University of Michigan

Arthur Rich

Bernard W Agranoff

James C Van House

Ralph S Conti

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.

Positron microscopy

An arrangement for counting detectable events, such as scintillation events in a specimen sample utilizes first and second detector elements arranged on either side of the sample. The first detector is of the type which is able to produce information relative to the position of the event in the sample. The second detector generates a timing signal responsive to the detected event. In certain embodiments, the first detector also issues a timing signal in response to the detection of the event, and both timing signals are compared for temporal coincidence, whereupon circuitry for determining the position of the detectable event is triggered. The total energy of the event can be obtained from addition of the analog amplitudes of the timing signals. In certain embodiments, the second detector also produces position information, and the first and second detectors may provide respective coordinate values of a coordinate pair.

Multi-sample scintillation counter using position-sensitive detector

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 enchancement is effected by a channel electron multiplier array (CEMA) which may have a plurality of plates. The cloud of electrons which is generated by a 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.

A liquid scintillation counter system utilizes multiplexing to monitor scintillation events in a continuously flowing effluent, using relatively few sensors, such as photomultiplier tubes, each such photomultiplier tube, in a specific embodiment, receiving light generated by scintillation events at a plurality of predetermined monitoring points along the flow path of the effluent. Each monitoring point, is coupled by means of light guides to at least two of the photomultiplier tubes. Some background noise is eliminated by use of discriminators which establish a predetermined threshold level for the magnitude of the outputs of the photomultiplier tube, above which the pulses are countable. Coincident circuitry is used to determine the presence of a scintillation event, and thereby issue a coincidence pulse which is counted. In accordance with the invention, n photomultiplier tubes can be used to monitor (n/2)(n-1) monitoring points along the flow path.

Scintillation multiplexer

A liquid scintillation counter system utilizes multiplexing to achieve monitoring of a plurality of scintillation samples using relatively few sensors, such as photomultiplier tubes, each such photomultiplier tube, in a specific embodiment, receiving light generated by scintillation events in a plurality of the scintillation samples. Each scintillation sample, which may be contained in a vial, is coupled by means of light guides to at least two of the photomultipler tube. Some background noise is eliminated by use of discriminators which establish a predetermined threshold level for the magnitude of the outputs of the photomultiplier tube, above which the pulses are countable. Coincident circuitry is used to determine the presence of a scintillation event, and thereby issue a coincidence pulse which is counted. In accordance with the invention, n photomultiplier tubes can be used to monitor (n/2)(n-1) samples.

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Ann Arbor, MI, United States of America

Arthur Rich