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Strong coupling of quantum emitters with confined electromagnetic modes of nanophotonic structures may be used to change optical, chemical, and transport properties of materials, with significant theoretical effort invested toward a better understanding of this phenomenon. However, a full theoretical description of both matter and light is an extremely challenging task. Typical theoretical approaches simplify the description of the photonic environment by describing it as a single mode or few modes. While this approximation is accurate in some cases, it breaks down strongly in complex environments, such as within plasmonic nanocavities, and the electromagnetic environment must be fully taken into account. This requires the quantum description of a continuum of bosonic modes, a problem that is computationally hard. We here investigate a compromise where the quantum character of light is taken into account at modest computational cost. To do so, we focus on a quantum emitter that interacts with an arbitrary photonic spectral density and employ the cumulant, or cluster, expansion method to the Heisenberg equations of motion up to first, second, and third order. We benchmark the method by comparing it with exact solutions for specific situations and show that it can accurately represent dynamics for many parameter ranges. [ABSTRACT FROM AUTHOR]

We describe and demonstrate a method to deterministically trap single atoms near nanoscale solid-state objects. The trap is formed by the interference of an optical tweezer and its reflection from the nano object, creating a one-dimensional optical lattice where the first lattice site is at z0 ∼ λ/4 from the surface. Using a tapered optical fiber as the nanoscopic object, we characterize the loading into different lattice sites by means of the AC-Stark shift induced by a guided fiber mode. We demonstrate a loading efficiency of 94(6)% into the first lattice site, and measure the cooperativity for the emission of the atom into the guided mode of the nanofiber. We show that by tailoring the dimensions of the nanofiber the distance of the trap to the surface can be adjusted. This method is applicable to a large variety of nanostructures and represents a promising starting point for interfacing single atoms with arbitrary nanoscale solid-state systems.

Existing thermal harrier coatings (TBCs) can be adapted enhancing their functionalities such that they not only protect critical components from hot gases but also can sense their own material temperature or other physical properties. The self-sensing capability is introduced by embedding optically active rare earth ions into the thermal barrier ceramic. When illuminated by light, the material starts to phosphoresce and the phosphorescence can provide in situ information on temperature, phase changes, corrosion, or erosion of the coating subject to the coating design. The integration of an on-line temperature detection system enables the full potential of TBCs to be realized due to improved accuracy in temperature measurement and early warning of degradation. This in turn will increase fuel efficiency and will reduce CO2 emissions. This paper reviews the previous implementation of such a measurement system into a Rolls-Royce jet engine using dysprosium doped yttrium-stabilized-zirconia (YSZ) as a single layer and a dual layer sensor coating material. The temperature measurements were carried out on cooled and uncooled components on a combustion chamber liner and on nozzle guide vanes (NGVs), respectively. The paper investigates the interpretation of those results looking at coating thickness effects and temperature gradients across the TBC. For the study, a specialized cyclic thermal gradient burner test rig was operated and instrumented using equivalent instrumentation to that used for the engine test. This unique rig enables the controlled heating of the coatings at different temperature regimes. A long-wavelength pyrometer was employed detecting the surface temperature of the coating in combination with the phosphorescence detector. A correction was applied to compensate for changes in emissivity using two methods. A thermocouple was used continuously measuring the substrate temperature of the sample. Typical gradients across the coating are less than 1 Klpm. /Is the excitation laser penetrates the coating, it generates phosphorescence from several locations throughout the coating and hence provides an integrated signal. The study successfully proved that the temperature indication from the phosphorescence coating remains between the surface and substrate temperature for all operating conditions. This demonstrates the possibility to measure inside the coating closer to the bond coat. The knowledge of the bond coat temperature is relevant to the growth of the thermally grown oxide (TGO) which is linked to the delamination of the coating and hence determines its life. Further, the data are related to a one-dimensional phosphorescence model determining the penetration depth of the laser and the emission. [ABSTRACT FROM AUTHOR]

