Monte Carlo simulation of a Bonner sphere spectrometer for application to the determination of neutron field in the Experimental Advanced Superconducting Tokamak experimental halla) Z. M. Hu, X. F. Xie, Z. J. Chen, X. Y. Peng, T. F. Du, Z. Q. Cui, L. J. Ge, T. Li, X. Yuan, X. Zhang, L. Q. Hu, G. Q. Zhong, S. Y. Lin, B. N. Wan, G. Gorini, X. Q. Li, G. H. Zhang, J. X. Chen, and T. S. Fan Citation: Review of Scientific Instruments 85, 11E417 (2014); doi: 10.1063/1.4891163 View online: http://dx.doi.org/10.1063/1.4891163 View Table of Contents: http://scitation.aip.org/content/aip/journal/rsi/85/11?ver=pdfcov Published by the AIP Publishing Articles you may be interested in Design of the radiation shielding for the time of flight enhanced diagnostics neutron spectrometer at Experimental Advanced Superconducting Tokamaka) Rev. Sci. Instrum. 85, 11E115 (2014); 10.1063/1.4891059 Neutron field parameter measurements on the JET tokamak by means of super-heated fluid detectorsa) Rev. Sci. Instrum. 83, 10E124 (2012); 10.1063/1.4739410 Gain stabilization control system of the upgraded magnetic proton recoil neutron spectrometer at JET Rev. Sci. Instrum. 80, 063505 (2009); 10.1063/1.3109682 Proposed neutron diagnostics for Wendelstein 7-X stellarator Rev. Sci. Instrum. 70, 1185 (1999); 10.1063/1.1149321 A neutron camera for ITER (invited) Rev. Sci. Instrum. 68, 514 (1997); 10.1063/1.1147619
This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitationnew.aip.org/termsconditions. Downloaded to IP: 164.76.102.52 On: Fri, 14 Nov 2014 12:15:39
REVIEW OF SCIENTIFIC INSTRUMENTS 85, 11E417 (2014)
Monte Carlo simulation of a Bonner sphere spectrometer for application to the determination of neutron field in the Experimental Advanced Superconducting Tokamak experimental halla) Z. M. Hu,1 X. F. Xie,1 Z. J. Chen,1 X. Y. Peng,1 T. F. Du,1 Z. Q. Cui,1 L. J. Ge,1 T. Li,1 X. Yuan,1 X. Zhang,1 L. Q. Hu,2 G. Q. Zhong,2 S. Y. Lin,2 B. N. Wan,2 G. Gorini,3,4 X. Q. Li,1 G. H. Zhang,1 J. X. Chen,1 and T. S. Fan1,b) 1
State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, China Institute of Plasma Physics, CAS, Hefei 230031, China 3 Dipartimento di Fisica, Università di Milano-Bicocca, Milano 20126, Italy 4 Istituto di Fisica del Plasma “P. Caldirola,” Milano 20126, Italy 2
(Presented 4 June 2014; received 2 June 2014; accepted 13 July 2014; published online 4 August 2014) To assess the neutron energy spectra and the neutron dose for different positions around the Experimental Advanced Superconducting Tokamak (EAST) device, a Bonner Sphere Spectrometer (BSS) was developed at Peking University, with totally nine polyethylene spheres and a SP9 3 He counter. The response functions of the BSS were calculated by the Monte Carlo codes MCNP and GEANT4 with dedicated models, and good agreement was found between these two codes. A feasibility study was carried out with a simulated neutron energy spectrum around EAST, and the simulated “experimental” result of each sphere was obtained by calculating the response with MCNP, which used the simulated neutron energy spectrum as the input spectrum. With the deconvolution of the “experimental” measurement, the neutron energy spectrum was retrieved and compared with the preset one. Good consistence was found which offers confidence for the application of the BSS system for dose and spectrum measurements around a fusion device. © 2014 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4891163] I. INTRODUCTION
With the increase of the fusion power and related plasma parameters, the neutron yield from the EAST is going up rapidly and the radiation protection is gaining more concern. Neutrons generated by fusion reaction, with energies about 2.5 MeV and 14.1 MeV, can easily penetrate the vacuum vessel of the experimental device, and possibly induce damages to the equipment in the experimental hall as well as threats to human health. Radiation protection from neutron are known essential issues for tokamaks,1, 2 and neutron measurements have also been performed at JET, TFTR, and other tokamaks.3–6 Therefore, it is crucial to investigate the