Acousto-Optics, Optical Computing, and Signal Processing - Applied Optics Fundamentals and Device Applications - page 146

the crosstie memory, and eliminates the problems associated with electri-
cally addressed readout.
3.12.4 Radiation Hardening Considerations
Radiation environments in which such a memory may be required to sur-
vive are a strong function of the particular system deployment. Tactical
man-operated systems are required to survive only modest ionizing dose
rates, low accumulated doses and low neutron levels, with man being the
limiting factor. Strategic ground-based systems are required to withstand
sharply higher levels. Space-based systems with no nuclear weapon envi-
ronment must survive only the natural Van Allen belt energetic electron
and proton environments, which may range up to several tens of kilo-
rads (Si0) depending on the orbit and the duration of the mission. Military
systems in space must survive the nuclear weapon environments of high
ionizing dose rates, high accumulated doses and neutron fluences. The
system memory requirements in terms of organization, power, speed, etc.,
will all be different in each of these applications; but in general will tend
toward higher speed, low power, high density, nonvolatility, and low soft
error rates.
The optical read crosstie memory discussed affords all these features in
addition to nuclear hardness. Since the optically read memory is inherently
free from soft errors, there will be no need to increase the word length to
allow for error detection and correction. Normally, 5 bits of a 16 bit word are
utilized for double error, single error correction; so an immediate savings
of 30% of the memory size and power supply requirement is realized. The
radiation environments in which memories may be required to survive vary
with application, but may include ionizing dose rates in excess of 10 12 rad
(Si)/s, total accumulated doses of up to 10 7 rad (Si), and neutron fluences of
up to 10 14 n cm −2 .
References
1. Oakley, W. S. October 1979. Acousto-optic processing opens new vistas in sur-
veillance warning receivers. Defense Electron . 11:91-101.
2. For the relations between index change and acoustic power, see: Pinnow, D.
1970. Guidelines for the selection of acoustooptic materials. IEEE J. Quant.
Electron . 6:223-238.
3. Korpel, A. January 1981. Acousto-optics—A review of fundamentals. IEEE Proc .,
Vol. 69(1):48-53.
4. Chang, I. C. March 1986. Acousto-optic channelized receiver. Microwave J .
29:142, 142-144.
5. Oakley, W. S. Acousto-optic processing opens new vistas. Defense Electron .