BARS apparatus

BARS (or "split sphere", transliteration from Russian: БАРС abbreviation of Russian: Беспрессовая Аппаратура Высокого Давления «РАЗРЕЗНАЯ СФЕРА», (bespressovaya apparatura vysokogo davleniya «razreznaya sfera»), "press-free high-pressure setup «split sphere»") a high-pressure high-temperature apparatus usually used for growing or processing minerals, especially diamond and boron nitride.^[1] Typical pressures and temperatures achievable with BARS are 10 GPa (99,000 atm) and 2,500 °C (4,530 °F; 2,770 K).^[2][1]

The BARS technology was invented around 1989–1991 by the scientists from the Institute of Geology and Geophysics of the Siberian Branch of the Academy of Sciences of the USSR.^[2] In the center of the device, there is a ceramic cylindrical reaction cell of about 2 cm³ in size. The cell is placed into a cubic-shaped pressure-transmitting material, which is pressed by elements made from cemented carbide (VK10 hard alloy).^[3] The outer octahedral cavity is pressed by 8 steel sectors. After mounting, the whole assembly is locked in a disc-type barrel with a diameter ~1 meter. The barrel is filled with oil, which pressurizes upon heating; the oil pressure is transferred to the central cell. The central cell is heated up by a coaxial graphite heater. Temperature is measured with a thermocouple. The exterior size is 2.2 х 1.0 х 1.2 meters. Weight of the sphere is 2.8 tonnes (6,200 lb). Claimed energy consumption is in between 1.5 - 2 kWh.^[4]

The growth rate for 5 carats (1.0 g) type Ib (yellow, nitrogen-rich) crystals using Fe–Ni catalyst reaches as high as ~20 mg/h towards the end of 100 h growth cycle, i.e. crystals of 5 carats (1.0 g) to 6 carats (1.2 g) can be grown in less than 100 h.^[5]

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