Grosswendt B, Pszona S
Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany.
Radiat Environ Biophys. 2002 Jun;41(2):91-102. doi: 10.1007/s00411-002-0144-9.
Probability distributions of the size of ion clusters created in "nanometric" volumes of nitrogen by single alpha-particles of a gold-plated 241Am source, were measured and compared with those calculated by Monte Carlo methods in the same geometry. The diameter of the sensitive volumes had a mass per area of between 0.015 microgram/cm2 and 1.3 micrograms/cm2 which, for a material at unit density, corresponds to a nanometric target volume 0.15-13 nm in diameter. These nanometre sizes were simulated experimentally in a device called the Jet Counter. This consists of a pulse-operated valve which injects into an interaction chamber an expansion jet of molecular nitrogen gas, which is crossed by a narrow beam of alpha-particles. The resulting ions are counted and analyzed from the point of view of ionization cluster formation. The measured or calculated cluster size probabilities prove that the formation of ionization clusters along a "nanometre" track is governed by Poisson's law only in the case of very small target volumes, due to the contributions by secondary electrons. The present ionization cluster probabilities produced in "nanometric" volumes 0.15-13 nm in diameter, are the first ever determined experimentally and confirmed by Monte Carlo simulation.
测量了由镀 241Am 源的单个α粒子在“纳米级”氮体积中产生的离子簇大小的概率分布，并将其与在相同几何形状下通过蒙特卡罗方法计算的结果进行了比较。敏感体积的直径对应的单位面积质量在 0.015 微克/平方厘米至 1.3 微克/平方厘米之间，对于单位密度的材料，这对应于直径为 0.15 - 13 纳米的纳米级目标体积。这些纳米尺寸是在一种称为喷射计数器的装置中通过实验模拟的。它由一个脉冲操作阀组成，该阀将分子氮气的膨胀射流注入相互作用室，一束狭窄的α粒子束穿过该射流。从电离簇形成的角度对产生的离子进行计数和分析。测量或计算得到的簇大小概率证明，由于二次电子的贡献，仅在非常小的目标体积情况下，沿“纳米级”轨迹的电离簇形成才受泊松定律支配。目前在直径为 0.15 - 13 纳米的“纳米级”体积中产生的电离簇概率，是首次通过实验确定并经蒙特卡罗模拟证实的。
