In the past decade,boron neutron capture therapy utilizing an accelerator-based neutron source(ABNS)designed primarily for producing epithermal neutrons has been implemented in the treatment of brain tumors and other ...In the past decade,boron neutron capture therapy utilizing an accelerator-based neutron source(ABNS)designed primarily for producing epithermal neutrons has been implemented in the treatment of brain tumors and other cancers.The specifications for designing an epithermal beam are primarily based on the IAEA-TECODC-1223 report,issued in 2001 for reactor neutron sources.Based on this report,the latest perspectives and clinical requirements,we designed an ABNS capable of adjusting the average neutron beam energy.The design was based on a 2.8 MeV,20 mA proton beam bombarding a lithium target to produce neutrons that were subsequently moderated and tuned through a tunable beam shaping assembly(BSA)which can modify the thicknesses and materials of the coin-shaped moderators,back reflectors,filters,and collimators.The simulation results demonstrated that epithermal neutron beams for deep seated tumor treatment,which were generated by utilizing magnesium fluoride with lengths ranging between 28 and 36 cm as the moderator,possessed a treatment depth of 5.6 cm although the neutron flux peak shifts from 4.5 to 1.0 keV.When utilizing a thinner moderator,a less accelerated beam power can meet the treatment requirements.However,higher powers reduced the treatment time.In contrast,employing a thick moderator can reduce the skin dose.In scenarios that required relatively low energy neutron beams,the removal of the thermal neutron filter can raise the thermal neutron flux at the beam port.And the depth of the dose rate peak could be adjusted between 0.25 and 2.20 cm by combining magnesium fluoride and polyethylene coins of different thicknesses.Hence,this device has a better adaptability for the treatment of superficial tumors.Overall,the tunable BSA provides greater flexibility for clinical treatment than common BSA designs that can only adjust the port size.展开更多
This paper presents a conceptual design for the first tentative surface muon source based on the proton beam provided by China Spallation Neutron Source （CSNS）. We have calcu- lated the optimal parameters of solid m...This paper presents a conceptual design for the first tentative surface muon source based on the proton beam provided by China Spallation Neutron Source （CSNS）. We have calcu- lated the optimal parameters of solid muon target, in which the method of Monte Carlo simula- tion is used to obtain the optimal muon beam parameters, such as beam fiuence rate, momentum spread and phase space distribution. A simple muon transport beamline system was also designed, which could transport the muons emitted from the muon target into the experimental area, where positrons from muon decay in a test sample are detected by a spectrometer. The beam optics of this new beam line is also described.展开更多
Utilizing the laser-driven Z-pinch e ect,we propose an approach for generating an ultrashort,intense Me V neutron source with femtosecond pulse duration.The self-generated magnetic field driven by a petawatt-class las...Utilizing the laser-driven Z-pinch e ect,we propose an approach for generating an ultrashort,intense Me V neutron source with femtosecond pulse duration.The self-generated magnetic field driven by a petawatt-class laser pulse compressed the deuterium in a single nanowire to more than 120 times its initial density,achieving an unprecedented particle number density of 10^(25)cm^(-3).Through full-dimensional kinetic simulations,including nuclear reactions,we found that these Z-pinches can generate high-intensity and short-duration neutron pulses,with the peak flux reaching 10^(27)cm^(-2)s^(-1).Such laser-driven neutron sources are beyond the capabilities of existing approaches and pave the way for groundbreaking applications in r-process nucleosynthesis studies and high-precision time-of-flight neutron data measurements.展开更多
Cooling water is an important part in a Spallation Neutron Source target cooling system, but the unstable vortexes at the exits of the slits between every two tungsten target slices have a negative impact on the stabl...Cooling water is an important part in a Spallation Neutron Source target cooling system, but the unstable vortexes at the exits of the slits between every two tungsten target slices have a negative impact on the stable running of the target system. We apply the field synergy principle for fluid flow to obtain the optimal flow field, which has a uniform velocity distribution without eddy, and then, optimize the geometrical structure of the cooling water flow channel based on the optimal flow field. The results show that when the cooling water flows in the optimized channel, the eddy sizes decrease, the time fluctuations of velocity and pressure almost vanish, and the volume flow rates of the cooling water in each parallel slit are uniform. Therefore, it effectively improves the running stability of the target system with the premise of satisfying the target heat load.展开更多
The polonium-210 activity in raw material targets which was used to make the start neutron source rods of Qinshan Nuclear Power Station was determined in calorimetry. The calorimeter used is a twin-cup isothermal one....The polonium-210 activity in raw material targets which was used to make the start neutron source rods of Qinshan Nuclear Power Station was determined in calorimetry. The calorimeter used is a twin-cup isothermal one. It works at room temperature and does not need any device of constant temperature. The instruments used for calorimetry are simple and have good properties. The background is from -1μV to + 2 μ V when the room temperature changs between 16℃ and 28 ℃. The data gotten in calorimetry are in correspondence within ±3.4 % with those from liquid scintillation method after the targets were dissolved, additionally in correspondence within ±1.7% with the data given by Amersham Laboratories for 241Am determination.展开更多
In the following paper an experiment dedicated to the accident protection system of a Liquid Metal Target is presented.The test was carried out at the liquid metal test stand(LIMETS)at PSI in which the malfunctioning ...In the following paper an experiment dedicated to the accident protection system of a Liquid Metal Target is presented.The test was carried out at the liquid metal test stand(LIMETS)at PSI in which the malfunctioning of a target during operation was simulated.It could be demonstrated that measurements and the proper(on-line)analysis of target vibrations and surrounding sound pressure fields allow the detection of a malfunctions like deformation or detaching of structural elements immeresed in the flow.Amplitudes of acceleration sensors and microphones signals as well as frequencies of the disturbances' signals are prospective parameters to be used in an automated accident protection system as indicators for a target malfunction.展开更多
