基于掺硼慢化体的多球中子谱仪的设计
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摘要
目的为了提高中子探测器低能及中能区的能量分辨率,为现场剂量防护仪表校准提供依据,提出了一种改进型多球中子谱仪。方法谱仪采用中心置有3He正比计数器的聚乙烯内慢化球外覆盖不同掺碳化硼聚乙烯球壳的形式,通过调整含硼聚乙烯厚度和硼含量改变慢化体对中子的慢化和吸收性能,降低对低能中子的响应从而形成一系列具有"阈值"的响应函数,由此构成一套改进的具有高分辨率的多球谱仪。结果通过与常规多球谱仪的比较,表明该设计可显著改善多球中子谱仪在1 e V至10 Me V的能量分辨率。结论由理论计算结果可知,利用响应函数"阈值"原理设计多球中子谱仪,可较大程度提高其对低能及中能区的能量分辨率。
Objective A modification of the multisphere neutron spectrometer is proposed in order to improve the energy resolution at low and intermediate energies around some radiation fields,and then to provide information for the calibration of radiation protection instruments. Methods The spectrometer is a set of detector assemblies made of spherical moderators of different sizes,which the polyethylene spheres are surrounded by layers of neutron moderators and absorbers( Boron-containing-PE),each one with a3 He proportional counter placed at the center. By adjusting the thickness and content of the boron shell,the response of the multisphere spectrometer in lower energy has been changed,then a series of response functions with different threshold values are obtained. By this way a set of improved multisphere spectrometer with good resolving power is acquired. Results This design improves the energy resolution of the multisphere neutron spectrometer in the energy range from 1 e V to 10 Me V significantly has been proved by comparing with the conventional multisphere spectrometers. Conclusion The theoretical calculation results indicate that the principle of response functions with different threshold values has greatly improved the energy resolution at low and intermediate energies.
Objective A modification of the multisphere neutron spectrometer is proposed in order to improve the energy resolution at low and intermediate energies around some radiation fields,and then to provide information for the calibration of radiation protection instruments. Methods The spectrometer is a set of detector assemblies made of spherical moderators of different sizes,which the polyethylene spheres are surrounded by layers of neutron moderators and absorbers( Boron-containing-PE),each one with a3 He proportional counter placed at the center. By adjusting the thickness and content of the boron shell,the response of the multisphere spectrometer in lower energy has been changed,then a series of response functions with different threshold values are obtained. By this way a set of improved multisphere spectrometer with good resolving power is acquired. Results This design improves the energy resolution of the multisphere neutron spectrometer in the energy range from 1 e V to 10 Me V significantly has been proved by comparing with the conventional multisphere spectrometers. Conclusion The theoretical calculation results indicate that the principle of response functions with different threshold values has greatly improved the energy resolution at low and intermediate energies.
引文
[1]Brooks F D,Klein H.Neutron spectrometry-historical review and present status[J].Nucl Instr and Meth,2002,A 476:1-11.
[2]Bramblett R L,Ewing R I,Bonner T W.A New Type of Neutron Spectrometer[J].Nucl Instr and Meth,1960,9:1-12.
[3]Alevra A V,Thomas D J.Neutron spectrometry in mixed fields:multisphere spectrometers[J].Radiat Prot Dosim,2003,107:37-72.
[4]Wang C K,Blue T E.A neutron spectrometry for neutrons with energies between 1 e V and 10 ke V[J].Nucl Instr and Meth,1990,A290:237-241.
[5]陈军,李春娟,李玮,等.多球谱仪测量BNCT医院中子照射器中子束能谱[J].原子能科学技术,2014,48(11):2127-2132.
[6]Ueda H,Tanaka H,Sakurai Y.Reprint of the improvement of the energy resolution in epi-thermal neutron region of Bonner sphere using boric acid water solution moderator[J].Appl Radiat Isot,2015,106:107-110.
