A heavy-ion time-of-flight spectrometer called HiToF,with magnet focusing accomplished by a quadrupole triplet lens,was constructed at the Beijing Tandem Accelerator National Laboratory,mainly for studies of multi-nuc...A heavy-ion time-of-flight spectrometer called HiToF,with magnet focusing accomplished by a quadrupole triplet lens,was constructed at the Beijing Tandem Accelerator National Laboratory,mainly for studies of multi-nucleon transfer reactions at energies near the Coulomb barrier.The spectrometer was equipped with a rotating chamber with a diameter of 40 cm and could be rotated over a large angular range from−40◦to 160◦.The length from the target to the focal plane is 2.7 m,enabling high-precision time-of-flight measurements using two microchannel plate detectors with a 1.9 m apart and a typical time resolution of 120 ps.A multisampling position-sensitive ionization chamber forΔE−E measurement is placed on the focal plane,which offers aΔZ∕Z resolution of 1/50.The setup provided a maximum solid angleΔΩ=20 msr.An experiment on^(32)S+^(90,94)Zr at a beam energy of 135 MeV was performed to test the performance.The projectile-like ions were identified with a mass resolution ofσ=0.2 amu.The results showed that the HiToF spectrometer is a powerful setup for studying heavy-ion reaction mechanisms at low energies.展开更多
The multiple nuclides identification algorithm with low consumption and strong robustness is crucial for rapid radioactive source searching.This study investigates the design of a low-consumption multiple nuclides ide...The multiple nuclides identification algorithm with low consumption and strong robustness is crucial for rapid radioactive source searching.This study investigates the design of a low-consumption multiple nuclides identification algorithm for portable gamma spectrometers.First,the gamma spectra of 12 target nuclides(including the background case)were measured to create training datasets.The characteristic energies,obtained through energy calibration and full-energy peak addresses,are utilized as input features for a neural network.A large number of single-and multiple-nuclide training datasets are generated using random combinations and small-range drifting.Subsequently,a multi-label classification neural network based on a binary cross-entropy loss function is applied to export the existence probability of certain nuclides.The designed algorithm effectively reduces the computation time and storage space required by the neural network and has been successfully implemented in a portable gamma spectrometer with a running time of t_(r)<2 s.Results show that,in both validation and actual tests,the identification accuracy of the designed algorithm reaches 94.8%,for gamma spectra with a dose rate of d≈0.5μSv∕h and a measurement time t_(m)=60 s.This improves the ability to perform rapid on-site nuclide identification at important sites.展开更多
The neutron total cross-section spectrometer(NTOX)applied on the Back-n beamline at the China Spallation Neutron Source(CSNS)is based on a multicell fission chamber and utilizes ^(235,238)U for neutron detection.To re...The neutron total cross-section spectrometer(NTOX)applied on the Back-n beamline at the China Spallation Neutron Source(CSNS)is based on a multicell fission chamber and utilizes ^(235,238)U for neutron detection.To reduce the experimental uncertainty in the resonance energy region of ^(235,238)U and improve the neutron detection efficiency,a fast scintillator-based neutron total cross-section(FAST)spectrometer was designed.A prototype based on a large-area square ^(6)Li-enriched Cs_(2)LiLaBr_(6)(CLLB)scintillator was constructed and beam-tested.The size of the CLLB scintillator was 50.8 mm×50.8 mm×6 mm,and its side was coupled to an array of 1×8 S14160 MPPC to avoid the irradiation from the high-intensity neutrons and rays.The beam test was performed using a broad-energy pulsed neutron and the time-of-flight(TOF)technique on the Back-n beamline.The results demonstrate that the prototype exhibits good neutron/ γ discrimination capability under strong flash irradiation.The prototype was applied to measure the neutron total cross-section of ^(nat)Pb and the result was compared with that obtained using the NTOX.The two results were consistent in the energy region of 0.3 eV to 1 keV,and the prototype showed a higher detection efficiency and did not exhibit fission resonance effect.This type of spectrometer can be used as a complement to the NTOX in the low-energy range and provides a technical reference and framework for developing the FAST spectrometer on the Back-n beamline.展开更多
