2010 Vol. 27, No. 2
Display Method:
2010, 27(2): 121-129.
doi: 10.11804/NuclPhysRev.27.02.121
Abstract:
A separable pairing interaction is introduced in the covariant density functional theory. The parameters of the separable force are adjusted to reproduce the pairing properties of the Gogny force in nuclear matter. It preserves translational invariance and has finite range. Applying well known techniques of Talmi and Moshinsky, this pairing interaction can be used in relativistic and in non-relativistic Hartree-Bogoliubov or Hartree-Fock-Bogoliubov calculation of finite nuclei. It avoids the complicated problem of a cutoff at large momenta or energies inherent in other zero range pairing forces. This finite range separable pairing force is applied to study the properties of the ground and excited states for spherical Snisotopes in the relativistic Hartree Bogoliubov and relativistic quasiparticle random phase approximation. The superfluid properties of the ground state for the axially deformed Smisotopes are also studied in the deformed RHB theory with the separable pairing force. It has been shown that with this force the pairing properties of ground states can be well depicted on almost the same footing as with the original Gogny pairing interaction. There are also many extensions of relativistic density functional theory beyond mean field, such as applications using projection onto subspaces with good symmetries, generator coordinate methods, or
investigation of complex configurations in the framework of particle vibrational coupling(PVC). All these methods require a more realistic description of pairing correlations in the future.
A separable pairing interaction is introduced in the covariant density functional theory. The parameters of the separable force are adjusted to reproduce the pairing properties of the Gogny force in nuclear matter. It preserves translational invariance and has finite range. Applying well known techniques of Talmi and Moshinsky, this pairing interaction can be used in relativistic and in non-relativistic Hartree-Bogoliubov or Hartree-Fock-Bogoliubov calculation of finite nuclei. It avoids the complicated problem of a cutoff at large momenta or energies inherent in other zero range pairing forces. This finite range separable pairing force is applied to study the properties of the ground and excited states for spherical Snisotopes in the relativistic Hartree Bogoliubov and relativistic quasiparticle random phase approximation. The superfluid properties of the ground state for the axially deformed Smisotopes are also studied in the deformed RHB theory with the separable pairing force. It has been shown that with this force the pairing properties of ground states can be well depicted on almost the same footing as with the original Gogny pairing interaction. There are also many extensions of relativistic density functional theory beyond mean field, such as applications using projection onto subspaces with good symmetries, generator coordinate methods, or
investigation of complex configurations in the framework of particle vibrational coupling(PVC). All these methods require a more realistic description of pairing correlations in the future.
2010, 27(2): 130-135.
doi: 10.11804/NuclPhysRev.27.02.130
Abstract:
The Skyrme energydensity functional together with the extended semiclassical ThomasFermi method is applied to the study of heavy ion fusion reactions at deep subbarrier energy. The relation between heavy ion fusion reactions at deep subbarrier energy and the equation of state (EOS) of nuclear matter is further probed by selecting different sets of Skyrme force parameters to reproduce the experimental excitation functions.
The Skyrme energydensity functional together with the extended semiclassical ThomasFermi method is applied to the study of heavy ion fusion reactions at deep subbarrier energy. The relation between heavy ion fusion reactions at deep subbarrier energy and the equation of state (EOS) of nuclear matter is further probed by selecting different sets of Skyrme force parameters to reproduce the experimental excitation functions.
2010, 27(2): 136-139.
doi: 10.11804/NuclPhysRev.27.02.136
Abstract:
The αdecay halflives of 443 nuclei are investigated within the cluster model(CM). The results are compared with the experimental data. The coincidence between theoretical results and the experimental data are satisfied, implying the CM works quite well for the study on ??decay properties. Then the ??decay halflives of Bi isotopes are calculated. The results are consistent with the known experimental data. The αdecay halflives of the Bi isotopes without experimental data are predicted, which is useful for the future experimental detection and identification of these nuclei.
The αdecay halflives of 443 nuclei are investigated within the cluster model(CM). The results are compared with the experimental data. The coincidence between theoretical results and the experimental data are satisfied, implying the CM works quite well for the study on ??decay properties. Then the ??decay halflives of Bi isotopes are calculated. The results are consistent with the known experimental data. The αdecay halflives of the Bi isotopes without experimental data are predicted, which is useful for the future experimental detection and identification of these nuclei.
