2014 Vol. 31, No. 3
Display Method:
2014, 31(3): 253-272.
doi: 10.11804/NuclPhysRev.31.03.253
Abstract:
The exploration of charge and mass limits of atomic nuclei and the synthesis of long-lived or stable superheavy nuclei (SHN) are on the frontier of modern nuclear physics. Recent theoretical progresses made by us on the study of structure and synthesis mechanism of SHN are reviewed. The study of structure properties includes a systematic study of low-lying spectra of actinide and transfermium nuclei by using a cranked shell model with the pairing treated by a particle number conserving method (PNC-CSM), the study of potential energy surfaces and fission barriers of actinide nuclei and non-axial octupole correlations in N = 150 isotones by using newly-developed multi-dimensional constraint covariant density functional theories (MDCCDFT).The study of the synthesis mechanism of SHN is carried out by examining in details of the three steps in producing SHN via heavy-ion fusion reactions: i) For the capture process, a new barrier penetration formula is proposed for potential barriers containing a long-range Coulomb interaction; ii) For the fusion process, a dinuclear system model with a dynamical potential energy surface (the DNS-DynPES model) is developed; and iii) For the survival process, a systematic study of the survival probability against fission in the 1n-channel of SHN with 100 6 Z 6 134 is made and it is found that the survival probability in the 1n-channel is mainly determined by the nuclear shell effects. By using the DNS-DynPES model, hot fusion reactions for synthesizing SHN with charge numbers Z =112s120 are studied. The calculated evaporation residue cross sections are in good agreement with available data and predictions are made for synthesizing SHN with Z=119 and 120.
The exploration of charge and mass limits of atomic nuclei and the synthesis of long-lived or stable superheavy nuclei (SHN) are on the frontier of modern nuclear physics. Recent theoretical progresses made by us on the study of structure and synthesis mechanism of SHN are reviewed. The study of structure properties includes a systematic study of low-lying spectra of actinide and transfermium nuclei by using a cranked shell model with the pairing treated by a particle number conserving method (PNC-CSM), the study of potential energy surfaces and fission barriers of actinide nuclei and non-axial octupole correlations in N = 150 isotones by using newly-developed multi-dimensional constraint covariant density functional theories (MDCCDFT).The study of the synthesis mechanism of SHN is carried out by examining in details of the three steps in producing SHN via heavy-ion fusion reactions: i) For the capture process, a new barrier penetration formula is proposed for potential barriers containing a long-range Coulomb interaction; ii) For the fusion process, a dinuclear system model with a dynamical potential energy surface (the DNS-DynPES model) is developed; and iii) For the survival process, a systematic study of the survival probability against fission in the 1n-channel of SHN with 100 6 Z 6 134 is made and it is found that the survival probability in the 1n-channel is mainly determined by the nuclear shell effects. By using the DNS-DynPES model, hot fusion reactions for synthesizing SHN with charge numbers Z =112s120 are studied. The calculated evaporation residue cross sections are in good agreement with available data and predictions are made for synthesizing SHN with Z=119 and 120.
2014, 31(3): 285-290.
doi: 10.11804/NuclPhysRev.31.03.285
Abstract:
This article briefly discusses the deviations appeared in the constraints on the density dependence of the symmetry energy obtained from the sensitive observables in the heavy ion collisions. The problems which possibly influence the constraints obtained from the comparison between the transport model calculations and experimental measurement of isospin sensitive observables are discussed. The three problems: (1) The momentum dependent part of symmetry potential and the neutron, proton effective mass splitting, (2) The isospin dependence of the medium correction of the thresholds and cross sections for different charged Δ production, (3) Many-body correlation and fluctuation treatment in transport model and other things in the transport model codes are discussed in more detail for the reference of the colleagues with common interest in nuclear community.
This article briefly discusses the deviations appeared in the constraints on the density dependence of the symmetry energy obtained from the sensitive observables in the heavy ion collisions. The problems which possibly influence the constraints obtained from the comparison between the transport model calculations and experimental measurement of isospin sensitive observables are discussed. The three problems: (1) The momentum dependent part of symmetry potential and the neutron, proton effective mass splitting, (2) The isospin dependence of the medium correction of the thresholds and cross sections for different charged Δ production, (3) Many-body correlation and fluctuation treatment in transport model and other things in the transport model codes are discussed in more detail for the reference of the colleagues with common interest in nuclear community.
