|MadSci Network: Physics|
Actually, my last lab is still studying exactly what these people are talking about. All the same isotopes, and the same stimulated emission process. However, it's not a gamma-laser. The somewhat fluid definition of a laser no longer means just what the acronym says (L.ight A.mplification by S.timulated E.mission of R.adiation), but implies a coherent source of light. Generally, the laser light itself stimulates the emission of further light of the same wavelength, making it coherent. What they're talking about is just pumping a nucleus with a low-energy X-ray to allow it to release energy stored in a higher-energy metastable state as a gamma ray. You can't make that coherent radiation, but you can use it to release stored energy (with very expensive isotopes, .5 g of the best test isotope we could find we *rented* from Oak Ridge National Lab for $100,000/year...purchasing would have cost millions for just that half a gram of Hf). What these people at UT are talking about is an old concept in nuclear physics, namely the nuclear battery. The military is interested, because it removes the restriction of storing and transporting fuel. With the right semi-short-lived isotopes, you could make sure it became non-radioactive in a few weeks in case it fell into the hands of terrorists. But the wavelengths for MeV gamma rays are far too short to create coherent light out of with any conceivable present technology. In theory it might be able to be done (as a superradiant laser, because the previous answerer was correct about there being no mirrors for gamma rays), if you could achieve energy densities in the lasing material of well above the energies being released at the exploding core of a nuclear weapon. You would need such high densities to overcome all the parasitic processes that would prevent you from achieving population inversion in the lasing medium (for examples, you can google search on "pair production," "Compton scattering," and the photoelectric effect). In short, if anyone does it within 50 years I'll be really surprised. Even beyond that it will require currently unimaginable technologies to achieve, but you never know. Go to grad school in nuclear physics, maybe you'll find a way someday.
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