Forget Radio! Transmitting With Neutrons

Throughout history, people have devised ways to send information across long distances. For centuries we relied on smoke signals, semaphores, and similar physical devices. Electricity changed everything. First the telegraph and then radio transformed communications. Now researchers at the University of Lancaster have demonstrated another way to send wireless data without using electromagnetic radiation. They’ve harnessed fast neutrons from californium-252 and modulated them with information with 100% success.

The setup was interesting. The radioactive material was encased in a cubic meter steel tank filled with water. A pneumatic system can move the material to one edge of the tank which allows fast neutrons to escape. A scintillating detector can pick up the increased neutron activity. It seems like it is akin to using what hams call CW and college professors call OOK (on off keying). You can do that with just about anything you can detect. A flashlight, knocking on wood, or — we suppose — neutrons.

We wondered what the practical application of this might be. The paper suggests that the technique could send data through metal containment structures like those of a nuclear reactor or, perhaps, a spacecraft where you don’t want anything unnecessarily breaching the containment. After all, neutrons cut through things that would stop a conventional radio wave cold.

It seems like you only have to prove you can detect something to make this work — it really doesn’t matter what it is you are detecting. It seems like it would be much harder to do more advanced types of modulation using neutrons. Maybe this is why we don’t hear aliens. They are all Morse code operators with neutron-based telegraphs.

50 thoughts on “Forget Radio! Transmitting With Neutrons

  1. neutrons are one thing but when you can reliably detect neutrinos and modulate the emissions of same, then you could do through planet communications and get the best possible ping times while eliminating large and complex cable networks. more neutral particle networking!

    1. Neutrinos would definitely be a way to do long distance communication, though their oscillation would be an interesting feature. Recent experiments using an accelerator at Fermilab directed a beam at a mine in Minnesota to study this effect. This path goes through the earth, so definitely feasible. The hardware required is a little daunting.

      1. Tell the stock market people what it can do for their ping times and you’ll never run out of money. You’ll have a neutrino link from Japan to New York in less than a year.

        Right now they’re setting up chains of microwave towers cross-country just to avoid the delay of beaming up to a satellite and back down (or the delay of light in fiber vs air).

        1. Someone who works for a pretty well known trading firm told me several years ago that they were working on this.

          They already made phenomenal amounts of money by building faster surface links than anyone else, so they had a very large budget for outside-the-box (and inside-the-sphere) R&D.

        2. “You’ll have a neutrino link from Japan to New York in less than a year.”

          Well, you would, if it were possible. It’s been done before, back in 2012, but the problem is that while the communication is faster by (at most) pi, the modulation and detection are always going to be much slower. Because the detection efficiency’s horrendous (like, you need an effective SNR of 1E12) the actual bit time is ridiculously longer than what you get with electronic/optical links.

          The fact that neutrinos go through anything is actually part of the problem. Think about it in terms of optical modulation – there’s two ways to do it. You can either deflect an always-on laser, or you can turn the laser on and off quickly. With neutrinos that requires either turning on/off or aiming a massive particle beam. It’s never going to be quick.

          (and yes, I’m aware that people have actually worked on these things, finding suckers is easy)

  2. Sounds like a great application for submarine under-water communication. Getting signals through the salt-water requires low frequencies, long antennas, and low bandwidth. This could change the game.

  3. So they should decay after 879 seconds right? And turn into a proton and some other particles. How far would they travel at that energy? The proton sure as heck won’t travel far with its charge. But physics is not exactly my strong suit. I just want to hear the thoughts of someone knowledgable on the subject.

    1. The average energy of Cf-252 neutrons is 2MeV, you can convert this to joules, then calculate the velocity based upon the resting mass of a neutron. This works out to 19,602km/s, giving 17,230,526km after 879 seconds or the distance covered by light in 57 seconds or 45x the distance to the Moon.

        1. Protons/neutrons have rest mass of ~1 GeV (well, “energy equivalent to a rest mass” but c’mon, you don’t measure particle masses in grams), so having an energy of ~2 MeV is 0.2% of its rest mass.

          Relativistic effects are much easier to understand when you think of energy as fractions of rest mass: the Lorentz factor’s just 1+(fraction of rest mass). So the time dilation here would be a factor of ~1.002, for instance.

          You don’t get significant relativistic effects (percent-level) until you pass 10% the speed of light because there’s a square involved.

    2. The fast neutrons mentioned travel very fast (a good fraction of ‘c’), but after thermalization (i.e., after they’ve hit a few hydrogen atoms) they are surprisingly slow: roughly the speed of sound.

    3. That’s the half-life, meaning only half of the neutrons have decayed after 879 seconds. Depending on how many neutrons you start with and how sensitive the detector is, the signal can travel considerably further.

      1. Sure there are commercial neutron generators which are compact linear particle accelerators, but they don’t give them away. I think using a fusor is more in line with the HACKADAY tradition.

  4. At $27,000,000 per gram with a half life of only 2.6 yrs, I have to question who’s funding research on californium 252. Could this money not be spent at, idk, stopping climate change?

