2015 Vol. 32, No. 3
Display Method:
2015, 32(3): 259-266.
doi: 10.11804/NuclPhysRev.32.03.259
Abstract:
A two-step model for combining the dynamical and statistical decay processes in heavy-ion collisions is used to reproduce the experimental results of the INDRA Collaborations on 40Ca+40Ca and 48Ca+48Ca reactions at 35 AMeV. We obtain the isoscaling parameters α(Z) and β(N) of isotopic distributions of the fragments, the reduced symmetry energy coefficient ζ(Z) and its dependence on the symmetry energy strength coefficient Cs in the mean field. Our results suggest that Isoscaling parameters strongly depend on the degree of neutron-rich. With the increasing atomic number, ζ(Z) represents a smoothly flat tendency during the dynamical process but shows the increasing tendency after decay, and such results are independent on the selected reaction systems. The effect of symmetry energy shows evidently in the isotopic distributions of fragments after statistical decay process.
A two-step model for combining the dynamical and statistical decay processes in heavy-ion collisions is used to reproduce the experimental results of the INDRA Collaborations on 40Ca+40Ca and 48Ca+48Ca reactions at 35 AMeV. We obtain the isoscaling parameters α(Z) and β(N) of isotopic distributions of the fragments, the reduced symmetry energy coefficient ζ(Z) and its dependence on the symmetry energy strength coefficient Cs in the mean field. Our results suggest that Isoscaling parameters strongly depend on the degree of neutron-rich. With the increasing atomic number, ζ(Z) represents a smoothly flat tendency during the dynamical process but shows the increasing tendency after decay, and such results are independent on the selected reaction systems. The effect of symmetry energy shows evidently in the isotopic distributions of fragments after statistical decay process.
2015, 32(3): 267-273.
doi: 10.11804/NuclPhysRev.32.03.267
Abstract:
The elliptic flow for proton, π+, K+ and their corresponding antiparticles are investigated at mid-rapidity for Au+Au collisions at √sNN =7.7, 11.5, 19.6, 27, 39, 62.4 GeV, utilizing ultrarelativistic quantum molecular dynamics (UrQMD-3.3p1). We analyze the difference in v2(pT) between the particles and the corresponding antiparticles as a function of the transverse momentum pT. We find that in UrQMD the v2 for K is larger than that for K+ at all BES energies. The v2(pT) values are almost identical for π+ and π-􀀀at 7.7s62.4 GeV. While in experiments, at lower energies, 7.7, 11.5 and 19.6 GeV,v2(π-) is larger than v2(π+) for all pT values. We can clearly see that in UrQMD the v2 for antiproton is larger than that for proton at all BES energies, which is in contradiction to the experimental result.The opposite trend observed in experiment is therefore an indication that the strong coupling in heavy ion collision and the non equilibrium in transport process may need further understanding.
The elliptic flow for proton, π+, K+ and their corresponding antiparticles are investigated at mid-rapidity for Au+Au collisions at √sNN =7.7, 11.5, 19.6, 27, 39, 62.4 GeV, utilizing ultrarelativistic quantum molecular dynamics (UrQMD-3.3p1). We analyze the difference in v2(pT) between the particles and the corresponding antiparticles as a function of the transverse momentum pT. We find that in UrQMD the v2 for K is larger than that for K+ at all BES energies. The v2(pT) values are almost identical for π+ and π-􀀀at 7.7s62.4 GeV. While in experiments, at lower energies, 7.7, 11.5 and 19.6 GeV,v2(π-) is larger than v2(π+) for all pT values. We can clearly see that in UrQMD the v2 for antiproton is larger than that for proton at all BES energies, which is in contradiction to the experimental result.The opposite trend observed in experiment is therefore an indication that the strong coupling in heavy ion collision and the non equilibrium in transport process may need further understanding.
2015, 32(3): 274-279.
doi: 10.11804/NuclPhysRev.32.03.274
Abstract:
The 22Na+α resonant scattering is studied via a conventional thick target inverse kinematic method with an extended gas target. A data analysis method is proposed for the two-body reaction kinematic reconstruction, in which the spatial geometry, the reaction kinematics and the energy losses are considered. The experimental data of 22Na+ αresonant scattering have been thus reconstructed, and the excitation function is obtained in the energy interval of Ec.m. =4.2~5.4 MeV. Five resonant states in 26Al are observed in the experimental excitation function. Since several decay modes coexist for the observed 26Al resonant states, multi-channel theoretical analysis is thus needed to reveal their structure and decay features.
