MC法模拟地层元素测井仪优化中子屏蔽体

摘要

The monte carlo method was used to simulate interaction of neutron between the detector and the neutron source shield structure.The neutrons were produced by the D-T neutron source.Access to the distribution of energy and nuclear reaction cross section by the different particles with different materials, the shielding efficiency of the different materials with different thickness is got.The simulation using three-layer composite structures of 17 cm shows good results, Tungsten(W)-Nickel(Ni) alloy as the first layer when the thickness is 10 cm;containing 20% Boron(B) polyethylene as the second layer when the thickness is 5 cm;the third layer is Pb when the thickness is 2 cm.At the same time neutron shielding rate reached 98.47% and γ-ray shielding rate reached 97.68%.It could reduce the interference of instrument internal elements and improve the accuracy and resolution of the logging tool formation elements.%利用MC法模拟了D-T中子源发出的粒子通过地层元素测井仪内部屏蔽体结构的过程,获得了不同粒子通过不同材料的屏蔽体后能量和核反应截面的分布,从而得出不同材料在不同厚度下的粒子屏蔽效果.模拟结果表明:采用17 cm厚的三层复合屏蔽体结构,所用材料第一层为10 cm厚的钨镍合金,第二层为5 cm厚含20%碳化硼的聚乙烯,第三层为2 cm厚的铅.三层结构对中子的屏蔽率达到98.47%,对γ光子的屏蔽率达到97.68%.可有效降低仪器内部元素干扰,提高分辨率与精确度.