Nuclear radiation used to transmit digital data wirelessly | Hacker News Reader

Nuclear radiation used to transmit digital data wirelessly

lancaster.ac.uk

202 pointssizzle154 comments

In case someone else is wondering, they modulated the neutron beam by pneumatically moving a polyethylene block in front of the Californium source which sits inside a one cubic meter water tank and can be pneumatically moved close to one of the walls for activation. The data rate was about one bit every ten seconds.

At this bitrate, and over short distances - maybe 1m, a rotating permanent magnet (or a powerful electromagnet) could also be competitive. It wouldn't work for anything with a high magnetic permeability (like iron) but for non magnetic metal or water a static field would penetrate at least a short distance, enough to go through a wall.

(BTW, I've imagined that in the distant future, we'll have gravity wave generators and detectors that don't have the same constraints as EM based data transmissions. I don't know how realistic this is.

Reminds me of that paper I read a long time ago, about how we could detect advanced alien civilizations by analysing pulsar signals. The hypothesis was that they would put massive devices in orbit of pulsars to modulate their high energy signals to use as ultra long range communication. Presumably pulsars would be the only strong enough carrier wave.

Now I'm imagining a future where some modulated binary star merger is being used to stream episodes over Netflix.

Hopefully we manage to find a way to miniaturize things.

Imagine waiting hundreds of years for the new episode to reach your distant star system

Really you only have to wait one week for each episode to reach you.

What would the throughput be on something like that?

But we already have gravity wave generators. E.g. I’ve just generated some by waving my arm!

Please prove it by measuring the resulting gravity wave :-p

I'm holding out for neutrino based communication: https://physicsworld.com/a/neutrino-based-communication-is-a...

The interesting bit I picked up from that article is “A neutrino could easily pass through 1000 light-years of lead, so an ocean would pose no problem whatsoever.”

That is crazy no wonder they are so hard to detect.

This will blow your mind.

https://en.wikipedia.org/wiki/Super-Kamiokande

>Mounted on an inside superstructure are about 13,000 photomultiplier tubes that detect light from Cherenkov radiation. A neutrino interaction with the electrons or nuclei of water can produce an electron or positron that moves faster than the speed of light in water, which is slower than the speed of light in a vacuum. This creates a cone of Cherenkov radiation light, the optical equivalent to a sonic boom. The Cherenkov light is recorded by the photomultiplier tubes

> A neutrino interaction with the electrons or nuclei of water can produce an electron or positron that moves faster than the speed of light in water, which is slower than the speed of light in a vacuum.

This is the important but I think confusing part for many people.

The electron/positron is not moving "faster than light" (nothing can) it is moving faster "than the light" in that specific medium (water).

It is moving faster than light, but c, the "speed of light" constant, is only called that because it's the speed of light in a vacuum and water isn't a vacuum. The constant c is actually a fundamental constant of our universe relating spatial and temporal dimensions, which is why going faster isn't possible (that's time travel) but the velocity of photons in one medium or another is just an observable fact like the viscosity of a particular brand of jam.

Two parts really blow your mind:

- the images are stunning, especially if you search for "super kamiokande boat"

- even with 50 kilotons of water they record just tens of events per day: https://www.slac.stanford.edu/econf/C0805263/Slides/Raaf.pdf

This is interesting .. https://www.abc.net.au/news/2019-06-17/inside-super-kamiokan...

And they had an unfortunate incident[1] resulting in the loss of 7000 out of the 11200 photon multiplier tubes.

Incompressible fluids are no joke.

[1]: https://www.nature.com/articles/35106691

A gravity wave occurs at the lowest of the lowest of low frequencies. In order to produce such a wave the object resonating would have to be many many miles long and be stronger than any material known to man as well as incredibly heavy. Think of a very long cable woven from a neutron star. That’s about what it would take :)

The concept has of course been written about a fair bit on science fiction. The dark forest trilogy comes to mind and used a gravity wave generator built into the hull of a massive ship whose purpose was to alert alien life to the existence of the earth.

A string made of collapsed matter. You could pluck it like a guitar and it would vibrate with gravity waves. As long as nothing else on earth was as dense as the string, the gravity waves would propagate easily through ordinary matter like sound waves through air.

