2012 Vol. 29, No. 4
Display Method:
2012, 29(4): 317-326.
doi: 10.11804/NuclPhysRev.29.04.317
Abstract:
This article outlines the progress in the study of the dineutron structure in various systems. Systematic theoretical investigations reveal that dineutron structure is a general phenomenon appeared at nucleus surface and in low density nuclear matter. But the underline mechanism of forming dineutron clusters at the surface of heavier nuclei is quite different to that for light halo nuclei or at the low density nuclear matter， with the former being basically due to the so called “size effect” and the latter due to the enhanced pairing interaction. It is also realized that the RMS radii of the dineutron cluster at the surface of light halo nuclei or heavier finite nuclei varies with the distance from the center of nuclei (or background density) and may attain a minimum of about 2～3 fm， whereas that in the low density nuclear matter may only attain about 5 fm. From experimental side， Coulomb excitation caused by heavy targets provides a good way to extract the mean distance from the center of the neutron pair to the center of nucleus. But up to now it is still difficult to experimentally determine the distance between the two valence neutrons， due primarily to the final state interactions which lead to two step emission of neutrons via resonances or virtual intermediate states. This problem happens in both Coulomb and nuclear breakup processes. Possible ways to avoid this problem might come from experiments based on “towing mode” or core knockout reactions. Detection of two neutrons in coincidence often suffers from low efficiencies and the need to reject the cross talk events. Therefore it is important to develop specially designed multineutron detection array to achieve high efficiency as well as good cross talk rejection performance using kinematics conditions. For data analysis， it was found that two neutron correlation function generated by iteration method is a good expression of the correlation situation， from which the RMS radii of the two neutron distribution may be deduced.
This article outlines the progress in the study of the dineutron structure in various systems. Systematic theoretical investigations reveal that dineutron structure is a general phenomenon appeared at nucleus surface and in low density nuclear matter. But the underline mechanism of forming dineutron clusters at the surface of heavier nuclei is quite different to that for light halo nuclei or at the low density nuclear matter， with the former being basically due to the so called “size effect” and the latter due to the enhanced pairing interaction. It is also realized that the RMS radii of the dineutron cluster at the surface of light halo nuclei or heavier finite nuclei varies with the distance from the center of nuclei (or background density) and may attain a minimum of about 2～3 fm， whereas that in the low density nuclear matter may only attain about 5 fm. From experimental side， Coulomb excitation caused by heavy targets provides a good way to extract the mean distance from the center of the neutron pair to the center of nucleus. But up to now it is still difficult to experimentally determine the distance between the two valence neutrons， due primarily to the final state interactions which lead to two step emission of neutrons via resonances or virtual intermediate states. This problem happens in both Coulomb and nuclear breakup processes. Possible ways to avoid this problem might come from experiments based on “towing mode” or core knockout reactions. Detection of two neutrons in coincidence often suffers from low efficiencies and the need to reject the cross talk events. Therefore it is important to develop specially designed multineutron detection array to achieve high efficiency as well as good cross talk rejection performance using kinematics conditions. For data analysis， it was found that two neutron correlation function generated by iteration method is a good expression of the correlation situation， from which the RMS radii of the two neutron distribution may be deduced.
2012, 29(4): 327-335.
doi: 10.11804/NuclPhysRev.29.04.327
Abstract:
The surrogate nuclear reaction approach plays an important role in the determination of nuclear reaction cross sections that are difficult to be measured directly. In this paper， we investigate its basis， factors affecting its accuracy， and its three variants: the external surrogate ratio method (ESRM)， the internal surrogate ratio method (ISRM) and the hybrid surrogate ratio method (HSRM). Each method was described， and their applications or experimental tests were given， from which we could see their respective advantages and disadvantages. And it is found that the spinparity mismatch， or the (weak) WeisskopfEwing limit equivalently， is an inherent limitation of the approach. It is also seen that the surrogate approach can reach a high accuracy， so it is a good indirect approach when the nuclear reaction cross sections are unavailable to be measured directly.
