Growing of oxide crystals by Czochralski method

The technological processes of growing the single crystals of sapphire, lithium niobate, yttrium aluminum garnet, neodymium-alloyed yttrium aluminum garnet (YAG Nd 3+) are implemented in the crystal growth laboratory on the installations NIKA-S and NIKA-3. These processes are fully automatic except for the seed melting procedure.

The new method of the automatic PID-regulator adjustment is used in the software of growth process control system, which consists of three stages: accumulation of experimental data on CO in the course of the process control by means of the relay regulator, calculation of the control object model factors and determination of PID-regulator factors on the basis of the created mathematic model and preset reference transient process. At the stage of the regulator factors determination use is made of the Nelder-Mid unconditional minimization method. It allows introduction of the additional conditions at selection of PID0regulator factors, such as: limitation of control action and its increase rate, availability of dead zone and saturation zone..

In order to set the generator power precisely use is made of the optical channel of heating power values transmission, eliminating signal distortion by electrical interference.