First results of a new positron-accumulation scheme using an electron linac and a Penning-Malmberg trap

The Gravitational Behaviour of Antihydrogen at Rest experiment - GBAR - is designed to perform a direct measurement of the weak equivalence principle on antimatter by measuring the acceleration (bar g) of antihydrogen atoms in free fall. Its originality is to produce bar H⁺ ions and use sympathetic cooling to minimize the initial velocity. These ions are produced using charge exchange reactions with a dense positronium cloud, created by an intense pulse of electron-linac-produced positrons that are accumulated in a Penning-Malmberg trap.