COHERENCE AND DOUBLE-PASS AMPLIFICATION IN GE SOFT-X-RAY LASER

From measurements of spatial coherence and beam divergence of Ge soft x-ray laser at a far field, the x-ray laser beam has been characterized as a partially coherent Gaussian beam. Double-pass amplification will improve spatial and temporal coherence, spectral brightness and efficiency. Close to 100% geometrical coupling efficiency has been obtained in double pass amplification in Ge. Transient loss of feedback is attributed to mirror structure damage within the build-up time of the x-ray laser. Prospect for generation of coherent x-ray laser beam is discussed.

NE-LIKE GE SLAB TARGET STUDIES CARRIED OUT AT RAL

The effect of non-uniform target illumination on the soft X-ray lasing output intensity of the J=2-1 Ne-like Ge transitions as a function of length was investigated. As the degree of nonunifonnity increased with length the Ne-like Ge 23.2 and 23.6 nm J=2-1 transitions did not show exponentiation of output intensity. Using an experimentally measured gain-intensity scaling relationship these results were modelled and good qualitative agreement obtained. The model indicates that for Ge targets which are non-uniformly illuminated, even with peak to valley ratios of up to 3 efficient operation can be achieved at between 2-3x threshold intensity. Further studies of the effect of increasing the separation between the two targets of a double target geometry are also presented.

AN INJECTOR AMPLIFIER DOUBLE TARGET CONFIGURATION FOR THE NE-LIKE GE X-RAY LASER SCHEME

The XUV lasing output from one germanium slab target has been efficiently coupled into, and further amplified in, a second plasma produced by irradiation of a similar target from the opposite direction. The operation of such a double target was shown to be strongly dependent on the distance by which the two target surfaces were displaced. The line brightness peaked for a surface displacement of approximately 200-mu-m and it was observed that the pointing direction of one output beam could be controlled by the surface separation in an asymmetric geometry. Gain length products of approximately 16 with estimated output powers close to the megawatt level were achieved on both the 23.2 and 23.6 nm J=2-1 transitions for an optimised target configuration. Maximum effective coupling efficiencies of the individual outputs from double targets, comprising 2.2 and 1.4 cm length components, approached 100% for beams propagating from the shorter to the longer target.

GAIN SCALING RELATIONSHIPS FOR NE-LIKE GE SLAB TARGETS

The gain coefficient of the strongest 3p --> 3s, J = 2 --> 1 lasing transition at 23.6 nm in the Ne-like Ge collisional excitation scheme has been measured, using the fundamental wavelength from a Nd:glass laser (1.06-mu-m), for a range of incident intensities on massive stripe targets up to 2.2 cm in length. From a threshold incident laser intensity of approximately 6 x 10(12) W/cm2, the gain coefficient rises to approximately 4.5 cm-1 for an irradiation intensity of approximately 2.5 x 10(13) W/cm2, tending towards still higher gain coefficients at higher incident intensities. For targets of maximum length, a gain-length product gL almost-equal-to 10 was reached with a resultant output power at 23.6 nm estimated to be at the approximately kW level. The beam divergence decreased with length to a minimum of approximately 7 mrad but no significant trend in beam pointing with plasma length was observed. From the trend in the gain coefficient, it appears that for a fixed energy laser irradiating a approximately 100-mu-m wide slab targets, an incident intensity of I(i) approximately 1.2 x 10(13) W/cm2 represents an optimum working level, assuming that plasma length is not limited by refractive effects. In addition to the usual valence electron excited 3p --> 3s transitions, the gain coefficient for the core excited 1s(2)2s2p(6)3d --> 1s(2)2s2p(6)3p transition at 19.9 nm has been measured to be approximately 1.5 cm-1 for an incident irradiance of approximately 2.5 x 10(13) W/cm2.

