Scintillation sensor

Figure 3. Depth-depending variations in the counting rate of PRM-K scintillation sensor within different...

Figure 4. Variations in gamma EDR in air, seawater and bottom sediments obtained using GGR-1 (a) and in the counting rate of PRM-K scintillation sensor within 1.8-2.5 MeV energy range (b) depending on depth in the NS K-1S9 sinking area ((o) - August-September 2003 ( ) - October-November 2003)...

Gamma EDR in air and water was entirely determined by cosmic rays, whereas in bottom sediments - by natural-origin radionuclides. Depth-depending increase in the counting rate of PRM-K scintillation sensor (from 50-m depth and below) within all energy ranges (Fig.3), save for 1.8-2.5 MeV (Fig. 4b), was due to natural factors -namely to increase in salinity, thus of concentration, with depth. 

The main error sources are noise in the wavefront sensor measurement, imperfect wavefront correction due to the finite number of actuators and bandwidth error due to the finite time required to measure and correct the wavefront error. Other errors include errors in the telescope optics which are not corrected by the AO system (e.g. high frequency vibrations, high spatial frequency errors), scintillation and non-common path errors. The latter are wavefront errors introduced in the corrected beam after light has been extracted to the wavefront sensor. Since the wavefront sensor does not sense these errors they will not be corrected. Since the non-common path errors are usually static, they can be measured off-line and taken into account in the wavefront correction. 

After each series of experiments with beams of various intensity the section plate would be removed from the cell and disassembled, with radioactive silver washed out by nitric acid. Radioactivity of the solutions obtained was measured by a multichannel spectrometric scintillation y-counter with sensitivity of up to 10 G, i. e. around 10 of atoms which, according to calculations, is 10 times lower than sensitivity of ZnO sensor 10 G or 10 of Ag atoms respectively [28]. This difference in sensitivity lead to great inconveniences when exposing of targets was used in above methods. Only a few seconds were sufficient to expose the sensor compared to several hours of exposure of the scintillation counter in order to let it accumulate the overall radioactivity. It is quite evident that due to insufficient stability during a long period of exposure time an error piled up. 

There are a number of possible sensor options for a y-ray spectrometer. These include a germanium sensor or scintillators made of various synthetic materials. Elements that are routinely analyzed with y-rays include silicon, iron, titanium, magnesium, calcium, and aluminum, plus the radioactive elements potassium and thorium (uranium concentrations are usually too low). 

The sensor is a crystal of Nal(TI) that transforms the 7 photon into luminescence whose intensity is proportional to the energy of the photon (assuming that the 7 photon is entirely absorbed by the crystal). The principle is similar to that of liquid scintillators used to measure 14C. If a Ge(Li) crystal is used, it behaves like the support gas in a Geiger-Muller tube. 

An expensive method is the use of nuclear radiation to obtain information on the level in an apparatus. The nuclear sensor is mounted at one side, and at the other side a scintillation counter is fixed near the surface of the apparatus. Both systems are sheathed with lead-screen shields to give protection from nuclear radiation. A continous level indicator using nuclear radiation is very complicated and therfeore seldom applied. 

Aliquat 336 "Tc sensing in water using impregnated polymer containing both extractant and scintillating fluors Radiometric column sensor 95,97... 

Aliquat 336 TEVA-Resin "Tc sensing in water using column containing mixture of TEVA-Resin particles and scintillating plastic beads Radiometric column sensor 96,97... 

Sr-Resin column containing mixture of Sr-Resin particles and sohd scintillator particles column sensor ... 

TRU-Resin type materials impregnated with both extractant and scintillating fluors column sensors ... 

Egorov, O. B., Fiskum, S. K., O Hara, M. J., and Grate, J. W., Radionuclide sensors based on chemically selective scintillating microspheres Renewable column sensor for analysis of 99Tc in water, Anal. Chem., 71, 5420-5429, 1999. 

Successful detection of S3P-labeled molecules separated by capillary electrophoresis using the above detection schemes, in which a sensor was positioned external to the separation channel, was made possible by several factors. These included (1) the large energy associated with 0 decay of S3P (1.7 MeV), (2) the high sensitivity and small size of commercially available semiconductor detectors, (3) the availability of efficient solid scintillator materials and sensitive photomultiplier tubes, (4) the short lengths of fused silica (capillary wall thickness) and aqueous electrolyte through which the radiation must pass before striking the detector, and (5) the relatively short half-life of S3P (14.3 days). 

Scintillation counter The sensor, the so-called scintillator, contains a transparent crystal that fluoresces when hit by ionizing radiation, thus a scintillation counter measures ionizing radiation. Light emitted from the crystal is measured by a sensitive photomultiplier tube which is attached to an electronic amplifier in order to count the amplitude of signals produced by the photomultiplier. Liquid scintillation counters are a very efficient and practical way to measure and quantify p radiation (see Figure 10.5b). 

Unfortunately the counting efficiency of the system was relatively poor, 0.2% for tritium and 17% for carbon. However, the advantage of this method is that due to the cell being packed with beads, it would have little flow resistance and limited peak dispersion and thus if used in conjunction with suitable low dispersion connecting tubes, it could be used with relatively high efficiency columns. As a consequence, many modem commercial radioactivity detectors are designed on the same principle, but with more efficient scintillators and more efficiently designed sensors. 

Ye L, Mosbach K (2001) Polymers recognizing biomolecules based on a combination of molecular imprinting and proximity scintillation A new sensor concept. J Am Chem Soc 123 2901... 

The semi-conductor transducer (scintillation counter). Each X-ray photon increases the conductivity of the active zone (the junction) of a lithium-doped silicon diode (one electron for around 3.6 eV). The background noise is reduced if the sensor is maintained at low temperature (cooled by liquid nitrogen or a Peltier device). The entry surface is protected by a beryllium film of a few pm (transparent for Z > 11) (Figure 12.8). In one or other cases the impulse furnished by the detector allows to go back to the energy of the incident photon. 

One of the most interesting applications of the HSAB concept consists in the prediction of the stability of the complexes formed owing to interaction of alkali metal halides with rare-earth metal halides. These systems are of great interest for the materials science of scintillation materials the said complex halides are now considered among the most promising scintillation detectors and sensors. Besides, the Li- and Gd-based materials are especially convenient as effective detectors of thermal neutrons. The compositions and stability of the formed compounds depend considerably on the kind of acids and bases from which the compound is formed. So, Li+ cation is one of the hardest cation acids, and, therefore, the formation of stable complex halides of Li and lanthanides according to reaction ... 

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