[7]ISO.Reference Neutron Radiations-Characteristics and Methods of Production of Simulated Workplace Neutron Fields,ISO 12789[J].2000.
[8]Griffith RV,Palfalvi J,Madhvanath U.IAEA Tech.Rep.318[R].1990.
[9]Griffith RV,Palfalvi J,Siebert B R L.IAEA Tech.Rep.403[R].2001.
[10]Apfel R E,d’Errico F.A neutron spectrometer based on temperature variations in superheated drop compositions[J].Nucl Instr and Meth,2002,A476:298-303.
[11]X-5 Monte Carlo Team.MCNP-A General Monte Carlo N-Particle Transport Code[R].Los Alamos National Laboratory Report,LA-CP-03-0245,Version 5,US:2003.
[12]Mazrou H,Idiri Z,Sidahmed T,et al.MCNP5 evaluation of a response matrix of a Bonner Sphere Spectrometer with a high efficiency6Li I(Eu)detector from 0.01 e V to 20 Me V neutrons[J].Radioanal Nucl Chem,2010,284:253-263.
[13]Backus G E,Gilbert J F.Numerical Applications of a Formalism for Geophysical Inverse Problems[J].Geophys J R Astr Soc,1967,13:247-276.
[14]Backus G,Gilbert F.The Resolving Power of Gross Earth Data[J].Geophys J R Astr Soc,1968,16:169-205.
[15]Reginatto M.Resolving power of a multisphere neutron spectrometer[J].Nucl Instr and Meth,2002,480:690-695.
[2]Bramblett R L,Ewing R I,Bonner T W.A New Type of Neutron Spectrometer[J].Nucl Instr and Meth,1960,9:1-12.
[3]Alevra A V,Thomas D J.Neutron spectrometry in mixed fields:multisphere spectrometers[J].Radiat Prot Dosim,2003,107:37-72.
[4]Wang C K,Blue T E.A neutron spectrometry for neutrons with energies between 1 e V and 10 ke V[J].Nucl Instr and Meth,1990,A290:237-241.
[5]陈军,李春娟,李玮,等.多球谱仪测量BNCT医院中子照射器中子束能谱[J].原子能科学技术,2014,48(11):2127-2132.
[6]Ueda H,Tanaka H,Sakurai Y.Reprint of the improvement of the energy resolution in epi-thermal neutron region of Bonner sphere using boric acid water solution moderator[J].Appl Radiat Isot,2015,106:107-110.
[7]ISO.Reference Neutron Radiations-Characteristics and Methods of Production of Simulated Workplace Neutron Fields,ISO 12789[J].2000.
[8]Griffith RV,Palfalvi J,Madhvanath U.IAEA Tech.Rep.318[R].1990.
[9]Griffith RV,Palfalvi J,Siebert B R L.IAEA Tech.Rep.403[R].2001.
[10]Apfel R E,d’Errico F.A neutron spectrometer based on temperature variations in superheated drop compositions[J].Nucl Instr and Meth,2002,A476:298-303.
[11]X-5 Monte Carlo Team.MCNP-A General Monte Carlo N-Particle Transport Code[R].Los Alamos National Laboratory Report,LA-CP-03-0245,Version 5,US:2003.
[12]Mazrou H,Idiri Z,Sidahmed T,et al.MCNP5 evaluation of a response matrix of a Bonner Sphere Spectrometer with a high efficiency6Li I(Eu)detector from 0.01 e V to 20 Me V neutrons[J].Radioanal Nucl Chem,2010,284:253-263.
[13]Backus G E,Gilbert J F.Numerical Applications of a Formalism for Geophysical Inverse Problems[J].Geophys J R Astr Soc,1967,13:247-276.
[14]Backus G,Gilbert F.The Resolving Power of Gross Earth Data[J].Geophys J R Astr Soc,1968,16:169-205.
[15]Reginatto M.Resolving power of a multisphere neutron spectrometer[J].Nucl Instr and Meth,2002,480:690-695.