The compensation of instabilities in charged-particle beams

Instability in the beam 10 of an electron microscope or other high- resolution instrument arises from externally induced periodic noise and lateral drift. The effect of the instability is measured directly in terms of the focal quality of the image while compensating waveforms are superimposed on th...

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Bibliographic Details
Main Authors MICHAEL MING-YUEN CHANG, KENNETH CHARLES ARTHUR SMITH, STEPHEN JUSTICE ERASMUS, PHILIP ATKIN, DAVID CHAMBLISS
Format Patent
LanguageEnglish
Published 30.10.1985
Edition4
Subjects
BASIC ELECTRIC ELEMENTS
ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
ELECTRICITY
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Summary:Instability in the beam 10 of an electron microscope or other high- resolution instrument arises from externally induced periodic noise and lateral drift. The effect of the instability is measured directly in terms of the focal quality of the image while compensating waveforms are superimposed on the instrument supplies and varied to restore the optimum focal quality. Focal quality at a screen 14 is continuously assessed by means of camera 20 and unit 21 which measure the variance of brightness in a succession of images. In response to the value of variance, a programmed computer 23 instructs a power supply unit 24 to produce waveforms of mains and harmonic frequencies and of EHT oscillator frequency, and to follow an iterative routine of steps in magnitude and phase until a desired value of variance is observed.
Bibliography:Application Number: GB19850009648