On the Crystallization of Terbium Aluminium Garnet

Attempts to grow terbium aluminium garnet (Tb3Al5O12, TAG) by the Czochralski method lead to crystals of millimeter scale. Larger crystals could not be obtained. DTA measurements within the binary system showed that TAG melts incongruently at 1840 deg. C. The perovskite (TbAlO3, TAP) with a congruent melting point of 1930 deg. C is the most stable phase in this system. The region for primary crystallization of TAP covers the chemical composition of TAG and suppresses the primary crystallization of the terbium aluminium garnet.Comment: 6 pages, 2 figure

Investigation of a 2-Colour Undulator FEL Using Puffin

Initial studies of a 2-colour FEL amplifier using one monoenergetic electron beam are presented. The interaction is modelled using the unaveraged, broadband FEL code Puffin. A series of undulator modules are tuned to generate two resonant frequencies along the FEL interaction and a self-consistent 2-colour FEL interaction at widely spaced non-harmonic wavelengths at 1nm and 2.4nm is demonstrated.Comment: Submitted to The 35th International Free-Electron Laser Conference, Manhattan, New York (2013

Smith-Purcell Radiation from Rough Surfaces

Radiation of a charged particle moving parallel to a inhomogeneous surface is considered. Within a single formalism periodic and random gratings are examined. For the periodically inhomogeneous surface we derive new expressions for the dispersion relation and the spectral-angular intensity. In particular, for a given observation direction two wavelengths are emitted instead of one wavelength of the standard Smith-Purcell effect. For a rough surface we show that the main contribution to the radiation intensity is given by surface polaritons induced on the interface between two media. These polaritons are multiply scattered on the roughness of surface and convert into real photons. The spectral-angular intensity is calculated and its dependence on different parameters is revealed.Comment: 6 pages, 2 figures, submitted to Phys. Rev. ST Accel. Beam

Mechanism Design and Non-Cooperative Renegotiation

We characterize decision rules which are implementable in mechanism design settings when, after the play of a mechanism, the uninformed party can propose a new mechanism to the informed party. The necessary and sufficient conditions are, essentially, that the rule be implementable with commitment, that for each type the decision is at least as high as if there were no mechanism, and that the slope of the decision function is not too high. The direct mechanism which implements such a rule with commitment will also implement it in any equilibrium without commitment, so the standard mechanism is robust to renegotiation

Contract design and non-cooperative renegotiation

We study a contract design setting in which the contracting parties cannot commit not to renegotiate previous contract agreements. In particular, we characterize the outcome functions that are implementable for an uninformed principal and an informed agent if, having observed the agent's contract choice, the principal can offer a new menu of contracts in its place. An outcome function can be implemented in this setting if and only if it is optimal for the principal for some belief over agent types which is more pessimistic, in the sense of the likelihood ratio order, than the prior. Furthermore, the outcome function cannot be too sensitive to variations in the agent's type. We show that the direct revelation mechanism which implements such a function when renegotiation can be prevented will also implement it in any equilibrium when it cannot, so the standard contract is robust to renegotiation

Investigation of implantation-induced damage in indium phosphide for layer transfer applications

100 keV H+ and He+ ion implantation was performed in 300 µm thick (100) InP substrates at liquid nitrogen temperature with a constant fluence of 1 × 1017 cm–2. The surface morphology of the as-implanted InP samples was studied by optical microscopy. The implantation-induced damage was investigated by cross-sectional TEM, which revealed the formation of damage band in both cases near to the projected range of implanted ions. The formation of hydrogen-induced nanocracks and helium filled nanobubbles was observed in as-implanted InP samples. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2792

Growth of Oxide Compounds under Dynamic Atmosphere Composition

Commercially available gases contain residual impurities leading to a background oxygen partial pressure of typically several 10^{-6} bar, independent of temperature. This oxygen partial pressure is inappropriate for the growth of some single crystals where the desired oxidation state possesses a narrow stability field. Equilibrium thermodynamic calculations allow the determination of dynamic atmosphere compositions yielding such self adjusting and temperature dependent oxygen partial pressures, that crystals like ZnO, Ga2O3, or Fe{1-x}O can be grown from the melt.Comment: 4 pages, 3 figures, talk on CGCT-4 Sendai, May 21-24, 200

Transportable setup for amplifier phase fidelity measurements

One possible laser source for the Laser Interferometer Space Antenna (LISA) consists of an Ytterbium-doped fiber amplifier originally developed for inter-satellite communication, seeded by the laser used for the technology demonstrator mission LISA Pathfinder. LISA needs to transmit clock information between its three spacecraft to correct for phase noise between the clocks on the individual spacecraft. For this purpose phase modulation sidebands at GHz frequencies will be imprinted on the laser beams between spacecraft. Differential phase noise between the carrier and a sideband introduced within the optical chain must be very low. We report on a transportable setup to measure the phase fidelity of optical amplifiers.DFG/EXC/QUESTDLR/50OQ1301DLR/50OQ060

Transport through open quantum dots: making semiclassics quantitative

We investigate electron transport through clean open quantum dots (quantum billiards). We present a semiclassical theory that allows to accurately reproduce quantum transport calculations. Quantitative agreement is reached for individual energy and magnetic field dependent elements of the scattering matrix. Two key ingredients are essential: (i) inclusion of pseudo-paths which have the topology of linked classical paths resulting from diffraction in addition to classical paths and (ii) a high-level approximation to diffractive scattering. Within this framework of the pseudo-path semiclassical approximation (PSCA), typical shortcomings of semiclassical theories such as violation of the anti-correlation between reflection and transmission and the overestimation of conductance fluctuations are overcome. Beyond its predictive capabilities the PSCA provides deeper insights into the quantum-to-classical crossover.Comment: 20 pages, 19 figure