dosimetry issues related to neutrons for the normal operation of EAST. At EAST, the DD neutrons during the deuterium discharges are scattered by the ambient materials around the device, thus the neutron energy spectrum can be divided into the fast and thermal neutron components, with the neutron energy ranging from thermal energies to several MeV. The BSS7–9 has been widely used for neutron spectrometry at various environments, especially for the application in a neutron field with broad neutron energy range. Although the energy resolution of this kind of system is generally not good, it could fit the need of dose measurement at some situations. Meanwhile, with some detectors such as 3 He proa) Contributed paper, published as part of the Proceedings of the 20th
Topical Conference on High-Temperature Plasma Diagnostics, Atlanta, Georgia, USA, June 2014. b) Author to whom correspondence should be addressed. Electronic mail: [email protected] 0034-6748/2014/85(11)/11E417/4/$30.00
portional counters, it is generally insensitive to gamma rays, which is very good for the neutron spectrum measurement in high gamma-ray ambient environment, for example, around a fusion reactor. A BSS system was developed at Peking University, and it is intended for the measurement of the neutron dose and neutron spectrum at various positions around the tokamak in the EAST experimental hall. A feasibility study was carried out before the experiments at EAST, using a default neutron energy spectrum simulated by dedicated MCNP model. The “experimental” results of the BSS system are obtained by Monte Carlo simulation of the detector response to the preset neutron energy spectrum. The neutron energy spectrum was then obtained by de-convolution of the measured result with the response functions.
II. METHODS AND MATERIALS A. Description of the BSS system
The BSS system in this work comprises nine spheres made of polyethylene with mass density of 0.94 g/cm3 . The diameters of the polyethylene spheres are 2.5, 3, 3.5, 4, 5, 6, 8, 10, 12 in., respectively. A 3 He filled spherical detector (SP9/524/KT), manufactured by CENTRONIC Ltd., is placed in the center of the Bonner spheres as the central detector to measure thermalized neutrons via the 3 He(n, p)3 H reaction. The sensitive volume of the detector is 17.38 cm3 , and the 3 He gas pressure is 7 atm.
85, 11E417-1
© 2014 AIP Publishing LLC
This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitationnew.aip.org/termsconditions. Downloaded to IP: 164.76.102.52 On: Fri, 14 Nov 2014 12:15:39
11E417-2
Hu et al.
Rev. Sci. Instrum. 85, 11E417 (2014)
TABLE I. Neutron process and G4NeutronHP-dataset used for the GEANT4 calculation. Process Elastic
Inelastic Fission Capture
Energy
G4-name
G4NeutronHP-dataset
This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitationnew.aip.org/termsconditions. Downloaded to IP: 164.76.102.52 On: Fri, 14 Nov 2014 12:15:39
REVIEW OF SCIENTIFIC INSTRUMENTS 85, 11E417 (2014)
Monte Carlo simulation of a Bonner sphere spectrometer for application to the determination of neutron field in the Experimental Advanced Superconducting Tokamak experimental halla) Z. M. Hu,1 X. F. Xie,1 Z. J. Chen,1 X. Y. Peng,1 T. F. Du,1 Z. Q. Cui,1 L. J. Ge,1 T. Li,1 X. Yuan,1 X. Zhang,1 L. Q. Hu,2 G. Q. Zhong,2 S. Y. Lin,2 B. N. Wan,2 G. Gorini,3,4 X. Q. Li,1 G. H. Zhang,1 J. X. Chen,1 and T. S. Fan1,b) 1
State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, China Institute of Plasma Physics, CAS, Hefei 230031, China 3 Dipartimento di Fisica, Università di Milano-Bicocca, Milano 20126, Italy 4 Istituto di Fisica del Plasma “P. Caldirola,” Milano 20126, Italy 2
