Purpose.
The “BZP” plant is designed for refining refractory metals using crucibleless zone melting with a ring cathode heater.

Design and operation of the plant and its components.
The “BZP” plant is a chamber plant consisting of complexes: electromechanical, vacuum, energy, automatic control systems, air supply systems and water cooling systems.
The working chamber contains:
- a workpiece fixed in a vertical position in a telescopic collet of a water-cooled rod of the top drive,
- a seed installed in the collet clamp of the water-cooled workpiece drive rod,
- water-cooled bottom drive rod,
- current lead with heater,
- protective screens.
The rods can move the workpiece and the seed in the vertical direction and carry out their independent rotation.
Vacuum system makes a working vacuum (1*10^-4 – 1*10^-5) mm Hg in the chamber.
After this, the process of refining the workpiece by zone melting is carried out in order to clean it.
The vacuum system is started from the control cabinet. The technological process is controlled from the operator's console.
The plant operator performs visual control of the technological process through one of the two inspection windows on the chamber door. A control system video camera is installed on the second window to monitor the technological process. Light filters are installed on the viewing windows to reliably protect the operator's eyes from radiation.
To protect against X-ray radiation that occurs when electrons decelerate on the product, the vacuum chamber has protective screens, and lead glass is installed in the viewing windows.
Excess pressure that arises in the chamber wile the technological process is relieved by a safety spring valve.

Control system.
The plant control system provides the ability to regulate and indicate main and auxiliary parameters and includes:
- an automatic control system for the growth process of single crystals with visual control on a computer monitor screen;
- regulation and maintenance in automatic mode of the power allocated to the heating unit;
- indication of accelerating voltage, heater current, cathode filament current and heating unit power;
- software control of drives of working and accelerated movement and rotation of the lower and upper rods;
- indication of speeds of rotation and movement of rods;
- control of units and elements of the vacuum system;
- measurement of residual pressure in the melting chamber in the range of 760 - 1∙10^-5 mmHg.
- indication of water pressure and alarm about an emergency in the water cooling system of the plant;
- video surveillance of the process of growth (refining) of the ingot on the operator’s monitor;
- control of the speeds of movement and rotation of the rods;
- control of residual pressure in the chamber;
- emergency light and sound warning;
- display of process parameters for automatic control of single crystal growth (ingot diameter, zone movement speed, zone diameter, etc.) on the monitor with simultaneous recording to a hard drive or removable media;
- continuous monitoring of all process parameters.
The plant is controlled automatically from the touch panel display. All information, including emergency situations, is displayed on the display.

Plant benefits:
- The chamber is made of stainless steel with a water cooling jacket. The walls, bottom and top of the chamber are cooled.
- The rectangular sliding door is made with a water cooling jacket. The size of the doorway provides free access to the plant units located in the chamber for their maintenance, for loading/unloading products, as well as for servicing of the inner surface of the chamber.
- Easily removable design of the electron beam heater (cathode unit).
- Replaceable elements of the cathode unit for growing single crystals of different materials and different diameters.
- Protection of glass viewing windows using a strobe light.
- Protection of the operator from light radiation using “Chameleon” filters.