The interaction process between fast heavy ions and dense plasma
was experimentally investigated. We injected 4.3-MeV/u or
6.0-MeV/u iron ions into a z-pinch-discharge helium
plasma and measured the energy loss of the ions by the time
of flight method. The energy loss of 4.3-MeV/u ions fairly
agreed with theoretical prediction when the electron density
of the target was on the order of 1018 cm−3.
With increasing electron density beyond 1019
cm−3, the difference between the experiment
and the theory became remarkable; the experimental energy loss
was 15% larger than the theoretical value at the peak density.
For 6.0-MeV/u ions, the deviation from the theory appeared
even at densities below 1019 cm−3.
These discrepancies indicated that density effects such as ladderlike
ionization caused the enhancement of the projectile mean charge in the
target.
Stopping power of dense helium plasma for fast heavy ions