Abstract: The scintillator uses a luminescent crystal (5) under the action of an ionizing radiation. It is particularly intended for use at high temperatures and accelerations. The crystal (5) is surrounded by PTFE powder (11) which is sintered cold and then conditioned hot and under pressure.

Abstract: A polydiacetylene coating layer deposited upon an organic microcrystal. The coating has a large, uniform surface area which is monoriented and without cracks. The preferred embodiment utilizes for the monomer a layer of [1,6-di- n(carbazolyl)-2,4-hexadiyne] deposited by epitaxy onto an acid orthophthalate monocrystal of an alkali metal, ammonium or thallium. The process of the invention comprises cleaving the acid orthophthalate monocrystal along its (001) plane; depositing a diacetylenic monomer onto the cleaved face of the crystal by heat evaporation under vacuum conditions, and polymerizing the monomer upon the crystal face. The coated layer may thereafter be removed from the crystalline substrate by applying a composition such as, e.g., cabon or an acrylic polymer onto the coating to form a backing therefore and separating the resultant monoriented film from the crystal by at least partially immersing the coated crystal in water.

Abstract: Mixed strontium and lanthanide oxides and a laser using monocrystals of these oxides.These oxides with a magnetolead type crystalline structure have the following formula:Sr.sub.x Ln1.sub.y1 Ln2.sub.y2 Ln3.sub.y3 M.sub.z A.sub.a B.sub.b O.sub.19--kin which Ln1 represents at least one trivalent element selected from lanthane, gadolinium and yttrium; Ln2 represents at least one trivalent element selected from neodymium, praseodymium, erbium, holmium and thulium; Ln3 represents an element selected from bivalent europium or trivalent cerium with retention of electric neutrality by virtue of oxygen holes; M represents at least one bivalent metal selected from magnesium, manganese and zinc; A represents at least one trivalent metal selected from aluminum and gallium; B represents a trivalent transition metal selected from chromium and titanium; x, yl, y2, y3, z, a, b and k represent numbers so that 0<x<1, 0.ltoreq.y1<1, 0<y2<1, 0.ltoreq.y3<1, 0<z<1, 10.5<a<12, 0.ltoreq.b.ltoreq.0.

Abstract: A method and apparatus for manufacturing one phase of a silica crucible including controlling the filling of a hollow mold of cylindrical shape, which rotates about its vertical axis, with grains of crystallized quartz. The grains of material are continuously introduced into the mold and are deposited on or near the lateral wall face of the mold in the form of a cylindrical layer, E, of internal radius R. A beam of light is directed to form a luminous spot on the summit of the layer from the commencement of its formation and the radial displacement of the spot on the layer is observed. The height at which the grains are introduced and the height of the trajectory of the luminous beam are modified as a function of the position of the luminous spot relative to determined reference points.

Abstract: Multimode optical fibers are described comprising a cylindrical core with a radius a.sub.o exhibiting an index of refraction n.sub.o surrounded by a cladding having an outer radius a in which the index of refraction varies continually from the core to the periphery from a value of n.sub.1 to a lower value n.sub.e. Between the core and cladding there is a step change .DELTA.n in their respective indices of refraction whose value is a function of the ratio a.sub.o /a. Such fibers have both slight attenuation and slight dispersion and can be manufactured using processes similar to those used in making step-index optical fibers.

Abstract: An optical waveguide is disclosed which exhibits only slight attenuation over both the visible and near infrared range. The waveguide comprises an optical fiber whose core is made up of a fluorine-doped silica glass possibly comprising an oxide that increases the index of refraction of said silica.