A low-background γ spectrometer named the Gamma spectrometer for Nuclear Activation Studies(GNAS)was developed to detect scarce γ radioactivity,with a special focus on conducting activation experiments in nuclear as...A low-background γ spectrometer named the Gamma spectrometer for Nuclear Activation Studies(GNAS)was developed to detect scarce γ radioactivity,with a special focus on conducting activation experiments in nuclear astrophysics.It consisted of a well-type HPGe detector surrounded by optimized multi-layer shielding,which reduced the laboratory background counting rate by 99.5%and enabled a sensitivity edge as low as 0.044 Bq for the 477.6 KeV γ line of ^(7)Be.The near 4π geometry of the HPGe detector introduces a severe true coincidence summing(TCS)effect along with its high detection efficiency.To determine the intrinsic detection efficiency and correct for the TCS effect,a Monte Carlo simulation method was developed with the Geant4 toolkit.The detector model was optimized by matching the simulated full energy peak(FEP)statistics with those of a ^(137)Cs monoenergetic source and calibrated ^(55,57,58)Co sources produced by low-energy proton beam bombardment of natural iron.The intrinsic detection efficiency curve was obtained,and an algorithm for the correction of the TCS effect was programmed using decay data from the ENSDF library and Nuclear Wallet Cards.The GNAS fulfills the requirements of the ongoing activation measurement of proton-and alpha-induced reactions in nuclear astrophysics on the ground and at the Jinping Underground Nuclear Astrophysics(JUNA)facility.展开更多
In section‘Track decoding’of this article,one of the paragraphs was inadvertently missed out after the text'…shows the flow diagram of the Tr2-1121 track mode.'The missed paragraph is provided below.
The accumulation of^(222)Rn and^(220)Rn progeny in poorly ventilated environments poses the risk of natural radiation exposure to the public.A previous study indicated that satisfactory results in determining the^(222...The accumulation of^(222)Rn and^(220)Rn progeny in poorly ventilated environments poses the risk of natural radiation exposure to the public.A previous study indicated that satisfactory results in determining the^(222)Rn and^(220)Rn progeny concentrations by measuring the total alpha counts at five time intervals within 560 min should be expected only in the case of high progeny concentrations in air.To complete the measurement within a relatively short period and adapt it for simultaneous measurements at comparatively lower^(222)Rn and^(220)Rn progeny concentrations,a novel mathematical model was proposed based on the radioactive decay law.This model employs a nonlinear fitting method to distinguish nuclides with overlapping spectra by utilizing the alpha particle counts of non-overlapping spectra within consecutive measurement cycles to obtain the concentrations of^(222)Rn and^(220)Rn progeny in air.Several verification experiments were conducted using an alpha spectrometer.The experimental results demonstrate that the concentrations of^(222)Rn and^(220)Rn progeny calculated by the new method align more closely with the actual circumstances than those calculated by the total count method,and their relative uncertainties are all within±16%.Furthermore,the measurement time was reduced to 90 min,representing an acceleration of 84%.The improved capability of the new method in distinguishing alpha particles with similar energies emitted from ^(218)Po and^(212)Bi,both approximately 6 MeV,contributed to realizing more accurate results.The proposed method has the potential advantage of measuring relatively low concentrations of^(222)Rn and^(220)Rn progeny in air more quickly via air filtration.展开更多