The 22Na+α resonant scattering is studied via a conventional thick target inverse kinematic method with an extended gas target. A data analysis method is proposed for the two-body reaction kinematic reconstruction, in which the spatial geometry, the reaction kinematics and the energy losses are considered. The experimental data of 22Na+ αresonant scattering have been thus reconstructed, and the excitation function is obtained in the energy interval of Ec.m. =4.2~5.4 MeV. Five resonant states in 26Al are observed in the experimental excitation function. Since several decay modes coexist for the observed 26Al resonant states, multi-channel theoretical analysis is thus needed to reveal their structure and decay features.
2015, 32(3): 280-285.
doi: 10.11804/NuclPhysRev.32.03.280
Abstract:
Measurements of neutron total cross sections of natural bismuth in the neutron energy region from 0.1 to 100 eV have been performed by using the time-of-flight method at the Pohang Neutron Facilitywhich consists of an electron linear accelerator, a water-cooled tantalum target with a water moderator,and a 12 m long time-of-flight path. A 6Li-ZnS(Ag) scintillator with a diameter of 12.5 cm and a thicknessof 1.6 cm is employed as a neutron detector, and a piece of high purity natural bismuth metallic plates with a thickness of 3 mm is used for the neutron transmission measurement. The present results were compared with the evaluated data from ENDF/B VII.1 and other previous reported experimental data.
Measurements of neutron total cross sections of natural bismuth in the neutron energy region from 0.1 to 100 eV have been performed by using the time-of-flight method at the Pohang Neutron Facilitywhich consists of an electron linear accelerator, a water-cooled tantalum target with a water moderator,and a 12 m long time-of-flight path. A 6Li-ZnS(Ag) scintillator with a diameter of 12.5 cm and a thicknessof 1.6 cm is employed as a neutron detector, and a piece of high purity natural bismuth metallic plates with a thickness of 3 mm is used for the neutron transmission measurement. The present results were compared with the evaluated data from ENDF/B VII.1 and other previous reported experimental data.
2015, 32(3): 286-290.
doi: 10.11804/NuclPhysRev.32.03.286
Abstract:
With the study of the cosmic rays' solar diurnal variation we can get the important information about Cosmic Ray's production and propagation. It's important issues of cosmic rays' studies. We analyze the temporal variation of cosmic rays rate observed with the Yangbajing neutron monitor during 2006 to 2011, and nd semidiurnal and diurnal period signals included in the rates of cosmic rays with vertical rigidity equal to 14.1 GV. We have checked the time dependence of the phase and the amplitude of semidiurnal and diurnal anisotropy, and nd that the phase of diurnal signal varies yearly, it could be a synthetic movement of the earth's rotation and revolution. The amplitude before 2010 is obvious smaller than that after 2010. These results are of great reference value for studying the anisotropy and time variation of cosmic rays.
With the study of the cosmic rays' solar diurnal variation we can get the important information about Cosmic Ray's production and propagation. It's important issues of cosmic rays' studies. We analyze the temporal variation of cosmic rays rate observed with the Yangbajing neutron monitor during 2006 to 2011, and nd semidiurnal and diurnal period signals included in the rates of cosmic rays with vertical rigidity equal to 14.1 GV. We have checked the time dependence of the phase and the amplitude of semidiurnal and diurnal anisotropy, and nd that the phase of diurnal signal varies yearly, it could be a synthetic movement of the earth's rotation and revolution. The amplitude before 2010 is obvious smaller than that after 2010. These results are of great reference value for studying the anisotropy and time variation of cosmic rays.
2015, 32(3): 291-295.
doi: 10.11804/NuclPhysRev.32.03.291
Abstract:
J/ψ suppression observed in hot nuclear matter from heavy-ion collisions is considered as a most reliable signature for the formation of Quark-Gluon Plasma. The study about the nuclear effects on J/ψ production in cold nuclear matter provides an important tool for clarifying the conventional nuclear suppression mechanism in heavy-ion collisions. J/ψ suppression in p-A collisions is studied by considering the nuclear effects on parton distribution, the energy loss of beam proton in initial state, and the finial state energy loss of c¯c pair.The leading-order computations for J/ψ production cross-section ratios RFe=Be(xF) are presented and compared with the selected E866 experimental data with the J/ψ production occurring outside the nucleus, the obtained energy loss of the color octet is (3.81±1.71) GeV/fm. It is found that the nuclear suppression from the nuclear effects on the parton distribution functions becomes larger as the increase of xF in the range xF > 0，the J/ψ suppression on RFe/Be(xF) induced by the energy loss of color octet c¯c is an important nuclear effect, in the region 0:656xF 60:92, the energy loss of beam proton in initial state is the dominant mechanism which causes a reduction of the J/ψ yield.
