Two-Photon Ionization and Three-Photon Above-Threshold Ionization of Argon

Studies of nonlinear laser-matter interaction have been so far limited to wavelengths from the near ultraviolet to infrared, because of the low brightness of currently available sources outside this range. However nonlinear processes in the VUV/Soft X-ray domain would initiate multiphoton innershell spectroscopy, XUV nonlinear optics and applications of such processes to metrology. The probability of multiphoton transitions decreases rapidly with the number of photons involved. A typical two-photon bound-free transition has a rate of the order of .1 ps{sup {minus}1} at 10{sup 12} W.cm{sup {minus}2} and scales as the square of the intensity. Such an intensity is therefore required to saturate a two-photon transition with a 100 fs pulse. This is difficult to achieve with the present state-of-the-art techniques for producing intense XUV pulses. To the authors knowledge, only two cases of such transitions have been reported so far. The first one is a two-photon ionization of argon by the third harmonic of a KrF laser. Since the photon energy (15 eV) is just below the ionization energy (15.75 eV) for argon, the transition is quasi-resonant. The second case is a two-photon ionization of helium by the 9th harmonic of a Ti:S laser. In the latter case an autocorrelation measurement of the harmonic pulse has been reported. In the present work, the authors report on two-photon ionization of argon at 133 nm (9.3 eV) from the third harmonic of a frequency doubled Ti:S laser, and a three-photon above-threshold ionization involving two 9.3 eV photons and one 3.1 eV photon

Large-scale solar district heating plants in Danish smart thermal grid: developments and recent trends

Large solar collector fields are very popular in district heating system in Denmark, even though the solar radiation source is not favorable at high latitudes compared to many other regions. Business models for large solar heating plants in Denmark has attracted much attention worldwide. Denmark is not only the biggest country in both total installed capacities and numbers of large solar district heating plants, but also is the first and only country with commercial market-driven solar district heating plants. By the end of 2017, more than 1.3 million m2 solar district heating plants are in operation in Denmark. Furthermore, more than 70% of the large solar district heating plants worldwide are constructed in Denmark. Based on the case of Denmark, this study reviews the development of large solar district heating plants in Denmark since 2006. Success factors for Danish experiences was summarized and discussed. Novel design concepts of large solar district heating plants are also addressed to clarify the future development trend. Potential integration of large solar district heating plants with other renewable energy technologies are discussed. This paper can provide references to potential countries that want to exploit the market for solar district heating plants. Policy-makers can evaluate the advantages and disadvantages of solar district heating systems in the national energy planning level based on the know-how and experiences from Denmark

Time-Frequency Characterization of Femtosecond Extreme Ultraviolet Pulses

A measurement of chirp and pulse duration of fifth harmonic of a frequency-doubled Ti:sapphire laser was presented. The photoelectron signal due to cross correlation of harmonics generated by 400 nm blue light and an 800 nm infrared probe pulse, was measured using energy resolved cross-correlation method. Results demonstrated that the technique could be used to characterize the time-frequency behavior of much higher-order harmonics

Production de l’eau chaude solaire et stockage latent par matériaux à changement de phase (MCPs) pour les applications de rafraîchissement solaire au Maroc

Cette thèse présente les résultats de recherche, de modélisation et de simulation d'un système de rafraîchissement solaire au Maroc dans le cadre du projet PRSM (Procédés de Rafraîchissement Solaire au Maroc) financé par l'IRESEN (Institut de Recherche en Energie Solaire et Energies Nouvelles). L'objectif est d'étudier les facteurs concernant l'optimisation d'une machine à absorption solaire (LiBr-H2O) sous les conditions marocaines. De plus, un certain nombre de critères de conception, qui peuvent être utilisés par les concepteurs de systèmes de climatisation et de chauffage solaires, ont été établis en tenant compte de considérations énergétiques et économiques. En conséquence, cette thèse couvre quatre aspects. Le premier aspect présente un aperçu de recherche bibliographique sur les technologies solaires, en mettant l'accent sur les systèmes du froid solaire, les processus pertinents existants, l'état du marché, les développements récents des technologies les plus prometteuses et les principaux indicateurs de performance qui figurent dans la littérature. De plus, l'aspect expérimental de l'installation de climatisation solaire adopté dans le projet PRSM a été décrit pour identifier les caractéristiques techniques importantes de l'installation et les difficultés rencontrées lors de la réalisation du prototype. La deuxième dimension concerne la faisabilité technique d'un système de climatisation solaire en se basant sur des indicateurs énergétiques et économiques et prenant en compte les effets combinés des climats, des catégories de bâtiments et des besoins en climatisation dans les conditions marocaines. Le troisième aspect présente le stockage latent de l'énergie thermique utilisant les matériaux à changement de phase (MCPs). Il porte sur l'étude des méthodes numériques utilisées dans la modélisation des phénomènes de changement de phase et se concentre également sur l'ajout des MCPs dans le système de climatisation solaire intégré à l'intérieur du ballon solaire connecté au générateur de la machine à absorption pour évaluer l'amélioration possible du rendement du système. Le quatrième volet de cette thèse présente l'analyse technico-économique et de sensibilité appliquée au développement d'un procédé solaire combiné d'eau chaude sanitaire, chauffage et climatisation au Maroc. L'analyse globale via une généralisation des résultats au niveau national a été réalisée en complément d'une analyse de sensibilité liée à l'investissement dans ces systèmes afin d'évaluer le potentiel de remplacement des technologies traditionnelles par les systèmes solaires et les gains éventuels liés à leur implantation au Maroc.This thesis reports the results of research into the modeling and simulation of a solar air-conditioning system for Morocco in the framework of the project SCPM (Solar Cooling Process in Morocco) funded by IRESEN (Research Institute for Solar Energy and New Energies). The aim is to investigate the factors concerning the optimization of a LiBr-H2O solar absorption chiller under Moroccan conditions. Further, a number of design criteria, which can be used by designers of solar cooling and heating systems, have been established using energy and economic considerations. Accordingly, this thesis covers four aspects. The first overviews the literature survey on solar technologies with a focus on solar cooling systems which reports the relevant processes, summarizes the market status, presents the recent developments of the most promising technologies and describes the main performance indicators figuring in the literature. Moreover, the experimental aspect of the solar air-conditioning installation adopted in the SCPM project was described to identify the important technical characteristics of the installation and the difficulties encountered during the realization of the prototype. The second dimension concerns the technical feasibility of solar air-conditioning system using energy and economic indicators taking into account the combined effects of climates, building categories and cooling demands under Moroccan conditions. The third aspect presents the latent thermal energy storage using Phase Change Materials (PCMs). It concerns the investigation of numerical methods used in the modeling of phase change phenomena and also focuses on PCMs addition in the solar cooling process integrated inside solar storage tank connected to the generator of the absorption chiller to evaluate the possible enhancement in the system efficiency. The fourth aspect of this thesis outlines the technico-economic and sensitivity analysis applied to the development of a combined processes of solar DHW, heating and air-conditioning in Morocco. The overall analysis via a generalization of the results to the national level was carried out in addition to a sensitivity analysis related to the investment in these systems in order to assess the potential of replacing traditional technologies with the solar systems and the possible earnings related to their implementation in Morocco