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I heard that equipment that uses vacuum tubes are generally less susceptible to electromagnetic pulses than those that employ solid-state devices.
I don't know if its true, because I didn't find any detailed research about this topic.

If its true, is this because of the physical size difference between these devices, or is there another reason?


I searched about this subject, and I found an article from the Science Magazine.
I searched for the relevant parts, and it says:

Most important, the U.S. military itself had not experienced problems, since most of the field equipment and ships exposed to EMP dated from the 1940's and 1950's, their electronic systems relying on vacuum tubes.

In the 1970's, it was discovered that vacuum tubes have about 10 million times more hardness against EMP than integrated solid-state circuitry (2).

As you can see at the end, it references another article:

M. A. King et al., An overview of the effects of nuclear weapons on communications capabilities," Signal (January 1980).

After 2 hours of searching for this article, I couldn't find any traces of a Signal magazine or anything like that, released in the 80's.
I found other citations of the same article, and it has the additional author not present in citation part of the Science article, P. B. Fleming, but still, no info on these guys apart from people with the same name but entirely different professions and other irrelevant research papers.

I have some doubts about the science behind the claim that vacuum tubes are 10 million times more resistant against EMP, it kinda sounds like an advertisement from that time.


Source:

Broad, William J. - Nuclear Pulse (I): Awakening to the Chaos Factor
Science 29 May 1981: Vol. 212, Issue 4498, pp. 1009-1012
DOI: 10.1126/science.212.4498.1009

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  • \$\begingroup\$ i think it might be that arcing inside a vacuum tube might not cause damage, but too much voltage applied to a semiconductor will definitely heat it up and damage it. \$\endgroup\$ – robert bristow-johnson Oct 21 '16 at 4:51
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    \$\begingroup\$ Can't remember which MiG fighter jet had a backup computer control using miniaturized vacuum tubes. No need for anything more than the basics because all F-* jets would have crashed anyway after the atomic blast and subsequent EMP. \$\endgroup\$ – winny Dec 31 '16 at 20:12
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    \$\begingroup\$ I think Signal might be the journal of the Armed Forces Communications and Electronics Associated (AFCEA). Unfortunately, their archives are only available to subscribers, and the fee isn't cheap. en.wikipedia.org/wiki/AFCEA#SIGNAL_Magazine \$\endgroup\$ – Adam Haun Dec 31 '16 at 21:10
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Most semiconductor devices are designed to operate at low voltage, and voltages significantly higher than their design operating voltage can destroy the components very easily. You're correct that this does have a lot to do with the size - the components inside of a modern integrated circuit are so close together that even relatively small applied voltages can damage thin oxide layers and cause semiconductor junctions to break down and conduct when they aren't supposed to. Vacuum tubes are just pieces of metal inside a glass tube. Not much there that can be damaged. And they are already operating at high voltages in most cases. Electromagnetic pulses just generate large voltages within insufficiently shielded equipment. The same induced voltages are far more likely to cause trouble in solid state electronics simply due to the nature of the components.

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You just need to consider two things:

(i) The level of induced voltage

(ii) Mode of breakdown.

Semiconductors used in modern integrated circuits have a relatively low breakdown voltage. This breakdown also tends to leave permanent damage in the form of a 'punch through' failure (insulation layer or PN junction).

Also consider that the modern intergrated circuit contains millions of semiconductor devices but it only requires one of these to breakdown rendering the whole chip useless.

Valves, on the other hand, operate at much higher voltages. A flash over between electrodes is unlikely to produce any permanent damage as the insulation is a vacuum. The EMP may temporarily effect the operation of a circuit.

Internal structures of the valve are likely to be screened from the EMP by the outermost metal plates acting as a Faraday cage.

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Following up on the search for the 1980 article by King et al in "Signal" magazine: Here is the complete citation to the King article:

Capt . Michael A . King , US Army and Paul B . Fleming, "An Overview of the Effects of Nuclear Weapons on Communications Capabilities," Signal . Vol 34, No 4, January 1980, p. 60 .

Many university libraries own "Signal" magazine. You can locate these libraries by searching in Worldcat.org. Your local public library can request a free copy of this article from any university library, using what librarians call "interlibrary loan".

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I'm no expert, but I am fairly sure that it's because of the size; solid state circuitry uses very small integrated wires that are easily overloaded to the breaking point by a burst of E.M.P.. Vacuum tubes, however, are definitely much bigger (the transistor was a breakthrough because of it's size!), so it stands to reason it would take a much more powerful E.M.P. to overload it's circuitry.

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