55 research outputs found
Développement d'un détecteur sans temps mort sensible en temps et en position : Application à l'étude des collisions de petits agrégats d'argon Ar+n sur une cible d'argon
No full textThe aim of this work is the development of a fast multi-hit position and time sensitive detector with zero dead-time for heavy particles in the keV energy range. This new type of detector makes use of a micro-channel plates MCP assembly and combines a detection based on delay line anode with a simultaneous particle imaging provided by CCD-camera. The time pickup accuracy is enhanced by digitalizing the MCP biasing signal. This detector, operating at kHz repetition rate, allows a position resolution better than 100 µm and a time resolution better than 100 ps to be achieved.We have studied the fragmentation induced by collision of small ionic argon clusters (Ar2+ and Ar3+) with an atomic argon target at keV energies range. All the fragmentation channels: collision induced dissociation (CID) and dissociative charge transfer (DCT) have been analysed by the method of vectorial correlation of all the fragments detected in coincidence. The importance of electronic processes in these collision systems is demonstrated through various results. The dependence of the electron transfer on the initial internal energy of the cluster has been stressed out. Ar3+ has been found to be mainly formed of a strongly bound Ar2+ core surrounded by loosely linked Ar atom.Nous avons développé un nouveau système de détection sans temps mort, résolu en temps et en position et basé sur des galettes de microcanaux. Le principe de ce détecteur est de coupler deux systèmes de détection indépendants qui observent le même événement pour aboutir à leur localisation sans temps mort. Le premier système est constitué d'une caméra CCD capable de fournir l'information position. Le deuxième est constitué d'une carte de numérisation pour enregistrer le signal temps issu des galettes de microcanaux. Le lien entre ces deux systèmes est assuré par une anode constituée de deux lignes à retard, placées derrière les galettes de microcanaux, capable de fournir les deux informations temps et position mais d'une façon moins précise. Ce détecteur opérant au kHz permet d'atteindre une résolution spatiale de 100 µm et temporelle de 100 ps.Nous avons étudié la fragmentation induite par collision des petits agrégats d'argon (Ar2+ et Ar3+) avec une cible d'argon atomique dans la gamme des énergies du keV. Toutes les voies de fragmentation : la dissociation induite par collision (CID) et l'échange de charge dissociatif (DCT) sont analysées par la corrélation vectorielle de tous les fragments détectés en coïncidence. En particulier, nous avons montré que le processus DCT dépendait fortement de l'énergie interne initiale de l'agrégat (i.e. du défaut de résonance). La comparaison de diverses observables mesurées en collision Ar2+-Ar et Ar3+-Ar nous a conduit à conclure que les agrégats Ar3+ produits dans notre source ont majoritairement la structure d'un dimère chargé (Ar2+) autour duquel orbite un troisième atome peu lié
Développement d'un détecteur sans temps mort sensible en temps et en position (application à l'étude des collisions de petits agrégats d'argon Ar+n sur une cible d'argon)
No full textNous avons développé un nouveau système de détection sans temps mort, résolu en temps et en position et basé sur des galettes de microcanaux. Le principe de ce détecteur est de coupler deux systèmes de détection indépendants qui observent le même événement pour aboutir à leur localisation sans temps mort. Le premier système est constitué d'une caméra CCD capable de fournir l'information position. Le deuxième est constitué d'une carte de numérisation pour enregistrer le signal temps issu des galettes de microcanaux. Le lien entre ces deux systèmes est assuré par une anode constituée de deux lignes à retard, placées derrière les galettes de microcanaux, capable de fournir les deux informations temps et position mais d'une façon moins précise. Ce détecteur opérant au kHz permet d'atteindre une résolution spatiale de 100 m et temporelle de 100 ps.Nous avons étudié la fragmentation induite par collision des petits agrégats d'argon (Ar2+ et Ar3+) avec une cible d'argon atomique dans la gamme des énergies du keV. Toutes les voies de fragmentation : la dissociation induite par collision (CID) et l'échange de charge dissociatif (DCT) sont analysées par la corrélation vectorielle de tous les fragments détectés en coïncidence. En particulier, nous avons montré que le processus