Ionization yields for heavy ions in gases as a function of energy

For the experimental determination of an average energy to produce an ion pair in gases, W, by heavy ions from accelerators an apparatus which consisted of an energy degrader, an ionization chamber, and a TOF system was designed and constructed, where two types of pulse operation modes in an ionization chamber were employed. Using this system the values of W were measured for He and C ions in pure argon and air as a function of energy of ions. For C ions the energy dependence of W was clearly observed, while W for He ions was approximately constant in a wide range of the energy. The values of W for He and for C ions obtained at the highest energies well agree with the values for alpha particles in each gas.