One of the fundamental questions of todays physics concerns the action of gravity upon antimatter. No experimental direct measurement has ever been successfully performed with antimatter particles. CERN has thus launched a research program with the Antiproton Decelerator (AD) allowing to prepare a measurement of the effect of gravity on antihydrogen atoms. The primary aim of this experiment is to determine how antimatter reacts to gravity. A first test will be to verify the sign of the gravitational acceleration for antimatter, as a theory opens the possibility for it to be negative, which would translate as an elevation rather than a fall of an antimatter atom only submitted to the gravity force of the Earth. Other theories predicting less spectacular deviations with respect to standard gravitation will also be tested.
The GBAR project has been approved by CERN in May 2012.
The R&D programme of IRFU consists in demontrating the feasibility of the production of + ions with the use of a target of positronium atoms (the bound state of an electron and a positron). This target, when bombarded with antiprotons, should allow to combine its positrons with the incoming antiprotons.
It will then be possible to create neutral anti-hydrogen
as well as positive anti-hydrogen ions +. Note that if protons are used as incident particles instead of antiprotons, one obtains hydrogen and H- ions.
ALPHA (Antihydrogen Laser PHysics Apparatus)
ATRAP (Antihydrogen Trap Collaboration)
ASACUSA (Atomic Spectroscopy And Collisions Using Slow Antiprotons)
AEGIS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy)
-The appatus to measure the performances of the converter of positons into positronium is located at ETH Zurich
-The SOPHI and SELMA projects are located in the CEA-Saclay site (former Saturne accelerator Hall)
-The confinement and extraction tests of the stored positrons were performed at RIKEN (Wako, Japan), and now at Saclay
-The GBAR experiment will take place at CERN in the AD/ELENA Hall.
IRFU (formerly DAPNIA) initiated this project.
It studies and builds an intense beam of positrons based on a small electron linear acelerator
It studies the conversion of positrons into positronium in collaboration with CEA/IRAMIS/LSI who has an expertise in the use of positrons to measure point like defects in materials ands CNRS/CEMHTI. This research is performed together with a group from ETH Zurich at CERN.
GBAR is a collaboration of 14 institutes and 49 physicists.
The IRFU team received funding from IRFU, the French National research Agency (ANR - SOPHI and POSITRAP projects) and the district of Essonne. This project has a human size allowing to have an overall vision of the way an experiment works. The goal, ambitious and complex, is fundamental for physics, because the discovery of antigravity would lead to revisit the classical models at the most fundamental level.
last update : 08-20 16:01:26-2012 (2095)
Publications The GBAR experiment: gravitational behaviour of antihydrogen at rest P. Pérez and Y. Sacquin, Class. Quantum Grav. 29 (2012) 184008. Positron annihilation in latex templated macroporous silica films: pore size and ortho-positronium escape L. Liszkay et al., New Journal of Physics 14 (2012) 065009. Muonium emission into vacuum from mesoporous thin films at cryogenic temperatures A. Antognini et al., Phys. Rev. Lett. 108, 143401 (2012). Etude et réalisation d’un faisceau de positons lents N. Ruiz, Université Pierre et Marie Curie, Paris, France ... More »
Principle of the experiment
Overall scheme In order to reach the final goal of the experiment, we must combine several elements coming each from a separate discipline in experimental physics. The production of positrons in large numbers will be obtained using an electron accelerator (see the SELMA and SOPHI projects). The storage of the produced positrons will be performed with a Penning-Malmberg trap as developed by C. Surko in San Diego or A. Mohri in Japan. They will then be extracted from this trap and dumped onto a material, with good properties to convert positrons into positronium, in a few tens of ns. The antiprotons coming from the AD at CERN are stored in a trap, such as the one developed by the ... More »
GBAR International Collaboration : CEA/IRFU - Saclay (France) CEA/IRAMIS - Saclay (France) CNRS/CSNSM - Orsay (France) ETH - Zurich (Switzerland) ILL - Grenoble (France) IPCMS - Strasbourg (France) JGU - Mainz (Germany) Lebedev - Moscow (Russia) LKB - Paris (France) NCBJ - Otvock (Poland) RIKEN -Wako (Japan) U. of Swansea (UK) U. of Tokyo - Komaba (Japan) Tokyo U. of Science (Japan) U. of Uppsala (Sweden) Detail of french collaborations : CNRS/CSNSM, Orsay (D. Lunney, P. Dupré) LKB, Paris (P. Indelicato, F. Biraben, L. Hilico, et al.) IPCMS, ... More »
History and main events 9/12/2004: The scientific comittee of Dapnia (Irfu) /SPP approves an R&D programme on methods leading to the production of antihydrogen using positronium. 15/04/2005: French Patent N° 2 852 480 11/2005: demonstration of the extraction of more than 1010 electrons from a Penning trap in less than 75 ns. This test was performed at the Atomic Physics Laboratory of RIKEN (Wako, Japan). 03/2008: SOPHI hardware arrived at the lab. 05/2008: A nanoporous SiO2 material converts 35% of incoming 2 keV e+ into o-Ps (with ETHZ, Orléans (CEMHTI), ... More »