3 ms·

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 ti

by jjk166 4y ago

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 4y ago
> 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 https://snoplus.phy.queensu.ca/about.html
- snophysics 4y ago
  I worked on the SNO+ experiment for grad school and actually got to go in a boat in the ultra pure water surrounding the acrylic vessel to search for leaks. It is an impressive piece of engineering to construct such a detector requiring a lot of money and effort. They actually had to bring down the acrylic vessel in pieces because the whole thing wouldn't fit down the mine shaft elevator. Then they glued them all together underground (this is no small feat since the acrylic vessel has to be optically clear for the photons to travel through to the photomultiplier tubes).
- kadoban 4y ago
  You say that like it's ridiculous, but is it? Seems pretty reasonable if a large nation wants to know where nukes are, or if a smaller one _really_ wants to know. Spies and satellite monitoring might be cheaper, but less reliable.
- Dylan16807 4y ago
  > Oh, okay, so you just want to scale this up ~200 times, and build multiple of them The equipment should only need to scale with the square of the radius, right? But sure, why not? The budget is orders of magnitude bigger. > 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. You don't need to triangulate. It's going to be in a thin shell near the earth's surface. So using more is optional.
- jjk166 4y ago
  Yeah, building a 70m diameter device is obviously going to be more expensive than building a 12m diameter device, but assuming the budget is available there's no technical obstacle to doing so. SNO+ cost about $100 million to build which is a decent bit for a science project but nothing for a military procurement project. Assuming cost scales with volume (which I am skeptical of), 200 times more expensive would be $20 Billion - about 1.5x the cost of a ford class carrier. Is knowing the location of nuclear reactors to that level of precision worth that price tag? I don't know but it's within the range that someone could make a plausible argument for it. If we assume construction takes 10 years, as it did for SNO+, then the project would represent 0.2% of the US's annual budget. And these are directional detectors, they don't need to triangulate. You can most definitely identify the location of a reactor with one detector, which is exactly what this study has done. If you were to go with multiple detectors, they can all get proportionally smaller and thus cheaper, to say nothing of potential economies of scale.

by jjk166 4y ago

dragonwriter 4y ago

> 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 https://snoplus.phy.queensu.ca/about.html

snophysics 4y ago
I worked on the SNO+ experiment for grad school and actually got to go in a boat in the ultra pure water surrounding the acrylic vessel to search for leaks. It is an impressive piece of engineering to construct such a detector requiring a lot of money and effort. They actually had to bring down the acrylic vessel in pieces because the whole thing wouldn't fit down the mine shaft elevator. Then they glued them all together underground (this is no small feat since the acrylic vessel has to be optically clear for the photons to travel through to the photomultiplier tubes).
kadoban 4y ago
You say that like it's ridiculous, but is it? Seems pretty reasonable if a large nation wants to know where nukes are, or if a smaller one _really_ wants to know. Spies and satellite monitoring might be cheaper, but less reliable.
Dylan16807 4y ago
> Oh, okay, so you just want to scale this up ~200 times, and build multiple of them The equipment should only need to scale with the square of the radius, right? But sure, why not? The budget is orders of magnitude bigger. > 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. You don't need to triangulate. It's going to be in a thin shell near the earth's surface. So using more is optional.
jjk166 4y ago
Yeah, building a 70m diameter device is obviously going to be more expensive than building a 12m diameter device, but assuming the budget is available there's no technical obstacle to doing so. SNO+ cost about $100 million to build which is a decent bit for a science project but nothing for a military procurement project. Assuming cost scales with volume (which I am skeptical of), 200 times more expensive would be $20 Billion - about 1.5x the cost of a ford class carrier. Is knowing the location of nuclear reactors to that level of precision worth that price tag? I don't know but it's within the range that someone could make a plausible argument for it. If we assume construction takes 10 years, as it did for SNO+, then the project would represent 0.2% of the US's annual budget. And these are directional detectors, they don't need to triangulate. You can most definitely identify the location of a reactor with one detector, which is exactly what this study has done. If you were to go with multiple detectors, they can all get proportionally smaller and thus cheaper, to say nothing of potential economies of scale.