2010, 27(2): 140-145.
doi: 10.11804/NuclPhysRev.27.02.140
Abstract:
One highspin rotational band in neutron deficient oddodd nucleus 170Re has been identified and assigned to the πh1/2νi13/2 configuration through the 142Nd(32S,1p3nγ)170Re reaction. The band is analyzed on the basis of the arguments of energy systematics, signature inversion systematics, intraband B(M1)/B(E2) ratios, quasiparticle Routhians, dynamic moment of inertia and Total Routhian Surface(TRS) calculations. From detailed analyses on its structural properties, the configuration, spins and parity have been further assigned for this rotational band.
One highspin rotational band in neutron deficient oddodd nucleus 170Re has been identified and assigned to the πh1/2νi13/2 configuration through the 142Nd(32S,1p3nγ)170Re reaction. The band is analyzed on the basis of the arguments of energy systematics, signature inversion systematics, intraband B(M1)/B(E2) ratios, quasiparticle Routhians, dynamic moment of inertia and Total Routhian Surface(TRS) calculations. From detailed analyses on its structural properties, the configuration, spins and parity have been further assigned for this rotational band.
2010, 27(2): 146-149.
doi: 10.11804/NuclPhysRev.27.02.146
Abstract:
Nuclear shape change and shape coexistence in the Selenium isotopes have been investigated by TotalRouthianSurface(TRS) calculations. It is found that nuclear shapes vary significantly with increasing neutron number. The TRS calculations for the ground states of 66, 72, 92, 94Se isotopes show that both neutrondeficient and neutrondripline Selenium isotopes have oblate and prolate shape coexistence. The cranking shellmodel calculations for 72, 94Se give that prolate and oblate shape coexistence in low rotational frequency. However, oblate rotational bands disappear and prolate rotational bands become yrast bands with increasing rotational frequency, which is due to the intrusion of the g9/2 orbitals.
Nuclear shape change and shape coexistence in the Selenium isotopes have been investigated by TotalRouthianSurface(TRS) calculations. It is found that nuclear shapes vary significantly with increasing neutron number. The TRS calculations for the ground states of 66, 72, 92, 94Se isotopes show that both neutrondeficient and neutrondripline Selenium isotopes have oblate and prolate shape coexistence. The cranking shellmodel calculations for 72, 94Se give that prolate and oblate shape coexistence in low rotational frequency. However, oblate rotational bands disappear and prolate rotational bands become yrast bands with increasing rotational frequency, which is due to the intrusion of the g9/2 orbitals.
2010, 27(2): 150-154.
doi: 10.11804/NuclPhysRev.27.02.150
Abstract:
We have investigated and analyzed the experimental data of the odd A nuclear IT (isomeric transiton) decay around Pb.We find a simple law for the IT decay halflives of the odd A nuclear isomer: there is a parabolic law between the logarithm of the halflives of the isomer with the same angular momentum and parity along the isotopic chain.This shows there is an exponential law between the halflives of IT decay and the mass number A. The analysis of the multipolarity of the IT decay could make us have a clear recognition for the physical properties.We have also discussed the possible physics behind this simple law.
We have investigated and analyzed the experimental data of the odd A nuclear IT (isomeric transiton) decay around Pb.We find a simple law for the IT decay halflives of the odd A nuclear isomer: there is a parabolic law between the logarithm of the halflives of the isomer with the same angular momentum and parity along the isotopic chain.This shows there is an exponential law between the halflives of IT decay and the mass number A. The analysis of the multipolarity of the IT decay could make us have a clear recognition for the physical properties.We have also discussed the possible physics behind this simple law.
2010, 27(2): 155-159.
doi: 10.11804/NuclPhysRev.27.02.155
Abstract:
As a quasiprobability distribution function in phasespace and a special representation of the density matrix, Wigner function has great significance in physics. In this paper, first, Wigner function’s characteristic and calculation approach are introduced. Then, with Stareigen equation we obtain the Wigner function for threedimensional harmonic oscillator. In the end, we discuss the method describing the interaction between phonons and electrons (or photons) and obtain the equation that transition probability satisfies in phase space.
