Smartphone camera sensor helps with antimatter research at CERN

At CERN, scientists from the AEgIS collaboration led by a team of the Technical University of Munich (TUM) have repurposed smartphone camera sensors to create a detector capable of tracking antiproton annihilations in real time with a resolution of about 0.6 micrometres, a 35-fold improvement over previous real-time methods. The detector was developed at the research neutron source FRM II.

Dr Francesco Guatieri, Michael Berghold and Markus Münster (from left) put the finishing touches to the detector before it is transported to CERN for further measurements. © Andreas Heddergott / TUM

Dr Francesco Guatieri, Michael Berghold and Markus Münster (from left) put the finishing touches to the detector before it is transported to CERN for further measurements. © Andreas Heddergott / TUM

The AEgIS cooperation (Antihydrogen Experiment: Gravity, Interferometry, Spectroscopy) at CERN is on a mission to measure the free-fall of antihydrogen under Earth’s gravity with high precision. This involves producing a horizontal beam of antihydrogen and measuring its vertical displacement using a device called a moiré deflectometer that reveals tiny deviations in motion and a detector that records the antihydrogen annihilation points.

60 smartphone chips with 3840 MPixels
“For AEgIS to work, we need a detector with incredibly high spatial resolution, and mobile camera sensors have pixels smaller than 1 micrometer,” says Dr. Francesco Guatieri, Principal Investigator of the research, from the group of Prof. Dr. Christoph Hugenschmidt at the research neutron source FRM II at TUM. “We have integrated 60 of them in the single photographic detector, the Optical Photon and Antimatter Imager (OPHANIM), with the highest number of pixels currently operational: 3840 MPixels. Previously, photographic plates were the only option, but they lacked real-time capabilities.

The TUM team built the optical photon and antimatter imager (OPHANIM) from 60 smartphone chips. © Andreas Heddergott / TUM

The TUM team built the optical photon and antimatter imager (OPHANIM) from 60 smartphone chips. © Andreas Heddergott / TUM

Our solution, demonstrated for antiprotons and directly applicable to antihydrogen, combines photographic-plate-level resolution, real-time diagnostics, self-calibration and a good particle collection surface, all in one device.”

Image sensors rebuilt
Specifically, the researchers used Sony optical image sensors that had previously been shown to be capable of imaging low-energy positrons in real time with unprecedented resolution.“ We had to strip away the first layers of the sensors, which are made to deal with the advanced integrated electronics of mobile phones,” says Guatieri. “This required high-level electronic design and micro-engineering.” The two Master’s students Michael Berghold and Markus Münster from the TUM School of Engineering and Design played a key role in this.

The Optical Photon and Antimatter Imager, integrating 60 sensors, and some examples of antiproton annihilations obtained with it. Annihilations appear as star-shaped events with multiple tracks emanating from one primary vertex. Green, cyan and orange arrows indicate examples of nuclear fragments, protons, and pions. © Ruggero Caravita

The Optical Photon and Antimatter Imager, integrating 60 sensors, and some examples of antiproton annihilations obtained with it. Annihilations appear as star-shaped events with multiple tracks emanating from one primary vertex. Green, cyan and orange arrows indicate examples of nuclear fragments, protons, and pions. © Ruggero Caravita

“Extraordinary resolution”
“This is a game-changing technology for the observation of the tiny shifts due to gravity in an antihydrogen beam travelling horizontally, and it can also find broader applications in experiments where high position resolution is crucial, or to develop high-resolution trackers.” says AEgIS spokesperson Dr. Ruggero Caravita. “This extraordinary resolution enables us also to distinguish between different annihilation fragments, paving the way for new research on low-energy antiparticle annihilation in materials,” concludes Caravita.

Original text: AEgIS/CERN