Heterogeneous oxidation of pyrimidine and alkyl thioethers in ionic liquids over mesoporous Ti or Ti/Ge catalysts

Heterogeneous catalytic oxidation of a series of thioethers (2-thiomethylpyrimidine, 2-thiomethyl-4,6-dimethyl-pyrimidine, 2-thiobenzylpyrimidine, 2-thiobenzyl-4,6-dimethylpyrimidine, thioanisole, and n-heptyl methyl sulfide) was performed in ionic liquids by using MCM-41 and UVM-type mesoporous catalysts containing Ti, or Ti and Ge. A range of triflate, tetrafluoroborate, trifluoroacetate, lactate and bis(trifluoromethanesulfonyl)imide-based ionic liquids were used. The oxidations were carried out by using anhydrous hydrogen peroxide or the urea-hydrogen peroxide adduct and showed that ionic liquids are very effective solvents, achieving greater reactivity and selectivity than reactions performed in dioxane. The effects of halide and acid impurities on the reactions were also investigated. Recycling experiments on catalysts were carried out in order to evaluate Ti leaching and its effect on activity and selectivity.

Energy levels, radiative rates and electron impact excitation rates for transitions in Be-like Cl XIV, K XVI and Ge XXIX

Results for energy levels, radiative rates and electron impact excitation (effective) collision strengths for transitions in Be-like Cl XIV, K XVI and Ge XXIX are reported. For the calculations of energy levels and radiative rates the general-purpose relativistic atomic structure package is adopted, while for determining the collision strengths and subsequently the excitation rates, the Dirac atomic R-matrix code is used. Oscillator strengths, radiative rates and line strengths are listed for all E1, E2, M1 and M2 transitions among the lowest 98 levels of the n ≤ 4 configurations. Furthermore, lifetimes are provided for all levels and comparisons made with available theoretical and experimental results. Resonances in the collision strengths are resolved in a fine energy mesh and averaged over a Maxwellian velocity distribution to obtain the effective collision strengths. Results obtained are listed over a wide temperature range up to 10^7.8 K, depending on the ion.

Energy levels, radiative rates and electron impact excitation rates for transitions in He-like Ga XXX, Ge XXXI, As XXXII, Se XXXIII and Br XXXIV

We report calculations of energy levels, radiative rates and electron impact excitation cross sections and rates for transitions in He-like Ga XXX, Ge XXXI, As XXXII, Se XXXIII and Br XXXIV. The grasp (general-purpose relativistic atomic structure package) is adopted for calculating energy levels and radiative rates. For determining the collision strengths, and subsequently the excitation rates, the Dirac atomic R-matrix code (darc) is used. Oscillator strengths, radiative rates and line strengths are reported for all E1, E2, M1 and M2 transitions among the lowest 49 levels of each ion. Additionally, theoretical lifetimes are provided for all 49 levels of the above five ions. Collision strengths are averaged over a Maxwellian velocity distribution and the effective collision strengths obtained listed over a wide temperature range up to 10⁸ K. Comparisons are made with similar data obtained using the flexible atomic code (fac) to highlight the importance of resonances, included in calculations with darc, in the determination of effective collision strengths. Discrepancies between the collision strengths from darc and fac, particularly for some forbidden transitions, are also discussed. Finally, discrepancies between the present results for effective collision strengths with the darc code and earlier semi-relativistic R-matrix data are noted over a wide range of electron temperatures for many transitions in all ions. © 2013 The Royal Swedish Academy of Sciences.

High temperature thermal stability of the HfO2/Ge (100) interface as a function of surface preparation studied by synchrotron radiation core level photo emission

High resolution soft x-ray photoemission spectroscopy (SXPS) have been used to study the high temperature thermal stability of ultra-thin atomic layer deposited (ALD) HfO2 layers (∼1 nm) on sulphur passivated and hydrofluoric acid (HF) treated germanium surfaces. The interfacial oxides which are detected for both surface preparations following HfO2 deposition can be effectively removed by annealing upto 700 °C without any evidence of chemical interaction at the HfO2/Ge interface. The estimated valence and conduction band offsets for the HfO2/Ge abrupt interface indicated that effective barriers exist to inhibit carrier injection.