As a quasiprobability distribution function in phasespace and a special representation of the density matrix, Wigner function has great significance in physics. In this paper, first, Wigner function’s characteristic and calculation approach are introduced. Then, with Stareigen equation we obtain the Wigner function for threedimensional harmonic oscillator. In the end, we discuss the method describing the interaction between phonons and electrons (or photons) and obtain the equation that transition probability satisfies in phase space.
2010, 27(2): 160-163.
doi: 10.11804/NuclPhysRev.27.02.160
Abstract:
It is pointed out that if the QGP SU(2) chiral phase transition in the LHC PbPb collision process is taken place and the phase transition is in the second order, then pion strings will be formed, and decay. These phenomena lead to the pion enhancement in the low momentum region(p150—400 MeV) and the number of pions produced from pion string decay can be estimated about Nt≈270, 150, 60 for different freeze temperature Tf=130, 120, 110 MeV respectively.
It is pointed out that if the QGP SU(2) chiral phase transition in the LHC PbPb collision process is taken place and the phase transition is in the second order, then pion strings will be formed, and decay. These phenomena lead to the pion enhancement in the low momentum region(p150—400 MeV) and the number of pions produced from pion string decay can be estimated about Nt≈270, 150, 60 for different freeze temperature Tf=130, 120, 110 MeV respectively.
Feasibility Analysis of Studying Dissociative Recombination Processes of Molecular Ions at HIRFL-CSR
2010, 27(2): 164-169.
doi: 10.11804/NuclPhysRev.27.02.164
Abstract:
In the present paper, it is introduced the scientific background and the current status of the high precision spectroscopy of the molecular ions at cooler storage ring. The advantages to study the dissociative recombination(DR) processes using cooler storage ring CSRe are discussed. The physics design,the main parameters of the injection beam line and the injection of the molecular ions into the CSRe and the key techniques are described in detail. With a new injection beam line,HIRFL-CSRe will be reconstructed to a multidiscipline research platform,offering good opportunities for the study of DR processes of molecular ions,especially for that of the molecular ions of m>70 amu with much improved resolution.
In the present paper, it is introduced the scientific background and the current status of the high precision spectroscopy of the molecular ions at cooler storage ring. The advantages to study the dissociative recombination(DR) processes using cooler storage ring CSRe are discussed. The physics design,the main parameters of the injection beam line and the injection of the molecular ions into the CSRe and the key techniques are described in detail. With a new injection beam line,HIRFL-CSRe will be reconstructed to a multidiscipline research platform,offering good opportunities for the study of DR processes of molecular ions,especially for that of the molecular ions of m>70 amu with much improved resolution.
2010, 27(2): 170-173.
doi: 10.11804/NuclPhysRev.27.02.170
Abstract:
In the HIRFL-CSR project,it needs the high performance requirement in real time and reliability for the control system of CSRe’s cooling equipment——Cooler. Simultaneously, the running environment of the Cooler is very complex and it is difficult to predict various kinds of interference. To solve these problems, we focus on the improvement on the control system of the Cooler. The high performance FPGA and ARM embedded systems are used to realize the beam commissioning automatically,and the P2P(Peer to peer) technology and the neural network algorithm are adopted to implement the automatic control of the Cooler. The system provides the advanced hardware platform and the design proposal for the cooling control system.
In the HIRFL-CSR project,it needs the high performance requirement in real time and reliability for the control system of CSRe’s cooling equipment——Cooler. Simultaneously, the running environment of the Cooler is very complex and it is difficult to predict various kinds of interference. To solve these problems, we focus on the improvement on the control system of the Cooler. The high performance FPGA and ARM embedded systems are used to realize the beam commissioning automatically,and the P2P(Peer to peer) technology and the neural network algorithm are adopted to implement the automatic control of the Cooler. The system provides the advanced hardware platform and the design proposal for the cooling control system.
2010, 27(2): 174-177.
doi: 10.11804/NuclPhysRev.27.02.174
Abstract:
A 64channel position sensitive current distribution detector with 1 mm position resolution was developed, while the data acquisition system is based on the LabVIEW software. The test result obtained by using a 2 nA, 200—2000 eV electron beam deflecting by different voltages and the position spectra of 10 μA, 2000 eV electrons transmitted through a glass capillary was measured. The result indicated that the detector can be used to detect the charged particles with strong beam current through the capillary.
