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Featured researches published by T. F. Du.


Nuclear Fusion | 2014

Diagnosing NB plasmas on the EAST tokamak with new time-of-flight neutron spectrometer

Xing Zhang; Zhongjing Chen; X. Y. Peng; Z. M. Hu; T. F. Du; Z. Q. Cui; Xufei Xie; Xi Yuan; Tieshuan Fan; Jan Källne; G. Gorini; M. Nocente; M. Tardocchi; Liqun Hu; Guoqiang Zhong; S. Y. Lin; Baonian Wan; Xiangqing Li; Guohui Zhang; Jinxiang Chen

The new neutron spectrometer time-of-flight enhanced diagnostics (TOFED) for the EAST tokamak is presented and its characteristics are described in terms of simulation results, as well as the interface in the torus hall along with new neutral beam (NB) injectors. The use of TOFED for studies of the slowing down of NB-injected deuterons is illustrated. The implications of measuring the neutron emission on a long pulse machine are discussed together with the experimental challenges and diagnostic possibilities approaching those to be encountered in continuous operation.


Review of Scientific Instruments | 2014

Data acquisition system with pulse height capability for the TOFED time-of-flight neutron spectrometer

Zhongjing Chen; X. Y. Peng; Xiang Zhang; T. F. Du; Z. M. Hu; Z. Q. Cui; L. J. Ge; Xufei Xie; Xi Yuan; G. Gorini; M. Nocente; M. Tardocchi; L. Q. Hu; G. Q. Zhong; S. Y. Lin; Bo Wan; Xiaotian Li; G. H. Zhang; Jinxiang Chen; Tieshuan Fan

A new time-of-flight neutron spectrometer TOFED has been constructed for installation at Experimental Advanced Superconducting Tokamak. A data acquisition system combining measurements of flight time and energy from the interaction of neutrons with the TOFED scintillators has been developed. The data acquisition system can provide a digitizing resolution better than 1.5% (to be compared with the >10% resolution of the recoil particle energy in the plastic scintillators) and a time resolution <1 ns. At the same time, it is compatible with high count rate event recording, which is an essential feature to investigate phenomena occurring on time scales faster than the slowing down time (≈100 ms) of the beam ions in the plasma. Implications of these results on the TOFED capability to resolve fast ion signatures in the neutron spectrum from EAST plasmas are discussed.


Review of Scientific Instruments | 2014

Design of a magnetic shielding system for the time of flight enhanced diagnostics neutron spectrometer at Experimental Advanced Superconducting Tokamak.

Z. Q. Cui; Zhongjing Chen; Xufei Xie; X. Y. Peng; Z. M. Hu; T. F. Du; L. J. Ge; Xiang Zhang; Xi Yuan; Z. W. Xia; L. Q. Hu; G. Q. Zhong; S. Y. Lin; Bo Wan; Tieshuan Fan; Jinxiang Chen; Xiaotian Li; G. H. Zhang

The novel neutron spectrometer TOFED (Time of Flight Enhanced Diagnostics), comprising 90 individual photomultiplier tubes coupled with 85 plastic scintillation detectors through light guides, has been constructed and installed at Experimental Advanced Superconducting Tokamak. A dedicated magnetic shielding system has been constructed for TOFED, and is designed to guarantee the normal operation of photomultiplier tubes in the stray magnetic field leaking from the tokamak device. Experimental measurements and numerical simulations carried out employing the finite element method are combined to optimize the design of the magnetic shielding system. The system allows detectors to work properly in an external magnetic field of 200 G.


Journal of Instrumentation | 2017

Experimental determination of the response functions of a Bonner sphere spectrometer to monoenergetic neutrons

Z. M. Hu; Zhongjing Chen; X. Y. Peng; T. F. Du; Z. Q. Cui; L. J. Ge; W.J. Zhu; Z. Wang; X. Zhu; Jinxiang Chen; Guohui Zhang; Xiangqing Li; Hong Zhang; G. Q. Zhong; L. Q. Hu; Baonian Wan; G. Gorini; Tieshuan Fan

A Bonner sphere spectrometer (BSS) plays an important role in characterizing neutron spectra and determining their neutron dose in a neutron-gamma mixed field. A BSS consisting of a set of nine polyethylene spheres with a (3)He proportional counter was developed at Peking University to perform neutron spectrum and dosimetry measurements. Response functions (RFs) of the BSS were calculated with the general Monte Carlo code MCNP5 for the neutron energy range from thermal up to 20 MeV, and were experimentally calibrated with monoenergetic neutron beams from 144 keV to 14 MeV on a 4.5 MV Van de Graaff accelerator. The calculated RFs were corrected with the experimental values, and the whole response matrix was completely established. The spectrum of a (241)Am-Be source was obtained after unfolding the measurement data of the BSS to the source and in fair agreement with the expected one. The integral ambient dose equivalent corresponding to the spectrum was 0.95 of the expected value. Results of the unfolded spectrum and the integral dose equivalent measured by the BSS verified that the RFs of the BSS were well established.


