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Gamma-ray laser moves a step closer to reality
- londons_explore 7y agoTo me this looks like someone has used a markov chain to massage together some buzzwords into something grammatically correct... Can someone actually in the field comment on the legit-ness of this article?
- jiggawatts 7y agoThe physics appears to be kosher, but I can't speak about the practicality of such as device. I suspect it's up there with graphene in that it'll generate a lot of papers, but no industrial applications.
- hammock 7y agoIt sounds like a powerful weapon to me.
- MisterTea 7y agoWell, I can say for sure that it's gammatically correct.
- londons_explore 7y agoSurely to make a gamma laser, you at a minimum need a gamma mirror. To my knowledge, such things don't exist (current gamma mirrors aren't 'shiny' - ie. they don't reflect the light, but instead diffuse it).
- ggm 7y agoCoherence doesn't depend on the mirror, that's surely just about efficiency? I thought coherence came from quantum states of the lasing medium.
- hoseja 7y agoCoherent radiation in all directions usually isn't something that one imagines when hearing 'LASER'.
- deleted 7y ago[deleted]
- wnkrshm 7y agoCoherence is also quantifiable - e.g. how many coherent photons travel into a certain direction within a time interval. A resonator increases that amount by many magnitudes. Edit: I mean this in terms of a maximum norm. You get a smaller maximum amount of mutually coherent photons without an optical resonator.
- salty_biscuits 7y agoI dunno, interstellar masers don't have mirrors. Kind of like a one shot pass through the lasing medium.
- jhiesey 7y agoFree electron lasers generate X-rays using a single pass through the lasing medium, which is essential because you can't make good mirrors at those wavelengths either.
- JumpCrisscross 7y ago> Surely to make a gamma laser, you at a minimum need a gamma mirror No. See free-electron lasers [1]. [1] https://en.m.wikipedia.org/wiki/Free-electron_laser https://en.m.wikipedia.org/wiki/Free-electron_laser
- sp332 7y agoI really liked this talk on how free electron lasers generate such powerful pulses. https://news.ycombinator.com/item?id=16028723 https://news.ycombinator.com/item?id=16028723
- deleted 7y ago[deleted]
- yummypaint 7y agoIf you're curious about the current state of the art see the high inte sity gamma source: http://faculty.virginia.edu/PSTP2013/Talks/HIGSCapabilities_PSTP2013_v2.pdf http://faculty.virginia.edu/PSTP2013/Talks/HIGSCapabilities_... This isnt a gamma laser because the gamma rays arent coherent, but they can be polarized more than 99%. The free electron laser makes optical laser light in a big cavity with dielectric mirrors, the next electron bunch in the storage ring collides with it and scatters it up to MeV level of energy. Flux and energy resolution can be exchanged by changing the diameter of the gamma collimator and the operating mode. Its generally something like 10^7 gammas/s for energies near 15 MeV with 3% resolution.
- DoofusOfDeath 7y agoNewbie question: Aren't gamma rays just a particular frequency range of e.m.? If so, why would they be any less capable of coherence than other e.m. frequencies?
- wbl 7y agoYou can make them coherent but it's technically hard.
- yummypaint 7y agoThat is true that photons are photons, the trick is getting them to be coherent in the first place. Optical lasers use stimulated emission in some form. I presume that positronium from the article is able to somehow also undergo stimulated emission in the form of the particles anihilating and making 511 kev photons. The distinction between that and how HIGS works is that HIGS is effectively bouncing laser light off a fast moving mirror made of electrons, which actually destroys the coherence, even though the resulting gamma rays are still very similar.
- ajstonge 7y agoYou want the hulk? This is how you get the hulk!
- LatteLazy 7y agoNot that I'm opposed to speculative research but... Does anyone know any actual uses for such a device? I know the article says medical and space propulsion. But it doesn't seem well suited to space propulsion (seems like a dangerous exhaust that doesn't do anything a microwave deam doesn't?). Sorry if I'm being dull
- foxyv 7y agoI think they are referring to this passage in wikipedia? Kinda a stretch... https://en.wikipedia.org/wiki/Nuclear_photonic_rocket#Power_sources https://en.wikipedia.org/wiki/Nuclear_photonic_rocket#Power_... > "A design proposed in the 1950s by Eugen Sänger used positron-electron annihilation to produce gamma rays. Sänger was unable to solve the problem of how to reflect, and collimate the gamma rays created by positron-electron annihilation; however, by shielding the reactions (or other annihilations) and absorbing their energy, a similar blackbody propulsion system could be created. An antimatter-matter powered photon rocket would (disregarding the shielding) obtain the maximum c specific impulse; for this reason, an antimatter-matter annihilation powered photon rocket could potentially be used for interstellar spaceflight."
- echelon 7y agoThis article is a bit out of date, and I'm not in the field, so I'm not sure what we've accomplished by other means : https://doi.org/10.1063/1.3068817 https://doi.org/10.1063/1.3068817 Copying introduced some artifacts. I'm pretty sure it was OCR'd: > "We believe it is worthwhile, because of the great potential for important ap-plication of radiation with enhanced co-herence in this spectral region. In every region of the spectrum in which coherent sources exist, they have great-ly multiplied the usefulness of radiation. Gamma rays have many impor-tant applications, because of their short wavelength, high penetrating power and ability to ionize. Controllable and directable sources of such radiation in which phase as well as intensity have significance, would greatly multiply its uses." >" However, detailed speculation upon specific apdetailed speculation upon specific applications is clearly impossi-ble at this stage, because the form, per-formance, output characteristics, cost—even the existence—of a graser are obviously impossible to describe at this stage of our knowledge, beyond the few characteristics enumerated above." >" Moreover, it is well known that the most significant applications of new de-vices are rarely foreseen. No one, for example, in 1958 could have predicted the use of lasers in computers, surgery, nuclear fusion, isotope separation, and soon." > "The most exciting possibility for co-herent radiation in this short wave-length range is that of holography, which might permit direct observation of the structure of molecules, crystals, proteins, genes." As an aside, SciHub is awesome. All of these publications should be open access. I wouldn't have been able to read many of the review papers in ML and biochem crucial for developing my own understanding if not for SciHub.
- dr_dshiv 7y agoI'd hypothesize that this would be useful for producing matter + anti-matter pairs