I was wondering, thank you! Surprised the article didn't bother with even a sentence to explain this.

I figured it was something like a trombone mute. Not sure why that was the image I got of how they did it.

This sounds like a line from the turbo encabulator.

> This sounds like a line from the turbo encabulator.

In case you're one of the lucky 10,000:

https://www.youtube.com/watch?v=Ac7G7xOG2Ag

That's about the same speed I get when I run out of "high speed" data on my mobile phone plan.

Don't see why they can't improve it to use a piezoelectric material to modulate the neutron beam. That would achieve a far higher data rate.

Presumably because the neutrons are only emitted sporadically.

Sounds like a more radioactive version of smoke signals.

The paper is here: https://www.sciencedirect.com/science/article/pii/S016890022...

Key takeaway here is novel fast neutron generators [1] that are flat and electronically modulated, so they are potentially good for data transmission through metallic vessels (ship hulls for example) that doesn't require vessel penetration and isn't heavily regulated like californium isotopes.

The researchers wanted to demonstrate the data transmission in practice, but used a more conventional setup instead (a Cf-252 source mechanically modulated by a HDPE slab).

[1] https://ieeexplore.ieee.org/document/6275497

> electronically modulated

Is it really electronic modulation when the modulation is handled by pneumatically moving a polyethylene block? I would call that mechanically modulated. Electronic modulation would be, say, a transistor switching the output on/off.

[1] in the post above links to a different paper (referenced in OP), which describes exactly that. The researchers in the OP used mechanical modulation instead (which is far less interesting)

Could they have used a Farnsworth fusor as a neutron source and electrically modulated it at radio frequencies?

For those wondering, will not really work over long distances (> 100 m) since fast neutrons will thermalize quickly in air and other materials. This means they scatter around approaching a random walk and lose energy, which makes the transmission beam harder to detect.

This is really mostly feasible for ~single wall transmission.

How far can you go until the losses are over 160 dB? Reason I'm asking is that LTE Cat-M (low-bandwidth IoT) go that low, or lower [0]. GLONAS (GPS) receivers deal with over 180 dB of loss [1]. It depends on the power level in the transmitter, and how well the receiver can lock on to very faint, but expected, patterns in the noise. One of the tricks is to re-transmit, sometimes literally thousands of times.

[0] https://www.altair-semi.com/wp-content/uploads/2017/02/Cover...

[1] https://en.wikipedia.org/wiki/DBm -- Satellites transmitting +55 dBm, receivers seeing -127 dBm.

The neutrons used here have a maxwellian energy distribution associated with fission. A single bit will contain neutrons with energies from nearly thermal up to a few MeV. These neutrons are not relativistic at all. For reference a 1 MeV neutron travels a meter in about 70 ns. This means the spread in the neutron spectrum and the transmission distance will conspire to place a fundamental limit on the data rate. Can't have neutrons from neighboring bits mixing together too much. This doesn't even include intermediate scattering which will make things harder.

Not great for long distances unfortunately, as your source will always be isotropic. One could also do this with neutrons with either 241am alphas on beryllium modulated electronically, or with d2 beam incident on d2 target, or proton beam on a tritiated titanium foil target. All should allow for faster modulation. The beam based methods also allow for control of the outgoing energy.

Great insight for us laymen. Curious, how are you so knowledgeable about such an esoteric topic? are you a nuclear physicist or…?

They have Q clearance(1), at least.

(1) https://news.ycombinator.com/item?id=29204027

I don't want to hate on this research but my first thought was "well duh of course you COULD but why WOULD you?" This is basically just Morse code with a neutron source. That this is possible is obvious to anybody with a passing familiarity with nuclear engineering, but equally clear is the lengthy list of downsides. Just because nobody has done it doesn't make it novel.

This is no doubt meant as a proof of concept and an electronically controlled neutron generator would solve some of the problems, but I still can't think of any use for this that isn't better solved some other way.

> I still can't think of any use for this that isn't better solved some other way.

What about this?