2014, 31(3): 273-284.
doi: 10.11804/NuclPhysRev.31.03.273
Abstract:
We summarize the current available constraints on the density dependence of the symmetry energy obtained from terrestrial laboratory measurements and astrophysical observations. While the magnitude Esym(ρ0) and density slope L of the symmetry energy at saturation density ρ0 can vary largely depending on the data or analysis methods, all the available constraints are in agreement with Esym(ρ0) =(32.5±2.5) MeV and L=(55±25) MeV. The determination of the high density behaviors of the symmetry energy remains a big challenge.
We summarize the current available constraints on the density dependence of the symmetry energy obtained from terrestrial laboratory measurements and astrophysical observations. While the magnitude Esym(ρ0) and density slope L of the symmetry energy at saturation density ρ0 can vary largely depending on the data or analysis methods, all the available constraints are in agreement with Esym(ρ0) =(32.5±2.5) MeV and L=(55±25) MeV. The determination of the high density behaviors of the symmetry energy remains a big challenge.
2014, 31(3): 291-305.
doi: 10.11804/NuclPhysRev.31.03.291
Abstract:
After inserting the Skyrme potential energy density functional for potential update, more detailed medium modifications for nucleon-nucleon elastic cross sections, and the isospin effect for cluster recognition into the Ultra-relativistic Quantum Molecular Dynamics (UrQMD), the dynamic process of heavy ion collisions (HICs) at low SIS energies (about 40s400 MeV/u) is primarily studied. And, after systematically studying the emission and collective flows of light clusters from HICs in such beam energy region, the sensitive observables especially to the density dependent symmetry energy at supra-normal densities are focused. It is found that: (1)the initial neutron/proton ratio dependence of the balance energy of neutrons from mass-symmetric Sn isotopes can be taken as a useful probe to constrain the stiffness of the nuclear symmetry energy; (2) the transverse velocity/momentum dependence of the elliptic flow ratio of neutrons and protons or hydrogen isotopes (vn 2 =vp;H2 )is also sensitive to symmetry energy. The 2 analysis from the difference bet e the theoretical (taking Skyrme potential parametrizations with incompressibility K0 being almost same but the slope parameter L of symmetry energy being largely different) and experimental (taking FOPI/LAND data) vn 2 =vH2 values determines the value of L to be (89±45) MeV within in a χ2 uncertainty.
After inserting the Skyrme potential energy density functional for potential update, more detailed medium modifications for nucleon-nucleon elastic cross sections, and the isospin effect for cluster recognition into the Ultra-relativistic Quantum Molecular Dynamics (UrQMD), the dynamic process of heavy ion collisions (HICs) at low SIS energies (about 40s400 MeV/u) is primarily studied. And, after systematically studying the emission and collective flows of light clusters from HICs in such beam energy region, the sensitive observables especially to the density dependent symmetry energy at supra-normal densities are focused. It is found that: (1)the initial neutron/proton ratio dependence of the balance energy of neutrons from mass-symmetric Sn isotopes can be taken as a useful probe to constrain the stiffness of the nuclear symmetry energy; (2) the transverse velocity/momentum dependence of the elliptic flow ratio of neutrons and protons or hydrogen isotopes (vn 2 =vp;H2 )is also sensitive to symmetry energy. The 2 analysis from the difference bet e the theoretical (taking Skyrme potential parametrizations with incompressibility K0 being almost same but the slope parameter L of symmetry energy being largely different) and experimental (taking FOPI/LAND data) vn 2 =vH2 values determines the value of L to be (89±45) MeV within in a χ2 uncertainty.
2014, 31(3): 306-314.
doi: 10.11804/NuclPhysRev.31.03.306
Abstract:
In this paper, we report and extend our recent work where the nucleon spin-orbit interaction and its spin degree of freedom were introduced explicitly for the first time in the isospin-dependent Boltzmann-Uehling-Uhlenbeck transport model for heavy-ion reactions. Despite of the significant cancellation of the time-even and time-odd spin-related mean-field potentials from the spin-orbit interaction,an appreciable local spin polarization is observed in heavy-ion collisions at intermediate energies because
of the dominating role of the time-odd terms. It is also found that the spin up-down differential transverse flow in heavy-ion collisions is a useful probe of the strength, density dependence, and isospin dependence of the in-medium spin-orbit interaction, and its magnitude is still considerable even at smaller systems.
