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For some reason I'm struggling to understand both the paper and the Ars writeup. It must be the same muon they're detecting passing through both the stationar

For some reason I'm struggling to understand both the paper and the Ars writeup. It must be the *same muon* they're detecting passing through both the stationary reference detector and the mobile one? Which generates multiple photons along its straight-line path? That must be why the nanosecond-precision clocks are so critical—to find the true coincidences and exclude everything else. And: the version with wires can navigate in real-time... but, the wireless version can only "navigate" retrospectively, because you need to link the receiver and reference to figure anything out (?). There's no (?) version of this method that lets you navigate outside of communications range, during the interval you are out of communications range.

yummypaint 3y ago
Yes, it's the same muon leaving a signal in the reference detector as in the mobile platform. Their example applications of guiding robots underground all allow for instrumenting the surface. It's not for navigating in the open ocean, but it could be an upgrade over radio based methods of guiding directional drilling heads and things like that.
chaxor 3y ago
The trick is, it's all the same muon! https://en.m.wikipedia.org/wiki/One-electron_universe https://en.m.wikipedia.org/wiki/One-electron_universe
lokimedes 3y ago
Having not read the article, nor really the Ars piece either, let me hand wave by saying that cosmic muons are produced as secondary particles emitted from a high energy collision of a primary extraterrestrial particle that collides with particles in the stratosphere (around 30km up). This shower of muons is “boosted” by kinetic energy of the primary particle. That means they have a lifetime that is longer than at rest when observed from Earth, but relevant to this method, they are also temporally correlated in such a way that by determining the time of arrival at multiple stations, the origin of the primary interaction can be determined - and more importantly, the timings between the stations can be deduced. Having fixed stations, and an unfixed one, means you can infer the latter’s position through geometric analysis.
- lokimedes 3y ago
  To actually answer you question, it is not the same muon hitting all stations, but a spray of highly correlated muons originating from the same interaction point. Philosophically, muons are considered elementary particles, and are as such considered identical particles. Though, that has no effect in this situation.
  - raattgift 3y ago
    Philosophically ... considered, what? Muons are leptons in the standard model. The ars article summarizes <https://www.cell.com/iscience/pdf/S2589-0042(23)01077-5.pdf https://www.cell.com/iscience/pdf/S2589-0042(23)01077-5.pdf>. See figure 4, which shows a photo of two scintillators (1m x 1m x 0.02m Eijen EJ-200 plastic scintillators <https://eljentechnology.com/products/plastic-scintillators/ej-200-ej-204-ej-208-ej-212 https://eljentechnology.com/products/plastic-scintillators/e...>) and a green ray representing a single muon passing through both. > it is not the same muon The green ray is not wrong because of multiple muons, but because of mutiple Coulomb scattering (MCS) within the scintillators. There is a brief overview of MCS in a muon tomography context starting at the top of the second column on the first page of <https://arxiv.org/abs/2212.04947 https://arxiv.org/abs/2212.04947>. Figures 1 and 2 therein show the trajectory of a single muon experiencing MCS within a plastic scintillator.
- SiempreViernes 3y ago
  Please don't read the article and instead just guess what they did. You are in fact entirely wrong: they use that the same muon passing trough two detectors, something that happens by chance, and you can identify by knowing the geometrical distance between the two detectors and convert to a very narrow time window during which you accept signals.
SiempreViernes 3y ago
Yeah, for some reason the Ars write-up is honouring the very poor explanations in the papers they reference...
perihelions 3y ago
Late update: I'm now convinced it's a single-muon thing, because of the paper's discussion about the distance between, and *solid angle* subtended by, the two detectors (eq. 2). If they go too far apart, the rate of individual muons that coincidentally hit both detectors drops to unusably low levels (eq. 3, the 1/D² dependence). If it were instead a "they're detecting secondary particles from the same cosmic shower" like someone proposed, this part would be totally different.
- raattgift 3y ago
  The principle is "Multiple Coulomb Scattering", and there is a nice brief overview of that in <https://arxiv.org/abs/2212.04947 https://arxiv.org/abs/2212.04947> notably in fig. 1 and fig. 2. There are even more gory details at <https://sci-hub.se/https://doi.org/10.1016/j.nima.2015.06.054 https://sci-hub.se/https://doi.org/10.1016/j.nima.2015.06.05...> (s c y h o b link to Anghel et al 2015, a Canadian muon tomography experiment interested in detecting high atomic number elements for e.g. anti-proliferation/anti-smuggling purposes).