A 64channel position sensitive current distribution detector with 1 mm position resolution was developed, while the data acquisition system is based on the LabVIEW software. The test result obtained by using a 2 nA, 200—2000 eV electron beam deflecting by different voltages and the position spectra of 10 μA, 2000 eV electrons transmitted through a glass capillary was measured. The result indicated that the detector can be used to detect the charged particles with strong beam current through the capillary.
2010, 27(2): 178-181.
doi: 10.11804/NuclPhysRev.27.02.178
Abstract:
It is introduced that a method and principle for calibrating 14.1 MeV neutron sensitivity of γray detector. A shield system for scattering neutrons and γrays has been optimized by MCNP code. The experimental results show that the signaltonoise ratio of the system is about 10:1, 7 times higher than the value of 1.35〖KG-*4〗∶〖KG-*4〗1 without shield system. Calibration of neutron sensitivity of γray detector is then accomplished.
It is introduced that a method and principle for calibrating 14.1 MeV neutron sensitivity of γray detector. A shield system for scattering neutrons and γrays has been optimized by MCNP code. The experimental results show that the signaltonoise ratio of the system is about 10:1, 7 times higher than the value of 1.35〖KG-*4〗∶〖KG-*4〗1 without shield system. Calibration of neutron sensitivity of γray detector is then accomplished.
2010, 27(2): 182-186.
doi: 10.11804/NuclPhysRev.27.02.182
Abstract:
In this paper, the multilayer model was established to calculate γradiation nonuniform shielding problem, and various combinations of methods were investigated to determine the optimal option. At the same time, the comprehensive analysis of the simulation results, the theoretical calculation and the experimental measurements show that the consistency among them. Practical significance is also shown that the application of Monte Carlo method to simulate the nonuniform shielding feasibility and multilayer shielding design.
In this paper, the multilayer model was established to calculate γradiation nonuniform shielding problem, and various combinations of methods were investigated to determine the optimal option. At the same time, the comprehensive analysis of the simulation results, the theoretical calculation and the experimental measurements show that the consistency among them. Practical significance is also shown that the application of Monte Carlo method to simulate the nonuniform shielding feasibility and multilayer shielding design.
2010, 27(2): 187-191.
doi: 10.11804/NuclPhysRev.27.02.187
Abstract:
Preparation of La, Sm, Eu, Gd, Tb and 238U targets from the mixture of isopropanol and nitric acid solution are studied by using singlecycle molecular plating technique. To determine the optimum conditions for the deposition process, the effect of current density, deposition time and distance between the two electrodes on the quality and electrodeposition yield of the target films are investigated individually. Depending on the deposited metal, the current densities are found to be 2—8 mA/cm2 and the suitable distance between the two electrodes is 3 cm. 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 composition and 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. Shortlived isotopes of Ta and W were produced from natural Gd and Tb targets bombarded by 19F beam at the SFC low energy radiochemical terminal of Institute of Modern Physics, Chinese Academy of Sciences, respectively, and successfully applied in the model experiment of Db(Z=105) and Sg(Z=106).
Preparation of La, Sm, Eu, Gd, Tb and 238U targets from the mixture of isopropanol and nitric acid solution are studied by using singlecycle molecular plating technique. To determine the optimum conditions for the deposition process, the effect of current density, deposition time and distance between the two electrodes on the quality and electrodeposition yield of the target films are investigated individually. Depending on the deposited metal, the current densities are found to be 2—8 mA/cm2 and the suitable distance between the two electrodes is 3 cm. 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 composition and 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. Shortlived isotopes of Ta and W were produced from natural Gd and Tb targets bombarded by 19F beam at the SFC low energy radiochemical terminal of Institute of Modern Physics, Chinese Academy of Sciences, respectively, and successfully applied in the model experiment of Db(Z=105) and Sg(Z=106).
