A Measurement of the Average Energy Required to Create an Ion Pair in Nitrogen by High-Energy Ions

Abstract
At energies above .apprx. 10 MeV/amu [atomic mass unit], the average energy required to create an ion pair, .hivin.w, in gases is apparently independent of mass or charge state of the ion and with increasing energy will tend toward the value for electrons, which in N is 34.6 eV. Measurements [22] of .hivin.w using 250 MeV/amu 12C6+, 375 MeV/amu 20Ne10+ and 479 MeV/amu 40Ar18+ were made. Values of 36.4 .+-. 0.6, 35.4 .+-. 0.8 and 34.7 .+-. 0.5 eV, respectively, were obtained for N2. These values were evaluated so accurate estimates of absorbed dose may be made with N2 filled ionization chambers.