J/ψ suppression observed in hot nuclear matter from heavy-ion collisions is considered as a most reliable signature for the formation of Quark-Gluon Plasma. The study about the nuclear effects on J/ψ production in cold nuclear matter provides an important tool for clarifying the conventional nuclear suppression mechanism in heavy-ion collisions. J/ψ suppression in p-A collisions is studied by considering the nuclear effects on parton distribution, the energy loss of beam proton in initial state, and the finial state energy loss of c¯c pair.The leading-order computations for J/ψ production cross-section ratios RFe=Be(xF) are presented and compared with the selected E866 experimental data with the J/ψ production occurring outside the nucleus, the obtained energy loss of the color octet is (3.81±1.71) GeV/fm. It is found that the nuclear suppression from the nuclear effects on the parton distribution functions becomes larger as the increase of xF in the range xF > 0，the J/ψ suppression on RFe/Be(xF) induced by the energy loss of color octet c¯c is an important nuclear effect, in the region 0:656xF 60:92, the energy loss of beam proton in initial state is the dominant mechanism which causes a reduction of the J/ψ yield.
2015, 32(3): 296-300.
doi: 10.11804/NuclPhysRev.32.03.296
Abstract:
Stochastic cooling, based on a feedback system, aims at damping the oscillation of particles. Stochastic cooling is more suitable to cool secondary beam with larger size and momentum spread, and it is therefore can be complemented with electron cooling, in order to obtain beam of higher quality. Stochastic cooling system is being designed and constructed on the experimental Cooling Storage Ring of HIRFL. By simulation of Betatron stochastic cooling, it is obtained that the importance for shortening the cooling time and reducing cooling equilibrium by improving bandwidth, increasing the numbers of pickup and kicker, and decreasing the system noises. Meanwhile, the heating during the cooling process caused by larger momentum spread or larger gain of amplifier is analyzed.
Stochastic cooling, based on a feedback system, aims at damping the oscillation of particles. Stochastic cooling is more suitable to cool secondary beam with larger size and momentum spread, and it is therefore can be complemented with electron cooling, in order to obtain beam of higher quality. Stochastic cooling system is being designed and constructed on the experimental Cooling Storage Ring of HIRFL. By simulation of Betatron stochastic cooling, it is obtained that the importance for shortening the cooling time and reducing cooling equilibrium by improving bandwidth, increasing the numbers of pickup and kicker, and decreasing the system noises. Meanwhile, the heating during the cooling process caused by larger momentum spread or larger gain of amplifier is analyzed.
2015, 32(3): 301-305.
doi: 10.11804/NuclPhysRev.32.03.301
Abstract:
The 31.02 MHz cyclotron RF system of Heavy Ion Medical Machine (HIMM) in IMP(Institute of Modern Physics, Chinese Academy of Sciences) has completed the design and commssioning，and now has already been put into operation. Its peak voltage requires 70 kV, but the precise calculation of the Dee voltage is still a difficulty problem, we can get the value Rp/Q0 of the cavity by CST simulation, and then combining the actual input power for cavity to calculate the real Dee voltage. In order to verify its accuracy, we use the bremsstrahlung method to test the cavity voltage under the condition of same input power. The error between test results and calculation is less than 0.6%.
The 31.02 MHz cyclotron RF system of Heavy Ion Medical Machine (HIMM) in IMP(Institute of Modern Physics, Chinese Academy of Sciences) has completed the design and commssioning，and now has already been put into operation. Its peak voltage requires 70 kV, but the precise calculation of the Dee voltage is still a difficulty problem, we can get the value Rp/Q0 of the cavity by CST simulation, and then combining the actual input power for cavity to calculate the real Dee voltage. In order to verify its accuracy, we use the bremsstrahlung method to test the cavity voltage under the condition of same input power. The error between test results and calculation is less than 0.6%.