In the field of deep space exploration,the rapid development of terahertz spectrometer has put forward higher requirements to the back-end chirp transform spectrometer(CTS)system.In order to simultaneously meet the me...In the field of deep space exploration,the rapid development of terahertz spectrometer has put forward higher requirements to the back-end chirp transform spectrometer(CTS)system.In order to simultaneously meet the measurement requirements of wide bandwidth and high accuracy spectral lines,we built a CTS system with an analysis bandwidth of 1 GHz and a frequency resolution of 100 kHz around the surface acoustic wave(SAW)chirp filter with a bandwidth of 1 GHz.In this paper,the relationship between the CTS nonlinear phase error shift model and the basic measurement parameters is studied,and the effect of CTS phase mismatch on the pulse compression waveform is analyzed by simulation.And the expander error optimization method is proposed for the problem that the large nonlinear error of the expander leads to the unbalanced response of the CTS system and the serious distortion of the compressed pulse waveform under large bandwidth.It is verified through simulation and experiment that the method is effective for reducing the root mean square error(RMSE)of the phase of the expander from 18.75°to 6.65°,reducing the in-band standard deviation of the CTS frequency resolution index from 8.43 kHz to 4.72 kHz,solving the problem of serious distortion of the compressed pulse waveform,and improving the uneven CTS response under large bandwidth.展开更多
A combination of high-field asymmetric waveform ion mobility spectrometry （FAIMS） with mass spectrometer （MS） was analyzed. FAIMS separates ions from the volatile organic compounds in the gas-phase as an ion-filte...A combination of high-field asymmetric waveform ion mobility spectrometry （FAIMS） with mass spectrometer （MS） was analyzed. FAIMS separates ions from the volatile organic compounds in the gas-phase as an ion-filter for MS. The sample ions were created at ambient pressure by ion source, which was equipped with a 10.6 eV UV discharge lamp （A=116.5 nm）. The drift tube of FAIMS is composed of two parallel planar electrodes and the dimension is 10 mm×8 mm×0.5 mm. FAIMS was investigated when driven by the high-filed rectangular asymmetric waveform with the peak-to-peak voltage of 1.36 kV at the frequency of 1 MHz and the duty cycle of 30%. The acetone, the butanone, and their mixture were adopted to characterize the FAIMS-MS. The mass spectra obtained from MS illustrate that there are ion-molecular reactions between the ions and the sample neutral molecular. And the proton transfer behavior in the mixture of the acetone and the butanone is also observed. With the compensation voltage tuned from -30 V to 10 V with a step size of 0.1 V, the ion pre-separation before MS is realized.展开更多
基金supported by the National Key R&D Program of China(No.2022YFA1602302)the National Natural Science Foundation of China(Nos.U2167204,12175314,and 12235020)the Continuous-Support Basic Scientific Research Project.
文摘A heavy-ion time-of-flight spectrometer called HiToF,with magnet focusing accomplished by a quadrupole triplet lens,was constructed at the Beijing Tandem Accelerator National Laboratory,mainly for studies of multi-nucleon transfer reactions at energies near the Coulomb barrier.The spectrometer was equipped with a rotating chamber with a diameter of 40 cm and could be rotated over a large angular range from−40◦to 160◦.The length from the target to the focal plane is 2.7 m,enabling high-precision time-of-flight measurements using two microchannel plate detectors with a 1.9 m apart and a typical time resolution of 120 ps.A multisampling position-sensitive ionization chamber forΔE−E measurement is placed on the focal plane,which offers aΔZ∕Z resolution of 1/50.The setup provided a maximum solid angleΔΩ=20 msr.An experiment on^(32)S+^(90,94)Zr at a beam energy of 135 MeV was performed to test the performance.The projectile-like ions were identified with a mass resolution ofσ=0.2 amu.The results showed that the HiToF spectrometer is a powerful setup for studying heavy-ion reaction mechanisms at low energies.
