氮气、二氧化碳、甲烷、氩气、氢气及罗西型组织等效气体中α粒子的W值的能量依赖性

Energy dependence of W for alpha particles in N2, CO2, CH4, Ar, H2 and Rossi-type tissue-equivalent gases.

作者信息

Varma M N, Baum J W

出版信息

Phys Med Biol. 1978 Nov;23(6):1162-72. doi: 10.1088/0031-9155/23/6/012.

Abstract

Average energy required to form an ion pair (W) was determined in N2, CO2, CH4, Ar, H2 and Rossi-type tissue-equivalent gas. Alpha particles from a 241Am source were used. W was determined at alpha energies of 5.37, 3.12, 1.08 and 0.46 MeV. The ratio of total ionisation produced (for fixed alpha particle energy) in experimental gas to that produced in argon was measured. This ratio was then multiplied by the previously determined W value for argon gas (26.29 eV per ion pair) to yield W for various experimental gases. Energy of the 241Am alpha particles was degraded by using air as an absorbing material. Empirical relations W = alpha + betaE-1/2 and W = alpha1 + beta1E-1 were fitted to the experimental data. Both functions fit reasonably well in the range 0.4--5.37 MeV. Below about 0.4 MeV the first function provides a better fit to the data of Boring et al. (1965).

摘要

在氮气、二氧化碳、甲烷、氩气、氢气和罗西型组织等效气体中测定了形成离子对所需的平均能量（W）。使用了来自241Am源的α粒子。在5.37、3.12、1.08和0.46 MeV的α能量下测定W。测量了实验气体中（对于固定的α粒子能量）产生的总电离与氩气中产生的总电离之比。然后将该比值乘以先前确定的氩气的W值（每离子对26.29 eV），以得出各种实验气体的W值。通过使用空气作为吸收材料来降低241Amα粒子的能量。将经验关系式W = α + βE-1/2和W = α1 + β1E-1拟合到实验数据。这两个函数在0.4 - 5.37 MeV范围内拟合得相当好。在约0.4 MeV以下，第一个函数能更好地拟合Boring等人（1965年）的数据。