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Proceedings Paper

Photon Counting Photodiode Array Detector For Far Ultraviolet (FUV) Astronomy
Author(s): G. F. Hartig; H. W. Moos; R. Pembroke; C. Bowers
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Paper Abstract

We have developed a compact, stable, single-stage intensified photodiode array detector for photon-counting, far ultraviolet astronomy applications. The intensifier, constructed by ITT, employs a saturable, 'C'-type MCP (Galileo S. MCP 25-25) to produce high gain (≈106) pulses with a narrowly peaked pulse height distribution. A high efficiency, opaque CsI photocathode is coated directly onto the MCP input surface. The P-20 output phosphor exhibits a very short (≈10μs) decay time, due to the high current density of the electron pulses. We are currently coupling this intensifier to a Reticon RL1024-SF self-scanning linear photodiode array, with 1024 - 25μ x 2.5 mm tall diodes. This device has a fiber optic input window which allows direct, rigid mechanical coupling with minimal light loss. Initial testing has been accomplished using the driver circuitry supplied by Reticon, followed by a 4 bit ADC and DMA interface with an HP 9845 desktop computer. The array was scanned at a 250 KHz pixel rate. The detector exhibits more than adequate signal-to-noise ratio for pulse counting and event location. Event location algorithms that compute the pulse centroids to 1/2 diode width accuracy have yielded detector spatial resolution limited by the MCP channel spacing (32μ). Designs for a fast amplifier/clock driver circuit and a bit-slice microprocessor device for real-time photon event location are now being implemented. We anticipate that the short phosphor decay time and use of a fast, dedicated microprocessor for event location will permit rapid scan speeds and hence large dynamic range. The small physical size, stability, insensitivity to environment, low bias voltage, wide dynamic range and independent pixel properties combine to make this detector very suitable for space flight astronomy applications.

Paper Details

Date Published: 16 November 1982
PDF: 8 pages
Proc. SPIE 0331, Instrumentation in Astronomy IV, (16 November 1982); doi: 10.1117/12.933438
Show Author Affiliations
G. F. Hartig, Johns Hopkins University (United States)
H. W. Moos, Johns Hopkins University (United States)
R. Pembroke, Johns Hopkins University (United States)
C. Bowers, Johns Hopkins University (United States)

Published in SPIE Proceedings Vol. 0331:
Instrumentation in Astronomy IV
David L. Crawford, Editor(s)

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