The surrogate nuclear reaction approach plays an important role in the determination of nuclear reaction cross sections that are difficult to be measured directly. In this paper， we investigate its basis， factors affecting its accuracy， and its three variants: the external surrogate ratio method (ESRM)， the internal surrogate ratio method (ISRM) and the hybrid surrogate ratio method (HSRM). Each method was described， and their applications or experimental tests were given， from which we could see their respective advantages and disadvantages. And it is found that the spinparity mismatch， or the (weak) WeisskopfEwing limit equivalently， is an inherent limitation of the approach. It is also seen that the surrogate approach can reach a high accuracy， so it is a good indirect approach when the nuclear reaction cross sections are unavailable to be measured directly.
2012, 29(4): 336-343.
doi: 10.11804/NuclPhysRev.29.04.336
Abstract:
The production of J/ψ originating from photoproduction processes in pp and
pÞ collisions at leading order is calculated. The color singlet and color octet mechanisms for heavy quarkonium production are reviewed within nonrelativistic QCD, and be used to deal with the direct photon and resolved photon processes respectively. Comparing with the leading order results of J/ψ production, the numerical results show that the modification of photoproduction processes for J/ψ production become obvious at large p-T region.
The production of J/ψ originating from photoproduction processes in pp and
pÞ collisions at leading order is calculated. The color singlet and color octet mechanisms for heavy quarkonium production are reviewed within nonrelativistic QCD, and be used to deal with the direct photon and resolved photon processes respectively. Comparing with the leading order results of J/ψ production, the numerical results show that the modification of photoproduction processes for J/ψ production become obvious at large p-T region.
2012, 29(4): 344-352.
doi: 10.11804/NuclPhysRev.29.04.344
Abstract:
Based on the generalized QCD vector meson dominance model and the QCD Inspired Eikonalized approximation, γγ interaction has been studied in this paper. Unlike the usual calculations of the γγ interaction by the Feynman box diagram technique, we explore the process by QCD theory in which γγ elastic scattering proceeds through a strong interaction between two pairs of quarkantiquark fluctuated by two scattering photons. Due to the fact that the mediator of strong interaction is colorful gluon，and gluon has a property of self-interaction which can bind exchanging gluons together to form glueballs. The colorless tensor glueball (two Reggeized gluon bound state) and Odderon (three Reggeized gluon bound state) could be the mediators of the interaction between the two quarkantiquark pairs. This mechanism is very different from the other theoretical descriptions of the process. In particular, the contributions from virtual gluon, bound quarkantiquark to form a fluctuated meson, are taken into account. We calculate the total cross section σtot, the differential cross section dσ/dt, the ratio of the real part to the imaginary part of the forward scattering amplitude ρ, and the nuclear slope parameter function β of γγ elastic scattering. Our theoretical predictions for σtot are consistent with the experimental data within error bars of the data. The data for dσ/dt, ρ and β are urgently needed to test our theoretical model.
Based on the generalized QCD vector meson dominance model and the QCD Inspired Eikonalized approximation, γγ interaction has been studied in this paper. Unlike the usual calculations of the γγ interaction by the Feynman box diagram technique, we explore the process by QCD theory in which γγ elastic scattering proceeds through a strong interaction between two pairs of quarkantiquark fluctuated by two scattering photons. Due to the fact that the mediator of strong interaction is colorful gluon，and gluon has a property of self-interaction which can bind exchanging gluons together to form glueballs. The colorless tensor glueball (two Reggeized gluon bound state) and Odderon (three Reggeized gluon bound state) could be the mediators of the interaction between the two quarkantiquark pairs. This mechanism is very different from the other theoretical descriptions of the process. In particular, the contributions from virtual gluon, bound quarkantiquark to form a fluctuated meson, are taken into account. We calculate the total cross section σtot, the differential cross section dσ/dt, the ratio of the real part to the imaginary part of the forward scattering amplitude ρ, and the nuclear slope parameter function β of γγ elastic scattering. Our theoretical predictions for σtot are consistent with the experimental data within error bars of the data. The data for dσ/dt, ρ and β are urgently needed to test our theoretical model.