In this paper, we report and extend our recent work where the nucleon spin-orbit interaction and its spin degree of freedom were introduced explicitly for the first time in the isospin-dependent Boltzmann-Uehling-Uhlenbeck transport model for heavy-ion reactions. Despite of the significant cancellation of the time-even and time-odd spin-related mean-field potentials from the spin-orbit interaction,an appreciable local spin polarization is observed in heavy-ion collisions at intermediate energies because
of the dominating role of the time-odd terms. It is also found that the spin up-down differential transverse flow in heavy-ion collisions is a useful probe of the strength, density dependence, and isospin dependence of the in-medium spin-orbit interaction, and its magnitude is still considerable even at smaller systems.
2014, 31(3): 315-325.
doi: 10.11804/NuclPhysRev.31.03.315
Abstract:
The ratio of shear viscosity (η) to entropy density (s) of nuclear fireball created in the
central region of intermediate-energy heavy-ion collisions has been investigated within two transport models, namely the Boltzmann-Uehling-Uhlenbeck (BUU) model and the isospin-dependent quantum molecular dynamics (IQMD) model. Different methods are used to calculate η and s. With the collisionenergy increasing, the η/s displays a saturation value or a local minimum value at a certain beam energy.We argue that the saturation or minimum point corresponds to an occurrence of nuclear liquid gas phase
transition.
The ratio of shear viscosity (η) to entropy density (s) of nuclear fireball created in the
central region of intermediate-energy heavy-ion collisions has been investigated within two transport models, namely the Boltzmann-Uehling-Uhlenbeck (BUU) model and the isospin-dependent quantum molecular dynamics (IQMD) model. Different methods are used to calculate η and s. With the collisionenergy increasing, the η/s displays a saturation value or a local minimum value at a certain beam energy.We argue that the saturation or minimum point corresponds to an occurrence of nuclear liquid gas phase
transition.
2014, 31(3): 326-332.
doi: 10.11804/NuclPhysRev.31.03.326
Abstract:
Dynamics of kaons (K0 and K+) produced in nuclear reactions near threshold energies has been investigated within the Lanzhou quantum molecular dynamics (LQMD) transport model.The production yields are consistent with the available experimental data. A repulsive kaon-nucleon potential is implemented in the model through fitting the kinetic energy spectra of inclusive cross sections in heavy-ion collisions, which enhances the energetic kaon emission squeezed out in the reaction zone and reduces the total kaon yields. The comparison to the available data supports a soft equation of state in the density region of 2 ~3ρ0 for isospin symmetric nuclear matter. It is found that the stiffness of nuclear symmetry energy plays a significant role on the isospin ratio with decreasing the incident energy, in particularly in the domain of subthreshold energies.
Dynamics of kaons (K0 and K+) produced in nuclear reactions near threshold energies has been investigated within the Lanzhou quantum molecular dynamics (LQMD) transport model.The production yields are consistent with the available experimental data. A repulsive kaon-nucleon potential is implemented in the model through fitting the kinetic energy spectra of inclusive cross sections in heavy-ion collisions, which enhances the energetic kaon emission squeezed out in the reaction zone and reduces the total kaon yields. The comparison to the available data supports a soft equation of state in the density region of 2 ~3ρ0 for isospin symmetric nuclear matter. It is found that the stiffness of nuclear symmetry energy plays a significant role on the isospin ratio with decreasing the incident energy, in particularly in the domain of subthreshold energies.
2014, 31(3): 333-338.
doi: 10.11804/NuclPhysRev.31.03.333
Abstract:
While the nuclear symmetry energy is usually studied in nite nuclei and nucleonic matter,we study the symmetry energy in relativistic mean- eld models with the inclusion of the hyperon and quark degrees of freedom at high densities. Apparent softening of the symmetry energy with the inclusion of hyperon and quark degrees of freedom is found and demonstrated in the relativistic mean-eld model. This softening would have associations with the symmetry energy extraction which needs detailed discriminations in dense matter with the admixture of new degrees of freedom created by heavy-ion collisions.
While the nuclear symmetry energy is usually studied in nite nuclei and nucleonic matter,we study the symmetry energy in relativistic mean- eld models with the inclusion of the hyperon and quark degrees of freedom at high densities. Apparent softening of the symmetry energy with the inclusion of hyperon and quark degrees of freedom is found and demonstrated in the relativistic mean-eld model. This softening would have associations with the symmetry energy extraction which needs detailed discriminations in dense matter with the admixture of new degrees of freedom created by heavy-ion collisions.
