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3.2.3.2. Measurings by means of numeral photo-videocameras

The same expedient of measuring of temperature in separate points of a surface of a melt in tigle which have been used for examination of a kinetics of growth paratellurita (paragraph 3.1.1.3), had been spent similar measurings at cultivation of crystals of germanium.

In the modernised installation for reception of monocrystals by a method Chohralsky «Редмет-10» the monocrystal of germanium from tiglja 300 mm was grown up by diameter. C the help of colour numeral camera SONY DSC - HXl through one of observation ports vakuumirovannoj rostovoj cabinets were yielded pictures of a melt and razrashchivaemogo a germanium monocrystal. One of such pictures is presented in drawing 3.28. The gained image from a camera video card is entered into the personal computer then the file was loaded into a window of the program of calculation of the temperature, also presented on drawing 3.28.

Drawing 3.28 - the Window of the user of the program for calculation of temperature with the loaded file of the image of a melt in tigle with an extended monocrystal of germanium

In the gauge window of the program the temperature of fusion of germanium Tpl = 1210 To (9370C) is written down. The cursor was directed at a point And in the image of a line of touch of a melt with a crystal (a three-phase line), the temperature along which was accepted to equal temperature of fusion. Further the cursor Would be directed at a point corresponding to a site of a melt, adjoining an interior lateral surface of a wall tiglja. The value of temperature equal 9430C has been thus gained. After cursor prompting on a point In, corresponding approximately to half of radius tiglja, the value of temperature equal 9410С is gained.

Similar measurings have been spent at vytjagivanii 6 crystals of germanium in diameter of 150-200 mm from graphite tiglja by diameter 300 mm. During each process the colour images gained consistently every 30 minutes vytjagivanija and reflecting changes were handled

Temperature fields. At processing of each image the number of points in which the temperature was measured, made from 3 to 10. Experience have given a material for calculation of radial lapse rates temperaturyih changes in process vytjagivanija, and also melt supercoolings

The analysis of observed datas and calculations allows to draw following deductions.

• Not only from the quantitative leg, but also qualitatively temperature fields, quantities of supercoolings and melt hydrodynamics in pripoverhnostnyh volumes in tigle at growth of crystals of germanium and crystals paratellurita essentially differ.

• Quantities AT - diversions of temperature of a melt from equilibrium

Temperature T0 (supercoolings and overheats) at vytjagivanii germanium crystals at 5-10 time is less, than at vytjagivanii than crystals paratellurita, also are in an interval of values AT = 1-5 To.

Temperature radial gradientytem not less, are close to

That for paratellurita, also are in limits 0,2-2,0 To/see C the points of view of the theory, it speaks major distinction of values measure Prandtlja for melts dioksida tellurium and germanium - 4 and 0,025, accordingly.

The affinity of radial temperature lapse rates in melts of germanium and paratellurita speaks that, despite a major thermal conduction, at the expense of smaller viscosity the fluid moves with higher velocity owing to what temperature the lateral view along radius tiglja is effectively flattened.

Unlike a melt dioksida tellurium, at cultivation of crystals of germanium the phenomenon of formation of vortexes of Taylor - visually is not revealed, at the computer analysis of temperature fields by means of numeral cabinets. This fact also finds the explanation within the limits of the theory of magnetohydrodynamic simularity. The matter is that at early stages razrashchivanija a germanium crystal relation Gr = R2 is carried out. In ours 109

Case it is carried out already for a crystal of germanium in radius R = 2-3 sm (Gr ≈ IO9, Re ≈ 3-JU4). At magnification of radius of a crystal to 5-7см and more, the Reynolds criterion quadrate at least 10 times surpasses measure Грасгофа:Такое a relation for cultivation process

paratellurita it is observed at very major radiuses of a crystal when the system of vortexes of Taylor is already destroyed, and the concentric motion of rings of a dark cold melt from centre to walls tiglja is observed. Unlike vytjagivanija paratellurita when measure Grasgofa in process fluxion decreases 10 times, and the long-term time can be supported equality Gr = Reза the account of reduction of velocity of gyration of a crystal, at germanium cultivation the further magnification of radius of a crystal even more strengthens inequality Re> Gr, and Taylor's any vortexes is not observed till the end of process.

At vytjagivanii germanium crystals the radial temperature lapse rates measured by means of numeral photographic cameras, change according to the diagramme presented in drawing 3.29.

Drawing 3.29 - Dependence of a radial temperature lapse rate on time

vytjagivanija monocrystals of germanium in radius of 10 sm from tiglja in radius 15

Sm an expedient Chohralsky

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A source: Aydinyan Narek Vaagovich. the KINETICS of GROWTH of LARGE-SIZED MONOCRYSTALS paratellurita And Germany In the METHOD of the CHOHRALSKY. The dissertation on competition of a scientific degree of the candidate of physical and mathematical sciences. Tver - 2017. 2017

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  9. magnetic measurings
  10. inductivity Measurings.
  11. MEASURINGS OF PARAMETERS OF DETECTORS
  12. 2.3.2 Estimate of an error of measurings
  13. magnetic measurings
  14. magnetic measurings
  15. 3.1.3. Measurings of temperature fields
  16. 3.2.3. Measurings of temperature fields