Stripping units take a key role in the neutral particle analyzer(NPA).A renovated gas-stripping unit was constructed for the newly designed E//B NPA.Using H_(2)as the working gas,we measured the gas inlet pressure(P_(...Stripping units take a key role in the neutral particle analyzer(NPA).A renovated gas-stripping unit was constructed for the newly designed E//B NPA.Using H_(2)as the working gas,we measured the gas inlet pressure(P_(0))and vacuum chamber pressure(P_(3)).The pressure distribution inside the gas-stripping room was calculated with Ansys Fluent,using the measured P_(0)and P_(3)as boundary conditions.The stripping efficiency of the stripping unit was then simulated utilizing the Geant4 Monte Carlo code for the H and D particles.The pressure P_(0)=40 Pa,which is one-sixth of what found in the previous design and corresponds to a thickness of 1.27×10^(17)atoms∕cm^(2),was obtained as the optimum working pressure for the upgraded stripping unit.An 50 kV electron cyclotron resonance(ECR)ion source platform was designed and constructed for E//B NPA calibration,and its performance has been measured.Using the ECR ion source platform,we measured the efficiency of the stripping unit through an inverse experiment with proton beams.We compared the current ratios of measurements with and without H_(2)gas to Geant4 simulation results.We found adequate agreement between the overall trends of the experiment and the simulation.The significant deviation for incident energies below 20 keV may result from the scattering effects of low-energy protons,leading to reduced accuracy in single-scattering physics in Geant4 simulations.Applying the scattering corrections observed in the reverse experiments obtains more accurate stripping efficiencies for H and D atoms in the energy range of 20–200 keV and the global efficiency with the maximum values of 95.0%for H atoms and 78.9%for D atoms at 200 keV.展开更多
The neutral particle analyzer(NPA)is one of the crucial diagnostic devices in a Tokamak facility.The stripping unit is one of the main parts of the NPA.A windowless gas-stripping room with two differential pipes has b...The neutral particle analyzer(NPA)is one of the crucial diagnostic devices in a Tokamak facility.The stripping unit is one of the main parts of the NPA.A windowless gas-stripping room with two differential pipes has been constructed in a parallel electric and magnetic fields(E//B)NPA.The pressure distributions in the stripping chamber are simulated by ANSYS Fluent together with MolFlow+.Based on the pressure distributions obtained from the simulation,the stripping efficiency of the E//B NPA is studied using GEANT4.Hadron reaction physics is modified to track the charge state of each particle in a cross-section-based method in GEANT4.The transmission rates(R)and stripping efficiencies f_(+1)are examined for particle energies ranging from 20 to 200 keV with the input pressure(P_(0)),ranging from 20 to 400 Pa.According to the combined global efficiency,R×f_(+1),P_(0)=240 Pa is obtained as the optimum pressure for the maximum global efficiency in the incident energy range investigated.展开更多
基金supported by the National MCF Energy R&D Program of China(MOST 2018YFE0310200)in part by the National Natural Science Foundation of China(Nos.11705242,11805138,12175156)in part by the Fundamental Research Funds for the Central Universities(Nos.YJ201820,YJ201954)in China.
文摘Stripping units take a key role in the neutral particle analyzer(NPA).A renovated gas-stripping unit was constructed for the newly designed E//B NPA.Using H_(2)as the working gas,we measured the gas inlet pressure(P_(0))and vacuum chamber pressure(P_(3)).The pressure distribution inside the gas-stripping room was calculated with Ansys Fluent,using the measured P_(0)and P_(3)as boundary conditions.The stripping efficiency of the stripping unit was then simulated utilizing the Geant4 Monte Carlo code for the H and D particles.The pressure P_(0)=40 Pa,which is one-sixth of what found in the previous design and corresponds to a thickness of 1.27×10^(17)atoms∕cm^(2),was obtained as the optimum working pressure for the upgraded stripping unit.An 50 kV electron cyclotron resonance(ECR)ion source platform was designed and constructed for E//B NPA calibration,and its performance has been measured.Using the ECR ion source platform,we measured the efficiency of the stripping unit through an inverse experiment with proton beams.We compared the current ratios of measurements with and without H_(2)gas to Geant4 simulation results.We found adequate agreement between the overall trends of the experiment and the simulation.The significant deviation for incident energies below 20 keV may result from the scattering effects of low-energy protons,leading to reduced accuracy in single-scattering physics in Geant4 simulations.Applying the scattering corrections observed in the reverse experiments obtains more accurate stripping efficiencies for H and D atoms in the energy range of 20–200 keV and the global efficiency with the maximum values of 95.0%for H atoms and 78.9%for D atoms at 200 keV.
基金This work was supported by the National MCF Energy R&D Program of China(No.MOST 2018YFE0310200)the National Natural Science Foundation of China(Nos.11805138 and 11705242)the Fundamental Research Funds For the Central Universities(Nos.YJ201820 and YJ201954)。
文摘The neutral particle analyzer(NPA)is one of the crucial diagnostic devices in a Tokamak facility.The stripping unit is one of the main parts of the NPA.A windowless gas-stripping room with two differential pipes has been constructed in a parallel electric and magnetic fields(E//B)NPA.The pressure distributions in the stripping chamber are simulated by ANSYS Fluent together with MolFlow+.Based on the pressure distributions obtained from the simulation,the stripping efficiency of the E//B NPA is studied using GEANT4.Hadron reaction physics is modified to track the charge state of each particle in a cross-section-based method in GEANT4.The transmission rates(R)and stripping efficiencies f_(+1)are examined for particle energies ranging from 20 to 200 keV with the input pressure(P_(0)),ranging from 20 to 400 Pa.According to the combined global efficiency,R×f_(+1),P_(0)=240 Pa is obtained as the optimum pressure for the maximum global efficiency in the incident energy range investigated.