2012, 29(4): 353-357.
doi: 10.11804/NuclPhysRev.29.04.353
Abstract:
The secondary thermal dileptons produced from the quarkgluon plasma are investigated. The secondary thermal dileptons produced at RHIC energy were concentrated in the low mass region of 0.2 GeV<M<0.8 GeV. The mechanism of the secondary thermal dileptons could be properly explained the enhancement of the dilepton yield in PHENIX experiments for Au-Au 200 AGeV collisions. For Pb-Pb 5.5 ATeV collisions at LHC, the enhancement is more evident in the low mass region of 0.3 GeV
The secondary thermal dileptons produced from the quarkgluon plasma are investigated. The secondary thermal dileptons produced at RHIC energy were concentrated in the low mass region of 0.2 GeV<M<0.8 GeV. The mechanism of the secondary thermal dileptons could be properly explained the enhancement of the dilepton yield in PHENIX experiments for Au-Au 200 AGeV collisions. For Pb-Pb 5.5 ATeV collisions at LHC, the enhancement is more evident in the low mass region of 0.3 GeV
2012, 29(4): 358-363.
doi: 10.11804/NuclPhysRev.29.04.358
Abstract:
To study intense pulsed beam transfer in electrostatic accelerate tube, the matrix method was applied to analyze the transport matrixes in electrostatic accelerate tube of non-intense pulsed beam and intense pulsed beam, and a computer code was written for the intense pulsed beam transporting in electrostatic accelerate tube. Optimization techniques were used to attain the given optical conditions and iteration procedures were adopted to compute intense pulsed beam for obtaining self-consistent solutions in this computer code. The calculations were carried out by using ACCT, TRACE-3D and TRANSPORT for different beam currents, respectively. The simulation results show that improvement of the accelerating voltage ratio can enhance focusing power of electrostatic accelerate tube, reduce beam loss and increase the transferring efficiency.
To study intense pulsed beam transfer in electrostatic accelerate tube, the matrix method was applied to analyze the transport matrixes in electrostatic accelerate tube of non-intense pulsed beam and intense pulsed beam, and a computer code was written for the intense pulsed beam transporting in electrostatic accelerate tube. Optimization techniques were used to attain the given optical conditions and iteration procedures were adopted to compute intense pulsed beam for obtaining self-consistent solutions in this computer code. The calculations were carried out by using ACCT, TRACE-3D and TRANSPORT for different beam currents, respectively. The simulation results show that improvement of the accelerating voltage ratio can enhance focusing power of electrostatic accelerate tube, reduce beam loss and increase the transferring efficiency.
2012, 29(4): 364-370.
doi: 10.11804/NuclPhysRev.29.04.364
Abstract:
To improve the control efficiency of Superconducting Electron Cyclotron Resonance Ion source (SECRAL) for Heavy Ion Research Facility in Lanzhou(HIRFL), a remote control system was designed and set up in July 2011. The control software package, as a part of the system, was implemented by Visual C++, which is able to control and monitor all of the equipments for the SECRAL system with about 110 parameters. And many kinds of control protocols were used for controlling different types of equipments in this software. Moreover, in order to prevent the misoperation which may cause the quench of the superconducting magnet, alarm and interlockprotection functions are added to the software and hardware too. If some errors occur during the running of SECARL, those functions should take effect within 1 s. Simultaneously, the data acquired from the equipments can be stored in disk every 1 s for following analysis.
To improve the control efficiency of Superconducting Electron Cyclotron Resonance Ion source (SECRAL) for Heavy Ion Research Facility in Lanzhou(HIRFL), a remote control system was designed and set up in July 2011. The control software package, as a part of the system, was implemented by Visual C++, which is able to control and monitor all of the equipments for the SECRAL system with about 110 parameters. And many kinds of control protocols were used for controlling different types of equipments in this software. Moreover, in order to prevent the misoperation which may cause the quench of the superconducting magnet, alarm and interlockprotection functions are added to the software and hardware too. If some errors occur during the running of SECARL, those functions should take effect within 1 s. Simultaneously, the data acquired from the equipments can be stored in disk every 1 s for following analysis.
