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Automatic Sublimation Pump Controller

IP.com Disclosure Number: IPCOM000080483D
Original Publication Date: 1973-Dec-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Gupta, SK: AUTHOR [+5]

Abstract

Described is a self-correcting titanium sublimation pump controller which permits unattended operation, maximizing filament life and minimizing pump down time, and providing responsive action to large unanticipated pressure changes. Sublimation pumps (usually using titanium) are useful for pumping getterable gases (H(2), N(2), O(2), CO, CO(2), & H(2)O) in the pressure range 10/-3/ to below 10/-10/ torr. They may be operated continuously or cycled on-off. To minimize the shroud cooling requirement, and maximize the life and utilization of the sublimating source (filament), cyclic operation is preferred.

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Automatic Sublimation Pump Controller

Described is a self-correcting titanium sublimation pump controller which permits unattended operation, maximizing filament life and minimizing pump down time, and providing responsive action to large unanticipated pressure changes. Sublimation pumps (usually using titanium) are useful for pumping getterable gases (H(2), N(2), O(2), CO, CO(2), & H(2)O) in the pressure range 10/-3/ to below 10/-10/ torr. They may be operated continuously or cycled on-off. To minimize the shroud cooling requirement, and maximize the life and utilization of the sublimating source (filament), cyclic operation is preferred.

The optimum cycle is a function of the pressure. At high pressures (approx. 10/-4/ torr) the source should be on most of the time, i.e., continuously, and at very low pressures, (approx. 10/-10/ torr) it need be on a few minutes every 10 - 20 hours. However, it is undesirable to have to open a vacuum system to change the sublimating source. Further, it is difficult to adjust the correct power input and time of a sublimating source filament, since its characteristics vary with time.

Described below is a controller which automatically alters the on-off cycle of the sublimation pump as a function of pressure. In one form, the controller cycles through a fixed sequence of on-off cycles once a selected pressure was obtained. This sequence is previously determined for the particular system. Alternatively, it is possible to sense the pressure with an ion gauge or ion-pump and select an off time based on the...