2015, 32(3): 305-309.
doi: 10.11804/NuclPhysRev.32.03.305
Abstract:
Cryogenic module provides important low temperature environment for half wave resonance superconducting cavity in C-ADS injector Ⅱ, to ensure the effective operation of cryogenic module, a remote control system which is based on the physical and experimental industrial control systems (EPICS) is introduced in this paper. PLC and serial port server are used as field controllers. Host computer runs EPICS and LabVIEW which are capable of getting and releasing data in local area net. Operators manage all the equipments through a CSS interface which is linked to local area net. The control system which is simple structure and reliable work, has played an important role in the level test of HWR superconducting cavity.
Cryogenic module provides important low temperature environment for half wave resonance superconducting cavity in C-ADS injector Ⅱ, to ensure the effective operation of cryogenic module, a remote control system which is based on the physical and experimental industrial control systems (EPICS) is introduced in this paper. PLC and serial port server are used as field controllers. Host computer runs EPICS and LabVIEW which are capable of getting and releasing data in local area net. Operators manage all the equipments through a CSS interface which is linked to local area net. The control system which is simple structure and reliable work, has played an important role in the level test of HWR superconducting cavity.
2015, 32(3): 310-317.
doi: 10.11804/NuclPhysRev.32.03.310
Abstract:
Preparation of Tb, Dy and Ho targets from the mixture of isopropanol and nitricacid solution are studied by using molecular plating technique. To determine the optimum conditions for the deposition process,the effect of distance between the two electrodes, current density, volume of 0.1 mol/L nitric acid, deposition time on the quality and electrodeposition yield of the target films are investigated individually. Preparation of Tb targets from the mixture of isobutylalcohol and nitricacid solution are also studied by using molecular plating technique. Depending on the similar chemical properties of Tb, Dy and Ho, the same process conditions are used.The suitable distance between the two electrodes is 15 mm. The current density is 5.7 mA/ cm2. The volume of nitric acid (0.1 mol/L) is 400 L. With the spectrophotometry method, the electrodeposition yields for all the targets prepared are found to be higher than 85% after one hour’s deposition. The morphological structure of some targets are characterized by scanning electron microscope (SEM) and it can be seen that the surface of the targets are uniform and intact. With EDS method, the composition of some targets are found to be very pure. The chemical structure of the targets are analyzed by Infrared Spectroscopy. It is found that the chemical structure of the targets are complex and the target membrane is not composed by only one compound. Short lived isotopes of W and Os were produced from natural Tb and Ho targets bombarded by 19F beam at the SFC low energy radiochemical terminal of Institute of Modern Physics, Chinese Academy of Sciences, respectively,and were successfully applied in the model experiment of Sg (Z =106) and Hs (Z =108).
Preparation of Tb, Dy and Ho targets from the mixture of isopropanol and nitricacid solution are studied by using molecular plating technique. To determine the optimum conditions for the deposition process,the effect of distance between the two electrodes, current density, volume of 0.1 mol/L nitric acid, deposition time on the quality and electrodeposition yield of the target films are investigated individually. Preparation of Tb targets from the mixture of isobutylalcohol and nitricacid solution are also studied by using molecular plating technique. Depending on the similar chemical properties of Tb, Dy and Ho, the same process conditions are used.The suitable distance between the two electrodes is 15 mm. The current density is 5.7 mA/ cm2. The volume of nitric acid (0.1 mol/L) is 400 L. With the spectrophotometry method, the electrodeposition yields for all the targets prepared are found to be higher than 85% after one hour’s deposition. The morphological structure of some targets are characterized by scanning electron microscope (SEM) and it can be seen that the surface of the targets are uniform and intact. With EDS method, the composition of some targets are found to be very pure. The chemical structure of the targets are analyzed by Infrared Spectroscopy. It is found that the chemical structure of the targets are complex and the target membrane is not composed by only one compound. Short lived isotopes of W and Os were produced from natural Tb and Ho targets bombarded by 19F beam at the SFC low energy radiochemical terminal of Institute of Modern Physics, Chinese Academy of Sciences, respectively,and were successfully applied in the model experiment of Sg (Z =106) and Hs (Z =108).
2015, 32(3): 318-322.
doi: 10.11804/NuclPhysRev.32.03.318
Abstract:
The value of prompt neutron multiplication, α, is measured under the condition of using a denser plasma focus(DPF) neutron-source irradiating zero power assembly for the first time in China. The acquired signal is lower three orders of magnitudes than that of the noise caused by direct and scattered neutrons from the extra-high-intensity neutron-source. Using different kinds of material to decrease the noise caused by neutron with different kinds of energies, an optimized design for radiation shielding is developed by the method of numerical simulation to suppress noise signal. Both neutron and γ-ray are shielded simultaneously. The Signal/Noise Ratio (SNR) with the optimal design was up to 7.5:1 and was consistent with the experimental results. The noise of neutron is decreased effectively by the new kind of unorganic crystals used.
