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Gamma-Ray Bending Opens New Door For Optics
sciencehabit writes "Lenses are a part of everyday life—they help us focus on words on a page, the light from stars, and the tiniest details of microorganisms. But making a lens for highly energetic light known as gamma rays had been thought impossible. Now, physicists have created such a lens, and they believe it will open up a new field of gamma-ray optics for medical imaging, detecting illicit nuclear material, and getting rid of nuclear waste."
... and irradiated spiders that bite school children who become photographers
While this is an interesting deveopment, it is important to note the caveats: The refractive index in silicon, the only material tested so far, is only 1.000000001. IF this theory of how this is accomplished is correct, this MIGHT be higher for heavier elements. That's a big IF.
those were the good old days when we still though gamma rays gave you super powers instead of cancer
when you think to yourself "I know, I'll mention something obscure that people will need to look up on Wikipedia to know wtf I'm talking about!", you might want to double-check that Wikipedia doesn't contradict your claim.
Humph. Next thing you'll be telling be cigarettes aren't a health giving natural way to relax
I want a list of atrocities done in your name - Recoil
Agree. Even if you do it with depleted uranium, and you suppose the "virtual electron effect" increases in proportional to the square of the number of protons in the nucleus, you might get an index of refraction in the ballpark of n = 1.000000033. Applying the lensmaker's formula, a convex lens with radii of curvature of 1 cm will have a focal length of ....
150 kilometers.
So the gamma ray imaging camera you want to build for airport security will have to be roughly the same size as your flight. No, not the length of the plane, the mileage.
don't tell TSA or they'll gamma nuke everybody until they glow.
Actually, gamma rays can be used to cure cancer rather than give you it - they are part of some radiotherapy regimes.
When I had a month of radiotherapy many years ago, it had a kind-of reverse Hulk effect though - rather than turning green, bulking up and gaining mega-strength, I went sunburn-red, dropped 30 pounds and needed to sleep up to 16 hours a day.
"I bless every day that I continue to live, for every day is pure profit."
I'm somewhat more hopeful than you, based on advances in x-ray optics.
For typical x-ray photons (e.g. 10 keV), the refractive index is 0.99999 (delta = 1E-5). Even though this is very close to 1, we've figured out how to make practical lenses. For instance Compound Refractive Lenses use a sequence of refracting interfaces to accumulate the small refractive effect. Capillary optics can be used to confine x-ray beams. A Fresnel lens design can be used to decrease the thickness of the lens, giving you more refractive power per unit length of the total optic. In fact, you can use a Fresnel zone plate design, which focuses the beam due to diffraction (another variant is a Laue lens which focuses due to Bragg diffraction, e.g. multilayer Laue lenses are now being used for ultrahigh focusing of x-rays). Clever people have even designed lenses that simultaneously exploit refractive and diffractive focusing (kinoform lenses).
All this to say that with some ingenuity, the rather small refractive index differences available for x-rays have been turned into decent amounts of focusing in x-ray optics. We have x-rays optics now with focal lengths on the order of meters. It's not trivial to do, but it can be done. It sounds like this present work is suggesting that for gamma-rays the refractive index differences will be on the order of 1E-7, which is only two orders-of-magnitude worse than for x-rays. So, with some additional effort and ingenuity, I could see the development of workable gamma-ray optics. I'm not saying it will be easy (we're still talking about tens or hundreds of meters for the overall camera)... but for certain demanding applications it might be worth doing.
Well, yeah, except that all of the bending occurs at the interface surface. So in principle, one could stack 150 lensing surfaces constructed Fresnel-style and bring that right down to a kilometer. Depending on what the "interface surface" is for gamma rays. Or, stack 1500 of them and bring it down to 100 meters. Or stack 15,000 of them, in a 3D structure created with e.g. molecular beam epitaxy, and bring it down to 10 meters (with a lens with a total length of perhaps a meter). At that point it is conceivable that it might be useful, although probably not as an optical grade lens (wouldn't it be uber cool to build a gamma ray telescope with an aperture lens a meter across? Sure it would!)
I think that a lot of these same principles are involved in building x-ray lenses -- the lens is less like a glass lens, more like building an interferometric scattering array that causes a single central primary peak. But not my specialty, just thinking out loud...
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Even when the experts all agree, they may well be mistaken. --- Bertrand Russell.