文摘The multiple nuclides identification algorithm with low consumption and strong robustness is crucial for rapid radioactive source searching.This study investigates the design of a low-consumption multiple nuclides identification algorithm for portable gamma spectrometers.First,the gamma spectra of 12 target nuclides(including the background case)were measured to create training datasets.The characteristic energies,obtained through energy calibration and full-energy peak addresses,are utilized as input features for a neural network.A large number of single-and multiple-nuclide training datasets are generated using random combinations and small-range drifting.Subsequently,a multi-label classification neural network based on a binary cross-entropy loss function is applied to export the existence probability of certain nuclides.The designed algorithm effectively reduces the computation time and storage space required by the neural network and has been successfully implemented in a portable gamma spectrometer with a running time of t_(r)<2 s.Results show that,in both validation and actual tests,the identification accuracy of the designed algorithm reaches 94.8%,for gamma spectra with a dose rate of d≈0.5μSv∕h and a measurement time t_(m)=60 s.This improves the ability to perform rapid on-site nuclide identification at important sites.
基金supported by the National Natural Science Foundation of China(No.12375296)the Key Laboratory of Nuclear Data Foundation(No.JCKY2022201C153)+1 种基金the Science and Technology Innovation Program of Hunan Province(No.2024RC3205)the Natural Science Foundation of Hunan Province,China(No.2024JJ2044).
文摘The neutron total cross-section spectrometer(NTOX)applied on the Back-n beamline at the China Spallation Neutron Source(CSNS)is based on a multicell fission chamber and utilizes ^(235,238)U for neutron detection.To reduce the experimental uncertainty in the resonance energy region of ^(235,238)U and improve the neutron detection efficiency,a fast scintillator-based neutron total cross-section(FAST)spectrometer was designed.A prototype based on a large-area square ^(6)Li-enriched Cs_(2)LiLaBr_(6)(CLLB)scintillator was constructed and beam-tested.The size of the CLLB scintillator was 50.8 mm×50.8 mm×6 mm,and its side was coupled to an array of 1×8 S14160 MPPC to avoid the irradiation from the high-intensity neutrons and rays.The beam test was performed using a broad-energy pulsed neutron and the time-of-flight(TOF)technique on the Back-n beamline.The results demonstrate that the prototype exhibits good neutron/ γ discrimination capability under strong flash irradiation.The prototype was applied to measure the neutron total cross-section of ^(nat)Pb and the result was compared with that obtained using the NTOX.The two results were consistent in the energy region of 0.3 eV to 1 keV,and the prototype showed a higher detection efficiency and did not exhibit fission resonance effect.This type of spectrometer can be used as a complement to the NTOX in the low-energy range and provides a technical reference and framework for developing the FAST spectrometer on the Back-n beamline.
基金supported by the National Key Research and Development Project(No.2022YFA1602301)the National Natural Science Foundation of China(Nos.U2267205 and 12275361)the Continuous-Support Basic Scientific Research Project.
文摘A low-background γ spectrometer named the Gamma spectrometer for Nuclear Activation Studies(GNAS)was developed to detect scarce γ radioactivity,with a special focus on conducting activation experiments in nuclear astrophysics.It consisted of a well-type HPGe detector surrounded by optimized multi-layer shielding,which reduced the laboratory background counting rate by 99.5%and enabled a sensitivity edge as low as 0.044 Bq for the 477.6 KeV γ line of ^(7)Be.The near 4π geometry of the HPGe detector introduces a severe true coincidence summing(TCS)effect along with its high detection efficiency.To determine the intrinsic detection efficiency and correct for the TCS effect,a Monte Carlo simulation method was developed with the Geant4 toolkit.The detector model was optimized by matching the simulated full energy peak(FEP)statistics with those of a ^(137)Cs monoenergetic source and calibrated ^(55,57,58)Co sources produced by low-energy proton beam bombardment of natural iron.The intrinsic detection efficiency curve was obtained,and an algorithm for the correction of the TCS effect was programmed using decay data from the ENSDF library and Nuclear Wallet Cards.The GNAS fulfills the requirements of the ongoing activation measurement of proton-and alpha-induced reactions in nuclear astrophysics on the ground and at the Jinping Underground Nuclear Astrophysics(JUNA)facility.
文摘In section‘Track decoding’of this article,one of the paragraphs was inadvertently missed out after the text'…shows the flow diagram of the Tr2-1121 track mode.'The missed paragraph is provided below.
