An international research team has developed a new imaging technique at the Research Neutron Source Heinz Maier-Leibnitz (FRM II) of the Technical University of Munich (TUM). In the future, it will not only enable many times better resolution measurements with neutrons, but could also reduce the radiation exposure during X-rays.

Even modern cameras still rely on the same principle as 200 years ago: instead of a film, an image sensor is exposed for a certain period of time to take a picture. However, the noise of the sensor is also recorded. For longer exposure times, this represents a significant source of interference.

Instrument scientist Adrian Losko at the neutron radiography instrument NECTAR. Source: Bernhard Ludewig / FRM II / TUMInstrument scientist Adrian Losko at the neutron radiography instrument NECTAR. Source: Bernhard Ludewig / FRM II / TUM

Together with colleagues from Switzerland, France, the Netherlands and the U.S., Dr. Adrian Losko and other colleagues from TUM at the Heinz Maier-Leibnitz Zentrum (MLZ) have now developed a new imaging method that measures individual photons with time and location resolution. Photons can thus be separated from noise, and the disturbing noise can be greatly reduced.

"With our new detector, we detect every single light particle and thus bypass many physical limits of classical cameras," said Dr. Adrian Losko, instrument scientist at the neutron radiography facility NECTAR of the MLZ at the Technical University of Munich.

Measurement of individual light particles

Typically, researchers in neutron radiography use scintillators in their measurements to detect neutrons and thus, for example, to illuminate petrified dinosaur eggs. When a neutron is absorbed by the scintillator material, photons are produced, light particles that can be measured.

With all previous cameras, the light is collected during the entire exposure time, which creates a blur depending on the thickness of the scintillator. The research team's new concept, on the other hand, detects every single one of the light particles generated by a neutron.

"The prerequisite for this was a new chip technology as well as hardware and software with computing speeds that enable evaluation in real time. So, we can now assemble an image neutron by neutron," explained Losko. Neutron research offers an ideal field of testing and application here.

Instead of a long exposure time, measure exactly what is happening

Since the absorption of a neutron in the detector produces several light particles, the new system can detect individual neutrons by measuring the coincidence of several light particles. "This takes us away from the classic model of exposure time and only measures the events that have taken place."

Overall, the new concept dwarfs all existing technologies on the market, as it already enables three times better local resolution and more than seven times less noise. "The limitation caused by the thickness of the scintillator is greatly reduced. This enables higher efficiency for high-resolution measurements," said Losko. The afterglow of scintillators, which creates a so-called ghost image, is also omitted.

"Many instruments at the research neutron source could benefit from our new concept," said Losko. As an example, he cites the instrument FaNGaS (Fast Neutron-induced Gamma-ray Spectrometry): "By knowing exactly when a neutron arrives, the time domain in which we measure the gamma particle can be reduced to one millionth of a second." This would reduce the underground noise by a factor of one million.

Lower radiation exposure and more details in X-ray

The new detector could also be used in medicine. In the X-ray of a bone fracture, fine structures, such as bone hairline cracks, would be easier to recognize and at the same time the radiation exposure for the patient would be minimized.

"Our method will definitely change the detectors in the scientific world," said Losko. And it is possible that similar principles will eventually find their way into normal cameras for private use. Recordings in the dark would improve greatly. In addition, photographers could adjust the exposure time and resolution even after shooting. The noise of cameras could be virtually eliminated.

The study, New perspectives for neutron imaging through advanced event-mode data acquisition, appears in the journal Scientific Reports.

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