Temperature profiling of components in gas turbines is of increasing importance as engineers drive to increase firing temperatures and optimize component's cooling requirements in order to increase efficiency and lower CO2 emissions. However, on-line temperature measurements and, particularly, temperature profiling are difficult, sometimes impossible, to petform due to inaccessibility of the components. A desirable alternative would be to record the exposure temperature in such a way that it can be determined later, off-line. The commercially available thermal paints are toxic in nature and come with a range of technical disadvantages such as subjective readout and limited durability. This paper proposes a novel alternative measurement technique which the authors call thermal history paints and thermal history coatings. These can be particularly useful in the design process, but further could provide benefits in the maintenance area where hotspots which occurred during operation can be detected during maintenance intervals when the engine is at ambient temperature. This novel temperature profiling technique uses optical active ions in a ceramic host material. When these ions are excited by light they start to phosphoresce. The host material undergoes irreversible changes when exposed to elevated temperatures and since these changes are on the atomic level they influence the phosphorescent properties such as the life time decay of the phosphorescence. The changes in phosphorescence can be related to temperature through calibration such that in situ analysis will return the temperature experienced by the coating. A major benefit of this technique is in the automated interpretation of the coatings. An electronic instrument is used to measure the phosphorescence signal eliminating the need for a specialist interpreter, and thus increasing readout speed. This paper reviews results from temperature measurements made with a water-based paint for the temperature range 100-800 °C in controlled conditions. Repeatability of the tests and errors are discussed. Further, some measurements are carried out using an electronic hand-held interrogation device which can scan a component surface and provide a spatial resolution of below 3 mm. The instrument enables mobile measurements outside of laboratory conditions. Further, a robust thermal history coaling is introduced demonstrating the capability of the coating to withstand long term exposures. The coating is based on thermal barrier coating (TBC) architecture with a high temperature bondcoat and deposited using an air plasma spray process to manufacture a reliable long lasting coating. Such a coating could be employed over the life of the component to provide critical temperature information at regular maintenance intervals for example indicating hot spots on engine parts. [ABSTRACT FROM AUTHOR]

We investigate the interplay between quenching and strong coupling in systems that include a collection of quantum emitters interacting with a metal nanoparticle. By using detailed numerical simulations and analytical modeling, we demonstrate that quantum emitters can exhibit strong coupling with the particle dipole resonance at distances at which the quenching to nonradiative channels is expected to dominate the dynamics. These results can be accounted for in terms of the pseudomode character of the higher multipole modes of the nanoparticle and the corresponding reduction of the induced loss rate. These findings expand the current understanding of light-matter interaction in plasmonic systems and could contribute to the development of novel quantum plasmonic platforms. [ABSTRACT FROM AUTHOR]

We present indications of thermalization and cooling of quasi particles, a precursor for quantum condensation, in a plasmonic nanoparticle array. We investigate a periodic array of metallic nanorods covered by a polymer layer doped with an organic dye at room temperature. Surface lattice resonances of the array-hybridized plasmonic-photonic modes-couple strongly to excitons in the dye, and bosonic quasi particles which we call plasmon-exciton polaritons (PEPs) are formed. By increasing the PEP density through optical pumping, we observe thermalization and cooling of the strongly coupled PEP band in the light emission dispersion diagram. For increased pumping, we observe saturation of the strong coupling and emission in a new weakly coupled band, which again shows signatures of thermalization and cooling. [ABSTRACT FROM AUTHOR]

Accurate knowledge of the operating temperature of thermal barrier coatings (TBCs) is not currently available, therefore significant safety margins are employed during operation of gas turbines, which limit the engine efficiency. Recently, phosphorescent sensor TBCs have been used to detect coating temperatures with a reported accuracy under isothermal conditions up to 4 K. However, the thermal gradient through a TBC in modern gas turbines is of the order of 1 K µm-1. The interpretation of the temperature provided by a sensor coating therefore requires a better understanding of the through thickness response of the material. Kubelka-Munk theory has been adapted to describe the light propagation and generation through the thickness of a sensor coating. The model indicates that the temperature measurement can be considered to come from a depth of 17 µm below the surface, depending on the coating type, thermal gradient and coating thickness. As such, the coating can be designed to suit the application, and the temperature variation due to the thermal gradient and coating thickness can be limited to 1%. Where coating design is restricted by its application, the sensor material can be embedded within the coating to avoid measurement errors due to thermal gradients, provided the sensor layer is sufficiently thin. This, however, causes a significant reduction in emission intensity, hence reducing the signal-to-noise ratio, and necessitating a compromise between signal amplitude and measurement accuracy. [ABSTRACT FROM AUTHOR]