2014, 31(3): 339-343.
doi: 10.11804/NuclPhysRev.31.03.339
Abstract:
The description of nuclear masses is one fundamental issue in nuclear structure theory. A number of odd-even staggerings of masses have been observed in double differences of neighboring nuclei. These oddeven staggerings are very useful to study local mass relations and nucleon-pair correlations. In this paper we discuss the odd-even features that we discerned in recent years, such as the odd-even staggering of the interaction between the last proton and the last neutron (denoted by δV1p-1n), the odd-even feature of the Garvey-Kelson mass relations, the odd-even feature of one-nucleon separation energies, and so on, exhibited in masses of neighboring nuclei and related quantities.
The description of nuclear masses is one fundamental issue in nuclear structure theory. A number of odd-even staggerings of masses have been observed in double differences of neighboring nuclei. These oddeven staggerings are very useful to study local mass relations and nucleon-pair correlations. In this paper we discuss the odd-even features that we discerned in recent years, such as the odd-even staggering of the interaction between the last proton and the last neutron (denoted by δV1p-1n), the odd-even feature of the Garvey-Kelson mass relations, the odd-even feature of one-nucleon separation energies, and so on, exhibited in masses of neighboring nuclei and related quantities.
2014, 31(3): 344-349.
doi: 10.11804/NuclPhysRev.31.03.344
Abstract:
The stochastic approach to ssion is employed to analyze measured ssion excitation functions in the reactions 3He+197Au, 3He+208Pb and 3He+186W. A pre-saddle friction strength of about 4 x 1021 s-1is extracted by comparing theoretical calculations with experimental data. The important role of level-density parameters in accurately determining the strength of nuclear friction is revealed.It is further shown that high-energy conditions can enhance the sensitivity of ssion cross sections to nuclear dissipation.
The stochastic approach to ssion is employed to analyze measured ssion excitation functions in the reactions 3He+197Au, 3He+208Pb and 3He+186W. A pre-saddle friction strength of about 4 x 1021 s-1is extracted by comparing theoretical calculations with experimental data. The important role of level-density parameters in accurately determining the strength of nuclear friction is revealed.It is further shown that high-energy conditions can enhance the sensitivity of ssion cross sections to nuclear dissipation.
2014, 31(3): 350-358.
doi: 10.11804/NuclPhysRev.31.03.350
Abstract:
Study of fusion barrier is very important for people to better understand fusion reactions. In this paper the Improved Isospin-dependent Quantum Molecular Dynamics(ImIQMD) model is introduced firstly.Then the shell correction effects, energy dependence, isospin effects and orientation effects of fusion barrier are studied. The fusion barriers for the fusion reactions 40Ca+40Ca, 48Ca+208Pb, 48Ca+204Pb and 16O+154Sm are extracted. The negative shell correction energies lower potential barriers of a certain reaction. A complex phenomenon of energy dependence is observed. It is also found that incident energy dependence of the barrier radius and barrier height shows opposite behaviors. The Coulomb potential shows weak energy dependence when distance of two colliding nuclei is lower than the touching distance. The isospin effects of the potential barrier are investigated. The orientation effects of the potential barrier are also discussed for the system 16O+154Sm.
Study of fusion barrier is very important for people to better understand fusion reactions. In this paper the Improved Isospin-dependent Quantum Molecular Dynamics(ImIQMD) model is introduced firstly.Then the shell correction effects, energy dependence, isospin effects and orientation effects of fusion barrier are studied. The fusion barriers for the fusion reactions 40Ca+40Ca, 48Ca+208Pb, 48Ca+204Pb and 16O+154Sm are extracted. The negative shell correction energies lower potential barriers of a certain reaction. A complex phenomenon of energy dependence is observed. It is also found that incident energy dependence of the barrier radius and barrier height shows opposite behaviors. The Coulomb potential shows weak energy dependence when distance of two colliding nuclei is lower than the touching distance. The isospin effects of the potential barrier are investigated. The orientation effects of the potential barrier are also discussed for the system 16O+154Sm.
2014, 31(3): 359-365.
doi: 10.11804/NuclPhysRev.31.03.359
Abstract:
The analysis of the laboratory data from the heavy-ion collisions and the correlated theoretical research prefer a soft equation of state (EOS) for the unsymmetric dense matters; and the presence of hyperons at density exceeding 2~3 times of normal nuclear density 0 also may soften the EOS of the dense matters.But a soft EOS cannot support a massive neutron star. After the observation of pulsar PSR J1614-2230 with a mass of (1.97±0.04) M⊙, we have to face this intractable contradiction. In order to solve this contradiction,people have proposed several possible mechanisms, including the modified gravity theory, the modified models for the description of the dense matters and so on. This paper has reviewed these mechanisms. In addition, we also calculated and discussed the effect of the strong electromagnetic field on the maximum mass of the neutron stars. It is found that the strong electromagnetic field can increase the maximum mass of the neutron stars efficaciously.
