Baek W Y, Grosswendt B
Physikalisch-Technische Bundesanstalt, Braunschweig, Germany.
Phys Med Biol. 1995 Jun;40(6):1015-29. doi: 10.1088/0031-9155/40/6/004.
An analytical model is presented that facilitates the calculation of the mean energy W expended to produce an ion pair upon complete slow-down for heavy particles in gases. This model is applied to the calculation of the W values for helium beams of energies from 10 keV to 10 MeV in argon and nitrogen gas. Good agreement of the theoretical W values with the experimental ones is found in the case of nitrogen. The theoretical results for argon are about 15% higher than the experimental values throughout the entire energy range. However, they show a similar energy dependence. The theoretical and the experimental W values for nitrogen exhibit an extraordinary energy dependence at energies around 300 keV, at which the cross-section for charge exchange cycles reaches the maximal value. Such a phenomenon was also observed in the case of the W values for protons, which show a clear minimum at the energy of the maximal cross-section for charge exchange cycles.
本文提出了一个分析模型，该模型有助于计算重粒子在气体中完全减速时产生一对离子所消耗的平均能量(W)。此模型用于计算能量在(10keV)至(10MeV)的氦束在氩气和氮气中的(W)值。在氮气的情况下，理论(W)值与实验值吻合良好。在整个能量范围内，氩气的理论结果比实验值高约(15%)。然而，它们表现出相似的能量依赖性。氮气的理论和实验(W)值在(300keV)左右的能量处表现出异常的能量依赖性，此时电荷交换循环的截面达到最大值。在质子的(W)值情况中也观察到了这种现象，质子的(W)值在电荷交换循环最大截面的能量处呈现出明显的最小值。
