LCT-pegmatiittien syntymekanismit ja esiintyminen Suomessa

Tiivistelmä. LCT-pegmatiitit edustavat pegmatiittiryhmää, joka on rikastunut harvinaisista alkuaineista, kuten litiumista, cesiumista ja tantaalista. Litium on tyypillinen alkuaine felsisissä pegmatiittisulissa, jotka kiteyttävät mineraaleja hyvin alhaisissa paine- ja lämpöolosuhteissa. Li-pitoisia mineraaleja ovat esimerkiksi spodumeeni ja lepidoliitti. Mineraaliseurueiden perusteella LCT-pegmatiitit jakaantuvat alaluokkiin; albiitti-, albiitti-spodumeeni-, kompleksi- ja berylliryhmä. Myöhäinen kiteytyminen mm. sopeutumattomien alkuaineiden vaikutuksesta saa aikaan pegmatiittien rikastumisen useammasta harvinaisesta alkuaineesta, mikä kasvattaa pegmatiitin kompleksisuutta. Suomessa tavataan jokaista LCT-pegmatiitin alalajia, ja ne ovat levittäytyneet vallitsevasti Länsi-Suomen puolelle. Esimerkiksi albiitti-spodumeeniryhmän pegmatiitit ovat yleisiä Kaustinen-Ullava sektorilla. Berylliryhmän pegmatiitteja taas tavataan lähempänä sisämaata ja kompleksisia pegmatiitteja on havaittu yleisesti etelämpänä Seinäjoen alueella ja esimerkiksi Kemiössä. Alueellisia vaihteluita on kuitenkin paljon, ja pegmatiitin koostumus pohjautuu lähtösulan koostumukseen. Työ perustuu kirjallisuuskatsaukseen graniittisten kivien synnystä ja LCT-pegmatiittien muodostumisesta. Työn tarkoituksena on tutustua pegmatiittien luokitteluperusteisiin ja tarkastella pegmatiittiesiintymiä Suomen alueella

Jet photonique simple ou double pour la détection d'objets sub-longueur d'onde

National audienceOn appelle « jet photonique » un faisceau électromagnétique ayant une grande concentration de puissance en champ proche. Ce jet photonique possède des propriétés comme une faible divergence et une faible largeur à mi-hauteur. Il peut être appliqué pour la détection d'objet de taille sub-longueur d'onde. Les jets photoniques peuvent être observés pour des longueurs d'onde optiques dans le voisinage d'une sphère diélectrique micrométrique. Ils peuvent être obtenus également dans la gamme des microondes. Dans cet article, nous montrons la réalisation et la mise en évidence de ces jets photoniques dans la gamme microondes. La modélisation développée a permis de mettre en oeuvre des systèmes produisant des jets simples ou doubles. L'expérimentation et ses résultats sont présentés et la détection facile d'objets de faible taille devant la longueur d'onde est mise en évidence ainsi que la mise en évidence de leur mouvement

Effect of Phase Noise on the Frequency Calibration of a Tunable Laser by Heterodyne Signal Filtering

Using a frequency comb as frequency reference to calibrate the instantaneous frequency of a tuning laser allows high spectral resolution and a wide calibration range. To obtain the instantaneous frequency of the laser under test, a classical method consists in filtering the heterodyne signal between the frequency comb and the tunable laser with a narrow bandpass filter. For free-running femtosecond lasers, the phase noise of the comb lines affects the instantaneous frequency of the heterodyne signal and the envelope of the filtered calibration signal. In this paper, the characteristics of the frequency calibration signal envelope is analyzed by modeling. Three different filters are used to determine the envelope characteristics. Simulation results show that the probability density function (pdf) of the envelope amplitude tend to be a uniform distribution at higher phase noise level. At low tuning speed, the pdf distributions are the same at symmetric frequency positions of the passband of the filter. At high tuning speed, their distributions become different. The standard deviation of the center of mass becomes larger at higher phase noise level and higher tuning speed

Ultra-narrow photonic nanojets through a glass cuboid embedded in a dielectric cylinder

A glass cuboid, embedded inside a dielectric cylinder is studied when illuminated with a monochromatic plane wave. A photonic nanojet (PNJ) with a full-width at half-maximum (FWHM) waist of around 0.25λ0 is obtained outside the external surface of the cuboid. The influence of the parameters of a square section cuboid is studied. Three particular phenomena can be obtained and are discussed: an ultra-narrow PNJ on the external surface of the cuboid, a long photonic jet and the excitation of whispering gallery modes (WGMs). A parametric study, over the width and the height of a rectangular section cuboid, shows that these parameters can be used to control the photonic jet properties. We also study several other geometries of the insert, which shows that the key parameter is the refractive index of the inserted material. Finally, we show that by changing the incident angle we can obtain a curved photonic jet

Roadmap on Label-Free Super-resolution Imaging

Label-free super-resolution (LFSR) imaging relies on light-scattering processes in nanoscale objects without a need for fluorescent (FL) staining required in super-resolved FL microscopy. The objectives of this Roadmap are to present a comprehensive vision of the developments, the state-of-the-art in this field, and to discuss the resolution boundaries and hurdles that need to be overcome to break the classical diffraction limit of the label-free imaging. The scope of this Roadmap spans from the advanced interference detection techniques, where the diffraction-limited lateral resolution is combined with unsurpassed axial and temporal resolution, to techniques with true lateral super-resolution capability that are based on understanding resolution as an information science problem, on using novel structured illumination, near-field scanning, and nonlinear optics approaches, and on designing superlenses based on nanoplasmonics, metamaterials, transformation optics, and microsphere-assisted approaches. To this end, this Roadmap brings under the same umbrella researchers from the physics and biomedical optics communities in which such studies have often been developing separately. The ultimate intent of this paper is to create a vision for the current and future developments of LFSR imaging based on its physical mechanisms and to create a great opening for the series of articles in this field.Peer reviewe

METALLIC ION DEVELOPMENTS AT GANIL

Radioactive ion beams (RIB) are routinely produced at GANIL by fragmentation of the projectile. A possible way to improve the RIB intensity is to increase the primary beam intensity impinging the target. Although high intensities can be obtained with an ECR ion source for gaseous elements, it is more difficult for metallic elements due to the poor ionization efficiency of the source. This report deals with metallic ion beam production at high intensity. Experimental results for Ca, Ni and Fe are presented. The oven and the MIVOC methods are compared