The analysis of the laboratory data from the heavy-ion collisions and the correlated theoretical research prefer a soft equation of state (EOS) for the unsymmetric dense matters; and the presence of hyperons at density exceeding 2~3 times of normal nuclear density 0 also may soften the EOS of the dense matters.But a soft EOS cannot support a massive neutron star. After the observation of pulsar PSR J1614-2230 with a mass of (1.97±0.04) M⊙, we have to face this intractable contradiction. In order to solve this contradiction,people have proposed several possible mechanisms, including the modified gravity theory, the modified models for the description of the dense matters and so on. This paper has reviewed these mechanisms. In addition, we also calculated and discussed the effect of the strong electromagnetic field on the maximum mass of the neutron stars. It is found that the strong electromagnetic field can increase the maximum mass of the neutron stars efficaciously.
2014, 31(3): 366-373.
doi: 10.11804/NuclPhysRev.31.03.366
Abstract:
In a pebble-bed core which employs the multi-pass scheme, it is mandatory to determine the burnup of each pebble after the pebble has been extracted from the core in order to determine whether its design burnup has been reached or whether it has to be reinserted into the core again. The burnup of the fuel pebbles can be determined by measuring the activity of 137Cs with an HPGe detector because of their good correspondence, which is independent of the irradiation history in the core. Based on experiments and Geant4 simulation, the correction factor between the fuel and calibration source was derived by using the efficiency transfer method. By optimizing spectrum analysis algorithm and parameters, the relative standard deviation of the 137Cs activity can be still controlled below 3.0% despite of the presence of interfering peaks. On the foundation of the simulation and experiment research, a complete solution for burnup measurement system in HTR-PM is provided.
In a pebble-bed core which employs the multi-pass scheme, it is mandatory to determine the burnup of each pebble after the pebble has been extracted from the core in order to determine whether its design burnup has been reached or whether it has to be reinserted into the core again. The burnup of the fuel pebbles can be determined by measuring the activity of 137Cs with an HPGe detector because of their good correspondence, which is independent of the irradiation history in the core. Based on experiments and Geant4 simulation, the correction factor between the fuel and calibration source was derived by using the efficiency transfer method. By optimizing spectrum analysis algorithm and parameters, the relative standard deviation of the 137Cs activity can be still controlled below 3.0% despite of the presence of interfering peaks. On the foundation of the simulation and experiment research, a complete solution for burnup measurement system in HTR-PM is provided.
2014, 31(3): 374-378.
doi: 10.11804/NuclPhysRev.31.03.374
Abstract:
162.5 MHz high-frequency low-level control system self-developed by Institute of Modern Physics for ADS project took digital technology. All parameters' reading & writing，including loop parameter setting,open& close-loop operation, and condition monitoring, were achieved through the monitoring system. The system used lightweight client-server working mode that client running in the PC sent command data, server running on high-frequency digital low level system responded instructions to complete parameter monitoring and control. The system consisted of three parts. Firstly, server hardware system was constructed based on Atera Stratix III family of eld-programmable gate array (FPGA) development board. Secondly，the server software system was designed based on Micro C/OS II real-time operating systems and lightweight TCP / IP protocol stack, and nally a client PC program was designed based on MFC. After a long test, it was indicated that the monitoring system works properly and stably. TCP sends and receives throughput reached 11.931 038 Mbps and 8.117 624 Mbps.
162.5 MHz high-frequency low-level control system self-developed by Institute of Modern Physics for ADS project took digital technology. All parameters' reading & writing，including loop parameter setting,open& close-loop operation, and condition monitoring, were achieved through the monitoring system. The system used lightweight client-server working mode that client running in the PC sent command data, server running on high-frequency digital low level system responded instructions to complete parameter monitoring and control. The system consisted of three parts. Firstly, server hardware system was constructed based on Atera Stratix III family of eld-programmable gate array (FPGA) development board. Secondly，the server software system was designed based on Micro C/OS II real-time operating systems and lightweight TCP / IP protocol stack, and nally a client PC program was designed based on MFC. After a long test, it was indicated that the monitoring system works properly and stably. TCP sends and receives throughput reached 11.931 038 Mbps and 8.117 624 Mbps.
