Division of Electronics, Detectors and Computing for Physics (DEDIP)

The GBAR collaboration, to which the IRFU makes a major contribution, presented the results of its first data collection at CERN at the end of 2022 at the Moriond conferences in March 2023. For the first time, it observed the production of anti-hydrogen atoms resulting from the interaction of a beam of antiprotons supplied by CERN's Antiproton Decelerator (AD) and decelerated to an energy of 6 keV, with a cloud of positronium produced locally in the experiment. GBAR thus joins the very select club of experiments that have successfully synthesised anti-hydrogen atoms!

The ultimate aim of the GBAR experiment is to measure the acceleration of an anti-hydrogen atom in the Earth's gravity field, and compare it with that of ordinary matter. The Equivalence Principle, the basis of Einstein's General Relativity, states that all forms of matter and energy behave in the same way with respect to gravity. Since Galileo, falling-body experiments have tested this principle for different chemical elements of ordinary matter, confirming it with increasingly precise agreement. Recently, the MICROSCOPE satellite experiment verified it with a remarkable uncertainty of one part in 3x10¹⁵. But the action of gravity on antimatter has never yet been measured! Several indirect arguments suggest that antimatter should respect the Principle of Equivalence, and should therefore "fall" towards the Earth like matter. However, the relationship between matter and antimatter is intrinsically quantum, and the theory of gravitation does not sit well with quantum theory. So only experimental measurement can remove this doubt. Of course, the first step is to measure the sign, i.e. whether antimatter 'rises' while matter 'falls'. But even a small quantitative difference between the acceleration of antimatter and matter in free fall would be a revolution in physics

CEA has delivered to CNES the flight version of the ECLAIRs instrument software for the SVOM satellite. This concludes a major instrumental development phase conducted by CEA over a period of 6 years to produce what is maybe one of the most complex software packages ever carried on a French scientific space instrument. The latest version of the software equips the ECLAIRs onboard computer, which departed to China in early 2023. It will be used during the satellite integration tests in Shanghai in preparation for the launch planned for early 2024. This software will analyse in real time the data from the instrument in flight, in order to detect gamma-ray bursts and localise them to better than 12 arcmin on the sky, to reorient automatically the satellite for follow-up observations, and to alert the scientific community.