Astrophysics Division
CEA Saclay

UMR Astrophysics Instrumentation Modelisation

picto-accueil Our research laboratories


Jun 17th, 2022

Weak gravitational lensing reveals dark-matter maps of the cosmic web


May 6th, 2022

Hyperfast white dwarfs and stellar explosions


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NICE: Unveiling the physics of galaxy cluster formation at high redshifts with NOEMA


Gazette of Dap #4


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picto 1 Research laboratories


The Astrophysics Division (DAp)

A major space astrophysics laboratory

The Astrophysics Division (DAp - UMR AIM) is among the major space laboratories in France, in Europe and internationally. In direct collaboration with CNES, which is responsible for the space activities of French laboratories, DAp is strongly involved in space missions for ESA's Cosmic Vision scientific program and on bilateral missions supported by CNES. The development of astrophysics at the CEA began in partnership with CNES since its creation in the early 1960s. Astrophysics has since been a growing science with high potential for discoveries. Instruments, ever more numerous and more powerful, whether from the ground or on board satellites, make it possible to probe the universe with increased angular resolution and sensitivity across the full range of the electromagnetic spectrum. Meanwhile, modeling, particularly using computational simulations, is of increasing importance in astrophysics; astrophysical problems are mostly complex problems that involve other disciplines of physics. Astrophysics and other fields of physics enrich each other.

The Astrophysics division

The DAp-UMR AIM includes nearly 200 people, including 130 permanent staff mainly UMR AIM, a joint research unit CNRS-CEA-Paris Diderot and also of the Astroparticle and Cosmology UMR APC, CEA-CNRS -University Denis Diderot-Paris Observatory. The Astrophysics Service brings together researchers, engineers and technicians from the Astrophysics Division at CEA Irfu as well as research engineers at Sedi Irfu, the Université Paris Diderot and CNRS.


Our scientific projects

picto 3Astrophysics

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Developing instruments

picto 4 Instrumentation

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Modelling the Universe

picto 5 Modelisation

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Knowledge management of data archives

picto 6 Data






Exploring the High Energy gamma ray sky

H.E.S.S   stands for "High Energy Stereoscopic System". This telescope system been designed and built by a large international collaboration which includes the DAPNIA as a member. This instrument is dedicated to the observation of high energy gamma ray sources with energies above a few tens of GeV.   The interaction of these very high energy gamma rays with the upper atmosphere creates a faint flash of blue light called "Cherenkov emission". This very fast (a few nanosecond) flash of light can be observed from the ground. Surveying the sky in the TeV energy range, which is observed by astrophysicists only since last two decades, allows the get an insight into the origin of cosmic rays and to study the acceleration of cosmic rays in various astrophysical objects such as supernovae remnants or active galactic nuclei.

The HESS experiment is located in NAMIBIA, on the Gamsberg highlands (latitude 23° 16' south, longitude 16° 30' east), at an altitude of 1800 m above sea level. It was named after a famous austrian physicist, Victor Hess (1883-1964),  who was awarded the Nobel price in physics in 1936 for discovering cosmic rays.
The HESS apparatus consists in four 12 meter telescopes at the corners of a square with 120 meter sides. Each of these telescopes has a camera at his focus.The camera are large arrays of 960 photomultipliers sensitive to blue light. These photomultipliers have a very fast response time, of the order of one nanosecond.
The sensitivity of HESS (the power to detect faint sources) is 10 times better than that of previous experiments (WHIPPLEHEGRA, CAT) with an energy threshold of 100 GeV.

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