2014, 31(3): 379-384.
doi: 10.11804/NuclPhysRev.31.03.379
Abstract:
This paper introduces the working principle of the power supplies for the septum magnets in HIRFL-CSR and presents a feasible scheme of digitalizing these power supplies. The scheme employed the SOPC (system-on-a-programmable-chip) technology based on FPGA, the software framework of NIOSII and the polycyclic adjustment algorithm realized by the hardware description language. Then, several key problems that could be encountered in realizing the power supply control algorithm on FPGA were discussed. After the power supplies were upgraded, the beam of HIRFL-CSR was extracted more reliably and the stability of beam spot position at the experimental terminals has been obviously improved. This work would provide a valuable reference for the engineers of digitalizing other magnetic power supplies in HIRFL-CSR and of developing magnetic power supplies for heavy ion cancer therapy.
This paper introduces the working principle of the power supplies for the septum magnets in HIRFL-CSR and presents a feasible scheme of digitalizing these power supplies. The scheme employed the SOPC (system-on-a-programmable-chip) technology based on FPGA, the software framework of NIOSII and the polycyclic adjustment algorithm realized by the hardware description language. Then, several key problems that could be encountered in realizing the power supply control algorithm on FPGA were discussed. After the power supplies were upgraded, the beam of HIRFL-CSR was extracted more reliably and the stability of beam spot position at the experimental terminals has been obviously improved. This work would provide a valuable reference for the engineers of digitalizing other magnetic power supplies in HIRFL-CSR and of developing magnetic power supplies for heavy ion cancer therapy.
2014, 31(3): 385-390.
doi: 10.11804/NuclPhysRev.31.03.385
Abstract:
Because of injecting an out-of-control beam pulse, thermal shock damage to the accelerator may well cause a failure of focusing and steering elements. In order to prevent RFQ accelerator,superconducting cavities and other accelerator components from thermal damage, t is essential to conduct a quantitative evaluation of the thermal stresses induced in the material during the thermal shock. The present study in this paper proposed a novel method to evaluate the thermal stresses quantitatively, which can clarify the characteristics of thermal shock of several materials, such as OFHC, SUS304 and Niobium. Transitional thermal stress is investigated by three dimensional nite element method (FEM) to obtain the temperature distribution for three materials at the beam incident angle of 90°. Finally the simulation results prove that the machine protect system response time meets the requirement when the allowable injection time is de ned as 20 μs.
Because of injecting an out-of-control beam pulse, thermal shock damage to the accelerator may well cause a failure of focusing and steering elements. In order to prevent RFQ accelerator,superconducting cavities and other accelerator components from thermal damage, t is essential to conduct a quantitative evaluation of the thermal stresses induced in the material during the thermal shock. The present study in this paper proposed a novel method to evaluate the thermal stresses quantitatively, which can clarify the characteristics of thermal shock of several materials, such as OFHC, SUS304 and Niobium. Transitional thermal stress is investigated by three dimensional nite element method (FEM) to obtain the temperature distribution for three materials at the beam incident angle of 90°. Finally the simulation results prove that the machine protect system response time meets the requirement when the allowable injection time is de ned as 20 μs.
2014, 31(3): 391-400.
doi: 10.11804/NuclPhysRev.31.03.391
Abstract:
This paper presents the status and recent progress on -decay induced X-ray spectroscopy (BIXS) for tritium measurements. The development history of BIXS method and its applications on tritium analysis are introduced, and at the same time the characteristics of three kinds of BIXS methods, i:e. calibration curve method, analytical method and Monte Carlo simulations combined with Tikhonov regularization method are also introduced. The recent studies on the BIXS method performed in our group, including the incorporation of Monte Carlo simulation and regularization method, effects of internal bremsstrahlung of tritium -decay, sample surface roughness, tritium content and geometrical parameter’s uncertainty of experimental setup in BIXS method, and the application are mainly presented. Finally, the general comments on the further improvements of the BIXS method are given.
This paper presents the status and recent progress on -decay induced X-ray spectroscopy (BIXS) for tritium measurements. The development history of BIXS method and its applications on tritium analysis are introduced, and at the same time the characteristics of three kinds of BIXS methods, i:e. calibration curve method, analytical method and Monte Carlo simulations combined with Tikhonov regularization method are also introduced. The recent studies on the BIXS method performed in our group, including the incorporation of Monte Carlo simulation and regularization method, effects of internal bremsstrahlung of tritium -decay, sample surface roughness, tritium content and geometrical parameter’s uncertainty of experimental setup in BIXS method, and the application are mainly presented. Finally, the general comments on the further improvements of the BIXS method are given.