DCT dépendait fortement de l'énergie interne initiale de l'agrégat (i.e. du défaut de résonance). La comparaison de diverses observables mesurées en collision Ar2+-Ar et Ar3+-Ar nous a conduit à conclure que les agrégats Ar3+ produits dans notre source ont majoritairement la structure d'un dimère chargé (Ar2+) autour duquel orbite un troisième atome peu lié.The aim of this work is the development of a fast multi-hit position and time sensitive detector with zero dead-time for heavy particles in the keV energy range. This new type of detector makes use of a micro-channel plates MCP assembly and combines a detection based on delay line anode with a simultaneous particle imaging provided by CCD-camera. The time pickup accuracy is enhanced by digitalizing the MCP biasing signal. This detector, operating at kHz repetition rate, allows a position resolution better than 100 m and a time resolution better than 100 ps to be achieved.We have studied the fragmentation induced by collision of small ionic argon clusters (Ar2+ and Ar3+) with an atomic argon target at keV energies range. All the fragmentation channels: collision induced dissociation (CID) and dissociative charge transfer (DCT) have been analysed by the method of vectorial correlation of all the fragments detected in coincidence. The importance of electronic processes in these collision systems is demonstrated through various results. The dependence of the electron transfer on the initial internal energy of the cluster has been stressed out. Ar3+ has been found to be mainly formed of a strongly bound Ar2+ core surrounded by loosely linked Ar atom.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF
MOSARIX: PROGRESS REPORT
No full textMOSARIX is a collaborative project between three research group in Sorbonne University to build a x-ray spectrometer (2-5 keV) portable to large scale facilities with high efficiency and good resolution. X-ray spectroscopy and coincidences experiment are planned. A prototype with a single HADP crystal with von Hamos geometry has been tested (resolution and efficiency). A fast time and position detector has been realized (patent and publication).We plan to build the spectrometer with 8 HADP (or 4) crystals under Helium atmosphere using a TimePix3 or a CCD camera. MOSARIX is a project of an x-ray spectrometer in the tender x-ray domain (2-5 keV) with high efficiency, allowing performing x-ray emission and coincidences (or covariance mapping) experiments using synchrotron radiation, XFEL, the future installation SPIRAL2/GANIL or CRYRING/FAIR. It involves 2 groups at LCPMR (Francis PENENT and Marc SIMON) and one group at INSP (Dominique VERNHET). The coincidences/covariance measurements will be between x-ray photons and ions or electrons. It would be the first time for such coincidences with energy-resolved photons. The spectrometer will be portable and will be brought to the different large-scale facilities. MOSARIX is a multi-crystal HAPG von Hamos spectrometer optimized for the 2-5 keV photon energy range. Its resolving power E/DE will be 4000. It will be equipped with a fast time and position sensitive detection system, allowing performing coincidences, or with a CCD camera. I. Scientific case and some possible experiments The accelerated development of x-ray sources, as 3 rd generation synchrotrons (and recent upgrades) or free-electron lasers, has opened new opportunities to investigate new phenomena by means of photoelectron and Auger spectroscopy, electron-ion coincidence techniques and x-ray emission. However, several processes of high scientific interests are still hard to measure; some of them require the measurement of photons with high efficiency, high resolution and even sometimes in coincidence mode. This is the purpose of MOSARIX development. As an example, we propose to revisit Resonance-Enhanced X-ray Multiple Ionization (REXMI) 1 with a significant amelioration of the detection of photons, i.e. measuring the photons not only with high efficiency and high resolution but also in coincidence with ions or electrons. This will allow accessing the involved intermediate states and obtaining a clearer image of the dynamic of the multiple ionization process. MOSARIX can also be used for the investigation of very low cross-section phenomena such as attosecond electron dynamics 2 and High-Energy Resolution Off-Resonant Spectroscopy (HEROS) 3,4. X-ray spectroscopy has also proved to be a very powerful tool to investigate quantum dynamics in heavy ions collisions with matter of whatever nature, dilute or condensed 5-7.