The value of prompt neutron multiplication, α, is measured under the condition of using a denser plasma focus(DPF) neutron-source irradiating zero power assembly for the first time in China. The acquired signal is lower three orders of magnitudes than that of the noise caused by direct and scattered neutrons from the extra-high-intensity neutron-source. Using different kinds of material to decrease the noise caused by neutron with different kinds of energies, an optimized design for radiation shielding is developed by the method of numerical simulation to suppress noise signal. Both neutron and γ-ray are shielded simultaneously. The Signal/Noise Ratio (SNR) with the optimal design was up to 7.5:1 and was consistent with the experimental results. The noise of neutron is decreased effectively by the new kind of unorganic crystals used.
2015, 32(3): 323-329.
doi: 10.11804/NuclPhysRev.32.03.323
Abstract:
Recently, the international society pays more and more attention to nuclear material protection,control and accounting. The focus on the material unaccounted for (MUF) is enhanced. The uncertainty assessment of uranium mass measurement plays an essential role in estimating the production of uranium. Due to the relatively weak radioactivity of uranium, the active neutron multiplicity counting (ANMC) method is usually applied to assess the mass of uranium material. In this paper, the relations and parameters between the masses of the uranium objects and the features of the ANMCs are formulated by fitting the simulated results of different sets of uranium shells. The result indicates that,each mass of the objects could be obtained by analyzing the ANMCs of different orders. In order to study the effects of the detection system settings on the mass estimation, the propagation of the aleatoric and epistemic uncertainty of the method is quantitatively studied by the simulations with different detection onditions. The optimized settings of source intensity and detection coincidence gate width, which result in the minimal uncertainty of the mass estimation, are obtained for the simulated detection system.
Recently, the international society pays more and more attention to nuclear material protection,control and accounting. The focus on the material unaccounted for (MUF) is enhanced. The uncertainty assessment of uranium mass measurement plays an essential role in estimating the production of uranium. Due to the relatively weak radioactivity of uranium, the active neutron multiplicity counting (ANMC) method is usually applied to assess the mass of uranium material. In this paper, the relations and parameters between the masses of the uranium objects and the features of the ANMCs are formulated by fitting the simulated results of different sets of uranium shells. The result indicates that,each mass of the objects could be obtained by analyzing the ANMCs of different orders. In order to study the effects of the detection system settings on the mass estimation, the propagation of the aleatoric and epistemic uncertainty of the method is quantitatively studied by the simulations with different detection onditions. The optimized settings of source intensity and detection coincidence gate width, which result in the minimal uncertainty of the mass estimation, are obtained for the simulated detection system.
2015, 32(3): 330-334.
doi: 10.11804/NuclPhysRev.32.03.330
Abstract:
The position-sensitive scintillator neutron detector (SSND) with high efficiency, high resolution and high n/ discriminate ability etc., is developed to replace the traditional 3He neutron detector. The wave-length shifting fibers (WLSF) are used in SSND. The performances of BCF-91A type WLSF, such as attenuation length, bend loss and lights transportation ability etc., are studied in this paper. The attenuation length is (1485) cm.The lights transportation ability is about 5.6%. When the length of WLSF is 1.1 m, the bend radius is 20 mm,the photon number N transferred by the fiber meet the demand of SSND. According to the result, BCF-91A type WLSF is a good candidate for SSND.
The position-sensitive scintillator neutron detector (SSND) with high efficiency, high resolution and high n/ discriminate ability etc., is developed to replace the traditional 3He neutron detector. The wave-length shifting fibers (WLSF) are used in SSND. The performances of BCF-91A type WLSF, such as attenuation length, bend loss and lights transportation ability etc., are studied in this paper. The attenuation length is (1485) cm.The lights transportation ability is about 5.6%. When the length of WLSF is 1.1 m, the bend radius is 20 mm,the photon number N transferred by the fiber meet the demand of SSND. According to the result, BCF-91A type WLSF is a good candidate for SSND.
