Energy loss of 6 MeV/u iron ions in partially ionized helium plasma

The energy loss of fast iron ions in a partially ionized helium plasma was investigated experimentally. Z-pinch discharge with a peak current of 60 kA produced a plasma column with a maximum electron density of 2.5×1018 cm−3. We injected 6-MeV/u iron ions into the plasma and monitored them with a micro-channel plate stop detector at 3.8 m downstream from the target. We determined the energy loss of these ions from the increase in the time of flight. The observed energy loss was compared with the calculated value taking into account the dynamic change of the effective charge of the projectile ions in the target. The results indicate that the recombination rate for the projectile ions was much smaller than the predicted value.