Gamma Ray Refraction Could Launch Nuclear Photonics

For the first time, gamma rays were bent like ordinary light in an experiment that overturns decades of theoretical predictions and opens the door to a new field of research called nuclear photonics.

Gamma rays are essentially a highly energetic form of light. Able to penetrate almost any material, they now have the ability to bend and focus, which could lead to powerful new medical applications, including imaging techniques and targeted cancer treatments.

Scientists from the Laue-Langevin Institute (ILL) and the Ludwig Maximilian University of Munich achieved this feat using a version of a common classroom experiment with glass prisms. They refracted the rays at the highest energies ever recorded.

In the same way that light beams can be bent and split with glass prisms, the researchers used a silicon prism to bend gamma rays. They analyzed the gamma rays produced using ILL’s PN-3 facility through two silicon crystals, the first pre-selecting them as they came out of the reactor and directing them into a very narrow and parallel beam. Further along the instrument, a silicon prism was placed at a height where it refracted half of the gamma ray beam. The refraction of this half-beam was then detected by a second silicon crystal and compared with the half consisting of unrefracted gamma rays.

What they discovered is that the energy of the gamma rays increased the falling refraction values, and then suddenly started to increase to larger positive refraction values similar to that of visible light. These were much higher values than anyone expected.

The researchers now believe that by replacing the silicon prisms with higher-refracting materials such as gold, they can increase refraction to a level where it can realistically be manipulated for optical techniques.

“Twenty years ago, many people doubted you could do optics with x-rays — no one even considered that it might be possible for gamma rays, too,” said Dr. Michael Jentschel, an ILL research scientist. “This is a remarkable and completely unexpected discovery with significant implications and practical applications. These include isotope-specific microscopy with benefits across the scientific disciplines, through to direct medical treatment and even tools to address major national security issues.”

Potential applications include more selective, less destructive medical imaging techniques achieved by enriching a particular isotope in a cancer and monitoring where it goes, improved production and trialing of new, more targeted radioisotopes for cancer treatment, and remote characterization of nuclear materials or radioactive waste.

The work appeared in Physical Review Letters.

For more information, visit: www.ill.eu