A new treatment of radiation behaviour beyond one-body observables
A new treatment of radiation behaviour beyond one-body observables
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超越单体可观测值的辐射行为的新治疗方法
DOI：
10.1051/ndata:07398
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发表时间：
2007
影响因子：
2
通讯作者：
H. Nakashima
中科院分区：
文献类型：
--
作者：
K. Niita;Y. Iwamoto;Tatsuhiko Sato;H. Iwase;N. Matsuda;Y. Sakamoto;H. Nakashima
我们通过引入一个事件发生器模型，对输运计算中的辐射行为提出了一种新的处理方法。在该模型中，我们将核数据和反应模型相结合，以便追踪发射体的所有关联，同时在碰撞中保持能量和动量守恒。通过这个新模型，我们能够估算单体可观测量平均值周围的涨落，例如，一个单元中的沉积能量分布，这是基于带有核数据的玻尔兹曼方程的输运计算无法得到的。核数据在蒙特卡罗输运计算中被广泛用于分析加速器设施、空间辐射和放射治疗等各个领域的辐射行为。大多数蒙特卡罗输运计算基于输运粒子单体相空间分布的玻尔兹曼方程。在这种输运计算中，人们只能得到相空间中单体可观测量的平均值，例如，热量、通量和剂量，但无法得到平均值周围的涨落，因为玻尔兹曼方程以及核数据都没有关于决定平均值周围涨落的二体及更高阶关联的信息。然而，近来常常需要更高阶的量，即单体可观测量平均值周围的涨落。这种关联量的一个典型例子是一个单元中的沉积能量分布，它对于估算探测器的响应函数、半导体存储单元的单粒子翻转概率以及微剂量学处理中的辐射效应是必要的。玻尔兹曼方程的解只能描述平均值，而不能描述分布。此外，使用核数据的蒙特卡罗计算无法处理这些量，因为核数据只包含单粒子总截面，而没有关联信息。因此，我们通过引入一个事件发生器模型，对输运计算中的辐射行为开发了一种新的处理方法，在该模型中我们将核数据和反应模型相结合，以便追踪发射体的所有更高阶关联，同时在碰撞中保持能量和动量守恒。
We propose a new treatment of radiation behaviour in transport calculations by introducing an event generator model in which we combine the nuclear data and the reaction models so as to trace all correlations of ejectiles keeping the energy and momentum conservation in a collision. By this new model, we can estimate the fluctuations around the mean values of one-body observables, for example, the deposit energy distribution in a cell, which cannot be obtained by the transport calculations based on the Boltzmann equation with the nuclear data. Nuclear data are extensively used in Monte Carlo transport calculations to analyze the radiation behaviour in various fields such as accelerator facilities, space radiation, and ra- diotherapy. Most of the Monte Carlo transport calculations are based on Boltzmann equation for one-body phase space distribution of the transport particles. In such transport cal- culations, one can obtain only the mean value of the one- body observables in the phase space, e.g., heat, flux, and dose, but not the fluctuations around the mean value, since the Boltzmann equation, nor the nuclear data has information on the two-body and higher order correlations which determine the fluctuation around the mean value. Recently, however, the higher order quantities, i.e., the fluctuations around the mean values of the one-body ob- servables are often required. A typical example for such a correlated quantity is the deposit energy distribution in a cell, which is necessary to estimate the response function of detectors, the single event upset probability of semiconductor memory cells and the radiation effects in a micro-dosimetric treatment. The solution of the Boltzmann equation cannot describe the distribution but only the mean value. Furthermore, Monte Carlo calculations using the nuclear data cannot deal with these quantities, since the nuclear data includes only the inclusive one-body cross sections but no information of the correlations. We have therefore developed a new treatment of radiation behaviour in the transport calculations by introducing an event generator model, in which we have combined the nuclear data and the reaction models so as to trace all higher correlations of ejectiles keeping the energy and momentum conservation in a collision.