Review of Scientific Instruments | 2014

Light output function and assembly of the time-of-flight enhanced diagnostics neutron spectrometer plastic scintillators for background reduction by double kinematic selection at EAST

X. Y. Peng; Zhongjing Chen; Xiang Zhang; Z. M. Hu; T. F. Du; Z. Q. Cui; Xufei Xie; L. J. Ge; Xi Yuan; G. Gorini; M. Nocente; M. Tardocchi; L. Q. Hu; G. Q. Zhong; S. Y. Lin; Bo Wan; Xiaotian Li; G. H. Zhang; Jinxiang Chen; Tieshuan Fan

The 2.5 MeV neutron spectrometer TOFED (Time-Of-Flight Enhanced Diagnostics) has been constructed to perform advanced neutron emission spectroscopy diagnosis of deuterium plasmas on EAST. The instrument has a double-ring structure which, in combination with pulse shape digitization, allows for a dual kinematic selection in the time-of-flight/recoil proton energy (tof/Ep) space, thus improving the spectrometer capability to resolve fast ion signatures in the neutron spectrum, in principle up to a factor ≈100. The identification and separation of features from the energetic ions in the neutron spectrum depends on the detailed knowledge of the instrument response function, both in terms of the light output function of the scintillators and the effect of undesired multiple neutron scatterings in the instrument. This work presents the determination of the light output function of the TOFED plastic scintillator detectors and their geometrical assembly. Results from dedicated experiments with γ-ray sources and quasi-monoenergetic neutron beams are presented. Implications on the instrument capability to perform background suppression based on double kinematic selection are discussed.


Review of Scientific Instruments | 2014

Design of the radiation shielding for the time of flight enhanced diagnostics neutron spectrometer at Experimental Advanced Superconducting Tokamak.

T. F. Du; Zhongjing Chen; X. Y. Peng; Xi Yuan; Xiang Zhang; G. Gorini; M. Nocente; M. Tardocchi; Z. M. Hu; Z. Q. Cui; Xufei Xie; L. J. Ge; L. Q. Hu; G. Q. Zhong; S. Y. Lin; Bo Wan; Xiaotian Li; G. H. Zhang; Jinxiang Chen; Tieshuan Fan

A radiation shielding has been designed to reduce scattered neutrons and background gamma-rays for the new double-ring Time Of Flight Enhanced Diagnostics (TOFED). The shielding was designed based on simulation with the Monte Carlo code MCNP5. Dedicated model of the EAST tokamak has been developed together with the emission neutron source profile and spectrum; the latter were simulated with the Nubeam and GENESIS codes. Significant reduction of background radiation at the detector can be achieved and this satisfies the requirement of TOFED. The intensities of the scattered and direct neutrons in the line of sight of the TOFED neutron spectrometer at EAST are studied for future data interpretation.


Review of Scientific Instruments | 2016

Measurement and simulation of the response function of time of flight enhanced diagnostics neutron spectrometer for beam ion studies at EAST tokamak

X. Y. Peng; Zhongjing Chen; Xiang Zhang; T. F. Du; Z. M. Hu; L. J. Ge; Y. M. Zhang; J. Q. Sun; G. Gorini; M. Nocente; M. Tardocchi; L. Q. Hu; G. Q. Zhong; N. Pu; S. Y. Lin; B. N. Wan; Xiaotian Li; G. H. Zhang; Jinxiang Chen; Tieshuan Fan

The 2.5 MeV TOFED (Time-Of-Flight Enhanced Diagnostics) neutron spectrometer with a double-ring structure has been installed at Experimental Advanced Superconducting Tokamak (EAST) to perform advanced neutron emission spectroscopy diagnosis of deuterium plasmas. This work describes the response function of the TOFED spectrometer, which is evaluated for the fully assembled instrument in its final layout. Results from Monte Carlo simulations and dedicated experiments with pulsed light sources are presented and used to determine properties of light transport from the scintillator. A GEANT4 model of the TOFED spectrometer was developed to calculate the instrument response matrix. The simulated TOFED response function was successfully benchmarked against measurements of the time-of-flight spectra for quasi-monoenergetic neutrons in the energy range of 1-4 MeV. The results are discussed in relation to the capability of TOFED to perform beam ion studies on EAST.