2015, 32(3): 335-340.
doi: 10.11804/NuclPhysRev.32.03.335
Abstract:
There are two methods of the HV power supply for the GEM detector. One is a HV channel divided by the resistive chain and the other is the several separate HV channels. In the smaller dose rate of X-ray, all of the methods are similar. When the dose rate increases, the resistive chain-dividing mode has more obvious saturation effect and the working voltage of the GEM detector is unstable. In the paper, a GEM detector with an effective area of 100 mm100 mm has been studied in the high dose rate using X-tube. The unit values in the divider resistance chain are set to 1, 2, 5 and 30 MΩ respectively in the test. With the resistive chain-dividing mode, the readout current of the GEM detector’s anode tends to saturate when the dose rate of X-ray increases,and the reasons of the saturation effect are analyzed. The results indicate that the effective absorbed dose of X-ray by the triple GEMs detector reaches to the pecific value and the divider resistance needs to re-select, even the several separate HV channels mode should be considered. It will keep the constant of the working voltage of the GEM detector without the saturation effect and gain variation and the performance of GEM detector is stable.
There are two methods of the HV power supply for the GEM detector. One is a HV channel divided by the resistive chain and the other is the several separate HV channels. In the smaller dose rate of X-ray, all of the methods are similar. When the dose rate increases, the resistive chain-dividing mode has more obvious saturation effect and the working voltage of the GEM detector is unstable. In the paper, a GEM detector with an effective area of 100 mm100 mm has been studied in the high dose rate using X-tube. The unit values in the divider resistance chain are set to 1, 2, 5 and 30 MΩ respectively in the test. With the resistive chain-dividing mode, the readout current of the GEM detector’s anode tends to saturate when the dose rate of X-ray increases,and the reasons of the saturation effect are analyzed. The results indicate that the effective absorbed dose of X-ray by the triple GEMs detector reaches to the pecific value and the divider resistance needs to re-select, even the several separate HV channels mode should be considered. It will keep the constant of the working voltage of the GEM detector without the saturation effect and gain variation and the performance of GEM detector is stable.
2015, 32(3): 341-346.
doi: 10.11804/NuclPhysRev.32.03.341
Abstract:
Penning trap mass spectrometry is one of the direct methods and maybe the most accurate tool for atomic mass measurements. The quadrupole electric eld produced in the trap should be very accurate in order to ensure the precision of measurements. The optimal amplitudes for the key electrodes of the Lanzhou Penning Trap(LPT) have been calculated by two methods|formula derivation and least-squares tting. For formula derivation method, the optimal values are based on the theory and deduced from the formulas. Least-squares tting method is to minimize the quadratic sum of sampling deviations, where the actual geometry of the electrodes has been considered by the simulation. The obtained C4 and C6 values can be used to estimate the experimental error produced by the deviation from the ideal quadrupole electric eld. The expected quadrupole electric led could be gotten by both methods.
Penning trap mass spectrometry is one of the direct methods and maybe the most accurate tool for atomic mass measurements. The quadrupole electric eld produced in the trap should be very accurate in order to ensure the precision of measurements. The optimal amplitudes for the key electrodes of the Lanzhou Penning Trap(LPT) have been calculated by two methods|formula derivation and least-squares tting. For formula derivation method, the optimal values are based on the theory and deduced from the formulas. Least-squares tting method is to minimize the quadratic sum of sampling deviations, where the actual geometry of the electrodes has been considered by the simulation. The obtained C4 and C6 values can be used to estimate the experimental error produced by the deviation from the ideal quadrupole electric eld. The expected quadrupole electric led could be gotten by both methods.
2015, 32(3): 347-352.
doi: 10.11804/NuclPhysRev.32.03.347
Abstract:
Oxide dispersion strengthened (ODS) ferritic steels have better high-temperature creep rupture strength and higher irradiation resistance than conventional ferritic steels, and show high prominence of application in advance nuclear reactors. Their stability under high-dose radiation conditions needs to be clarified. In the present study, a commercial ODS ferritic steel MA956 were irradiated with high 20Ne ions at a terminal chamber of the Sector-focused Cyclotron (SFC) at HIRFL (Heavy-ion Research Facility in Lanzhou). With the energy gradient degrader of the irradiation chamber, the primary energy (123.4 MeV) of the Ne-ion was dispersed into 30 different energies between 38.5~ 121.0 MeV, which resulted in a plateau distribution of lattice damage in the specimens. The specimens were irradiated from both sides so that the whole 60 m thickness was nearly uniformly damaged. The specimen temperature was maintained around 440 ℃ during the irradiation. The irradiation dose is about 9x1016 ions/cm2, corresponding to a damage level of 0.7 dpa and a Ne concentration of 350 appm. The specimens before and after irradiation were tested with the Small-punch Test technique, at room temperature and 500 ℃, respectively. The fracture morphology was observed by scanning electron microscopy.The results show that MA956 underwent some loss of ductility and fracture toughness after the irradiation with high-energy 20Ne ions. It may be ascribed to the formation of nano-scale cavities at the oxides/matrix interfaces
in the ODS steel specimens under irradiation .
