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Comment Re:Really? (Score 4, Interesting) 1354

Yes, yes, it's Slashdot and supposedly the blind leading the blind on this question. r-d-r-r. I get it. But I've been enjoying this site for a full decade now (late 20s) and I find that whenever these sorts of non-tech/science questions come up, the responses are often some of the most highly thoughtful and interesting on offer. So as long as we're all here and considering justshootme's question of "where do you meet fellow geeks -- preferably including some of the opposite gender", I would like to ask about fellow geeks interested in meeting the SAME gender for said purposes implied in the original question. I find that this exceptionally difficult, as there are very few other gay dudes willing to tolerate discussions about supersymmetry or the history of thermodynamics or mediaeval history for more than a few milliseconds at most. Should I resign myself to the fact that my demographic is simply to narrow and settle? I am beginning to think so.

Comment Re:Let me hi-jack this to ask a serious question.. (Score 1) 97

It's literally entirely harmless. Tritium is a pure beta emitter (electrons). The maximum energy of a beta particle from a decaying T atom is 18.6 KeV. A beta particle of 18 KeV can penetrate no more than about 5mm in air or 6-7 MICROmeters in water (or your skin). Exactly zero beta particles are escaping the phosphor coated glass ampoule (let alone the plastic outer case). ok so now what about bremsstrahlung. Well the percent of incident 18 KeV betas on the glass ampoule that actually produce bremsstrahlung is VERY low, 0.1% at absolute most and remember, the number of betas emitted that are >than even 15 KeV is VERY low (few percent). This ampoule likely contains about 10 millicuries of T or ~370 million betas emitted per second. We can assume (extremely) roughly that 10K X-rays of >15KeV are produced every second from this source then. The half value layer of 20 KeV x-rays is 1mm for aluminum, so 3mm of aluminum will block ~90% of a 20 KeV x-ray source, I assume the thickness (mass) of the glass of the ampoule and the lucite plastic is at least roughly equal to 3mm of Al so now we're down to 1,000 x-rays per second emitted isotropically (500 per second toward you, ~half of which would be absorbed merely while penetrating your skin alone). Even this, though it's very tiny, has got to be a ridiculous over estimate. How do I know? Because fortunately someone has taken the time to measure the emanation from a HUGE tube of this sort taken from an emergency exit sign. What did he find? It was giving off 60 counts per MINUTE of x-rays. An utterly, totally trivial amount of radiation. You will get thousands of times this sort of dose from cosmic rays on a half hour plane ride.

Comment Re:192 lasers? (Score 2, Informative) 97

Well you probably should be unimpressed by the project from the point of view of power generation, since it was never designed with the objective of generating power in mind. And in the very long term I DO think this is going to be cheaper than fission since its fuel source is water an pinch of lithium. Additionally, it will burn radioactive waste from fission plants.

Comment Re:What's it sound like? (Score 1) 97

The noise is very unique. If you are near the laser bay the noise you hear is a LOUD BANG from the thousands of enormous Xe flashlamps going off simultaneously. The capacitor bay that discharges to fire the lamps produces deeper thud. The noise that comes from the target bay is very different. It's very similar to the quick fsss you hear when opening a can of soda (minus the click), but louder and more resonant. I suspect this has to do with the fact some residual IR light is absorbed by the backplanes of the turning mirrors, so this noise may not be present on all ICF lasers. The target in the implosion chamber itself can make almost no noise at all or a moderate muffled bang, depending on the target type and laser energy used for the shot. there used to be a recording of the GEKKO XII system in Osaka firing, but that site is gone now.

Comment Re:192 lasers? (Score 4, Informative) 97

Those Wired pictures are nice and all but if you want wallpaper, why don't you just go to the source, LLNL's Flickr page? As an aside, as someone who works at the US's other major laser fusion facility (there aren't many, I'll leave it to you to figure out), I can tell you that all the scaled implosions we've been doing for the past 10 years here validate the expectation that NIF will achieve fusion ignition, burn, and high gain when they go to 2MJ cryogenic DT ice implosions next year. We are extremely excited. This will be the first time nuclear fusion breakeven and ignition will have been achieved in a laboratory. I want you to think for a little while about what the long term implications of fusion energy on technologically advanced human civilization will be. I still don't think very many people realize that this experiment is a MAJOR step in that ultimate goal.

Comment Re:This capability has been around for 20 years (Score 4, Interesting) 71

NIR would be inappropriate for this application. If you're looking for contaminant poisons in drinking water you need to have exquisitely sensitive detection thresholds in the part per billion level. A NIR spectrometer using conventional (quartz) fiber optics would be forced to look at the second and third overtones of the fundamental molecular absorption lines in the mid-IR. These overtones have a mere thousandth or hundredth of the relative absorption intensity as the fundamental lines and therefore your signal for extremely low concentrations of contaminants is going to be waaaaay below the noise in your detector. NIRS is best suited for detection of percent level deviations in chemical mixtures, not trace analysis. What this guy from Israel has done is use drawn fibers of silver chloride/bromide, which have spectacular transmittance in the mid-IR, to detect the fundamental absorption bands of trace contaminants using the evanescent waves of IR light that poke slightly outside the surface of a fiber optic. I wish I could find his latest paper that this press release is about though.....

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