(Presented 4 June 2014; received 2 June 2014; accepted 13 July 2014; published online 4 August 2014) To assess the neutron energy spectra and the neutron dose for different positions around the Experimental Advanced Superconducting Tokamak (EAST) device, a Bonner Sphere Spectrometer (BSS) was developed at Peking University, with totally nine polyethylene spheres and a SP9 3 He counter. The response functions of the BSS were calculated by the Monte Carlo codes MCNP and GEANT4 with dedicated models, and good agreement was found between these two codes. A feasibility study was carried out with a simulated neutron energy spectrum around EAST, and the simulated “experimental” result of each sphere was obtained by calculating the response with MCNP, which used the simulated neutron energy spectrum as the input spectrum. With the deconvolution of the “experimental” measurement, the neutron energy spectrum was retrieved and compared with the preset one. Good consistence was found which offers confidence for the application of the BSS system for dose and spectrum measurements around a fusion device. © 2014 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4891163] I. INTRODUCTION
With the increase of the fusion power and related plasma parameters, the neutron yield from the EAST is going up rapidly and the radiation protection is gaining more concern. Neutrons generated by fusion reaction, with energies about 2.5 MeV and 14.1 MeV, can easily penetrate the vacuum vessel of the experimental device, and possibly induce damages to the equipment in the experimental hall as well as threats to human health. Radiation protection from neutron are known essential issues for tokamaks,1, 2 and neutron measurements have also been performed at JET, TFTR, and other tokamaks.3–6 Therefore, it is crucial to investigate the dosimetry issues related to neutrons for the normal operation of EAST. At EAST, the DD neutrons during the deuterium discharges are scattered by the ambient materials around the device, thus the neutron energy spectrum can be divided into the fast and thermal neutron components, with the neutron energy ranging from thermal energies to several MeV. The BSS7–9 has been widely used for neutron spectrometry at various environments, especially for the application in a neutron field with broad neutron energy range. Although the energy resolution of this kind of system is generally not good, it could fit the need of dose measurement at some situations. Meanwhile, with some detectors such as 3 He proa) Contributed paper, published as part of the Proceedings of the 20th
Topical Conference on High-Temperature Plasma Diagnostics, Atlanta, Georgia, USA, June 2014. b) Author to whom correspondence should be addressed. Electronic mail: [email protected] 0034-6748/2014/85(11)/11E417/4/$30.00
portional counters, it is generally insensitive to gamma rays, which is very good for the neutron spectrum measurement in high gamma-ray ambient environment, for example, around a fusion reactor. A BSS system was developed at Peking University, and it is intended for the measurement of the neutron dose and neutron spectrum at various positions around the tokamak in the EAST experimental hall. A feasibility study was carried out before the experiments at EAST, using a default neutron energy spectrum simulated by dedicated MCNP model. The “experimental” results of the BSS system are obtained by Monte Carlo simulation of the detector response to the preset neutron energy spectrum. The neutron energy spectrum was then obtained by de-convolution of the measured result with the response functions.
II. METHODS AND MATERIALS A. Description of the BSS system
The BSS system in this work comprises nine spheres made of polyethylene with mass density of 0.94 g/cm3 . The diameters of the polyethylene spheres are 2.5, 3, 3.5, 4, 5, 6, 8, 10, 12 in., respectively. A 3 He filled spherical detector (SP9/524/KT), manufactured by CENTRONIC Ltd., is placed in the center of the Bonner spheres as the central detector to measure thermalized neutrons via the 3 He(n, p)3 H reaction. The sensitive volume of the detector is 17.38 cm3 , and the 3 He gas pressure is 7 atm.
85, 11E417-1
© 2014 AIP Publishing LLC
This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitationnew.aip.org/termsconditions. Downloaded to IP: 164.76.102.52 On: Fri, 14 Nov 2014 12:15:39
11E417-2
Hu et al.
Rev. Sci. Instrum. 85, 11E417 (2014)
TABLE I. Neutron process and G4NeutronHP-dataset used for the GEANT4 calculation. Process Elastic
Inelastic Fission Capture
Energy
G4-name
G4NeutronHP-dataset
