Helix Technology Corporation

John T Harvell

David Edward Roche

Peter W Gaudet

Philip A Lessard

Michael J Eacobacci

Donald A Olsen

Robert J Lepofsky

Steven A Bender

Allen J Bartlett

Domenico S Sarcia

Stephen J Yamartino

Robert M Lewis

A cryogenic vacuum pump includes, in an integral assembly, temperature sensors and heaters associated with the first and second stages of the cryopumping array, a roughing valve and a purge valve. An electronic module removably coupled in the assembly responds to all sensors and controls all operations of the cryopump including regeneration thereof. System parameters are stored in a nonvolatile memory in the module. Included in the regeneration procedures are an auto-zero of the pressure gauge, heating of the array throughout rough pumping, and a change in pressure rate test to determine stall in rough pumping. The electronic module also restarts the system after power failure, limits use of a pressure gauge to safe conditions, provides warnings before allowing opening of the valves while the cryopump is operating and stores sensor calibration information. Control through a control pad on the pump may be limited by a password requirement. Password override is also provided.

Electronically controlled cryopump

Condensation on a cryopump second stage refrigerator cylinder is prevented by arranging a passageway between a colder second stage cylinder shield in thermal contact with the coldest section of the second stage and a warmer radiation shield in thermal contact with the warmer first stage. This arrangement produces a uniform and significant temperature differential in the passageway. The passageway is arranged so that the ratio of its length, L, to its width, W, is ideally greater than five. This ensures molecular collisions with the cold surface of the cylinder shield so that gas molecules are tightly bound to the cylinder shield. As a result, condensation on the refrigerator cylinder and resultant pressure variations are prevented.

Cryopump with improved second stage passageway

In a vacuum system having a load lock cooperating with a work chamber, a flow line is connected between the cryopump of the load lock and the work chamber. The flow line passes noncondensible gases which are not absorbed by the cryopump of the load lock to the work chamber 12 for absorption by the cryopump of the work chamber. Alternatively, the flow line is connected between the load lock cryopump and the cryopump of the work chamber for directly passing the noncondensible gases to the work chamber cryopump. The flow line prevents buildup of noncondensible gases within the cryopump of the load lock. The flow line may include baffles to damp pressure surges during cryopumping of the load lock. A control valve connected to the flow line allows operator control of the passing of noncondensible gases from the load lock cryopump to the work chamber or to the work chamber cryopump through the flow line. The dimensions of the flow line provide molecular flow of the noncondensible gases.

Vacuum system with molecular flow line

A stacked disc heat exchanger for a refrigerator cold finger includes a plurality of discs positioned within a cold finger cylinder and clamped to a cylinder end plate. Radial gas flow passages between the plates join inner and outer longitudinal gas flow passages. The radial passages provide a large surface area for contacting refrigeration gas and effecting efficient heat exchange with a load attached to the end plate. In a preferred embodiment the radial passages are flat grooves in the faces of discs. The stack of discs provides ease in assembly and great flexibility in designing the heat exchanger for particular applications.

Stacked disc heat exchanger for refrigerator cold finger

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Sudbury, MA, United States of America

John T Harvell