"In some safety-critical scenarios, such as concerning the integrity of reactor containments, and metal vaults and bulkheads in maritime structures, it can be important to minimise the number of penetrations made through such metal structures for communications cabling. The use of neutrons for information transmission through such structures could negate the need for such penetrations and is perhaps also relevant to scenarios where limited transmissions are desirable in difficult circumstances, such as for emergency rescue operations."

Well what about mechanical waves /sound waves. I mean we are talking about rates of less than a bit per second. Just have a small hammer ping your metal container. Will go much further is much cheaper and can easily do a higher data rate.

More moving parts than an electrically-modulated neutron source. But this was my first thought as well.

Piezoelectrics?

Acoustic was also my first thought. Neutron generators are quite complicated and relatively delicate. Meanwhile acoustic transducers (e.g. piezo) are super simple and low power.

Piezoelements would work well. Not really a moving part in the traditional sense, with worn surfaces from friction.

The danger zone for humans is smaller though.

You can probably do something with optical communications through a thick, leaded glass window, depending on your containment needs.

The ‘safety critical maritime structures’ they are talking about are probably pressure hulls on nuclear submarines. They are well equipped to handle radiological material and really want to be quiet.

That's still more than a bit of a stretch considering the drawbacks, such as making that vault or bulkhead material radioactive even after the neutron beam has been shut off. In practice the duraction of the induced radioactivity varies considerably depending on the material; just hope it's not an alloy that includes cobalt.

Yeah I read that, but it's not going to be good for that. For one thing that isn't going to work in a nuclear reactor core because the neutron background is orders of magnitude higher than any neutron generator could hope to produce. For the other uses they mentioned... I mean like I said there's no reason it wouldn't work (over short ranges) but there are simpler solutions that don't involve [very dangerous] neutron radiation. Plus a neutron generator requires a decent bit of power to run (they're basically a compact particle accelerator) so you're back to needing a vessel penetration. And the idea that such a device would be useful for emergency rescue operations is frankly silly.

I know nothing about nuclear energy but I immediately thought about the Tokamak. The article said it could be useful for scenarios where penetration of a wall of a device would be problematic. I thought I wonder if the Tokamak had the need to be sealed in some way and being able to send a signal inside it wirelessly would help. Maybe they need a completely sealed room but they also need to trigger a switch but no one can be in the room and typical communication can not penetrate it. You just need one bit to make it through to flip that switch from a 1 to a 0. This would be the perfect device. Ya I know that probably has no use for the Tokamak and I can’t think of a scenario where you need a completely sealed device with no holes but still need to send a signal inside. Like in the article they also mentioned submarine communications. You sound smart but surely if they could just do other forms of communication they would have already the US military budget is massive. Currently subs float a device to the surface so they can talk. The article says this slows them down and risks exposing them. Beside the couple mentioned in the article already I’m sure there has to be more use cases someone smarter then your or I can see.

Neutron transmission is not useful in any of these scenarios. Not in a fusion reactor because a fusion reactor produces a ton of neutrons itself, many orders of magnitude higher than any transmission you'd be able to make so it'd be drowned out (most neutron generators use fusion to produce neutrons too so they're probably also at similar energies to what the reactor makes). Plus the problem with the inside of a tokamak vessel is that it's a super extreme environment and not much can survive in there and like I said in another comment you still have to power your neutron generator.

Neutrons are also relatively short ranged and more-or-less isotropic in emission (not able to be focused effectively), meaning you need really high fluence (=dangerous) to transmit more than a few meters. For submarines, water actually attenuates neutrons extremely quickly making it completely useless there. And also let's not forget that neutrons activate materials and make them radioactive for long periods even after you stop with the neutrons. For totally sealed rooms there are better solutions (e.g an acoustic transducer). On top of all this, the physics of neutrons mean this will always be very low bandwidth.

None of the applications mentioned in the article are remotely credible, IMO, and this is my area of expertise. Perhaps there is some application where this is the best solution. My point is that at best it's extremely niche; the article makes it out like this is revolutionary but it is definitely not nor is it even particularly interesting. This is not military research with an intended application, this is someone slowly moving a block of plastic back and forth in front of a californium source in a university lab and a press release declaring victory. The actual article published by the scientists in NIM is much more reasonable, but the one linked here is greatly playing up the utility.