2012, 29(4): 371-378.
doi: 10.11804/NuclPhysRev.29.04.371
Abstract:
Beam of MeV ions from particle accelerators can be confined by collimators or focused by electrical/magnetic quadruples into micrometer size， and this microbeam can be used to obtain spatial information or radiation effect in solids and biological samples. This paper reviews the technical developments and the multidisciplinary applications of microbeam， including ion beam analysis， single event effect in semiconductor devices， proton beam writing and cellular response to targeted particle irradiations. Finally， the high energy heavy ion microbeam facility at the Institute of Modern Physics of Chinese Academy of Sciences is introduced， which has successfully focused 1 GeV Carbon ions into a beam spot of 1 μm×2 μm in air.
Beam of MeV ions from particle accelerators can be confined by collimators or focused by electrical/magnetic quadruples into micrometer size， and this microbeam can be used to obtain spatial information or radiation effect in solids and biological samples. This paper reviews the technical developments and the multidisciplinary applications of microbeam， including ion beam analysis， single event effect in semiconductor devices， proton beam writing and cellular response to targeted particle irradiations. Finally， the high energy heavy ion microbeam facility at the Institute of Modern Physics of Chinese Academy of Sciences is introduced， which has successfully focused 1 GeV Carbon ions into a beam spot of 1 μm×2 μm in air.
2012, 29(4): 379-383.
doi: 10.11804/NuclPhysRev.29.04.379
Abstract:
With the application of the twodimensional GEM gaseous detector in X ray imaging, the correction method of gain uniformity caused by tripleGEM avalanche structures and electric field uniformity should be studied. The paper reported the study of the tripleGEM detector with effective area 100 mm×100 mm used the Pad’s size of 9.5 mm×9.5 mm. In the test, 100 readout channels were designed. Results showed that gain remained stable over time; as air flow increases, gain from increases obviously to changes very little. Particularly, triple GEM’s gain uniformity was very good (more than 80%) and the range of energy resolution was from 0.18 to 0.22. To improve gain consistency of results, the difference value revised was obtained to be about 0.1 by the least square method. It provided a better method to improve gain uniformity of GEM detector.
With the application of the twodimensional GEM gaseous detector in X ray imaging, the correction method of gain uniformity caused by tripleGEM avalanche structures and electric field uniformity should be studied. The paper reported the study of the tripleGEM detector with effective area 100 mm×100 mm used the Pad’s size of 9.5 mm×9.5 mm. In the test, 100 readout channels were designed. Results showed that gain remained stable over time; as air flow increases, gain from increases obviously to changes very little. Particularly, triple GEM’s gain uniformity was very good (more than 80%) and the range of energy resolution was from 0.18 to 0.22. To improve gain consistency of results, the difference value revised was obtained to be about 0.1 by the least square method. It provided a better method to improve gain uniformity of GEM detector.
2012, 29(4): 384-387.
doi: 10.11804/NuclPhysRev.29.04.384
Abstract:
In the present article, several previous methods for damage detection of spent fuel assembly, as well as the existing limitations of these methods are reviewed. A new sampling system, including the working procedure and operating schedule, was developed in order to meet the practical demands and to solve the disadvantages mentioned. The measurement method for sampling and the criterion practical results provided evidence that, in this system, each operating process could successfully achieve a sample for a single certain spent fuel assembly with high precision. Moreover, all the operations were carried out under water, which made the radiation protection much easier.
In the present article, several previous methods for damage detection of spent fuel assembly, as well as the existing limitations of these methods are reviewed. A new sampling system, including the working procedure and operating schedule, was developed in order to meet the practical demands and to solve the disadvantages mentioned. The measurement method for sampling and the criterion practical results provided evidence that, in this system, each operating process could successfully achieve a sample for a single certain spent fuel assembly with high precision. Moreover, all the operations were carried out under water, which made the radiation protection much easier.
2012, 29(4): 388-394.
doi: 10.11804/NuclPhysRev.29.04.388
Abstract:
In order to investigate the agreement and difference between adjoint and forward calculations with Monte Carlo method， three models have been simulated， and the calculated results are compared and analyzed. First， the comparison shows that the calculated results of the adjoint calculation are basically consistent with those of the forward calculation in modelⅠ. The FOM value of adjoint calculation is about two times of the value of forward calculation. Second， it is investigated with modelⅡ that the applicability of the adjoint calculation for the different materials， and the results show that the difference is about 20% for the case of strong scattering between the adjoint calculation and forward calculation. The FOM value of the forward calculation is larger than that of the adjoint calculation. Finally， the important function is generated by the adjoint calculation in model Ⅲ， and the results are compared with ones of the weight window game. Although their important functions are produced by different mechanisms， the values of functions are in agreement with each other， and the FOM value of ajoint calculation is about 1.5 times of the value from the weight windows.
