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16 November 1982 Photon Counting Photodiode Array Detector For Far Ultraviolet (FUV) Astronomy
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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.
© (1982) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
G. F. Hartig, H. W. Moos, R. Pembroke, and C. Bowers "Photon Counting Photodiode Array Detector For Far Ultraviolet (FUV) Astronomy", Proc. SPIE 0331, Instrumentation in Astronomy IV, (16 November 1982); https://doi.org/10.1117/12.933438
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