A new way to make X-rays

The most widely used technology for producing X-rays – used in everything from medical and dental imaging, to testing for cracks in industrial materials – has remained essentially the same for more than a century. But based on a new analysis by researchers at MIT, that might potentially change in the next few years.

The finding, based on a new theory backed by exact simulations, shows that a sheet of graphene – a two-dimensional form of pure carbon – could be used to generate surface waves called plasmons when the sheet is struck by photons from a laser beam. These plasmons in turn could be triggered to generate a sharp pulse of radiation, tuned to wavelengths anywhere from infrared light to X-rays.

What’s more, the radiation produced by the system would be of a uniform wavelength and tightly aligned, similar to that from a laser beam. The team says this could potentially enable lower-dose X-ray systems in the future, making them safer. The new work is reported this week in the journal Nature Photonics, in a paper by MIT professors Marin Soljačić and John Joannopoulos and postdocs Ido Kaminer, Liang Jie Wong (now at the Singapore Institute of Manufacturing Technology), and Ognjen Ilic.

Soljačić says that there is growing interest in finding new ways of generating sources of light, especially at scales that could be incorporated into microchips or that could reduce the size and cost of the high-intensity beams used for basic scientific and biomedical research. Of all the wavelengths of electromagnetic radiation commonly used for applications, he says, “coherent X-rays are particularly hard to create.” They also have the highest energy. The new system could, in principle, create ultraviolet light sources on a chip and table-top X-ray devices that could produce the sorts of beams that now require huge, multimillion-dollar particle accelerators.

To make focused, high-power X-ray beams, “the usual approach is to create high-energy charged particles [using an accelerator] and ‘wiggle’ them,” says Kaminer. “The oscillations will produce X-rays. But that approach is very expensive,” and the few facilities available nationwide that can produce such beams are highly oversubscribed. “The dream of the community is to make them small and inexpensive,” he says.

Most sources of X-rays rely on extremely high-energy electrons, which are hard to produce. But the new method gets around that, using the tightly-confined power of the wave-like plasmons that are produced when a specially patterned sheet of graphene gets hit by photons from a laser beam. These plasmons can then release their energy in a tight beam of X-rays when triggered by a pulse from a conventional electron gun similar to those found in electron microscopes.

“The reason this is unique is that we’re substantially bypassing the problem of accelerating the electrons,” he says. “Every other approach involves accelerating the electrons. This is unique in producing X-rays from low-energy electrons.”

In addition, the system would be unique in its tunability, able to deliver beams of single-wavelength light all the way from infrared, through visible light and ultraviolet, on into X-rays. And there are three different inputs that can be used to control the tuning of the output, Kaminer explains – the frequency of the laser beam to initiate the plasmons, the energy of the triggering electron beam, and the “doping” of the graphene sheet.

Such beams could have applications in crystallography, the team says, which is used in many scientific fields to determine the precise atomic structure of molecules. Because of its tight, narrow beam, the system might also allow more precise pinpointing of medical and dental X-rays, thus potentially reducing the radiation dose received by a patient, they say.

So far, the work is theoretical, based on precise simulations, but the group’s simulations in the past have tended to match quite well with experimental results, Soljačić says. “We have the ability in our field to model these phenomena very exactly.”

They are now in the process of building a device to test the system in the lab, starting initially with producing ultraviolet sources and working up to the higher-energy X-rays. “We hope to have solid confirmation of the principles within a year, and X-rays, if that goes well, optimistically within three years,” Soljačić says.

But as with any drastically new technology, he acknowledges, the devil is in the details, and unexpected issues could crop up. So his estimate of when a practical X-ray device could emerge from this, he says with a smile, is “from three years, to never.”

Hrvoje Buljan, a professor of physics at the University of Zagreb in Croatia, who was not involved in this study, says the work provides “a significant new approach to produce X-ray radiation.” He adds, “The experimental implementation still needs to be performed. Based on the proposal, all of the ingredients for the proof of principle experiments are there, and such experiments will be feasible.”

The work was supported by the U.S. Army Research Laboratory and the U.S. Army Research Office, through the Institute for Soldier Nanotechnologies, by the Science and Engineering Research Council, A*STAR, Singapore, and by the European Research Council Marie Curie IOF grant.

The material in this press release comes from the originating research organization. Content may be edited for style and length. Want more? Sign up for our daily email.

