Method of determining the x-ray limit of an ion gauge
AssigneeThe United States of America as represented by the United States Department of Energy
InventorsDavid Edwards, Jr., Christopher P. Lanni
Life of this patent
Estimating the term…
Abstract
An ion gauge having a reduced "x-ray limit" and means for measuring that limit. The gauge comprises an ion gauge of the Bayard-Alpert type having a short collector and having means for varying the grid-collector voltage. The "x-ray limit" (i.e. the collector current resulting from x-rays striking the collector) may then be determined by the formula: ##EQU1## where: I.sub.x ="x-ray limit", I.sub.l and I.sub.h =the collector current at the lower and higher grid voltage respectively; and, .alpha.=the ratio of the collector current due to positive ions at the higher voltage to that at the lower voltage.
Claims3
A method for determining the "x-ray limit", I.sub.x, in an ion gauge of the Bayard-Alpert type having a short collector where the portion of ions collected is substantially dependent on the grid to collector potential, comprising the steps of:
- (a) measuring the collector current, I.sub.h, at a first, higher potential;
- (b) measuring the collector current, I.sub.l, at a second, lower, potential;
- and
- (c) determining I.sub.x by the formula:
- ##EQU6## where .alpha. is the ratio of the collector current due to positive ions at said first potential to the collector current due to positive ions at said second potential.
Dependencies are inferred from the claim text.