Cryogenic pump having maximum aperture throttled part

Low temperature pumping apparatus comprising,

• a cryogenic pump of the type having a chilled outer surface wall for first stage pumping of gases condensable at medium temperatures and a chilled inner surface wall for second stage pumping of gases condensable at low temperatures, said pump having a port facing a process chamber being pumped, and
• a radial vane throttling valve disposed across said port in a manner such that the valve throttles said port, said valve comprising,
• a group of N radially disposed vanes adapted to open and close said port with (N-1) vanes being mechanically linked for joint motion to a first coupling means supported near the port for communicating opening and closing motion from outside the pump to the (N-1) vanes and an Nth vane being independently linked to a second coupling means associated with the Nth vane for communicating opening and closing motion from outside the pump to the Nth vane, and
• control means operating the (N-1) vanes and the Nth vane independently of each other for providing coarse valve control by the (N-1) vanes and fine control by the Nth vane.

Low temperature pumping apparatus comprising,

• a cyrogenic pump of the type having a chilled outer surface for first stage pumping of gases condensable at medium temperatures and a chilled inner wall surface for second stage pumping of gases condensable at low temperatures, said pump having a port facing a process chamber being pumped, and
• a radial vane throttling valve disposed across said port in a manner such that the valve throttles said port, said valve comprising,
• an annular flange having a continuous inner peripheral surface and a spaced apart, outer peripheral surface connected to the inner peripheral surface in a gas barrier relation between opposed side walls,
• a plurality of movable vanes disposable in a common plane closing the inside of the annular flange, said common plane parallel to the flange side walls, said vanes radially mounted for rotational shutter-like movement out of said common plane by inclining on an axis out of said common plane,
• a plurality of rotatable shims having an outer toric surface, matching the curvature of the inner peripheral surface of the flange and having a rotational support means for connection to the inner peripheral surface of the flange, each shim having a support side connected to a vane for transmitting shim rotation to a connected vane and further having rim means for transmitting rotational motion to rim means of adjacent shims, and the shims arranged in an endless rim-to-rim motive communication relation,
• coupling means supported in the flange from the outside peripheral region to the inside peripheral region for communicating rotary motion from outside the flange to one of the shims.