The main purpose of this study is to measure the contribution of the thermal and fast neutron dose along the central axis of the 15 MV Elekta Precise linac in a tissue equivalent phantom. In order to achieve this purpose, different points were selected in three field sizes of 5 × 5 cm2, 10 × 10 cm2 and 15 × 15 cm2. Fast and thermal neutrons were measured using CR-39 nuclear track detectors with and without thermal neutron converter of 10B, respectively. According to the results, the fast neutron dose equivalent was decreased as the depth increased (field size 5 × 5, 10 × 10 and 15 × 15 cm2 fall from 0.35 to 0.15, 0.5 to 0.3 and 0.5 to 0.3, respectively). Thermal dose equivalent was increased as the depth increased in the tissue equivalent phantom (field size 5 × 5, 10 × 10 and 15 × 15 cm2 rise from 0.1 to 0.4, 0.4 to 0.8 and 0.4 to 0.9, respectively). In conclusion, at depth <3 cm, most existing neutrons are fast and CR-39 films are sensitive to fast neutrons; therefore, they are more appropriate than thermoluminescent dosemeters in measuring neutron dose equivalent.

中文翻译：

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使用 CR-39 核跟踪探测器对 15 MV 线性加速器进行热和快中子剂量等效分布测量。

本研究的主要目的是测量热中子剂量和快中子剂量在组织等效体模中沿 15 MV Elekta Precise 直线加速器的中心轴的贡献。为了达到这个目的，在 5 × 5 cm2、10 × 10 cm2 和 15 × 15 cm2 三个场尺寸中选择了不同的点。分别使用带有和不带有 10B 热中子转换器的 CR-39 核径迹探测器测量快中子和热中子。根据结果​​，快中子剂量当量随着深度的增加而降低（视场大小 5 × 5、10 × 10 和 15 × 15 cm2 分别从 0.35 降至 0.15、0.5 至 0.3 和 0.5 至 0.3）。热剂量当量随着组织等效体模深度的增加而增加（视野大小 5 × 5、10 × 10 和 15 × 15 cm2 从 0.1 增加到 0.4、0.4 到 0.8 和 0.4 到 0.9，分别）。总之，在深度<3 cm 处，大多数现有中子是快中子，而 CR-39 薄膜对快中子敏感；因此，它们比热释光剂量计更适合测量中子剂量当量。