Time and position sensitive photon detector for coincidence measurements in the keV energy range
No full textInternational audienc
From Rabi'a to Ibn al-Farid : towards some paradigms of the Sufi conception of love
No full textThis thesis aims to investigate the significance of Divine Love in the Islamic tradition with reference to Sufis who used the medium of Arabic to communicate their ideas. Divine Love means the mutual love between God and man. It is
commonly accepted that the Sufis were the forerunners in writing about Divine Love. However, there is a relative paucity of literature regarding the details of their conceptions of Love. Therefore, this attempt can be considered as one of the first of its kind in this field.
The first chapter will attempt to define the nature of love from various perspectives, such as, psychology, Islamic philosophy and theology. The roots of Divine Love in relation to human love will be explored in the context of the ideas that were prevalent amongst the Sufi authors regarded as authorities; for example, al-Qushayri, al-Hujwiri and al-Kalabadhi.
The second chapter investigates the origins Of Sufism with a view to establishing the role that Divine Love played in this. The etymological derivations of the term Sufi will be referred to as well as some early Sufi writings.
It is an undeniable fact that the Qur'an and tladith are the bedrocks of the Islamic religion, and all Muslims seek to justify their ideas with reference to them. This
was especially true for the Sufis. The third and fourth chapters will, therefore, focus on the concept of Divine Love in the textual sources of Islam in order to
determine the role that these played in the development of the Sufi conceptions of love in general.
Having highlighted the origins and general context of Divine Love, the following five chapters will focus on selected Sufis whose contributions can be regarded
as significant, original and representative of the Sufi tradition. The exclusive characteristics of each Sufi's concept of love will be analysed and an attempt will be made to present them as a paradigm of Sufi love. The paradigms of love of the following Sufis will be presented: Rabi`a, al-I-Jallaj, al-Ghazäli, Ibn 'Arabi and Ibn al-F5ricl. The concluding chapter will provide a synthesis of these paradigms of love by putting forward a framework which identifies the key stages in the development of the Sufi paradigm of love.
Regarding the scope and limitations of this study, it should not be seen as a historical or biographical research. The historical analysis and information are
presented merely to give some insight into the social and historical context of the Sufi's time. The primary aim of this research is to establish the different paradigms of love of the Sufis referred to above, by analysing the exclusive motives specific to each paradigm.
Finally, this research is by no means a comprehensive account of the Sufi paradigms of love. The development of the thesis showed that this research can be approached from many different angles. For example, the concept of love is
closely associated with the concept of ma`rifia, and the concept of God. The relationship of the two with the concept of love is a possible area of further research. In addition, the historical information available on each individual Sufi provides ample material for a detailed study of the concept of love in that particular Sufis paradigm. This work provides a general framework for further
studies
Periodic Multilayer for X-ray Spectroscopy in the Li K Range
No full textX-ray spectroscopy of lithium is very difficult, even impossible, with wavelength dispersive spectrometers commonly deployed on scanning electron microscopes or electron microprobe analyzers. This is due to the absence of crystals and lack of efficient periodic multilayer for this spectral range, around 50 eV. To address this issue, we propose using a Be/Si/Al multilayer having a period of about 29 nm. The multilayer was deposited by magnetron sputtering and its reflectivity measured as a function of the glancing angle in the spectral range of the Li K emission and as a function of the incident energy up to ~200 eV. This characterization demonstrates that the designed multilayer is suitable to efficiently perform spectroscopy in the range of the Li K emission in terms of reflectance (0.32 at 51.5 eV), bandwidth (around 3.5 eV) and rejection of high order diffracted radiation
Study of buried interfaces in Fe/Si multilayer by hard x‐ray emission spectroscopy
No full textInternational audienceHard x-ray emission spectroscopy (XES) has been used to study buried layers and interfaces in a Fe/Si periodic multilayer. Until now, buried layers could be studied using the XES in the soft x-ray range. Here we extend the methodology to study the buried interfaces in hard x-ray region (photon energy ≥ 5 keV). We report the formation of FeSi2 at all the interfaces with thicknesses of 1.4 nm. X-ray reflectivity measurements enable us to deduce the structure and thickness of the multilayer stack, thereby confirming the presence of FeSi2
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