Experimental apparatus for the measurement of non-linear stopping of low-energy heavy ions

We developed an experimental apparatus for the study of non-linear stopping of low-energy heavy ions in non-ideal plasmas. The target plasma was produced by an electromagnetically driven shock tube. A pair of 50-μmμm-diameter beam apertures was attached to the shock tube wall. These apertures confined hydrogen gas of ≈5Torr in the tube and sustained the pressure difference (∼105∼105–106106) between the tube and the beam line. In order to measure the energy loss in the plasma in the tube, we used a semiconductor charged-particle detector, which could directly measure the kinetic energy of single particles, since the beam transmission through these apertures was very small. To synchronize the plasma production in the shock tube and the injection of projectiles, a fast beam kicker was installed in front of the plasma target. Results of preliminary experiments using thin carbon foil targets showed that the measured energy loss of single projectiles after passing through the target was in agreement with other data. The time resolution of the energy-loss measurement system was ≈150ns, which is enough to measure the projectile energy loss during the life time of the target plasma.