Oxide dispersion strengthened (ODS) ferritic steels have better high-temperature creep rupture strength and higher irradiation resistance than conventional ferritic steels, and show high prominence of application in advance nuclear reactors. Their stability under high-dose radiation conditions needs to be clarified. In the present study, a commercial ODS ferritic steel MA956 were irradiated with high 20Ne ions at a terminal chamber of the Sector-focused Cyclotron (SFC) at HIRFL (Heavy-ion Research Facility in Lanzhou). With the energy gradient degrader of the irradiation chamber, the primary energy (123.4 MeV) of the Ne-ion was dispersed into 30 different energies between 38.5~ 121.0 MeV, which resulted in a plateau distribution of lattice damage in the specimens. The specimens were irradiated from both sides so that the whole 60 m thickness was nearly uniformly damaged. The specimen temperature was maintained around 440 ℃ during the irradiation. The irradiation dose is about 9x1016 ions/cm2, corresponding to a damage level of 0.7 dpa and a Ne concentration of 350 appm. The specimens before and after irradiation were tested with the Small-punch Test technique, at room temperature and 500 ℃, respectively. The fracture morphology was observed by scanning electron microscopy.The results show that MA956 underwent some loss of ductility and fracture toughness after the irradiation with high-energy 20Ne ions. It may be ascribed to the formation of nano-scale cavities at the oxides/matrix interfaces
in the ODS steel specimens under irradiation .
2015, 32(3): 353-357.
doi: 10.11804/NuclPhysRev.32.03.353
Abstract:
Microelectronic devices are used in a harsh radiation environment for space missions. Among all the reliability issues concerned, proton induced single event upset (SEU) is becoming more and more noticeable for semiconductor components exposed on space. In this work, an experimental research of SEU induced by 10 MeV proton for static random access memory (SRAM) of 0.5, 0.35 and 0.15 m feature size is carried out on HeavyIon Research Facility in Lanzhou for the rst time. The experimental results show that proton induced SEUs in submicron and deep-submicron (SRAMs) are dominated by secondary ions generated by proton nuclear reaction events. The silicon-on-insulator SRAMs characters natural radiation-hardened SEU by proton. For the deep-submicron bulk-silicon technology SRAM, the proton SEU cross section is closely related to the proton energy and there is a threshold energy for the SEU occurrence by proton indirect ionization. CREME-MC simulation indicates that the SEU events in deep-submicron SRAM are induced by the proton nuclear reaction.
Microelectronic devices are used in a harsh radiation environment for space missions. Among all the reliability issues concerned, proton induced single event upset (SEU) is becoming more and more noticeable for semiconductor components exposed on space. In this work, an experimental research of SEU induced by 10 MeV proton for static random access memory (SRAM) of 0.5, 0.35 and 0.15 m feature size is carried out on HeavyIon Research Facility in Lanzhou for the rst time. The experimental results show that proton induced SEUs in submicron and deep-submicron (SRAMs) are dominated by secondary ions generated by proton nuclear reaction events. The silicon-on-insulator SRAMs characters natural radiation-hardened SEU by proton. For the deep-submicron bulk-silicon technology SRAM, the proton SEU cross section is closely related to the proton energy and there is a threshold energy for the SEU occurrence by proton indirect ionization. CREME-MC simulation indicates that the SEU events in deep-submicron SRAM are induced by the proton nuclear reaction.
2015, 32(3): 358-362.
doi: 10.11804/NuclPhysRev.32.03.358
Abstract:
In the detection of space ions, solar ultraviolet (UV) can also enter the detector and generate a noise to the signal of ions. A testing system on the ground is built to test the UV response of detector. Experiments on a home-made principle prototype of space low-energy ion detector are carried out by using this system. The results show that the response of detector to the UV entering the electrostatic analyzer along the horizontal direction can be negligible and counts of the response to the UV along a bias direction are about 102 ~103 s−1. According to the measured results, the UV suppression ratio is estimated to be about 10−8 and the inuence of solar UV on the detection of space low-energy ions such as proton and alpha particle has been analyzed. For proton, the inuence is insigni cant due to its high ux. But for the low ux alpha particle, the inuence of solar UV is noticeable and further rejection is needed. In addition, this system can also be applied to test the UV response of other space particle detectors.
