Exploring stopping power in ion traps – ESPRIT

Ions stored in a radio-frequency trap form a one-component plasma of finite size. Experimental control over the density of the ion cloud as well as its temperature through laser cooling allows its plasma parameter to be varied from a few units to several hundred in the same experimental setup. These ions are used here as a platform to study the stopping power of highly correlated ultra-cold plasmas, through the energy loss of a charged projectile. The two devices involved in this study allow to cover projectile-to-target mass ratios ranging from 1:10 to more than 200:1 and to vary the projectile energy, temperature, size and density of the target cloud by controlling the laser cooling and confinement conditions. The common objective is to develop new non-destructive diagnostics of projectile energy loss based on laser-induced fluorescence emitted by the target ions. The energy exchange will also be studied numerically using two complementary simulation codes. This original project will have an impact on the understanding of fundamental processes in plasmas. It will also enable the experimental demonstration of two applications. The first one concerns chemical analysis and mass spectrometry and aims to develop a non-destructive detector for molecules as heavy as proteins or viruses. The principle of the detection is based on the observation of a perturbation in the fluorescence signal of the target cloud, signature of the passage of the heavy ion-the projectile-through the target cloud. The second application concerns the preparation of the GBAR experiment at CERN and aims to demonstrate the capture of a light ion by a cloud of heavier cold ions, in a ratio close to 1/9, the mass ratio we have to work with for the capture of anti-hydrogen positive ions by a cloud of beryllium ions.