In order to investigate the agreement and difference between adjoint and forward calculations with Monte Carlo method， three models have been simulated， and the calculated results are compared and analyzed. First， the comparison shows that the calculated results of the adjoint calculation are basically consistent with those of the forward calculation in modelⅠ. The FOM value of adjoint calculation is about two times of the value of forward calculation. Second， it is investigated with modelⅡ that the applicability of the adjoint calculation for the different materials， and the results show that the difference is about 20% for the case of strong scattering between the adjoint calculation and forward calculation. The FOM value of the forward calculation is larger than that of the adjoint calculation. Finally， the important function is generated by the adjoint calculation in model Ⅲ， and the results are compared with ones of the weight window game. Although their important functions are produced by different mechanisms， the values of functions are in agreement with each other， and the FOM value of ajoint calculation is about 1.5 times of the value from the weight windows.
2012, 29(4): 395-398.
doi: 10.11804/NuclPhysRev.29.04.395
Abstract:
Amidoximed fiber and fabric were synthesized with the purpose of adsorbing U in salt lake and the adsorption mechanism was discussed. IR indicated that amidoxime was graft to the fabric which was irradiated by electron beam. Batch experiments were conducted to study the effects of initial pH， amount of adsorbent， shaking time on uranium sorption efficiency. The sorption of uranium on amidoxime was dependent on the pH value of the solution， and the optimal pH was 4.0. Uranyl was taken out from solution in the form of complex with amidoxime. Uranium recovery efficiency from salt lake was more than 50% with amidoximed fiber and fabric which can be used as uranium extraction material.
Amidoximed fiber and fabric were synthesized with the purpose of adsorbing U in salt lake and the adsorption mechanism was discussed. IR indicated that amidoxime was graft to the fabric which was irradiated by electron beam. Batch experiments were conducted to study the effects of initial pH， amount of adsorbent， shaking time on uranium sorption efficiency. The sorption of uranium on amidoxime was dependent on the pH value of the solution， and the optimal pH was 4.0. Uranyl was taken out from solution in the form of complex with amidoxime. Uranium recovery efficiency from salt lake was more than 50% with amidoximed fiber and fabric which can be used as uranium extraction material.
2012, 29(4): 399-405.
doi: 10.11804/NuclPhysRev.29.04.399
Abstract:
Current advance in ionizing radiationinduced mitochondrial DNA damage and mutations is reviewed， in addition with the essential differences between mtDNA and nDNA damage and mutations. To extent the knowledge about radiation induced mitochondrial alterations， the researchers in Institute of Modern Physics， Chinese Academy of Sciences developed some technics such as realtime PCR， longPCR for accurate quantification of radiation induced damage and mutations， and indepth investigation about the functional changes of mitochondria based on mtDNA damage and mutations were also carried out. In conclusion， the important role of mitochondrial study in radiation biology is underlined， and further study on mitochondrial study associated with late effect and metabolism changes in radiation biology is pointed out.
Current advance in ionizing radiationinduced mitochondrial DNA damage and mutations is reviewed， in addition with the essential differences between mtDNA and nDNA damage and mutations. To extent the knowledge about radiation induced mitochondrial alterations， the researchers in Institute of Modern Physics， Chinese Academy of Sciences developed some technics such as realtime PCR， longPCR for accurate quantification of radiation induced damage and mutations， and indepth investigation about the functional changes of mitochondria based on mtDNA damage and mutations were also carried out. In conclusion， the important role of mitochondrial study in radiation biology is underlined， and further study on mitochondrial study associated with late effect and metabolism changes in radiation biology is pointed out.
