Performance of Au transmission photocathode on a microchannel plate detector.
X-ray framing cameras, employing microchannel plates (MCPs) for detection and signal amplification, play a key role in research in high-energy-density physics. These instruments convert radiographic x-rays into electrons produced by plasma during such experiments into electrons that are amplified in the channels and then detected by a phosphor material. The separation of detection from signal amplification offers potential improvements in sensitivity and noise properties. We have implemented a suspended Au transmission photocathode (160 A thick) on a MCP and are evaluating it using a 1.5 keV Al K alpha x-ray source. We find an approximately twofold increase in the ratio of detected events to incident photons when the photocathode-to-MCP voltage difference is sufficiently large. Our calculations indicate that this increase is probably caused by a combination of signal produced by the photocathode and an increase in the efficiency of detection of x-rays that reach the MCP surface through modification of the local electric field.
Lowenstern
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ME
University of Michigan, 2455 Hayward Street, Ann Arbor, Michigan 48109, USA.
Harding
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Huntington
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CM
Visco
A J
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Rathore
G
G
Drake
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RP