光子能量沉积计算的一种新方法
A New Calculation Method for Energy Deposition of Photon
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摘要: 光子沉积能广泛地应用于放射医疗和辐射防护领域。 MCNP程序中*F8功能统计的是进出网格的光子与电子能量差。 *F8只能采用真实网格， 计算效率较低。 由于光子的能量沉积都是通过次级电子来完成的， 对光子能量沉积的计算可转换为次级电子能量沉积的计算。 文中据此给出了一种新的光子能量沉积统计方法， 该方法只统计次级电子能量沉积， 且可以采用虚拟网格计数。 新方法若采用真实网格， 计算精度与效率与*F8完全一样； 若采用虚拟网格， 新方法计算精度略低， 但几何建模简单， 计算效率较高。 Energy deposition distribution is very important to study radiotherapy or radioprotection. The *F8 method of MCNP program counts the energy loss of photon and electron together. Only real grid is allowed to *F8, so its computation efficiency is low. This paper gives a new calculation method for energy deposition of photon. Because the energy deposition of photon is accomplished by secondary electron, only electron is counted in the new method. The real collision of the electron is counted by the new method, whereas *F8 only counts the information of particle across the interface. Moreover, virtual grid is allowed in the new method. With real grid, the new method has the same precision and efficiency as *F8. If virtual grid is adopted by the new method, although the precision is slightly down, the efficiency is greatly increased.Abstract: Energy deposition distribution is very important to study radiotherapy or radioprotection. The *F8 method of MCNP program counts the energy loss of photon and electron together. Only real grid is allowed to *F8, so its computation efficiency is low. This paper gives a new calculation method for energy deposition of photon. Because the energy deposition of photon is accomplished by secondary electron, only electron is counted in the new method. The real collision of the electron is counted by the new method, whereas *F8 only counts the information of particle across the interface. Moreover, virtual grid is allowed in the new method. With real grid, the new method has the same precision and efficiency as *F8. If virtual grid is adopted by the new method, although the precision is slightly down, the efficiency is greatly increased.
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