2012, 29(4): 406-413.
doi: 10.11804/NuclPhysRev.29.04.406
Abstract:
As an important step of the application of spot scanning technique to heavy ion therapy， an experimental calibration procedure of online beam monitors based on standard of absorbed dose to water has recently been developed for scanned pencillike carbon ion beam in the deep seated tumor therapy terminal at the Heavy Ion Research Facility in Lanzhou (HIRFL). In this work， creating homogeneous irradiation field with steerable spot beam was tested using a 207 MeV/u penci like carbon ion beam. Then the verification of energy dependence of the calibration factors (CFs) and the influence of scanning step on the CF were also shown， as a part of the heavy ion clinic dosimetry researches. The results showd that the monitor CF presented energy dependence and performed stable response with deviation of 1.8% for the variation of scan steps. In this paper， the suitability and effectiveness of beam monitor calibration procedure for dynamic particle beam delivery were verified and the further research points to improve the calibration procedure were suggested.
As an important step of the application of spot scanning technique to heavy ion therapy， an experimental calibration procedure of online beam monitors based on standard of absorbed dose to water has recently been developed for scanned pencillike carbon ion beam in the deep seated tumor therapy terminal at the Heavy Ion Research Facility in Lanzhou (HIRFL). In this work， creating homogeneous irradiation field with steerable spot beam was tested using a 207 MeV/u penci like carbon ion beam. Then the verification of energy dependence of the calibration factors (CFs) and the influence of scanning step on the CF were also shown， as a part of the heavy ion clinic dosimetry researches. The results showd that the monitor CF presented energy dependence and performed stable response with deviation of 1.8% for the variation of scan steps. In this paper， the suitability and effectiveness of beam monitor calibration procedure for dynamic particle beam delivery were verified and the further research points to improve the calibration procedure were suggested.
2012, 29(4): 414-418.
doi: 10.11804/NuclPhysRev.29.04.414
Abstract:
At room temperature， monocrystalline plates of rutile (TiO2) were implanted with cobalt ions of an energy of 80 keV to fluences of 1×1016 and 1×1017 ions/cm2 respectively . The 1×1017 ions/cm2 Co implanted samples were annealed in nitrogen at 900 ℃ for 30 min. The magnetic properties of Co implanted samples were measured with a superconducting quantum interference device magnetometer (SQUID) at room temperature. Furthermore, the X ray diffraction (XRD) and Extended X ray Absorption Fine Structure (EXAFS) were applied to investigate the structural and compositional properties of Co implanted samples. The magnetic measurements of samples showed that the size of the saturation magnetization of the Co implanted samples were related to the fluence of ions, and the saturation magnetization of the sample after annealed decreased significantly. The EXAFS measurements showed the presence of cobalt metallic clusters in the sample implanted to ion fluence of 1×1017 ions/cm2. The Co metallic clusters disappeared in the sample after annealed, and resulted in the oxidized Co, which is presumed to substitute into the Ti site. The formation of Co clusters or not was determined by the ion fluence. The relation between ferromagnetic behavior and microscopic structure of the Co implanted samples is discussed.
At room temperature， monocrystalline plates of rutile (TiO2) were implanted with cobalt ions of an energy of 80 keV to fluences of 1×1016 and 1×1017 ions/cm2 respectively . The 1×1017 ions/cm2 Co implanted samples were annealed in nitrogen at 900 ℃ for 30 min. The magnetic properties of Co implanted samples were measured with a superconducting quantum interference device magnetometer (SQUID) at room temperature. Furthermore, the X ray diffraction (XRD) and Extended X ray Absorption Fine Structure (EXAFS) were applied to investigate the structural and compositional properties of Co implanted samples. The magnetic measurements of samples showed that the size of the saturation magnetization of the Co implanted samples were related to the fluence of ions, and the saturation magnetization of the sample after annealed decreased significantly. The EXAFS measurements showed the presence of cobalt metallic clusters in the sample implanted to ion fluence of 1×1017 ions/cm2. The Co metallic clusters disappeared in the sample after annealed, and resulted in the oxidized Co, which is presumed to substitute into the Ti site. The formation of Co clusters or not was determined by the ion fluence. The relation between ferromagnetic behavior and microscopic structure of the Co implanted samples is discussed.
