Turning smartphone sensors into an antimatter camera

A team from the Technical University of Munich has repurposed smartphone camera sensors to create a detector capable of imaging antiproton annihilations in real time

From the CERN report:

Unlocking the secrets of antimatter has taken a significant leap forward with the development of a new detector by the AEgIS collaboration, led by Professor Christoph Hugenschmidt’s team from the research neutron source FRM II at the Technical University of Munich (TUM). This innovative detector, utilizing modified mobile camera sensors, can now image in real time the precise locations where antimatter annihilates with matter. The breakthrough device, detailed in a recent paper published in Science Advances, boasts the ability to pinpoint antiproton annihilations with an impressive resolution of about 0.6 micrometres, marking a substantial 35-fold enhancement over previous real-time imaging methods.

As part of the broader efforts at CERN’s Antimatter Factory, experiments like AEgIS, ALPHA, and GBAR are dedicated to measuring the free-fall of antihydrogen within Earth’s gravitational field with exceptional precision, each employing distinct methodologies. AEgIS’s strategy revolves around generating a horizontal antihydrogen beam and gauging its vertical displacement through a moiré deflectometer, which detects subtle deviations in motion, alongside a detector that captures the annihilation points of antihydrogen.

Francesco Guatieri, the principal investigator on the paper, emphasized the critical role of high spatial resolution in the success of AEgIS: “For AEgIS to function effectively, we require a detector with remarkably high spatial resolution, and mobile camera sensors possess pixels smaller than 1 micrometre. By integrating 60 camera sensors into our detector, we have achieved an unparalleled resolution of 3840 mega pixels – the highest pixel count ever recorded for an imaging detector.”

Previously, the use of photographic plates was the primary option, albeit lacking real-time capabilities, as Guatieri pointed out. The team’s innovative solution, demonstrated for antiprotons and directly applicable to antihydrogen, combines the resolution of photographic plates with real-time diagnostics, self-calibration, and an efficient particle collection surface, all within a single device.

The researchers leveraged commercial optical image sensors that had previously demonstrated the ability to image low-energy positrons in real time with unprecedented resolution. Guatieri explained the intricate process of adapting the sensors for their purposes: “We had to remove the initial layers of the sensors, designed for the integrated electronics of mobile phones, which necessitated advanced electronic design and micro-engineering.”

One unexpected element that significantly contributed to achieving the record resolution was crowdsourcing. Guatieri highlighted the superiority of human intuition over automated methods in this context. The AEgIS team enlisted their colleagues to manually identify the positions of antiproton annihilation points in over 2500 detector images, a meticulous process that proved to be more accurate and precise than any algorithm, despite each colleague spending up to 10 hours analyzing every annihilation event.

AEgIS spokesperson Ruggero Caravita emphasized the significance of the new detector in enabling research on low-energy antiparticle annihilation and its transformative potential for observing the minute gravitational shifts in antihydrogen. The exceptional resolution achieved by the detector now allows researchers to differentiate between various annihilation fragments, such as those produced by protons or pions, opening up new avenues for exploration in the field of antimatter research.