Lead tungstate ( PbWO4 ) is a new scintillating crystal discovered in 1990s. It is one of the most dense oxide crystal ( 8.3g/cm3), and is distinguished by its short radiation length ( 0.9 cm), small Moliere radius ( 2.19cm) and strong irradiation hardness. Its scintillation light output peaks between 450-550nm with a fast component decay time in the range from 2-20ns. After irradiation with g-ray, the degradation in the optical transmittance is not large up to 106 rad. PbWO4 is considered as a promising scintillation material for electromagnetic spectrometer in high energy, nuclear physics experiment as well as nuclear medicine. Main Properties Crystal structure Tetragonal Space group I 41 /a Lattice constant (Å ) a = b = 5.416 , c = 12.049 Density (g/cm3) 8.28 Radiation length (cm) 0.92 Molere radius (cm) 2.19 Decay constant (ns) 6/30 Peak emission (nm) 440/530 Light output (%) 0.5 Index of refraction 2.16 Melting point (oC ) 1123 Hygroscopicity No Cleavage (101) Crystal boule size 30 mm in diameter x 100 mm in length
Scintillation single crystals 4.1. PbWO4 crystals The Czochralski method was considered to be the most suitable for large-scale industrial production of PbWO4 crystals. In particular, it was used to provide huge amounts of these crystals (about 100 000 scintillation elements) for the CMC and ALICE projects at CERN . A crystal growth technology of large-size PbWO4 crystals (35 mm in diameter and 250 mm long) for scintillation detectors was developed at Institute. It is characterized by comprehensive approach to technological preparation of the starting material (including re- -crystallization) and to the doping of the crystals with dierent ions for the formation of preset properties, such as maximum position of luminescence spectrum, radiation hardness, absence of colour centres which re-absorb the host luminescence . Experimental investigations of PbWO4 crystal growth were carried out by use of the setups with high-frequency heating Crystal 3M and Analog. Lead tungstate crystals were grown by the Czochralski method from platinum crucibles in an atmosphere with a composition close to that of air or inert gases. At rst the homogeneous mechanical mixture of tungsten and lead oxides (99.999% purity) was melted to increase the density and perform preliminary synthesis. For additional purication, averaging of the chemical composition, as well as for reducing the deviation from the stoichiometry, the charge was preliminarily re- -crystallized. During successive crystallization processes the melt composition is being corrected, the doping is realized taking into account the measurements of the parameters of the scintillation elements. Lanthanum, yttrium or niobium doped PbWO4 crystals were grown. The dopant concentration was few tens of ppm. The single crystals and rectangular scintillation elements are shown in Fig. 8. Fig. 8. PbWO4 single crystal and scintillation elements. The Czochralski method was successively applied for crystal growth where the formation of preset properties was achieved by modication of both the cationic and anionic sublattices. Experimental choice of growth conditions and dopants for modication of the cationic and anionic sublattices of PbWO4 crystal allows to control the properties of these crystals within wide range, in particular, to vary the luminescence kinetics and position of host luminescence maximum and to achieve essential increase of light yield or radiation hardness, for example
Gadolinium Gallium Garnet
Gadolinium Gallium Garnet (GGG, Gd3Ga5O12) is a magneto-optical and microwave substrate. It is the best substrate material for infrared optical isolator (1.3 and 1.5um), which is a very important device in optical communication. It is made of YIG or BIG film on the GGG substrate plus birefringence parts. Also GGG is an important substrate for microwave isolator and other devices. Its physical, mechanical and chemical properties are all good for the above applications.
Phase and amplitude diffraction gratings
Phase and amplitude diffraction gratings are intended for the UFO observations, anomalous zones, and torsion generator fields. They are fastened to video cameras and mobile phones. The anomalous zones make an influence upon the passage of light through the air. That is why the spectral decomposition of the light after the diffraction gratings the spaces which contain the anomalous zones or the torsion generator field changes their color configuration. When such a grating is aimed at the UFO, a light spectrum is scattered and radiates the UFO by the constituent parts. This makes possible the analysis of the UFO radiations which are not visible by the naked eye.