A fairly reasonable analogy that captures some of the downsides of using neutrons for this is that you could also transmit information by shooting at a metal plate with a pellet gun and having someone listen for the pinging sound. Sure it's possible, but the list of drawbacks is pretty long.

Next step: move from CW(code word) to CDMA. Hedy Lamar owns the patent on CDMA with punch cards but you could own the neutron patent.

CW is "continuous waveform" not "code word" at least in the context of radio and is probably the only way this can work. You can't really modulate neutron energy/frequency with any sort of fine control, so most of the fancy techniques with radio waves are out. CDMA is sorta possible, but bandwidth is always gonna be low.

>241am alphas on beryllium modulated electronically

sounds like a primitive logic gate to me :) One can imagine a self powered logic circuits built along this way.

If you're allowed an accelerator, perhaps something like https://en.wikipedia.org/wiki/ISIS_neutron_source if not in a confined space.

That could be a fun activity for Boy Scouts; one boy, standing outside of the concrete shed, is watching a geiger counter, and the other sends Morse Code by moving a leaden lid up and down on a sample of Plutonium.

There was a nuclear badge in the boys scouts, and one kid actually got it, to the dismay of his mother.

More generally, had nuclear not been demonized as part of the fear of mutual destruction ideology (I’m not saying it was wrong), maybe we would have lived in a parallel world where tinkering with radioactive elements would have been more widespread, and innovation wouldn’t have stalled for 60 years. Maybe we’d have a lot of nuclear-in-a-box batteries by now.

https://en.wikipedia.org/wiki/David_Hahn

The article doesn't state what distance they were able to transmit over.

During the Cold War, I've heard rumors of one directional communication system with submarines using neutrinos.

I don't know what the utility of the system described in the article though - neutrons will be absorbed pretty quickly, so the communication must have a very short range.

It takes something like 18 light years of lead to attenuate a neutrino beam by half, so they’d need a pretty big receiver :)

It's possible to detect neutrinos with a scintillation chamber, but in general only a tiny fraction of neutrinos passing through would be observed. They really don't interact with regular matter much.

However, it's the transmitter that would be nearly impossible, because blocking neutrinos or affecting them in such a way as to modulate the beam would be extremely difficult.

I think we can probably rule out neutrino based communications during the cold war, especially since VLF did the job just fine.

The "rumor" referred to an array of scintillators dragged behid the submarine, with the ocean water as a detecting medium. In theory, with clear enough water and large enough detector volume, that idea might work. I vaguely recall data rate of less than one bit per second.

That sounds a lot like the ELF radio system they used, which basically was used to order submarines to surface (or near enough) to receive new orders as the bandwidth was <1 baud.

https://en.m.wikipedia.org/wiki/Extremely_low_frequency

The data-rate would be far below 1 bps. The event-rate in SuperK [1] from the Sun was ~0.1/day/kiloton of water.

Signalling to submarines would require a Fermilab or T2K-caliber accelerator with an ability to direct a beam, with a properly-oriented pion-decay hall, generally in the known direction of the submarine and highly-synchronized clocks (or a clever time-structure strategy) to allow coincidence-detection for background-suppression.

For scale, the MINOS detector [2] detected a couple thousand events with a couple of years of beam-time.

[1] https://en.wikipedia.org/wiki/Super-Kamiokande#/media/File:N...

[2] https://arxiv.org/pdf/1103.0340.pdf

Sure you can detect neutrinos that way, especially at higher energies. But you're going to be swamped by natural neutrinos (e.g. atmospherics), unless you have quite the beam. And how do you know where to point the beam?

Modulating neutrinos is easy. You just control the production rate. For example ramping a fission reactor up and down will create pulses of neutrinos (though it's not terribly efficient). For practical neutrino communications, you'd want to use a muon beam to generate your neutrinos. The neutrinos are emitted roughly in the same direction the muons were moving when they decay, so you can make a directional beam, and by controlling the number of muons decaying at any given point in time, either by directly controlling the number of muons or how much time dilation they experience in the beam, you can ramp up and down neutrino production.

For that modulation to be reflected in the detection array, the beam would have to be accurately targeted on the submarine?