In the detection of space ions, solar ultraviolet (UV) can also enter the detector and generate a noise to the signal of ions. A testing system on the ground is built to test the UV response of detector. Experiments on a home-made principle prototype of space low-energy ion detector are carried out by using this system. The results show that the response of detector to the UV entering the electrostatic analyzer along the horizontal direction can be negligible and counts of the response to the UV along a bias direction are about 102 ~103 s−1. According to the measured results, the UV suppression ratio is estimated to be about 10−8 and the inuence of solar UV on the detection of space low-energy ions such as proton and alpha particle has been analyzed. For proton, the inuence is insigni cant due to its high ux. But for the low ux alpha particle, the inuence of solar UV is noticeable and further rejection is needed. In addition, this system can also be applied to test the UV response of other space particle detectors.
2015, 32(3): 363-367.
doi: 10.11804/NuclPhysRev.32.03.363
Abstract:
A Monte Carlo code was used to study the discrepancy resulted from the emergence of magnetic field in MRI guided radiotherapy. In this work, four different tissue phantoms with magnetic field and 6 MV photon were studied, and the dose distributions at the interface of phantom-air were evaluated. It is found that the differences of the dose perturbation are small between the materials with similar ionization energy. However, the dose perturbation decreased significantly for the material with high ionization energy. The results of this study demonstrate that magnetic field will change the dose distribution of photon beam and the dose perturbation associated with ionization energy of materials. It means that magnetic resonance imaging guided radiotherapy can enhance the target accuracy, but the magnetic field will change the dose distribution of photon beam, and the perturbation was not the same for the different materials of human tissue, it has brought new challenges for the research of dose algorithm.
A Monte Carlo code was used to study the discrepancy resulted from the emergence of magnetic field in MRI guided radiotherapy. In this work, four different tissue phantoms with magnetic field and 6 MV photon were studied, and the dose distributions at the interface of phantom-air were evaluated. It is found that the differences of the dose perturbation are small between the materials with similar ionization energy. However, the dose perturbation decreased significantly for the material with high ionization energy. The results of this study demonstrate that magnetic field will change the dose distribution of photon beam and the dose perturbation associated with ionization energy of materials. It means that magnetic resonance imaging guided radiotherapy can enhance the target accuracy, but the magnetic field will change the dose distribution of photon beam, and the perturbation was not the same for the different materials of human tissue, it has brought new challenges for the research of dose algorithm.
2015, 32(3): 368-374.
doi: 10.11804/NuclPhysRev.32.03.368
Abstract:
R-matrix theory is an important theory of light, medium and heavy mass nuclide nuclear reaction in the resonance energy range. Full R-matrix formalism contains the un-diagonal element of energy levels matrix and it is rigorous in theory. Because of different assumptions and approximations, many kinds of R-matrix methods are obtained. The new R-matrix code FDRR is presented and includes 4 kinds of R-matrix methods, reduced multi-level Breit-Wigner R-matrix method, full reduced R-matrix method, un-diagonal energy shift reduced Rmatrix method, and diagonal energy shift reduced R-matrix method. It can be used for calculating integral cross sections and angular distributions of 2-bodies reactions. The cross sections and angular distributions of n+6Li reaction are calculated and analyzed by FDRR code below 20 MeV. The calculation results are compared with the experimental data, and the cross sections and angular distributions are in good agreement with experimental data.
R-matrix theory is an important theory of light, medium and heavy mass nuclide nuclear reaction in the resonance energy range. Full R-matrix formalism contains the un-diagonal element of energy levels matrix and it is rigorous in theory. Because of different assumptions and approximations, many kinds of R-matrix methods are obtained. The new R-matrix code FDRR is presented and includes 4 kinds of R-matrix methods, reduced multi-level Breit-Wigner R-matrix method, full reduced R-matrix method, un-diagonal energy shift reduced Rmatrix method, and diagonal energy shift reduced R-matrix method. It can be used for calculating integral cross sections and angular distributions of 2-bodies reactions. The cross sections and angular distributions of n+6Li reaction are calculated and analyzed by FDRR code below 20 MeV. The calculation results are compared with the experimental data, and the cross sections and angular distributions are in good agreement with experimental data.
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