Bringing the power of nanotechnology to particle physics

Posted: Sep 11, 2018

(News from Nanowerk) Particle physicists are looking for light. Not just any light, but a characteristic signal produced by the interaction of certain particles – such as ghostly neutrinos, which are neutral fundamental particles of very low mass – with a detector which contains an atomic sea of ​​liquefied noble gases.

Even if it were brighter, this light signal would be undetectable by our eyes because it is in the ultraviolet (UV) range of the electromagnetic spectrum. And just as our eyes are not equipped to see UV light, most conventional photodetector systems for particle physics experiments work much better in the visible than in UV.

However, new work at the US Department of Energy’s (DOE) Argonne National Laboratory is bringing the power of nanotechnology to particle physics with the aim of improving the operation of photosensors in experimental environments where UV light is produced, like huge detection modules filled with liquid argon. .

“You can go online and buy photosensors from companies, but most of them are in the visible range, and they detect photons that we can see, visible light,” said Stephen Magill, a physicist from high energies of Argonne.

To make their photosensors more sensitive to UV light, Magill and his colleagues at Argonne and the University of Texas at Arlington applied coatings of different nanoparticles to conventional photosensors (Scientific reports, “Wavelength shift properties of luminescence nanoparticles for the detection of high-energy particles and the observation of specific physical processes”). Across a wide range of varied compositions, the results have been spectacular. The enhanced photosensors demonstrated significantly greater sensitivity to UV light than the uncoated photosensors.

In this artist’s rendering, ultraviolet light is converted by nanoparticles (black dots) into visible light. Nanoparticles of different sizes will move light to different wavelengths or colors. (Photo: Argonne National Laboratory)

The reason nanoparticles work, according to Magill, has to do with their size. Smaller nanoparticles can absorb photons of shorter wavelengths, which are then re-emitted as longer wavelength photons with lower energy, he said. This transition, known to scientists as the “Stokes shift”, converts UV photons into visible photons.

“We are always looking to find better materials that will allow us to detect our particles,” Magill said. “We would like to find a single material that allows us to identify a specific particle and not see other particles. These nanoparticles help us get closer.

The types of experiments for which scientists use these improved photosensors are considered part of the “intensity frontier” of high-energy physics. By being more sensitive to the small ultraviolet signal produced, these nanoparticle coatings increase the chances of detecting rare events and may allow scientists to better see phenomena such as neutrino oscillations, in which a neutrino changes type.

The benefits of this type of new material could also go beyond particle physics. Magill suggested that the particles could be embedded in transparent glass that could improve the amount of visible light available in certain dark environments.

“There’s a lot of light out there between 300 nanometers and 400 nanometers that we don’t see and use,” Magill said. “By shifting the wavelength, we could create a way for this light to become more useful.”

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