Open AccessOn optimum illumination for channeling experiments
Author(s) -
Eades J. A.
Publication year - 1994
Publication title -
scanning
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.359
H-Index - 47
eISSN - 1932-8745
pISSN - 0161-0457
DOI - 10.1002/sca.4950160206
Subject(s) - counterintuitive , brightness , sample (material) , optics , beam (structure) , divergence (linguistics) , computer science , beam divergence , physics , beam diameter , laser beams , laser , linguistics , philosophy , quantum mechanics , thermodynamics
In experiments in which channeling effects are important, it may be desirable simultaneously to maximize the current, minimize the area of the sample that is illuminated, and, in particular, minimize the divergence of the beam. The ability to meet these incompatible conditions is limited by the source brightness. The optimum illumination in such cases is achieved by focusing the illumination on the sample. This result is, perhaps, counterintuitive and in conflict with frequently given advice “to get more parallel illumination, defocus the beam”.