2012, 29(4): 419-424.
doi: 10.11804/NuclPhysRev.29.04.419
Abstract:
In this paper, the sensitive volume of SRAMs was constructed based on RPP(Rectangular ParallelePiped Volume) model using the Monte-Carlo code Geant4. The interactions of heavy ion with materials and the SEU(Single Event Upset) cross section calculation method were presented in the program. The SEU crosssection curves with the linear energy deposition ware obtained. The SEU threshold value and saturation cross section were consistent with the testing data with heavy ions beam. The δ electrons distribution were different in the device material, which were generated by Bi ion with LETs of 99.67 MeV/(cm2·mg) and Bi ion, Xe ion with LETs of 69 MeV/(cm-2·mg). These results indicate δ electrons distribution impacts on the SEU cross section. According to the relation of energy deposition in the sensitive volume, the δ electrons distribution have more and more important effect on the Single Event Effect with reducing the feature size of semiconductor devices.
In this paper, the sensitive volume of SRAMs was constructed based on RPP(Rectangular ParallelePiped Volume) model using the Monte-Carlo code Geant4. The interactions of heavy ion with materials and the SEU(Single Event Upset) cross section calculation method were presented in the program. The SEU crosssection curves with the linear energy deposition ware obtained. The SEU threshold value and saturation cross section were consistent with the testing data with heavy ions beam. The δ electrons distribution were different in the device material, which were generated by Bi ion with LETs of 99.67 MeV/(cm2·mg) and Bi ion, Xe ion with LETs of 69 MeV/(cm-2·mg). These results indicate δ electrons distribution impacts on the SEU cross section. According to the relation of energy deposition in the sensitive volume, the δ electrons distribution have more and more important effect on the Single Event Effect with reducing the feature size of semiconductor devices.
2012, 29(4): 425-429.
doi: 10.11804/NuclPhysRev.29.04.425
Abstract:
The transmission of 105 keV Ar7+ ions with high incident current (about 80 nA) through the gap formed by a paired parallel glass plates was investigated. The intensity and angular distribution of the transmitted ions for various tilt angles were measured using a onedimensional position sensitive detector. The results indicate the existence of a guiding effect when Ar7+ ions pass through the gap， but it is different from that for ions passing through nonacapillaries. We found a measurable dependence of the full width at half maximum (FWHM) of the transmitted ions as a function of the tilt angle. In addition， when the gap was tilted with respect to the direction of the incident beam， the observation angle related to the center of the transmitted ions profile was not equal to the tilt angle.
The transmission of 105 keV Ar7+ ions with high incident current (about 80 nA) through the gap formed by a paired parallel glass plates was investigated. The intensity and angular distribution of the transmitted ions for various tilt angles were measured using a onedimensional position sensitive detector. The results indicate the existence of a guiding effect when Ar7+ ions pass through the gap， but it is different from that for ions passing through nonacapillaries. We found a measurable dependence of the full width at half maximum (FWHM) of the transmitted ions as a function of the tilt angle. In addition， when the gap was tilted with respect to the direction of the incident beam， the observation angle related to the center of the transmitted ions profile was not equal to the tilt angle.
2012, 29(4): 430-435.
doi: 10.11804/NuclPhysRev.29.04.430
Abstract:
Based on the recently released ENDF/B-VII.1 library, high temperature neutron cross section files are generated through SIGACE code using low temperature ACE format files. To verify the processed ACE file of SIGACE, benchmark calculations are performed in this paper. The calculated results of selected ICT, standard CANDU assembly, LWR Doppler coefficient and SEFOR benchmarks are well conformed with reference value, which indicates that high temperature ACE files processed by SIGACE can be used in related neutronics calculations.
Based on the recently released ENDF/B-VII.1 library, high temperature neutron cross section files are generated through SIGACE code using low temperature ACE format files. To verify the processed ACE file of SIGACE, benchmark calculations are performed in this paper. The calculated results of selected ICT, standard CANDU assembly, LWR Doppler coefficient and SEFOR benchmarks are well conformed with reference value, which indicates that high temperature ACE files processed by SIGACE can be used in related neutronics calculations.
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