    1. It’s a by-product of commercial power reactors. Cf and Am-Be are pretty common compact sealed neutron sources used when you don”t have a fission reactor available. Am-Be is used more often, as it is less expensive and lasts far longer, but the energy spectrum is different, and not suitable to all uses.

    2. The specific activity of Californium-252 is 2×10^13 Bq/g, and the activity of the sample used in this experiment was 11.76 MBq. The mass of the sample was therefore less than 6×10^-7 g, which, at your quoted price, would cost around $16.

  5. Neutrons > photons> electrons?

    ” …the encoding stage is carried out by a neutron chopper designed and built specifically for this purpose (Fig. 2b) comprising a polyethylene block which is shuttled into position in correspondence with the requirements of the encoded signal; the system detail showing the source, modulator (attenuator and piston)…”

    That the “modulator” is a simple plastic shutter says a lot about the immediate practicality, but this may take some interesting turns when we entangle it with some of the quantum/Qbit research. Pun intended.

  6. Nuclear reactor containment vessels are generally going to stop or severely slow neutrons unless I am mistaken. They are designed to contain radioactive matter but as a result are usually made of things like heavy concrete and thick steel. To my understanding these will slow significant neutron transmission. But perhaps if you are only going through the metal reactor vessel and receiving inside the concrete containment structure, it would be useful.

    1. Concrete needs to have a high moisture content to have much impact on neutron energy. Concrete is not used (on purpose) for neutron shielding because of the large assortment of elements in it that become radioactive due to neutron capture. When it is used as a secondary containment vessel, large amounts of boron are added to it, which purposely captures the neutrons (boron has a large neutron cross section).

  7. Ya, this sounds to pie-in-sky (not to mention too pricey) to replace nice cheap modulated electromagnetic waves any time soon. How far each travels and through what makes the comparison apples/orangey. I can just picture the next development being some talk radio network glomming on to neutron modulation. Can you propagate THAT by bouncing it around the world via the ionosphere? Oh, just picture the Rush Limbaugh show re-runs all tapped out in Morse. Wunnerful.

  8. This is the first time I have ever seen the word “scintillant” which appears to be something the scintillates in the same way as a scintillator. I wonder if it can be used as a differntiatant of multiple energies? I suppose it is common in the field today?

  9. Try “Neutrino-based communication is a first” from 2012 and “Electromagnetic modulation of monochromatic neutrino beams” from 2015 for a more likely scenario for communications links.

  10. Intriguing.
    Back in the olden days it was quite common to make neutron pulsed tubes using a specially shaped anode and cathode, using a D2 fill and a tritiated target.
    Needless to say this was generally a one shot process after which instant sunshine would occur.
    A fusor would likely work, as would some variant on a neutron tube but pretty sure that the problem here is modulating th stream.
    One way I’d do this is a superconductive plate, and run a pulsed current through it to choke off the neutron flow like a transistor as the superconductor shifts out of the superconducting state.
    Works for other radiation so why not neutrons?

    1. Pulsed neutron tubes are still around, and they commonly last up to 1000 hours at full output, so definitely not “one shot”. They’re used in oil well logging among other things. Some of the main manufacturers are Thermo Fisher Scientific in the US and Sodern in France.

      I could definitely imagine a pulsed neutron tube being modulated for data transmission.

  11. Well it would work but you’d need to use a superconductor that wouldn’t be degraded (much) by neutrons.
    MgB2 would work, as you’d simply used the isotopes that are lighter. (10B vs 11B)

  12. “It seems like it is akin to using what hams call CW and college professors call OOK (on off keying).”

    Sadly, yes. My fellow hams seem to have forgotten the original meaning of CW. CW means Continuous Wave. It’s usually a sinusoidal carrier wave.

    In the early days of radio, there also were damped waves and modulated telegraphy (AM) which carried morse signals, too, but were not “CW”.

    However, in most ham’s heads, CW equals morse telegraphy, which isn’t exactly right. Hellschreiber (Feldhell) also uses CW signals (or more precisely, on/off keying).

    It’s too late to change that, unfortunately. If hams had just kept saying “telegraphy”. *sigh*

    1. I think that’s one of those windmills you just can’t really tilt. Mine is the “DB9” connector (actually a DE9 but no one cares anymore). Of course, you can say A1A vs A2A A2J/J2A (depending on your age).

      1. Mine is the word/name ‘ham’. When I was a kid, I wanted a radio license (and eventually got it/still have it) but was really off-put at being called ‘a ham’. It came off as too nerdy even for me, a self described nerd at the time. This one syllable might be part of reason amateur radio saw such declines in the later 20th century, even before we had the internet situation.

  13. Yes, but the real trick is to entangle pairs of them and send each one in a different direction to facilitate a quantum communications link between two other parties such that the link is established at twice the speed of light. Once they have their entangled streams flowing they communicate instantly, no delay. ;-)

  14. I am amazed that no one here thought of something *SUPER* IMPORTANT: Neutron ACTIVATION! The thing you’re shooting the beam through will become radioactive in the process!

    My immediate thought was, “Why not gammas instead? No activation to worry about!”


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