[HN Gopher] Evidence of Antineutrinos from Distant Reactors Usin...
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Evidence of Antineutrinos from Distant Reactors Using Pure Water at
SNO+
Author : PaulHoule
Score : 35 points
Date : 2023-04-12 19:34 UTC (3 hours ago)
(HTM) web link (phys.org)
(TXT) w3m dump (phys.org)
| LargoLasskhyfv wrote:
| ISTR something about that from a few years ago, and thinking
| about the eventual possibility about triangulating nuclear subs
| and carriers with a network of such 'sensors'. Through the whole
| earth, maybe. In real-time.
|
| Wouldn't that be something?
| lapetitejort wrote:
| Governments can easily guard against this by encasing their
| nuclear subs in a 11 trillion km diameter lead sphere.
| treeman79 wrote:
| Trick is getting it to stay a 11 trillion km sphere. Has a
| habit of turning into a black hole.
| [deleted]
| matthewdgreen wrote:
| More seriously I assume there's a team at a US National
| Laboratory working out the parameters for building such a
| sensor, and (if they're even remotely practical) another team
| figuring out how many false sources would be needed to
| hopelessly confuse it.
| openasocket wrote:
| To do that you would need the sensor to provide either the
| distance or direction of the "signal," right? Does this
| actually do that? Given how unreactive neutrinos are I can't
| imagine there being much decay or defraction or distortion over
| distance. Can this experimental sensor produce a direction that
| the neutrinos are coming from?
| dragonwriter wrote:
| > To do that you would need the sensor to provide either the
| distance or direction of the "signal," right?
|
| It was specifically called out that one of the things this
| relied on is that their detector method provides an estimated
| direction. OTOH, when you have to integrate a half year of
| data to detect _any_ signal, triangulation of non-stationary
| sources, especially if there is more than one potential
| source, is going to be...beyond difficult.
| jjk166 wrote:
| You can integrate the same amount of data in less time by
| increasing the size of the detector. With a detector 182.5
| times greater in volume (which is only 6 times the radius),
| you only need a day's worth of data - still probably not
| useful for targeting but now you know the search area to
| look within. You can also build a network of multiple
| detectors, which in addition to increasing the amount of
| data you collect also makes it easier to differentiate
| signals. For a nation state this would be chump change.
| dragonwriter wrote:
| > With a detector 182.5 times greater in volume (which is
| only 6 times the radius), you only need a day's worth of
| data
|
| Oh, okay, so you just want to scale this up ~200 times,
| and build multiple of them (deep underground, because the
| water is shielding for the ambient radiation from the
| rock, which it has a couple km of shielding it from
| _external_ radiation):
|
| "The heart of the SNO+ detector is a 12m diameter acrylic
| sphere filled with 780 tonnes of liquid scintillator that
| is surrounded by 7000 tonnes of ultrapure water which
| serves as shielding from external ambient radioactivity.
| This volume is monitored by nearly 10,000 photomultiplier
| tubes (PMTs) that are very sensitive light detectors."
| [0]
|
| > You can also build a network of multiple detectors
|
| Well, yes, you can't triangulate with only one detector,
| you _have_ to do that at a minimum. That's not an "also
| you can" option, its a minimum requirement because you
| need multiple _simultaneous_ (or close enough) signals
| from the same source to triangulate.
|
| [0] https://snoplus.phy.queensu.ca/about.html
| jjk166 wrote:
| Yes, when neutrinos do react (rare though that is) it
| produces electrons that move in the same direction as the
| neutrino, and which move at extremely high speed, faster than
| the speed of light in the medium in fact, which produces
| cherenkov radiation. This radiation is what the sensors
| actually detect. Essentially they are giant cameras looking
| for brief streaks of light. By seeing how long and in what
| direction the streak is, you can determine both the direction
| and energy of the incoming neutrino.
| snophysics wrote:
| In this case they are detecting inverse beta decay events.
| The antineutrino interacts with a proton producing a
| positron and a neutron. The positron annihilates with an
| electron producing two gamma rays and the neutron then
| captures on a proton and releases a 2.22 MeV gamma ray
| which is what is being detected. I think the only realistic
| way to determine the direction is by looking at the
| direction of the neutron, but typically the neutron
| scatters so much in these detectors that it is not possible
| to do on an event by event basis (although see [0] for a
| possible detector that could).
|
| What you're talking about is elastic scattering and I think
| this may be possible (see [1]), but I don't know of anyone
| who is able to do this at these low energies.
|
| As a side note, the WATCHMEN collaboration has been
| studying the ability to monitor nuclear reactors using
| these sorts of detectors for a while.
|
| [0] https://arxiv.org/pdf/1410.8530.pdf [1]
| https://www.osti.gov/servlets/purl/1332127
| bumby wrote:
| By any chance, do you have any suggestions for further reading
| on this topic?
| LargoLasskhyfv wrote:
| Not exactly. I can't even remember where I've read that. Most
| probably on some (pop-)science aggregator like phys.org, or
| similar. About a few times, popping up again several years
| later. Then somewhere else on some blogs, maybe even scmp.com
| firstlink wrote:
| It would indeed be something. Neutrino-based sensors are seen
| sometimes in hard science fiction. I always assumed that was a
| little implausible because of the compounding problem of
| neutrinos interacting poorly with the target and with the
| sensor. But here we are, a stone's throw from making such
| sensors a reality, albeit looking for sources rather than
| shadows.
| PaulHoule wrote:
| This turns up in Vernor Vinge's
| https://en.wikipedia.org/wiki/The_Peace_War
| dragonwriter wrote:
| We've had neutrino sensors for a half century. They just tend
| to be inconveniently sized and located.
| PaulHoule wrote:
| Popular article here: https://phys.org/news/2023-04-sno-
| collaboration-evidence-ant...
| dang wrote:
| Thanks! It's great to have both links, but in cases like this
| where the material is highly specialized (and not on a topic
| like computing that the audience here is familiar with), it's
| usually better to submit the best available popular article and
| then link to the paper in the comments. I've switched to that
| from https://arxiv.org/abs/2210.14154 now.
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