Lithium Niobate (LiNbO3 or LNB) and Lithium Tantalate (LiTaO3 or LTA) possess a combination of unique electro-optical, acoustic, piezoelectric, pyroelectric and non-linear optical properties making it a suitable material for applications in acoustic, electro-optical and non-linear optical devices, high-temperature acoustic transducers, receivers-transmitters of acoustic vibrations, air force acceleration meters, acoustic wave delay lines, deflectors, generators of non-linear distorted waves, acoustic filters, electro-optical Q-modulators (Q-switch), encoders-decoders, filters in television receivers, video-recorders and decoders, converters, frequency doublers and resonators in laser systems, non-linear elements in parametric light generators, etc. An indispensable condition of some of these applications is a high degree of optical uniformity of Lithium Niobate crystals used for fabrication of active elements. Crystal growth technology by low temperature-gradient Czochralsky method allows the growth of large-size high-quality LNB (up to 1-1.5 kg) and LTA single crystals for such non-conventional applications. It should be noted that both crystals are non-hygroscopic, colourless, water-insoluble and have low transmission losses. LiNbO3 damage due to photorefractive effect in congruent melt grown LiNbO3 certainly limits it's applications in high optical power devices. For this purpose specially grown LiNbO3 with composition near stoichiometric can be offered. It is similar to the Li-rich VTE LiNbO3 with the obvious advantage that bulk samples can be obtained. Another possibility to increase laser damage threshold of LiNbO3 is doping with MgO. MolTech can offer both MgO:LiNbO3 and stoichiometric LiNbO3 elements cut from boules up to 60 mm dia. Some other crystals of LiNbO3 series are available, including LiNbO3 doped with Fe, Zn, Gd, Cu , Y, B, Er etc. For some applications similar in properties to Lithium Tantalate (LiTaO3) crystal is more advantageous than LiNbO3 (E-O modulators, pyroelectric sensors etc.). Lithium Tantalate exhibits unique electro-optical, pyroelectric and piezoelectric properties combined with good mechanical and chemical stability and wide transparency range and high optical damage threshold. This makes LiTaO3 well-suited for numerous applications including electro-optical modulators, pyroelectric detectors, optical waveguide and SAW substrates, piezoelectric transducers etc. MolTech can offer parts cut from high quality boules grown along X axis, fully poled, with dia. and length of up to 60 mm.
Transparency range, µm
0.4 - 5
0.4 - 5
Lattice parameters (hexagonal), Å
a = 5.148, c = 13.863
a = 5.154, c = 13.784
Refractive indexes :
no = 2.28647, ne = 2.20240 (at 0.633 µm)
no = 2.183, ne = 2.188 (at 0.6 µm)
no = 2.2273, ne = 2.1515 (at 1.1523 µm)
no = 2.131, ne = 2.134 (at 1.2 µm)
Non-linear coefficient at 1.06 µm, pm/V
d22 = 5.6, d31 = -11.6, d33 = 8.6
d22 = 2, d31 = -1, d33 = -21
Electroptical coefficient at 0.63 µm, pm/V
r31 = 8.6, r22 = 3.4, r33 = 30.8, r51 = 28
r13 = 8, r22 = -0.2, r33 = 30
MolTech provides LiNbO3 and LiTaO3 crystals with high optical quality as finished wafers, elements or blanks at your request. Orientation, polishing, single-band and dual-band AR-coatings by customers' order. The AR-coatings are characterized by low reflectance, high damage threshold and long durability.
Акимов А.Е. о Спиноре ( Spinor )
Transfer of information on Lupichev
Anatoly Pavlenko offered the hypothesis that a torsion field consists of virtual particles. Like this, the operation of mobile telephones causes left torsion fields producing virtual electrons that generate free radicals in the human body and unhealthy affect it. This theory is partially confirmed by wave genetics. After listening to the matrices created by the laser apparatus, virtual quantum organs appear on which the organism begins to work.