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对漂移管周围不同方向剂量水平及其影响因素进行定量评估,有助于对电子辐照加速器主厅内辐射分布建立定性认识。由于加速管沿程束流损失和来自辐照室的透射辐射对加速器主厅的贡献极小,辐照室内经过漂移管外孔隙的散射辐射是加速器主厅的主要辐射源。本文利用蒙特卡罗程序MCNP5对某3MeV高频高压加速器机房进行建模,着重探索不同类型地板圆形通孔对加速器主厅剂量的影响程度。结果表明,通孔直径对垂直方向剂量率的影响极小,而水平方向剂量率随直径的不同而变化明显。对于直径10cm左右的漂移管,通孔采用直径40–60cm圆孔较佳;通孔中采用阶梯型圆台结构不仅节省了加速器轴向高度,更能有效地降低漂移管周围的辐射水平。
Quantitative assessment of the dose levels in different directions around the drift tube and its influencing factors can help to establish a qualitative understanding of the radiation distribution in the main hall of the electron irradiation accelerator. Due to the contribution of the accelerating tube along the beam loss and the contribution of the transmitted radiation from the irradiation chamber to the main hall of the accelerator, the scattered radiation in the irradiation chamber passing through the pores outside the drift tube is the main radiation source of the accelerator main hall. In this paper, a Monte Carlo MCNP5 is used to model a 3MeV high-frequency high-pressure accelerator room, with a focus on exploring the influence of circular through-holes of different types on the dosage of the main hall of an accelerator. The results show that the diameter of the through hole has little effect on the vertical dose rate, while the horizontal dose rate changes obviously with the diameter. For the drift tube with a diameter of about 10cm, the through hole is preferably a circular hole with a diameter of 40-60cm. The adoption of the stepped circular table structure in the through hole not only saves the axial height of the accelerator but also effectively reduces the radiation level around the drift tube.