L'agencement des relations père-enfant et mère-enfant : liens avec le développement social d'enfants d'âge préscolaire de familles nucléaires

Ce mémoire s'intéresse à l'agencement des relations qu'un enfant maintient avec ses deux parents et à leurs effets sur le développement social de l'enfant. Plus spécifiquement, ce mémoire explore les relations d'attachement et d'activation. Si le premier terme ferait traditionnellement référence à la relation spécifique entre une mère et son enfant, l'activation concernerait plutôt, selon certains auteurs, la relation entre un père et son enfant. Les psychoéducatrices et psychoéducateurs sont très souvent appelés à soutenir les personnes sur le plan de leur développement social. L'une des fondations cruciales du développement de la socialité serait la première relation créée et maintenue entre un enfant et son premier donneur de soins : la relation d'attachement. En effet, la relation d'attachement, selon la définition classique, référerait davantage à la relation spécifique que les enfants maintiendraient généralement avec leur mère. La façon dont l'enfant entrera ultérieurement en contact avec les personnes de son environnement pourrait être calquée sur cette première relation. Si, au départ, on s'intéressait davantage à l'attachement mère-enfant, plusieurs études ont tenté d'intégrer le père au modèle classique de l'attachement. Il semble que les pères s'intégreraient plus difficilement à ce modèle classique. Certains l'expliquent en faisant valoir que les prémisses théoriques de l'attachement se seraient plutôt concentrées sur la dimension simplement sécuritaire qui serait plus adaptée pour les mères. Les pères auraient un mode d'entrée en relation avec leurs enfants qui serait beaucoup plus dynamique, caractérisé par des jeux physiques chaleureux, mais où les limites seraient clairement définies par l'autorité du parent. Ce type de relation s'appelle la relation d'activation. La relation d'activation favoriserait chez l'enfant la persévérance et l'autorégulation face à l'exploration sécuritaire de son environnement, et par le fait même, constituerait le pendant exploratoire de la relation d'attachement. Des études ont déjà montré les liens de la relation d'activation avec le développement social de l'enfant. Si le cadre théorique de l'activation a été pensé en fonction du père, il reste encore à savoir si la mère peut aussi prendre sa place dans cette relation dynamisante. Alors qu'au Québec, l'organisation des rôles familiaux est en constante évolution, il convient de bien comprendre d'abord les agencements relationnels de la famille nucléaire afin d'éventuellement outiller les parents de familles d'autres types. Pour explorer les mécanismes relationnels, une recension des écrits systématique a été réalisée. L'un des constats les plus intéressants de cette recension est l'absence d'études ayant étudié l'activation et le développement social auprès des enfants de plus de 36 mois. De plus, les deux types de relations (attachement et activation) n'ont pas été vérifiés chez les deux parents d'une famille nucléaire. Un dernier constat concerne enfin les instruments utiliser pour mesurer le construit de la sécurité d'attachement : il semble que, selon l'outil choisi et le type de variable utilisé, les constats réalisés sur la sécurité d'attachement diffèrent. Afin de répondre à cette lacune, le présent projet propose une avenue novatrice, à titre exploratoire : vérifier l'agencement des relations d'activation et d'attachement dans une triade familiale (un enfant et ses deux parents biologiques), et son lien avec le développement social de l'enfant. Étant donné les ressources limitées, seulement cinq cas ont été recrutés. Des données ont été collectées par observation directe et indirecte, selon un devis transversal. Puis les données ont été analysées d'abord de façon descriptive. Quelques analyses corrélationnelles ont toutefois été réalisées à titre exploratoire. Malgré l'impossibilité de généraliser les résultats de cette étude, ces derniers présentent plusieurs points similaires à la littérature scientifique. Le constat le plus évident est le lien entre les problèmes d'activation et les difficultés de comportements internalisés qui ont aussi été documentés dans la littérature scientifique. Ce projet consolide l'intérêt de s'intéresser aux deux dimensions de la relation parent-enfant, tant en recherche que sur le plan de l'évaluation psychosociale de l'enfant.