2014, 31(3): 401-406.
doi: 10.11804/NuclPhysRev.31.03.401
Abstract:
Artificial neural network methods have been introduced in high energy physics experiments and have been widely applied to the identification of the quark-gluon injection, electronic hadron discrimination,top quark, and the Higgs particle searching and so on. This paper introduces a modified conjugate gradient optimization algorithm, which is applied to the identification of high-energy particles. In the application, the algorithm can obtain optimal step size in the search direction for minimizing the objective function, and can overcome the local vibration problem, so that the fast convergence of the objective function is obtained and the stability of the algorithm is improved. The analysis of experimental data shows that our new BP neural network algorithm can effectively improve the identification of particles in high energy physics.
Artificial neural network methods have been introduced in high energy physics experiments and have been widely applied to the identification of the quark-gluon injection, electronic hadron discrimination,top quark, and the Higgs particle searching and so on. This paper introduces a modified conjugate gradient optimization algorithm, which is applied to the identification of high-energy particles. In the application, the algorithm can obtain optimal step size in the search direction for minimizing the objective function, and can overcome the local vibration problem, so that the fast convergence of the objective function is obtained and the stability of the algorithm is improved. The analysis of experimental data shows that our new BP neural network algorithm can effectively improve the identification of particles in high energy physics.
2014, 31(3): 407-410.
doi: 10.11804/NuclPhysRev.31.03.407
Abstract:
This work illustrated a wavelet threshold method by combining soft and hard threshold function of wavelet for energy spectrum under the natural radioactive condition as a kind of smooth processing. By using Matlab Program, we compared five different smooth de-noising methods including smoothing by five points, the Fourier transform method, soft and hard threshold method and average wavelet threshold method.We showed that the average wavelet threshold method can reflect the ratio of the peak and the peak-to-total ratio of characteristic peak of energy spectrum as 7.1609 and 0.394 5, respectively. Thus, this method is superior to the other four methods in de-nosing, and it is able to keep the original signal properties with the largest extent and has a high value of application.
This work illustrated a wavelet threshold method by combining soft and hard threshold function of wavelet for energy spectrum under the natural radioactive condition as a kind of smooth processing. By using Matlab Program, we compared five different smooth de-noising methods including smoothing by five points, the Fourier transform method, soft and hard threshold method and average wavelet threshold method.We showed that the average wavelet threshold method can reflect the ratio of the peak and the peak-to-total ratio of characteristic peak of energy spectrum as 7.1609 and 0.394 5, respectively. Thus, this method is superior to the other four methods in de-nosing, and it is able to keep the original signal properties with the largest extent and has a high value of application.
2014, 31(3): 411-415.
doi: 10.11804/NuclPhysRev.31.03.411
Abstract:
In this study, three kinds of alfalfa including Zhonglan 1, BC-04-477 and Ta Cheng were treated with different doses of 12C6+ (75 keV) heavy ion radiation, and then the influence of survival rate, catalase(CAT) and peroxidase(POD) activity of M1 with low temperature stress were tested. The results showed that under the condition of 400 Gy radiation dose , the survival rate and CAT activity of Zhonglan 1 under low temperature stress have increased by 33.3%, 56.3% respectively compared with those of the control group, while there was no difference in POD activity between those two groups. The survival rate, CAT and POD activity of BC-04-477 treated with low temperature have been improved by 33.3%, 69.2%, 5.1% respectively compared with those of the control group when the radiation dose was 400 Gy. Compared with those of the control group, the survival rate, CAT and POD activity of Ta Cheng under low temperature stress have been improved by 25%, 26%,22.8% respectively when the radiation dose was 800 Gy. These results indicate that the viability and the cold resistance ability of Zhong Lan 1, BC-04-477 and Ta Cheng can be improved by 12C6+ radiation.
In this study, three kinds of alfalfa including Zhonglan 1, BC-04-477 and Ta Cheng were treated with different doses of 12C6+ (75 keV) heavy ion radiation, and then the influence of survival rate, catalase(CAT) and peroxidase(POD) activity of M1 with low temperature stress were tested. The results showed that under the condition of 400 Gy radiation dose , the survival rate and CAT activity of Zhonglan 1 under low temperature stress have increased by 33.3%, 56.3% respectively compared with those of the control group, while there was no difference in POD activity between those two groups. The survival rate, CAT and POD activity of BC-04-477 treated with low temperature have been improved by 33.3%, 69.2%, 5.1% respectively compared with those of the control group when the radiation dose was 400 Gy. Compared with those of the control group, the survival rate, CAT and POD activity of Ta Cheng under low temperature stress have been improved by 25%, 26%,22.8% respectively when the radiation dose was 800 Gy. These results indicate that the viability and the cold resistance ability of Zhong Lan 1, BC-04-477 and Ta Cheng can be improved by 12C6+ radiation.
