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Comment by Kapura | Hacker News Reader

I'm no scientographer, but it seems to me that a dependence on helium may be a stumbling point for getting cheap vacuum transistors to the market. The ongoing helium shortage[1] is driving the price of helium up which could make helium-based vacuum transistors expensive, limiting widespread adoption. It could be that high-speed helium vacuum transistors become a speciality product for those projects that feel the need justifies the additional cost.

[1] http://www.decodedscience.com/helium-shortage-situation-upda...

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Intuitively, this makes sense at human scales.

But microprocessors are tiny. The i7 4770, which is in my machine right now, has a die size of 177mm^2. The die has a thickness of 775um, for a volume of ~137mm^3.

Even if you made the whole processor out of helium, you could make 100,000 of them out of a single 14 liter party balloon.

The Zeppelin NT, which holds 8225m^3 of helium, contains enough for 60 billion high end processors.

Well, let's see, a modern chips die size is on the order of 300mm^2. Let's be generous (I think) and call it 5mm thick. A single helium canister can contain around 300 cubic feet of helium [1]. Those are nasty units to work with by hand, but https://www.google.com/search?q=%28300+cubic+feet%29+%2F+%28... suggests one such cylinder would be enough for 5.5 million new chips, assuming the entire chip was just helium. You can probably safely add at least two more entire factors of magnitude for the fact the chip will still mostly be silicon (or something), my gut suggests 3 or 4 is probably even closer.

Oh, sure, there will be losses and such, but this is still a trivial expense next to the billions of dollars of fab work that will be required. In these quantities we literally use gold without hardly a second thought for price.

[1]: http://www.praxairdirect.com/Product2_10152_10051_14626_-1_1...

300mm^2 * 5mm = 1.5 milliliters

24k Gold is 42$/gram, 1 gram is 0.052 milliliters.

So, 42 / .052 * 1.5 = 1,211$.

Note: The important parts are not 5mm thick etc, but gold is rather expensive by volume.

Sorry, by "these quantities" I meant "at computer-chip quantities" in general; gold we pretty much use by area, and not much of that, either. The numbers I gave were purposely quite generous for volume. After all, I did say they were probably 3 or 4 orders of magnitude too generous. Per reitzensteinm's post, looks like you can recover another 1.5 or so out of my chip-height estimate, too.

If I understand the basic premise, then other mostly stable and abundant gases (like Nitrogen, or even air) could probably be used as well, if the transistor size and voltage are small enough. (That's wholly conjecture, though. I also am not a sciencer).

> That is, you don’t, in fact, need to maintain any sort of vacuum at all for what is nominally a miniaturized piece of “vacuum” electronics!

According to the article, if the device is small enough it doesn't require helium or a vacuum.

"And we’ll have to devise proper packaging methods for these 1-atmosphere, helium-filled devices."

Actually it does require helium, but no vacuum.

And vacuum, at least comparatively soft vacuum, isn't a big deal either. I've got functional vacuum tubes around here older than I am.

"For example, the mean free path of electrons in air under normal atmospheric pressure is about 200 nanometers, which on the scale of today’s transistors is pretty large."

It doesn't require helium; helium is just a bit better.

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