Thermal barrier coatings are used to reduce the actual working temperature of the high pressure turbine blade metal surface and; hence permit the engine to operate at higher more efficient temperatures. Sensor coatings are an adaptation of existing thermal barrier coatings to enhance their functionality, such that they not only protect engine components from the high temperature gas, but can also measure the material temperature accurately and determine the health of the coating e.g., ageing, erosion and corrosion. The sensing capability is introduced by embedding optically active materials into the thermal barrier coatings and by illuminating these coatings with excitation light phosphorescence can be observed. The phosphorescence carries temperature and structural information about the coating. Accurate temperature measurements in the engine hot section would eliminate some of the conservative margins which currently need to be imposed to permit safe operation. A 50 K underestimation at high operating temperatures can lead to significant premature failure of the protective coating and loss of integrity. Knowledge of the exact temperature could enable the adaptation of the most efficient coating strategies using the minimum amount of air. The integration of an on-line temperature detection system would enable the full potential of thermal barrier coatings to be realized due to improved accuracy in temperature measurement and early warning of degradation. This, in turn, will increase fuel efficiency and reduce CO2 emissions. Application: This paper describes the implementation of a sensor coating system on a Rolls-Royce jet engine. The system consists of three components: industrially manufactured robust coatings, advanced remote detection optics and improved control and readout software. The majority of coatings were based on yttria stabilized zirconia doped with Dy (dysprosium) and Eu (europium), although other coatings made of yttrium aluminum garnet were manufactured as well. Coatings were produced on a production line using 1 atmospheric plasma spraying. Parallel tests at Didcot power station revealed survivability of specific coatings in excess of 4500 effective operating hours. It is deduced that the capability of these coatings is in the range of normal maintenance schedules of industrial gas turbines of 24,000 h or even longer. An advanced optical system was designed and manufactured permitting easy scanning of coated components and also the detection of phosphorescence on rotating turbine blades (13 k rotations per minute) at stand-off distances of up to 400 mm. Successful temperature measurements were taken from the nozzle guide vanes (hot), the combustion chamber (noisy) and the rotating turbine blades (moving) and compared with thermocouple and pyrometer installations for validation purposes. [ABSTRACT FROM AUTHOR]

We explore excitation and ionization by neutron impact as a novel tool for the investigation of electronelectron correlations in helium. We present single- and double-ionization spectra calculated in accurate numerical ab initio simulations for incoming neutrons with kinetic energies of up to 150 keV. The resulting electron spectra are found to be fundamentally different from photoionization or charged particle impact due to the intrinsic many-body character of the interaction. In particular, doubly excited resonances that are strongly suppressed in electron or photon impact become prominent. The ratio of double to single ionization is found to differ significantly from those of photon and charged-particle impact. [ABSTRACT FROM AUTHOR]

We show that the correlation dynamics in coherently excited doubly excited resonances of helium can be followed in real time by two-photon interferometry. This approach promises to map the evolution of the two-electron wave packet onto experimentally easily accessible noncoincident single-electron spectra. We analyze the interferometric signal in terms of a semianalytical model which is validated by a numerical solution of the time-dependent two-electron Schrödinger equation in its full dimensionality. [ABSTRACT FROM AUTHOR]