How could a nuclear-powered submarine possibly host a neutrino detector? You're sitting meters away from one of the brightest neutrino sources on the planet!

please see my comment below in this thread.

“… using neutrinos”

“… neutrons will be absorbed…”

I made the same confusion for a second. Neutrons are easily absorbed. Neutrinos (little neutrons) are almost impossible to interact with (and therefore absorb)

Yea, I'm curious about this as well and what bit rate they were able to achieve. Wondering if it could be used for high frequency trading in the future since I would think neutrons going straight from source to destination would be faster than any other communication method (no idea if this would be too dangerous or not tho).

I would be very surprised if neutrons travel faster than a microwave beam.

Radio waves already travel at the speed of light, I'm curious what speed-up you're imagining? A shortcut through the earth is the only option I can think of to beat radio's latency.

Yeah, you would significant time on some routes (e.g. NYC to Sydney or whatever), but in practice, the modulation time is probably going to kill you even if the neutrinos make it there faster. In the most extreme case (antipodal communication), the neutrinos take 43 ms to traverse the Earth and radio takes 67 ms to go around the Earth (ok, in practice a bit more since your fastest path would be via LEO satellites, and each hop adds a bit of latency, but it could be made small). But RF signals have MHz-GHz of bandwidth and huge SNR.

To take advantage of being 20 ms early, you'd need to be able to detect neutrinos at greater than 50 Hz from the other side of the world. For context, the planned 40 kton DUNE far detector a mere 1300 km from the world's most powerful neutrino beam at Fermilab, will have a neutrino rate from the beam of a few a day. So yes, highly impractical.

If you managed to crack the detection problem, you’d still likely be so saturated with solar / background neutrinos as to confound any real prospect of a signal.

There are two handles on this: reconstructing the energy/direction and making sure it's consistent with the beam and gating on the beam duty cycle (since at least the beams I'm familiar with produce neutrinos in short bunches, but I'm no expert).

You can also add modulation to the beam to encode more information to help discriminate against backgrounds but that might require even more rate...

You're taking about neutrinos, but the original comment was about neutrons; I think that must add another layer of infeasibility (or was a typo).

indeed, a sibling was talking about neutrinos and somehow I got mixed up where it started.

Radio waves in a vacuum travel at c. They move more slowly in things like copper. Light in fiber cables travel at about 2/3 c so a neutrino beam would be faster and potentially have a shorter distance by going through the earth. Actually designing and implementing a communications system using neutrinos is an exercise left to the reader.

With neutrons, no. They’re slow, isotropic and thermalize easily.

With neutrinos that’d be a different story. They travel at the speed of light (or just below it - depends who you ask) and they aren't readily absorbed by anything. Therefore they can travel through the earth instead of around it.

Problem?

Generation, modulation and detection of neutrinos.

> They’re slow, isotropic

Not necessarily, if produced with an accelerator. (Potentially a nuisance to gamma-ray spectroscopists, generating spurious anisotropic scattering peaks.) Otherwise, yes.

https://arxiv.org/abs/1203.2847

Yep, I was still asleep, good call.

As many have pointed out, this doesn't seem practically useful. However, if you add an "i" and flip the "n" and "o" on that messenger particle, I could see it being greatly useful.

Neutrino communications could travel into every nook and cranny, very fast and far indeed.

The radiation in the article is modulated by shielding and deshielding the neutron source. How would you modulate a neutrino?

That's the question and precisely what would make it novel and interesting.

If you can easily modulate the source of your signal as is the case with the neutron source, it becomes as uninteresting as morse code.

Neutrino beams are produced by having a muons circulate in an accelerator with long straight sections. As the muons decay, they release neutrinos moving approximately in the same direction the muon was. You modulate the neutrinos by modulating the muon beam. The simplest way to do this is to introduce or take away muons from the beam, but another option is changing their energy. Muons have a half life of approximately 2 microseconds in their inertial reference frame, but from the standpoint of an observer, relativity can make them seem to live much longer. Decrease the energy to the beam energy such that they're moving slower and it is as if their half life decreases, causing them to decay more frequently and thus produce more neutrinos.

The real issue is the detection end. Because of how little neutrinos interact with matter, you need a lot of neutrinos to pass through a detector before you can expect to see a signal, and then you need to distinguish that signal from noise.

