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Initialization of Input Power Levels in Granular Chrome Evaporation System

IP.com Disclosure Number: IPCOM000076803D
Original Publication Date: 1972-Apr-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Hanlon, JS: AUTHOR [+4]

Abstract

Establishing a stable initial evaporation input power level in a granular chrome evaporation system -- wherein the chrome reaches vapor phase by sublimation -- is complicated by variations in size and shape of chrome source, in amounts and kinds of impurities, in tolerable variations in carrier resistance, and in operator differences in loading. Furthermore, since vaporization proceeds by sublimation rather than through a more gradual intermediate phase of liquification, the system must be brought convergently to the desired operating condition if stable control is to be achieved rapidly.

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Initialization of Input Power Levels in Granular Chrome Evaporation System

Establishing a stable initial evaporation input power level in a granular chrome evaporation system -- wherein the chrome reaches vapor phase by sublimation -- is complicated by variations in size and shape of chrome source, in amounts and kinds of impurities, in tolerable variations in carrier resistance, and in operator differences in loading. Furthermore, since vaporization proceeds by sublimation rather than through a more gradual intermediate phase of liquification, the system must be brought convergently to the desired operating condition if stable control is to be achieved rapidly.

Stable yet efficient power buildup is achieved by monitoring out-gassing pressure at intervals of approximately 1 second and stepping source power from a nominal low-threshold level in increments of 5 amps, at intervals of approximately 15 seconds, while the monitored outgassing condition is below a preset value representing stable operational levels. When outgassing pressure reaches the correct level representative of stable operation, source power is held constant until the pressure decreases below a second predetermined level indicative of complete outgassing.

Conveniently an IBM 1800 Process Control System is employed in the initialization system control loop to monitor and store outgassing data, and to provide appropriate control of source power adjustment. After the stable state is reached further c...