Average energy to produce an ion pair in gases for high energy heavy ions

The differential W-values, w, an average energy required to produce an ion pair, were measured for C⁶⁺, Ne¹⁰⁺ and Ar¹⁸⁺ with energies more than 100MeV/n from a heavy-ion accelerator in argon, air, and propane-base tissue-equivalent gas of the pressures more than 0.1MPa. The values of w are almost equal to those of W for He²⁺ in each gas, which are approximately constant over a wide range of the energy.