Could we simply use another muon beam as a detector?

No, neutrinos are simply a decay product, and in fact there isn't anything particularly special about a muon beam, neutrinos are a common product of many reactions, muons are just convenient because they don't cost much energy to produce and form into a beam, and they decay quickly while still living long enough to be useful.

Neutrino detectors work because there is an astronomically small but non-zero chance that a neutrino emit either a Z or W boson. A Z boson can hit a nearby electron, accelerating it, or a W boson can decay into a fast moving electron, either of which can be observed in various ways. There's no way to prompt this behavior, but if you're watching enough matter while enough neutrinos are passing through, eventually you'll see some events. The number of events are proportional to how many neutrinos are passing through, so if you see a large number of events in a short period of time, you know something has sent a pulse of neutrinos.

That said, you could most certainly have a muon beam neutrino detector located at the same site as a neutrino detector, allowing you to both send and receive messages. Because the neutrino beam is highly directional, it won't interfere with the detector.

You don't modulate the neutrino beam itself, but you could modulate the pion production beam. For typical neutrino beam experiments this is done with a large magnetic horn which focuses/defocuses (+/-) charged pions which then decay to (anti)neutrinos and (anti)leptons. By changing the current in the horn you could modulate the intensity of the beam to send data.

Needless to say this is woefully impractical, would require an extremely large neutrino flux and detector, and would have an absolutely abysmal bit-rate. Not to mention you'd likely only be able to send messages in one direction. But it could be done.

see: https://www.fnal.gov/pub/today/archive/archive_2014/today14-...

It was actually demonstrated (over relatively short distance) using the MINERvA detector at Fermilab: https://arxiv.org/abs/1203.2847

Why modulate it at all? Just use CW.

There is speculation about usage of neutrinos for wireless financial trading faster than ground lines. One could transmit information in straight line without having to bother with earth's curvature.

Why not use a laser?

Neutrinos would go right _through_ the earth. Can't get a shorter path than that!

I already have an existing IPoAC/RFC1149 connection, can I run this one simultaneously or would it cause too many drops on the old line?

Speaking of mechanical devices to selectively obstruct radiation ...

I had a manager who is a clever fellow. He used some construction toy with electrical motor abilities to rig together a test apparatus whereby a mobile device was placed into a steel cooking skillet, and the apparatus was periodically lifting the lid.

This caused the device to go into and out of mobile coverage, allowing for testing of in-and-out-of-coverage transitions, and reproducing problems reported with respect to them.

Imagine a neutrino based communication system. It could always take the shortest route: a straight line thru anything, the earth for example. No connections but probably huge transmitters and receivers.

https://cerncourier.com/a/long-distance-neutrinos/

This seems like non-news? They're just using the amplitude of neutron emission to encode data. This isn't unique at all to radioactive decay - they're basically just using AM radio tech over radioactive decay instead of radio waves. It doesn't provide any benefits, it's more just a "neat!" thing.

Is this really a good idea? Also reminds me that neutrons will degrade a material over time:

https://en.wikipedia.org/wiki/Neutron_embrittlement

Don’t high velocity neutrons irradiate the materials they go through? I would imagine this could lead to interference in long lived installations. Also how would this be safe in a maritime environment?

Submarine communication. Acoustic signals can be detected at VERY long distances. These signals cannot.

Spy communication from inside a nuclear facility.

This sounds like something Cave Johnson would do. "Science isn't about 'Why?', it's about 'Why not?'"

Electrostatic positional modulation of a heavy water droplet ultrasonic suspended over the aperture of the radiation source?

Now I actually wonder how to do it over a wire. That is use nuclear radiation to transfer data...

But won't the range be limited by neutron decay?

Thermal neutrons move at approximately 2000 m/s, with a half life of about 612 seconds. Decay is a non issue but scattering does put some limits (mean free path of a 14 MeV neutron in air is about 140 meters), though if your goal is just to get a signal through a wall you don't need particularly long range.

252G?