1 thought on “A new way to make X-rays”

  1. , I will try to give you my take, on your take:Problem 1:The columns along one face of the bunidilg were sheared for a height of several floors, as were many of the columns at the core.There is no evidence of the condition of the internal core colums, only speculation.They are likely basing their comments on the computer models. This is not direct physical evidence, but is detailed, well constructed “reinactment”. Beyond that, they may have determined the severing of internal columns based on some of the metal they examined at GZ. I mean, for starters, the internal columns, I believe were made of a different steel type than the external columns, so they could seperate the two this way. Then, by examining the sites of sheering, perhaps, as qualified professionals in that area, the NIST scientists were able to determine that the aircraft was the causeof the sheering. I am not an expert in this…are you.Problem 2:The exploding fuel from the airliner ignited fires throughout the levels within the impact zone, as well as dropping fire down the stairwells and elevator shafts at the bunidilg’s core.. There is no evidence of fuel pouring down the elevator shafts, especially since firefighters were able to travel up said shafts. This is used to try to explain the janitor’s testimony, marble knocked off the wall, testimony of explosions etc.,and white smoke billowing from the base of the towers prior to collapse. Some victims exited the elevator shafts with no burns at all.Noone said all the elevators had fuel come down them. Also, the man who did exit, had physical damage to his body (skin falling off) that was consistent with burning from fire, rather than a blast explosion event. Of course there is no physical evidence of fuel going down…how could there be, unless a video tape that captured said fuel pouring down was available.Problem 3:The shocks of impact and detonation loosened the “fire protection” thermal insulation on steel beams in the impact zone.Pure speculation without evidence used to explain how the steel was weakened by fire that wasn’t hot enough to weaken it.1. Given the insulation was “spray on” and could be removed with a firm brush of the hand, it is GOOD Speculation, that a 757 passing through the bunidilg could rip a fair bit of it off.2. The Certification Testing of the Steel, that was done for safety, was done on, according to one of the original architects/engineers of the WTC, Steel that HAD the fireproofing on it.3. If Kerosene was the ONLY thing to burn in the fire, than I would agree, it would likely not have been hot enough for long enough to weaken the steel considerably. Carpet, Curtains, Plastics, Furniture, Aluminum, and many other things, were also within the bunidilgs and burned in the fires, making them much hotter than simple “Hydrocarbon” fires.Problem 4:The added compression of the perimeter columns could only be distributed to the three undamaged faces, and because of the irregularity of the damage one face assumed a much higher load than the other two. Perhaps true, but does not account for a symmetrical collapse. Based upon this statement the collapse should have been assymetrical. No reason is given for the discrepency.Not true. The initiation may have had a higher tendancy to be asymetrical due to these factors, but once collapse was initiated, the overwhelming energy from the “in motion” weight of the floors above, would have insured and essentially “symmetrical” collapse of the entire bunidilg.Problem 5:The fuel fire burned up to 1,100 degrees C (2,000 degrees F) for perhaps 10 minutes. In each case the fuel exploded in a massive fireball upon impact. In perfect conditions the maximum temperature that can be reached by hydrocarbons such as jet fuel burning in air is 1520b0 F (825b0 C) not 2000 F. Melting Point of Iron: 1535.0 b0C (1808.15 K, 2795.0 b0F) This explanation does not account for the steel flowing like lava in the debris pile. In fact, nothing about the OS can be attributed to the liquid steel.1. NO, I repeat, NO proof that the metal in question was STEEL. Grainy photos, easily photoshopped, showing orange and yellow, or purple and pokadots, for that matter, is not evidence of STEEL.2. One only needs to reach temps of 600-700 C to SIGNIFICANTLY weaken Steel.3. To reach temps required to melt Aluminum or Copper or Iron (all found in debris of GZ) Fuel initiated fires, sustained via bunidilg components, and maintained for prolonged time via insulation from debris pile, as well as extra heat disipated from friction of collapse, could easily resulted in the scenario you describe.To judge the effects of a fire on structural steel, it is necessary to consider what happens in such an exposure. Peculiarities of this exposure are : (1)temperature attained by the steel can only be estimated, (2)time of exposure at any given temperature is unknown, (3)heating is uneven, (4)cooling rates vary and can only be estimated, and (5)the steel is usually under load , and is sometimes restrained from normal expansion. (source: Manual of Steel Construction, 8th editionPage 6-5)I do not disagree, but you are talking about what “most likely happened” given the