Apparatus and method for monitoring the intensities of charged particle beams

摘要

Charged particle beam monitoring means (40) are disposed in the path of a charged particle beam (44) in an experimental device (10). The monitoring means comprise a beam monitoring component (42) which is operable to prevent passage of a portion of beam (44), while concomitantly permitting passage of another portion thereof (46) for incidence in an experimental chamber (18), and providing a signal (Im) indicative of the intensity of the beam portion which is not passed. Calibration means (36) are disposed in the experimental chamber in the path of the said another beam portion and are operable to provide a signal (If) indicative of the intensity thereof. Means (41 and 43) are provided to determine the ratio (R) between said signals whereby, after suitable calibration, the calibration means may be removed from the experimental chamber and the intensity of the said another beam portion determined by monitoring of the monitoring means signal, per se.