes im Trennrohr sowie die Behandlung des hydrodynamischen Problems werden angegeben. Eine Anwendung des beschriebenen Trennrohres zur Isotopentrennung und zur Gashochanreicherung erscheint aussichtsreich.