Development of the oil-free vacuum unit operating at the pressure of 150-300 Pa for the Tokamak-15

Advantages of oil-free vacuum units based on the water-ring pumps and multistage air ejectors are discussed. A set of equations describing the operation of the e ector with a conical mixing chamber is presented as well as the main parameters of the vacuum unit for the Tokamak-15 device. The unit consists of two rotational-lamellar pumps and air two-stage ejector. Limiting vacuum is 100 Pa, pumping rate is over 100 h.p. at the 300 Pa pressure. The unit can pump any gases including agreesive ones. The unit is tested with the cryostal designed for testing superconducting longitudinal field magnet coils having the working volume of about 90 m3. Pressure of about 100 Pa has been achieved for 5 hours