Review of Scientific Instruments | 2014

Neutron emission measurement at the HL-2A tokamak device with a liquid scintillation detector

Xufei Xie; Zhongjing Chen; X. Y. Peng; Xi Yuan; Xing Zhang; G. Gorini; Z. Q. Cui; T. F. Du; Z. M. Hu; Tao Li; Tieshuan Fan; Jinxiang Chen; Xiangqing Li; Guohui Zhang; Guoliang Yuan; Jinwei Yang; Qingwei Yang

Neutron emission measurement at the HL-2A tokamak device with a liquid scintillation detector is described. The detector was placed at a location with little structure material in the field of view, and equipped with a gain monitoring system which could provide the possibility to evaluate the gain variation as well as to correct for the detector response. Time trace of the neutron emissivity was obtained and it was consistent with the result of a standard (235)U fission chamber. During the plasma discharge the neutron yield could vary by about four orders of magnitude and the fluctuation of the detector gain was up to about 6%. Pulse height spectrum of the liquid scintillation detector was constructed and corrected with the aid of the gain monitoring system, and the correction was found to be essential for the assessment of the neutron energy spectrum. This successful measurement offered experience and confidence for the application of liquid scintillation detectors in the upcoming neutron camera system.


Journal of Instrumentation | 2016

Conceptual design of a camera system for neutron imaging in low fusion power tokamaks

Xufei Xie; Xi Yuan; Xing Zhang; M. Nocente; Zhongjing Chen; X. Y. Peng; Z. Q. Cui; T. F. Du; Z. M. Hu; Tao Li; Tieshuan Fan; Jinxiang Chen; Xiangqing Li; Guohui Zhang; G. Yuan; J. Yang; Q. Yang

The basic principles for designing a camera system for neutron imaging in low fusion power tokamaks are illustrated for the case of the HL-2A tokamak device. HL-2A has an approximately circular cross section, with total neutron yields of about 1012 n/s under 1 MW neutral beam injection (NBI) heating. The accuracy in determining the width of the neutron emission profile and the plasma vertical position are chosen as relevant parameters for design optimization. Typical neutron emission profiles and neutron energy spectra are calculated by Monte Carlo method. A reference design is assumed, for which the direct and scattered neutron fluences are assessed and the neutron count profile of the neutron camera is obtained. Three other designs are presented for comparison. The reference design is found to have the best performance for assessing the width of peaked to broadened neutron emission profiles. It also performs well for the assessment of the vertical position.


Review of Scientific Instruments | 2018

Velocity-space sensitivity of time-of-flight neutron spectrometer at EAST in deuterium plasma

L. J. Ge; Z. M. Hu; Y. M. Zhang; J. Q. Sun; Xi Yuan; X. Y. Peng; Z.J. Chen; T. F. Du; M. Nocente; G. Gorini; M. Tardocchi; L. Q. Hu; G. Q. Zhong; Bo Wan; Xiaotian Li; Tieshuan Fan

The Time-Of-Flight Enhanced Diagnostics (TOFED) neutron spectrometer with a double-ring structure has been installed at the Experimental Advanced Superconducting Tokamak (EAST) to perform advanced neutron emission spectroscopy diagnosis for deuterium plasma. In order to reduce the random coincidence from the background neutrons and gamma-rays, TOFED was moved outside the experimental hall and placed in the newly-built nuclear diagnostics laboratory in 2017. In this paper, the instrument-specific weight functions of TOFED are derived by taking the instrument response matrix and the radial line of sight in this new layout into consideration. The results show that the instrument is predominantly sensitive to counter-passing particles in the region where time-of-flights < 69.4 ns, while events at higher time-of-flights (corresponding lower neutron energies) are mostly representative of co-passing ions. The instrument-specific weight functions express the relationship between data in a given channel of the spectrum and the velocity space region that contributes to that. The results can be applied for energetic particle physics studies at EAST, in particular to compare data from different diagnostic techniques.

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Xufei Xie

China Academy of Engineering Physics

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