This paper describes recent developments of the thermal barrier sensor concept for nondestructive evaluation (NDE) of thermal barrier coatings (TBCs) and online condition monitoring in gas turbines. Increases in turbine inlet temperature in the pursuit of higher efficiency will make it necessary to improve or upgrade current thermal protection systems in gas turbines. As these become critical to safe operation, it will also be necessary to devise techniques for online condition monitoring and NDE. The authors have proposed thermal barrier sensor coatings (TBSCs) as a possible means of achieving NDE for TBCs. TBSCs are made by doping the ceramic material (currently yttria-stabilized zirconia (YSZ)) with a rare-earth activator to provide the coating with luminescence when excited with UV light. This paper describes the physics of the thermoluminescent response of such coatings and shows how this can be used to measure temperature. Calibration data are presented along with the results of comparative thermal cycle testing of TBSCs, produced using a production standard air plasma spray system. The latter show the durability of TBSCs to be similar to that of standard YSZ TBCs and indicate that the addition of the rare-earth dopant is not detrimental to the coating. Also discussed is the manufacture of functionally structured coatings with discreet doped layers. The temperature at the bond coat interface is important with respect to the life of the coating since it influences the growth rate of the thermally grown oxide layer which in turn destabilizes the coating system as it becomes thicker Experimental data are presented, indicating that dual-layered TBSCs can be used to detect luminescence from, and thereby the temperature within, subsurface layers covered by as much as 500 ~m of standard TBC material. A theoretical analysis of the data has allowed some preliminary calculations of the transmission properties of the overcoat to be made, and these suggest that it might be possible to observe phosphorescence and measure temperature through an overcoat layer of up to approximately 1.56 mm thickness. [ABSTRACT FROM AUTHOR]

The W7-X machine is a low-shear stellarator of the Wendelstein line being assembled in Greifswald, Germany. The manufacture of its superconducting magnets is in a well advanced phase. After the acceptance tests in the factory, the magnets are tested in cold conditions in a dedicated facility at CEA Saclay. This paper gives an overview of the status of the manufacture of the W7-X coils, including the production of the superconductor, the windings and casings for the magnets, the final assembly and in-factory test procedures. Several design changes and re-work have been implemented in the course of the manufacture due to more detailed engineering analyses or weaknesses and quality problems found in some components. The status of the cold tests of the coils will also be presented. [ABSTRACT FROM AUTHOR]

This article describes recent developments of the thermal barrier sensor concept for non-destructive evaluation (NDE) of thermal barrier coatings (TBCs) and on-line condition monitoring in gas turbines. Increases in turbine entry temperature in pursuit of higher efficiency will make it necessary improve or upgrade current thermal protection systems in gas turbines. As these become critical to safe operation it will also be necessary to devise techniques for on-line conditions monitoring and NDE. Thermal barrier sensor coatings, which consist of a ceramic doped with rare-earth activator to provide luminescence, may be a possible solution. The thermo-luminescent response of such materials has been shown to be suitable for surface and sub-surface temperature measurement and possibly for material phase determination. Herein we describe a number of steps in the development of the sensor coating technology. For the first time sensor coatings have been successfully produced using a production standard air plasma spray (APS) process. Microscopic analysis of the coatings showed them to be similar to standard TBCs and thermal cycle testing of the coatings to destruction showed them to exhibit durability similar to that of standard TBCs suggesting that the addition of rare earth dopants to produce sensor coatings does not change the material structure or the longevity of coatings. Calibration of the coatings using the lifeteime decay response mode showed them to have a dynamic range for temperature measurement extending to just under 1000°C. However, it should be noted that newer compositions have been shown to respond up to 1300°C. Finally, a study of surface temperatures and film cooling has been conducted in a research combustor using APS sensor coatings and some preliminary results are presented. [ABSTRACT FROM AUTHOR]

The paper describes the application of thermographic phosphors for surface temperature measurements in gas turbine combustors and on surrounding components. Thermographic phosphors enable many of the problems associated with the application of conventional thermometry techniques in a combustion environment to be overcome. They consist of a ceramic host matrix with a lanthanide ion dopant. When illuminated with UV light, they exhibit luminescence which is temperature dependent by virtue of variations in the relative intensities of distinct emission lines or in the time constant of the exponential decay that occurs once excitation has ceased. The authors have calibrated the response of a range of phosphors and demonstrated that a useful dynamic response exists up to at least 1400 °C. Furthermore, to demonstrate the utility of the technique, surface temperatures have been measured over a small region within a model gas turbine combustor. In this region the temperature distribution was measured with an estimated uncertainty of ±10 K, with the absolute temperature values confirmed by thermocouple measurements within the experimental uncertainties of this technique. [ABSTRACT FROM AUTHOR]