2014, 31(3): 416-422.
doi: 10.11804/NuclPhysRev.31.03.416
Abstract:
5-Aza-CdR is a specific inhibitor of DNMTs which could suppress tumor growth by demethylation of genomic DNA. There have only few studies thus far concerning it as radiosensitizers in three-dimensional (3D) cells. The principal aim of this study is to evaluate the effects of 5-Aza-CdR on the radiosensitivity of A549 cells in monolayer (2D) and 3D cultures in an attempt to find out a new combination treatments with radiotherapy. The cell proliferation was detected by MTT assay after pretreated with different doses of 5-Aza-CdR for 72 h. A549 cells were treated with or without 5-Aza-CdR (2, 5 μmol/L) for 72 h before be exposed to X-rays of 1, 2, 4, 6 Gy, respectively. The DNA damage was evaluated by micronucleus assay and clonogenic assays. Pretreatment with 5-Aza-CdR inhibited the A549 cell proliferation significantly. More micronucleus were observed after irradiation in 3D cells pretreated with 2 and 5 μmol/L concentration of drug than those without treatment. The survival fractions of cells pretreated by both 2 and 5 mol/L drug reduced significantly in 3D cultures after irradiation. These significances, however, were found in 2D cells pretreated by only 5 μmol/L drug. Our results suggest that 5-Aza-CdR can inhibit the A549 cells proliferation and apparently enhance the radiosensitivity of cells in 3D cultures. Using of the low dose 5-Aza-CdR in clinical radiotherapy may reduce side effects and enhance effectively the cancer target therapy.
5-Aza-CdR is a specific inhibitor of DNMTs which could suppress tumor growth by demethylation of genomic DNA. There have only few studies thus far concerning it as radiosensitizers in three-dimensional (3D) cells. The principal aim of this study is to evaluate the effects of 5-Aza-CdR on the radiosensitivity of A549 cells in monolayer (2D) and 3D cultures in an attempt to find out a new combination treatments with radiotherapy. The cell proliferation was detected by MTT assay after pretreated with different doses of 5-Aza-CdR for 72 h. A549 cells were treated with or without 5-Aza-CdR (2, 5 μmol/L) for 72 h before be exposed to X-rays of 1, 2, 4, 6 Gy, respectively. The DNA damage was evaluated by micronucleus assay and clonogenic assays. Pretreatment with 5-Aza-CdR inhibited the A549 cell proliferation significantly. More micronucleus were observed after irradiation in 3D cells pretreated with 2 and 5 μmol/L concentration of drug than those without treatment. The survival fractions of cells pretreated by both 2 and 5 mol/L drug reduced significantly in 3D cultures after irradiation. These significances, however, were found in 2D cells pretreated by only 5 μmol/L drug. Our results suggest that 5-Aza-CdR can inhibit the A549 cells proliferation and apparently enhance the radiosensitivity of cells in 3D cultures. Using of the low dose 5-Aza-CdR in clinical radiotherapy may reduce side effects and enhance effectively the cancer target therapy.
2014, 31(3): 423-427.
doi: 10.11804/NuclPhysRev.31.03.423
Abstract:
The radio-protective effects on human embryonic lung fibroblast MRC-5 of an oxazolone derivative named GANRA-5 were studied. MTT test was used to evaluate the toxicity and H2AX foci assay was used to test the influence of GANRA-5 on the DSB (double-stranded break) formation after irradiation. It is found that GANRA-5 exhibited low toxicity and high radio-protective effects on MRC-5 cells against both X-ray and 12C6+ ion beam. It is also found that it can act as a scavenger of free radicals. These results suggest that GANRA-5 is a promising radioprotectant.
The radio-protective effects on human embryonic lung fibroblast MRC-5 of an oxazolone derivative named GANRA-5 were studied. MTT test was used to evaluate the toxicity and H2AX foci assay was used to test the influence of GANRA-5 on the DSB (double-stranded break) formation after irradiation. It is found that GANRA-5 exhibited low toxicity and high radio-protective effects on MRC-5 cells against both X-ray and 12C6+ ion beam. It is also found that it can act as a scavenger of free radicals. These results suggest that GANRA-5 is a promising radioprotectant.
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