For some reason I'm struggling to understand both the paper and the Ars writeup. It must be the *same muon* they're detecting passing through both the stationar

yummypaint 3y ago

Yes, it's the same muon leaving a signal in the reference detector as in the mobile platform. Their example applications of guiding robots underground all allow for instrumenting the surface. It's not for navigating in the open ocean, but it could be an upgrade over radio based methods of guiding directional drilling heads and things like that.

chaxor 3y ago

The trick is, it's all the same muon! https://en.m.wikipedia.org/wiki/One-electron_universe https://en.m.wikipedia.org/wiki/One-electron_universe

lokimedes 3y ago

Having not read the article, nor really the Ars piece either, let me hand wave by saying that cosmic muons are produced as secondary particles emitted from a high energy collision of a primary extraterrestrial particle that collides with particles in the stratosphere (around 30km up). This shower of muons is “boosted” by kinetic energy of the primary particle. That means they have a lifetime that is longer than at rest when observed from Earth, but relevant to this method, they are also temporally correlated in such a way that by determining the time of arrival at multiple stations, the origin of the primary interaction can be determined - and more importantly, the timings between the stations can be deduced. Having fixed stations, and an unfixed one, means you can infer the latter’s position through geometric analysis.

lokimedes 3y ago
To actually answer you question, it is not the same muon hitting all stations, but a spray of highly correlated muons originating from the same interaction point. Philosophically, muons are considered elementary particles, and are as such considered identical particles. Though, that has no effect in this situation.
- raattgift 3y ago
  Philosophically ... considered, what? Muons are leptons in the standard model. The ars article summarizes <https://www.cell.com/iscience/pdf/S2589-0042(23)01077-5.pdf https://www.cell.com/iscience/pdf/S2589-0042(23)01077-5.pdf>. See figure 4, which shows a photo of two scintillators (1m x 1m x 0.02m Eijen EJ-200 plastic scintillators <https://eljentechnology.com/products/plastic-scintillators/ej-200-ej-204-ej-208-ej-212 https://eljentechnology.com/products/plastic-scintillators/e...>) and a green ray representing a single muon passing through both. > it is not the same muon The green ray is not wrong because of multiple muons, but because of mutiple Coulomb scattering (MCS) within the scintillators. There is a brief overview of MCS in a muon tomography context starting at the top of the second column on the first page of <https://arxiv.org/abs/2212.04947 https://arxiv.org/abs/2212.04947>. Figures 1 and 2 therein show the trajectory of a single muon experiencing MCS within a plastic scintillator.
SiempreViernes 3y ago
Please don't read the article and instead just guess what they did. You are in fact entirely wrong: they use that the same muon passing trough two detectors, something that happens by chance, and you can identify by knowing the geometrical distance between the two detectors and convert to a very narrow time window during which you accept signals.

SiempreViernes 3y ago

Yeah, for some reason the Ars write-up is honouring the very poor explanations in the papers they reference...

perihelions 3y ago

Late update: I'm now convinced it's a single-muon thing, because of the paper's discussion about the distance between, and *solid angle* subtended by, the two detectors (eq. 2). If they go too far apart, the rate of individual muons that coincidentally hit both detectors drops to unusably low levels (eq. 3, the 1/D² dependence). If it were instead a "they're detecting secondary particles from the same cosmic shower" like someone proposed, this part would be totally different.

raattgift 3y ago
The principle is "Multiple Coulomb Scattering", and there is a nice brief overview of that in <https://arxiv.org/abs/2212.04947 https://arxiv.org/abs/2212.04947> notably in fig. 1 and fig. 2. There are even more gory details at <https://sci-hub.se/https://doi.org/10.1016/j.nima.2015.06.054 https://sci-hub.se/https://doi.org/10.1016/j.nima.2015.06.05...> (s c y h o b link to Anghel et al 2015, a Canadian muon tomography experiment interested in detecting high atomic number elements for e.g. anti-proliferation/anti-smuggling purposes).