That sounded a lot like U-235 or U-238 (I only know that because of Dan Brown's book where "the difference is three", for those that get that reference, so that's like my level of physics understanding right there). Not sure how to get to Californium's radioactive, um, configurations, I typed U-235 into Wikipedia, found a link to "isotopes of" which listed all of Uranium's, then near the bottom was a handy table with all the "isotopes of" links to other elements, Californium's code is apparently Cf so I found the right link and... 252 has a note saying "most common"! I think I get your reference :D but also, while typing this I realized I probably took the long way of getting there... indeed, re-opening the article, it's also right there, heh.

In Soviet Russia all email radioactive.

neutrino messaging was mentioned in The Hummingbird Project... Good movie

So we can be assured of internet coverage even in the case of a nuclear holocaust? Google and Facebook are launching the balloon based service and selling ads tomorrow :)

On a serious note what can the practical implications be to f this?

In essence, they have invented the cellphone that actually causes cancer ;-)

I've heard there's a lot of prior art.

Neutron bombardment is unhealthy, but it was never used for communication until now.

I mean about a cell phone that causes cancer, it's too late to patent that.

We used to do this by opening a port in the shield over an x-ray source and detecting it with the predecessor of digital x-ray sensors back in the lab, sending morse code.

I was imagining a Monty Python scene where someone was using two halves of lead, like coconuts, and slamming them repeatedly over the radioactive material.

Shades of the Demon Core.

The Demon Core also came to my mind when reading GP's comment. For those unaware, the Demon Core was a piece of radioactive material and received its name after two people died in different accidents while experimenting with it on criticality .

https://en.wikipedia.org/wiki/Demon_core

0.1 Baud? Hah!

It raises the question... Why? It's not practical and very unwelcome for many obvious reasons. Like really in what environment does it make sense to introduce radiation just for the sake of data transfer?

Space?

“In some safety-critical scenarios, such as concerning the integrity of reactor containments, and metal vaults and bulkheads in maritime structures, it can be important to minimise the number of penetrations made through such metal structures for communications cabling. The use of neutrons for information transmission through such structures could negate the need for such penetrations and is perhaps also relevant to scenarios where limited transmissions are desirable in difficult circumstances, such as for emergency rescue operations.”

I don't buy it. Clearly one has to run power to this transmission device. Once you've drilled a single hole for this all it takes is one tiny wire to vastly exceed the data capacity of this system. You could probably even send data at far higher bitrate over the existing power cable itself.

Why is that obvious? Couldn't they use an RTG to power the device without the need for a wire?

Though... it does seem like a piezoelectric transducer, or even a relay, could transmit an audio signal through a solid metal bulkhead much more efficiently.

Submarines often track each other via noise. I don't think you want to make noises loud enough to be heard through a solid metal bulkhead on a regular basis, since the same will likely be true outside the submarine. Those bulkheads are also structural components, I believe, so the metal is quite thick, and the sound would likely echo through the submarine and drive the sailors mad.

You don't need to penetrate the wall if you have power sources on both sides of the wall.

Use a magnet instead then. Flip it over with the pneumatic arm.

Probably military applications too if it evades conventional detection.

There can be many innovative use cases in industry or military applications where wires cannot penetrate the surface of an object and other signals are too weak to penetrate the object to transmit data about something mission critical.

This warrants future investigation at the very least, however impractical it may be. Quantum computers may also benefit from this technology, etc.

It would be interesting to see what places some other alternative like sound, light, laser, VLF, etc, aren't viable options.

I believe the theoretical throughput of a modulated neutrons is very very high - substantially higher than the electromagnetic waves we send today.

Given that, perhaps the people of 1000 years from now will be using them to do data transfer because electromagnetic waves are far too primitive and low bandwidth.

On the basis of what physics?

Just because it doesn’t have any immediate applications right now doesn’t mean it won’t in the future.

The first trans-atlantic telegraph message took 16 hours to send.

You’re basically right.

Miners trapped in a cave not penetrated by E&M waves?

Wont work.

Signal from inside a reactor?

No. No logic can modulate the signal in said reactor that isn't destroyed by the radiation.

If you have a pneumatic arm to modulate this thing, use it to flip a magnet. That’ll better penetrate any shield than neutrons.

Why wouldn't it work for the miners or the reactor?

Neutrons pass through rock quite well.

