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为计算医用加速器中束流经过270°偏转磁铁系统电子损失所造成的辐射剂量问题,将束流传输相应的计算公式和蒙特卡罗抽样方法相结合,在一阶近似条件下计算了电子在偏转系统中的输运过程,分析了不同初始条件对电子输运和电子损失的影响;模拟结果表明能散是产生电子损失的主要因素之一.计算得到了损失电子所处位置、能量和飞行方向等信息,把计算得到的信息作为蒙特卡罗程序的输入源,进一步计算出束流损失所产生的辐射剂量分布,从而能更完善地设计医用加速器照射头的屏蔽.文中给出在电子束初始半径为1mm、散角为5mrad、能散为10%条件下电子损失率为13.5%,损失电子主要是向加速器照射头部上方辐射出去.
In order to calculate the radiation dose caused by the electron loss of the beam in a medical accelerator passing through a 270 ° deflection magnet system, the corresponding calculation formula of the beam current is combined with the Monte Carlo sampling method to calculate the electron deflection in the first-order approximation And the influence of different initial conditions on electron transport and electron loss is analyzed.The simulation results show that energy dispersion is one of the main factors that cause the electron loss.The calculated location, energy and flight direction And other information, the calculated information is used as the input source of Monte Carlo program to further calculate the radiation dose distribution caused by the beam loss, so as to design the shielding of the irradiation head of the medical accelerator more completely.In this paper, Radius of 1mm, scattered angle of 5mrad, can be scattered as 10% under the condition of electron loss rate of 13.5%, the loss of electrons is mainly irradiated to the accelerator radiation above the head out.