基金supported by the National Natural Science Foundation of China(No.12075112)Natural Science Foundation of Hunan(No.2023JJ50121),Natural Science Foundation of Hunan Province(No.2023JJ50091)Key Projects of Hunan Provincial Department of Education(No.23A0516).
文摘The accumulation of^(222)Rn and^(220)Rn progeny in poorly ventilated environments poses the risk of natural radiation exposure to the public.A previous study indicated that satisfactory results in determining the^(222)Rn and^(220)Rn progeny concentrations by measuring the total alpha counts at five time intervals within 560 min should be expected only in the case of high progeny concentrations in air.To complete the measurement within a relatively short period and adapt it for simultaneous measurements at comparatively lower^(222)Rn and^(220)Rn progeny concentrations,a novel mathematical model was proposed based on the radioactive decay law.This model employs a nonlinear fitting method to distinguish nuclides with overlapping spectra by utilizing the alpha particle counts of non-overlapping spectra within consecutive measurement cycles to obtain the concentrations of^(222)Rn and^(220)Rn progeny in air.Several verification experiments were conducted using an alpha spectrometer.The experimental results demonstrate that the concentrations of^(222)Rn and^(220)Rn progeny calculated by the new method align more closely with the actual circumstances than those calculated by the total count method,and their relative uncertainties are all within±16%.Furthermore,the measurement time was reduced to 90 min,representing an acceleration of 84%.The improved capability of the new method in distinguishing alpha particles with similar energies emitted from ^(218)Po and^(212)Bi,both approximately 6 MeV,contributed to realizing more accurate results.The proposed method has the potential advantage of measuring relatively low concentrations of^(222)Rn and^(220)Rn progeny in air more quickly via air filtration.
文摘In the field of deep space exploration,the rapid development of terahertz spectrometer has put forward higher requirements to the back-end chirp transform spectrometer(CTS)system.In order to simultaneously meet the measurement requirements of wide bandwidth and high accuracy spectral lines,we built a CTS system with an analysis bandwidth of 1 GHz and a frequency resolution of 100 kHz around the surface acoustic wave(SAW)chirp filter with a bandwidth of 1 GHz.In this paper,the relationship between the CTS nonlinear phase error shift model and the basic measurement parameters is studied,and the effect of CTS phase mismatch on the pulse compression waveform is analyzed by simulation.And the expander error optimization method is proposed for the problem that the large nonlinear error of the expander leads to the unbalanced response of the CTS system and the serious distortion of the compressed pulse waveform under large bandwidth.It is verified through simulation and experiment that the method is effective for reducing the root mean square error(RMSE)of the phase of the expander from 18.75°to 6.65°,reducing the in-band standard deviation of the CTS frequency resolution index from 8.43 kHz to 4.72 kHz,solving the problem of serious distortion of the compressed pulse waveform,and improving the uneven CTS response under large bandwidth.
文摘A combination of high-field asymmetric waveform ion mobility spectrometry （FAIMS） with mass spectrometer （MS） was analyzed. FAIMS separates ions from the volatile organic compounds in the gas-phase as an ion-filter for MS. The sample ions were created at ambient pressure by ion source, which was equipped with a 10.6 eV UV discharge lamp （A=116.5 nm）. The drift tube of FAIMS is composed of two parallel planar electrodes and the dimension is 10 mm×8 mm×0.5 mm. FAIMS was investigated when driven by the high-filed rectangular asymmetric waveform with the peak-to-peak voltage of 1.36 kV at the frequency of 1 MHz and the duty cycle of 30%. The acetone, the butanone, and their mixture were adopted to characterize the FAIMS-MS. The mass spectra obtained from MS illustrate that there are ion-molecular reactions between the ions and the sample neutral molecular. And the proton transfer behavior in the mixture of the acetone and the butanone is also observed. With the compensation voltage tuned from -30 V to 10 V with a step size of 0.1 V, the ion pre-separation before MS is realized.