基金supported by the National Nature Science Foundation of China(No.1210050454)the program of Chinese Scholarship Council(No.202106280126)。
文摘In the past decade,boron neutron capture therapy utilizing an accelerator-based neutron source(ABNS)designed primarily for producing epithermal neutrons has been implemented in the treatment of brain tumors and other cancers.The specifications for designing an epithermal beam are primarily based on the IAEA-TECODC-1223 report,issued in 2001 for reactor neutron sources.Based on this report,the latest perspectives and clinical requirements,we designed an ABNS capable of adjusting the average neutron beam energy.The design was based on a 2.8 MeV,20 mA proton beam bombarding a lithium target to produce neutrons that were subsequently moderated and tuned through a tunable beam shaping assembly(BSA)which can modify the thicknesses and materials of the coin-shaped moderators,back reflectors,filters,and collimators.The simulation results demonstrated that epithermal neutron beams for deep seated tumor treatment,which were generated by utilizing magnesium fluoride with lengths ranging between 28 and 36 cm as the moderator,possessed a treatment depth of 5.6 cm although the neutron flux peak shifts from 4.5 to 1.0 keV.When utilizing a thinner moderator,a less accelerated beam power can meet the treatment requirements.However,higher powers reduced the treatment time.In contrast,employing a thick moderator can reduce the skin dose.In scenarios that required relatively low energy neutron beams,the removal of the thermal neutron filter can raise the thermal neutron flux at the beam port.And the depth of the dose rate peak could be adjusted between 0.25 and 2.20 cm by combining magnesium fluoride and polyethylene coins of different thicknesses.Hence,this device has a better adaptability for the treatment of superficial tumors.Overall,the tunable BSA provides greater flexibility for clinical treatment than common BSA designs that can only adjust the port size.
基金supported by National Natural Science Foundation of China (No. 11075154)
文摘This paper presents a conceptual design for the first tentative surface muon source based on the proton beam provided by China Spallation Neutron Source （CSNS）. We have calcu- lated the optimal parameters of solid muon target, in which the method of Monte Carlo simula- tion is used to obtain the optimal muon beam parameters, such as beam fiuence rate, momentum spread and phase space distribution. A simple muon transport beamline system was also designed, which could transport the muons emitted from the muon target into the experimental area, where positrons from muon decay in a test sample are detected by a spectrometer. The beam optics of this new beam line is also described.
基金supported by the National Key R&D Program of China(Nos.2022YFA1602402,2022YFA1602404)the National Natural Science Foundation of China(Nos.12235003,12388102)。
文摘Utilizing the laser-driven Z-pinch e ect,we propose an approach for generating an ultrashort,intense Me V neutron source with femtosecond pulse duration.The self-generated magnetic field driven by a petawatt-class laser pulse compressed the deuterium in a single nanowire to more than 120 times its initial density,achieving an unprecedented particle number density of 10^(25)cm^(-3).Through full-dimensional kinetic simulations,including nuclear reactions,we found that these Z-pinches can generate high-intensity and short-duration neutron pulses,with the peak flux reaching 10^(27)cm^(-2)s^(-1).Such laser-driven neutron sources are beyond the capabilities of existing approaches and pave the way for groundbreaking applications in r-process nucleosynthesis studies and high-precision time-of-flight neutron data measurements.
基金supported by the National Natural Science Foundation of China (Grant Nos. 51006060, 51036003)the Foundation for the Author of National Excellent Doctoral Dissertation of China (Grant No.201150)
文摘Cooling water is an important part in a Spallation Neutron Source target cooling system, but the unstable vortexes at the exits of the slits between every two tungsten target slices have a negative impact on the stable running of the target system. We apply the field synergy principle for fluid flow to obtain the optimal flow field, which has a uniform velocity distribution without eddy, and then, optimize the geometrical structure of the cooling water flow channel based on the optimal flow field. The results show that when the cooling water flows in the optimized channel, the eddy sizes decrease, the time fluctuations of velocity and pressure almost vanish, and the volume flow rates of the cooling water in each parallel slit are uniform. Therefore, it effectively improves the running stability of the target system with the premise of satisfying the target heat load.
文摘The polonium-210 activity in raw material targets which was used to make the start neutron source rods of Qinshan Nuclear Power Station was determined in calorimetry. The calorimeter used is a twin-cup isothermal one. It works at room temperature and does not need any device of constant temperature. The instruments used for calorimetry are simple and have good properties. The background is from -1μV to + 2 μ V when the room temperature changs between 16℃ and 28 ℃. The data gotten in calorimetry are in correspondence within ±3.4 % with those from liquid scintillation method after the targets were dissolved, additionally in correspondence within ±1.7% with the data given by Amersham Laboratories for 241Am determination.
文摘In the following paper an experiment dedicated to the accident protection system of a Liquid Metal Target is presented.The test was carried out at the liquid metal test stand(LIMETS)at PSI in which the malfunctioning of a target during operation was simulated.It could be demonstrated that measurements and the proper(on-line)analysis of target vibrations and surrounding sound pressure fields allow the detection of a malfunctions like deformation or detaching of structural elements immeresed in the flow.Amplitudes of acceleration sensors and microphones signals as well as frequencies of the disturbances' signals are prospective parameters to be used in an automated accident protection system as indicators for a target malfunction.
