EDWARDJ@RMC.BITNET (01/17/90)
Sorry if this comes in a little late. With the Christmas hiatus in SPACE
Digest, I just got caught up with the last 1.5MBytes of it!
A while back, Robert Casey asked a question about work on vacuum integrated
circuits. Leonard Ericson replied to the effect that some work had been done
in the 60's, but implied that interest had died off. Well, not quite. There is
a lot of interest in these things today, which are rad hard like nobody's
business, and mechanically robust to boot. One article I read described vacuum
IC's being exposed to 1e17 n/cm^2 with no degradation in performance. 1e16
would toast most silicon based circuitry. They also ran some of these inside a
furnace at 500C - for 13,000 hours! (That's what the article said, though I
find a year-and-a-half a bit hard to believe!)
There are apparently two kinds of vacuum IC's - thermionic integrated
circuits, and field emission vacuum devices. (Dammit Jim, I'm an
archaeologist, not an electrical engineer! I don't know what any of these
words mean...) Research is apparently being carried out on these things at GEC
in Britain, at Livermore (why would they be interested?), and Jupiter
Technologies in Austin, TX. (Any people from Jupiter listening?) Lots of other
companies too, I'm sure.
I don't have an extensive bibliography on the subject. The two articles
that come to mind are: B.C. Cole, Electronics, v62 no12 (1989) p.74-77, and
D.K. Lynn et al., IEEE Trans. Nucl. Sci., vNS-32 no6 (1985) p.3996-4000.
What I have read suggests that vacuum IC's would be ideal for harsh, high
radiation environments, including space applications. The Van Allen belts, the
neighbourhood of Jupiter, and close (relatively) approaches to the sun should
cause less degradation in their performance than in semiconductor based IC's.
Does anyone know of active research on space based applications of vacuum
IC's? (Now, if only we could get vacuum based solar cells...)
Jeremy Edward
EDWARDJ@RMC.BITNET
Disclaimer: I'm always dangerous when I don't know what I'm doing.