Engineering topics

Choisser, J. P.

Publications and source records attributed to Choisser, J. P..

5 records

NASA NTRS1980

State-of-the-art Space Telescope Digicon performance data

The Digicon has been chosen as the detector for the High Resolution Spectrograph and the Faint Object Spectrograph of the Space Telescope. Both tubes are 512 channel, parallel-output devices and feature CsTe photocathodes on MgF2 faceplates. Using a computer-assisted test facility, the tubes have been characterized with respect to diode array performance, photocathode response (1100-9000 A), and imaging capability. Data are presented on diode dark current and capacitance distributions, pulse height resolution, photocathode quantum efficiency, uniformity and blemishes, dark count rate, distortion, resolution, and crosstalk.

Ginaven, R. O.↗

NASA NTRS1976

Recent progress in photoelectron image detection with CCDs

Intensified CCDs (ICCDs) were built and operated. These ICCDs were electrostatically and magnetically-focussed image tubes which use CCDs as anodes. The ICCDs detected single photoelectrons, and have electron gain very near that which was predicted. The first single-pixel pulse-height distributions were presented, and the leakage current was shown to increase as a function of photoelectron irradiation. The advantages and disadvantages of front- and rear-illuminated designs were discussed in light of differing applications requirements.

Choisser, J. P.↗

NASA NTRS1976

A photon counting array photometer

The operation and performance of an array photometer with the ability to discriminate on single photoelectrons are discussed. The system consists of a 100 by 100 array of channels which count single photoelectrons. The photosensor is an Intensified Charge Coupled Device using a Fairchild CCD201 which was fabricated by the Electronic Vision Company. This system has demonstrated a noise level which permits single photoelectron discrimination, high scan rate (400 frames/sec), and low lag. The UMAP system has been successfully operated in the photon counting mode on a 36-inch telescope and on a 48-inch telescope. Data from these observations illustrate the system sensitivity and the spacial resolution which is better defined by the size of an individual pixel element on the CCD.

Currie, D. G.↗

NASA NTRS1975

Experiments on the use of CCD's to detect photoelectron images

Image tube design and processing requirements for building an ICCD are discussed. Work is under way at EVC for building an ICCD using the Fairchild CCD 201 (100 x 100) array, and progress will be reported. Demountable tests have been made, exposing parts of a CCD 201 to 15 kilovolt electrons over five radiation levels from approximately 10 to 1 million rads. Other tubes built by EVC over the last few years which successfully use semiconductors to detect photoelectrons will be described briefly.

Choisser, J. P.↗

NASA NTRS1975

Self-scanned Digicon - A digital image tube for astronomical spectroscopy

We have successfully fabricated, tested, and operated a digital image tube consisting of a magnetically focused image intensifier tube in which a self-scanned linear array of 1024 silicon photodiodes operating in the EBS mode serves as the photoelectron image detector, amplifier, and intermediate image storage device. Integral on-chip MOS shift registers driven by an external clock sequentially interrogate the photodiodes through MOS FET multiplex switch arrays. Each output frame is a sequence of 256 analog pulses on each of four video lines. Laboratory and observing tests show that the output signal is photoelectron shot noise limited over at least a range of 1-100,000 detected photoelectrons per picture element, indicating that single photon detection is achieved. High-resolution astronomical spectroscopy has been carried out in the coude spectrograph of the 2.7-m telescope at McDonald Observatory. Examples are shown.

Tull, R. G.↗