overwhelming evidence, and based on the EXPERT opinions of the civil engineers that investigated the attakcs for NIST.Problem 6:The NIST response is that the lower structure was only designed to hold up the weight above any given floor statically, not dynamically. This is highly doubtful. If true, the designers of the bunidilg should be held responsible. If true, they knowingly designed a bunidilg that would collapse to the ground based upon the assymetrical collapse of *drum roll please* 1 FLOOR!1. The amount of money that would have to be added to bunidilg costs to hold up such an enormous dynamic load, would make skyscrapers non-feasable.2. the impact zones were multiple floors, and collapse likely occured/initiated over several floors, not one floor.Problem 7:The sudden shifts in the volume of rooms and office spaces being compressed and twisted by the elastic wave trains can easily expel jets of air and dust out of windows A subtle theory on the ejected debris squibs. But it doens’t answer why the squibs took place in random spots not uniformly and at random times not in sequence.That is the whole point. In a CD, as is proposed by the CTers, the squibs would have come out in a sequential, uniform sequence, not in a random fashion as they did. The “squibs occured as they did, likely froma a complex number of reasons, which I do not have the skill to explain.Problem 8:Sprey’s comments on CDFirst assumption is that terrorist using planes and CD would plant explosives in a traditional CD manner. He cleverly avoids other evidence that might lead to CD conventional or unconventional.The alternative is that the evil Cabal went WAY, WAY, WAY out on a limb and planted the alleged explosives in an unconventional, UNPROVEN fashion, and then just …HOPED IT WORKED. Come on.Problem 9:It is noted that the time to reach critical temperature for bare columns is less than the one hour period during which the bunidilgs withstood intense fires. The bunidilgs indeed did not have intense fires in them. Madrid on the other hand did have intense fires. (Fire behavior and appearance not collapse comparisons.)The video and Photographic evidence I have seen, shows 8-10 floors afire, with huge seering flames through out. This, in comparison to the one reference comment from a fireman, several floors away, who said they could manage the fires…the one comment all the CTers cling on to for this entire point of contention.Problem 10:Airplane impact sheared columns along one face and at the bunidilg’s core. Again speculation as to the core’s condition.See my comments on this from earlier.Problem 11:Let us pretend that the framework of the bunidilg is made of “ironcrete,” I stopped at this point with the section HOW HOT… I’m not interested in pretending but this ‘expert’ is.ok…whatever.Problem 12:Within minutes, the aviation fuel was largely burned off, and the oxygen in the impact zone depleted. The minutes timeframe is debateable. Which leads to office fires melting steel and 1/2 of the equation for collapse. Riiighhttt.. This still does not account for steel flowing like rivers of lava.Where, on gods earth, do you see “rivers of flowing steel” prior to bunidilg collapse? the only video I have seen of “liquid metal” prior to collapse are some sparks and melted bits flowing from one side of the impact zone, that could have been, and likely was, aluminum siding.As to rivers of molten steel after the collapse, see my comments above.Problem 13:This process of “preheating the oven” would slowly raise the average temperature in the impact zone while narrowing the range of extremes in temperature. Within half an hour, heat had penetrated to the interior of the concrete, and the temperature everywhere in the impact zone was between 200 C and 700 C, away from sites of active burning.Sounds plausible until you consider the photographs of survivors on the edge of the ‘pre-heated’ oven and stories of survivors in and around the impact zone.I am not an expert, but it seems plausible that there would be some pockets of lower temps, especially where the impact zones were openly exposed to, and adjacent to the open air.Problem 14:Thermal Decomposition — “Cracking” Littered with ‘might’ do this, ‘might’ do that. Again speculation used to justify how office fires contributed to the collapse.Short of having tools to measure it at the actual event, of course there is an element of “educated” speculation, which I would trust much more than “CT-uneducated” speculation.Problem 15:Smoldering Rubble Does not explain how said items and temps could reach a point to cause steel to flow like lava. Why? Because it could not get that hot. The author again litters his explanation with speculation to support the facts.You have stated, as a fact, that it could not have gotten that hot, so where is your proof of this “fact” you have spued?Problem 16:…that DNA was formed. This guy goes on to claim that it was possible for the bunidilg blocks of life to form at the bottom of the ruble pile! LOL! Now I’ve never heard that one before. Hell that should have been left in place for biologists to study it.No idea what this is all about, I will leave it.TAM

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