Abstract: A monoclinic single crystal with a lutetium pyrosilicate structure is described. The crystal is formed by crystallization from a congruent molten composition of LU2(1-x)M2x Si2O7 where LU is lutetium or a lutetium-based alloy which also includes one or more of scandium, ytterbium, indium, lanthanum, and gadolinium; where M is cerium or cerium partially substituted with one or more of the elements of the lanthanide family excluding lutetium; and where x is defined by the limiting level of LU substitution with M in a monoclinic crystal of the lutetium pyrosilicate structure. The LU alloy should contain greater than about 75 weight percent lutetium. The crystals exhibit excellent and reproducible scintillation response to gamma radiation.

Abstract: A monoclinic single crystal with a lutetium pyrosilicate structure is described. The crystal is formed by crystallization from a congruent molten composition of LU2(1−x)M2x Si2O7 where LU is lutetium or a lutetium-based alloy which also includes one or more of scandium, ytterbium, indium, lanthanum, and gadolinium; where M is cerium or cerium partially substituted with one or more of the elements of the lanthanide family excluding lutetium; and where x is defined by the limiting level of LU substitution with M in a monoclinic crystal of the lutetium pyrosilicate structure. The LU alloy should contain greater than about 75 weight percent lutetium. The crystals exhibit excellent and reproducible scintillation response to gamma radiation.

Abstract: Non-linear single crystal obtained by crystallization of a congruent molten composition of general formula:M.sub.4 LnO(BO.sub.3).sub.3in which:M is Ca, or Ca partially substituted with Sr or Ba;Ln is one of the lanthanides of the group comprising Y, Gd, La and Lu.

Abstract: Process for the production of bismuth germanate (BGO monocrystals) with a high scintillation response, based on the growth of a monocrystal from a molten bath in a crucible or container.The container is made from iridium and the melting and growth are carried out under a neutral or weak oxidizing atmosphere. This process makes it possible to produce BGO monocrystals with a high scintillation response, of all random sizes, which are free from light diffusion centers and which can be used as high energy radiation detectors.

Abstract: The invention relates to a process for the control of a monocrystal pulling machine.The process consists of recording in a computer memory parameters relating to the geometry of the monocrystal and the growth thereof, signals representative of the weight of the crystal and processed by processing circuits, then recording in said memory a programme so that the computer successively controls the raising to the appropriate temperature of the heating means for successively bringing about the melting of the product for forming the monocrystal, a fast automatic approach of the product bath by a pin carrying a nucleus up to a predetermined distance from the surface of said bath. Finally, the process consists of controlling a slower bath approach until the nucleus is in contact with the bath surface. Following this contact, the temperature of the heating means is automatically regulated for a zero growth of the crystal, the automatic pulling of the crystal and the cooling of the heating means at the end of pulling.

Abstract: The invention relates to a monocrystal pulling head.A carriage carrying the vertical pulling spindle, in which is placed a weight transducer, moves parallel to said axis under the action of a torque motor, which is controlled in position and speed and which is directly connected to the threaded rod of a screw - nut system. During its displacement, the carriage is guided by a rail, on which roll at least two pairs of rollers. A torque motor is mounted in the carriage for directly rotating the pulling spindle. Thus, the spindle displacement speeds are very accurately controlled. An electronic system integral with the pulling spindle processes the signals from the weight transducer. Contactless means make it possible to supply the electronic system, feed the useful information to the fixed parts and return thereto control instructions.