Radiant energy – Inspection of solids or liquids by charged particles – Including a radioactive source
Patent
1990-11-23
1991-11-05
Berman, Jack I.
Radiant energy
Inspection of solids or liquids by charged particles
Including a radioactive source
250306, 250307, 250309, H01J 3726
Patent
active
050632930
ABSTRACT:
A positron microscope system utilizing image enhancement to overcome problems associated with low positron source flux can be operated in transmission and reflection modes. In the practice of the invention, slow positrons which are emitted after moderation of a positron source are focused, as a source beam, on a specimen target. In some embodiments, the source beam is swept over the specimen target, to effect scanning thereof. Image enhancement is effected by a channel electron multiplier array (CEMA) which may have a plurality of plates. The cloud of electrons which is generated by the CEMA in response to each incident positron is accelerated toward a long persistence phosphor screen. Image acquisition is achieved by a low light video system which delivers its signal to a memory which stores the data. The data is subsequently subjected to an image analysis algorithm which facilitates accumulation and signal averaging. In one system according to the invention, secondary electrons generated in response to incidence of positrons on a specimen target are imaged, and such imaging may employ information obtained from detection of gamma rays.
REFERENCES:
patent: 2928943 (1960-03-01), Bartz et al.
patent: 3885157 (1975-05-01), Heinemann
patent: 4740694 (1988-04-01), Nishimura et al.
patent: 4864131 (1989-09-01), Rich et al.
Zitzewitz et al., Physical Review Letters, vol. 43, No. 18, Oct. 29, 1979, pp. 1281-1284.
Rich Arthur
Van House James C.
Berman Jack I.
Monsanto Raphael A.
Rohm Benita J.
The University of Michigan
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