Reactors are basically just giant neutron transmitters, by modulating reactor output you also modulate their neutron output.

Flipping a magnet definitely won't penetrate a shield better than neutrons, in fact because of Gauss' law it probably won't penetrate at all.

Rock’s absorption of neutrons doesn’t matter. Neutron thermalize. Since rock has mostly low atomic weight isotopes, it thermalizes them very well [1]. Once they are thermal they scatter easily.

Gauss’ law is for the electric field. The magnetic field is very difficult to block and we have incredibly sensitive magnetometers (probably ones that can detect magnetic anomalies of a submarine from space)

In fact, thats pretty much how deep submarine communication works very low frequency fields. Thats why I proposed a magnet: a basically static field that cant be blocked.

Is my proposal practical? Well, typically not. But if the alternative is neutron communication, I dont see why not.

[1] to a first approx think of thermalizing as momentum exchange upon collision. If you’re similar in mass to the colliding mass you’ll exchange more momentum. Assuming rock is mostly silicon, w/ a mass 28 times larger than a neutron. And there’s at least a km of rock above miners.

[2] throttle a reactor to modulate neutron? Oh boy!

EDIT: actually the crust is mostly oxygen, atomic mass 16. That only strengthens my argument.

Nothing's going through a kilometer of rock, but if you have a few meters of blocked tunnel, neutrons will go through that just fine. If you actually had a kilometer of rock between the miners and help, the miners are dead.

https://en.wikipedia.org/wiki/Gauss%27s_law_for_magnetism

Flipping a dipole is literally just radio.

How do you think nuclear reactors are controlled? Nuclear reactors can vary their power output at a rate of tens or even hundreds of MW/minute. While it takes special designs to throttle at high enough speeds for load following, to send a signal you only need to change the power output enough to be detectable by a neutron detector, which need only be slightly greater than the variation due to random noise.

I like to point at the signal fire in lord of the rings. Absurdly elaborate communication system that can only one shot a single bit. But it's far far faster than any alternative. And if both sides understand the meaning of the message, it could be worth it.

I could see a regular pulse being a useful monitoring system for (whatever they care about). no pulse, send help.

You don’t have to use a fictional example of a signal fire... it was used in ancient China to send exactly this message: “Send the army”

Neat! I didn't know, thank you!

Although the beacon system (technically a form of semaphore) could likely have been much better optimized.

For example, if a single pyre went unattended or was otherwise unable to light their fire (for example say an orc band attacked it), the whole system would fail, and there would be no way of knowing that it had failed. Consider also the possibility that one of the teams may have been able to light their fire, but for fear of drawing enemy attention to themselves, choose not to. Same effect. A more failsafe option would be to have the fires constantly burning with the light being cut off as the signal bit. This could be accomplished quickly and easily by having some shutter that drops down and blocks the fire's light. If one of the stations were abandoned or damaged, its fire would go out, alerting the network that something was amiss. This also means that the cowards who don't want to alert orcs to their position need only stop tending their station when in danger, and they are free to flee.

Of course once you have some shutter in place to quickly block out light, you can presumably raise and lower the shutter. With an appropriate protocol, you can essentially achieve a visual telegraph. If each station maintains two fires, you can achieve bi-directional communication. This is also good for eliminating false positives for the main alert function if one fire just goes out for some reason.

It's interesting that real life semaphore systems like Phryctoria or the Byzantine Beacons did not implement fail-safe methods.

Logistically, fail-safes are expensive. Keeping a fire burning for days and years takes a lot of firewood, which in turn requires manpower. Having two fires also places limitations on the distance they can be due to the angular resolution of the human eye. That'd be anywhere from 5-10 miles on basic assumptions. A signal fire can be seen from farther if you have the elevation and a smoke signal doesn't even require that (+ carries more information).

"Please don't post shallow dismissals, especially of other people's work. A good critical comment teaches us something."

https://news.ycombinator.com/newsguidelines.html

(We detached this subthread from https://news.ycombinator.com/item?id=29203516.)

Got it, though it wasn't meant as a dismissal...just surprise.

Ah. These things don't always come across.

This is probably the tech that drives the Pip-Boy

It's a smoke signal.

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