Distribution of spatial photoneutrons inside a 70kg water phantom via neutron activation analysis

This study evaluated spatial Φ th inside a 70kg water phantom using the NAA method. Fifty indium foils were placed inside the water phantom and exposed under 15MV LINAC for 2.5min to yield the 10Gy X-ray dose. The Φ th value at the isocenter of the water was 1.03×10 6ncm -2/Gy-X, and the maximum quantity of Φ th appeared at the water surface along the z-axis, 3.99×10 6ncm -2/Gy-X. The thermal neutron dose at isocenter of the water phantom occupied approximately 0.151% of the whole photo and neutron dose.