In the paper the production and testing of a prototype smart thermal barrier coating (TBC) consisting of yttria-stabilized zirconia (YSZ) doped with dysprosium is described. The coating was produced using the electron beam physical vapour deposition (EBPVD) technique and consisted of a 180 µm thick layer of YSZ doped with 10 per cent dysprosium layed down on an aluminized C263 substrate. The thermoluminescent properties of the coating were investigated with the sample placed in a temperature-controlled furnace and illuminated with UV light from a pulsed laser. Using an intensity ratio technique comparing emission at 455, 482 and 493 nm (the preferred ratio being 455 nm/482 nm), the coating was shown to be suitable for temperature measurement from 534 K to at least 950 K with an uncertainty of better than ±2.6 per cent. The research therefore demonstrates the possibility of producing smart TBCs with both thermal insulating and temperature sensing properties using a production coating technique. Further work is now required to optimize the concentration of the dysprosium dopant for maximum dynamic range and measurement precision and to investigate the thermomechanical properties of the coating. [ABSTRACT FROM AUTHOR]

In this paper a study of the temperature-dependent luminescence properties of europium-doped yttria-stabilized zirconia (YSZ:Eu) powder are presented with a view to evaluating the potential of this material and lanthanide-doped YSZ generally for temperature measurement in the thermal barrier coating systems used in gas turbines. The time constant of the exponential emission decay occurring after ultraviolet excitation with a pulsed neodymium-doped yttrium aluminium garnet (YAG:Nd) laser was shown to be temperature dependent with a dynamic range from 26 to 800 °C. Temperature dependence was observed for two distinct emission lines at 591 and 607 nm and the precision with which temperatures can be measured was estimated to be ±0.05 °C at the elevated temperature. The results demonstrate that YSZ:Eu can be considered as a thermographic phosphor and employed for temperature or heat flux measurements on surfaces in gas turbines or for monitoring purposes during coating production where the temperature is an important controlling parameter. Possible improvements in the measurement system to enhance its performance, the optimization of the YSZ:Eu formulation and the use of other lanthanides dopants are proposed for future work. [ABSTRACT FROM AUTHOR]

Describes a proposed system for neutral beam injection for the International Tokamak Experimental Reactor (ITER). Design of the ITER injector; Basic specification for ITER ion source; Insulator column; Beam optics, beam steering and beam alignment; D[sup -] ion extraction by a three-grid extractor and accelerator.

We propose to use subwavelength confinement of light associated with the near field of plasmonic systems to create nanoscale optical lattices for ultracold atoms. Our approach combines the unique coherence properties of isolated atoms with the subwavelength manipulation and strong light-matter interaction associated with nanoplasmonic systems. It allows one to considerably increase the energy scales in the realization of Hubbard models and to engineer effective long-range interactions in coherent and dissipative many-body dynamics. Realistic imperfections and potential applications are discussed., Physics

Investigates the large-area radio frequency (rf) plasma sources for fusion applications. Use of an extraction area in the positive ion rf source; Relationship between the negative hydrogen-current density and rf power; Similarity of the electron with the plasma grid temperature.

We study coherent wave scattering through waveguides with a step-like surface disorder and find distinct enhancements in the reflection coefficients at well-defined resonance values. Based on detailed numerical and analytical calculations, we can unambiguously identify the origin of these reflection resonances to be higher-order correlations in the surface disorder profile which are typically neglected in similar studies of the same system. A remarkable feature of this new effect is that it relies on the longitudinal correlations in the step profile, although individual step heights are random and thus completely uncorrelated. The corresponding resonances are very pronounced and robust with respect to ensemble averaging, and lead to an enhancement of wave reflection by more than one order of magnitude. [ABSTRACT FROM AUTHOR]