2010, 27(2): 192-196.
doi: 10.11804/NuclPhysRev.27.02.192
Abstract:
The present study was to evaluate the effect and mechanism of Nacetylcysteine(NAC) and AcetylLCarnitine hydrochloride(ALCAR) against 12C6+ ion beams on acute injury in the mouse liver. Pretreated with NAC (100 mg/kg) and ALCAR(100 mg/kg), KunMing mice were exposed to wholebody irradiation with the dose of 4 Gy. Mice were killed 2 h after irradiation, and then the liver tissues were quickly removed. TAC was measured by using chemical reagent kids, and DNAsingle strand breaks were determined by single cell gel electrophoresis, and the percentage of cell apoptosis were assayed by flow cytometry method. The results showed that NAC and ALCAR pretreatment significantly enhanced TAC(P<0.001), alleviated DNAsingle strand breaks(P<0.001) and cell apoptosis(P<0.001) of the liver tissues. Moreover, ALCARmediated radioprotection induced by 12C6+ ions is stronger than that of NAC (P<0.05). The data suggests that NAC and ALCAR both can ameliorate acute injury caused by 12C6+ ions in mice. In this study, NAC and ALCAR exert their radioprotective effect by virtue of resisting oxidative stress, enhancing TAC, alleviating DNAsingle strand breaks as well as cell apoptosis. Furthermore, the data imply that NAC and ALCAR may be suitable and promising as radioprotective drug against carbon heavy ions.
The present study was to evaluate the effect and mechanism of Nacetylcysteine(NAC) and AcetylLCarnitine hydrochloride(ALCAR) against 12C6+ ion beams on acute injury in the mouse liver. Pretreated with NAC (100 mg/kg) and ALCAR(100 mg/kg), KunMing mice were exposed to wholebody irradiation with the dose of 4 Gy. Mice were killed 2 h after irradiation, and then the liver tissues were quickly removed. TAC was measured by using chemical reagent kids, and DNAsingle strand breaks were determined by single cell gel electrophoresis, and the percentage of cell apoptosis were assayed by flow cytometry method. The results showed that NAC and ALCAR pretreatment significantly enhanced TAC(P<0.001), alleviated DNAsingle strand breaks(P<0.001) and cell apoptosis(P<0.001) of the liver tissues. Moreover, ALCARmediated radioprotection induced by 12C6+ ions is stronger than that of NAC (P<0.05). The data suggests that NAC and ALCAR both can ameliorate acute injury caused by 12C6+ ions in mice. In this study, NAC and ALCAR exert their radioprotective effect by virtue of resisting oxidative stress, enhancing TAC, alleviating DNAsingle strand breaks as well as cell apoptosis. Furthermore, the data imply that NAC and ALCAR may be suitable and promising as radioprotective drug against carbon heavy ions.
2010, 27(2): 197-201.
doi: 10.11804/NuclPhysRev.27.02.197
Abstract:
The inducement of hyperradiosensitivity/increased radioresistance(HRS/IRR) and activities of antioxidases in Escherichia coli implanted by 30 keV N+ and relationship between them were investigated. The results showed the change trend of the survival rate and the activity of superoxide dismutase(SOD) and Catalas(CAT) of E. coli K12 was consistent. The activity of SOD and CAT of E.coli were lower, less than 10 and 8 U/mg, when the HRS was induced at 0—5×1014 N+/cm2 doses. And the activity of SOD and CAT of E.coli increased and reached highest rate, were 58 and 26 U/mg respectively, when the IRR was induced at 5×1014—10×1014 N+/cm2 doses. It could be concluded that the change of SOD and CAT activity was related with the HRS/IRR.
The inducement of hyperradiosensitivity/increased radioresistance(HRS/IRR) and activities of antioxidases in Escherichia coli implanted by 30 keV N+ and relationship between them were investigated. The results showed the change trend of the survival rate and the activity of superoxide dismutase(SOD) and Catalas(CAT) of E. coli K12 was consistent. The activity of SOD and CAT of E.coli were lower, less than 10 and 8 U/mg, when the HRS was induced at 0—5×1014 N+/cm2 doses. And the activity of SOD and CAT of E.coli increased and reached highest rate, were 58 and 26 U/mg respectively, when the IRR was induced at 5×1014—10×1014 N+/cm2 doses. It could be concluded that the change of SOD and CAT activity was related with the HRS/IRR.
2010, 27(2): 202-205.
doi: 10.11804/NuclPhysRev.27.02.202
Abstract:
It has been proven that over expression of survivin in cancerous cell lines is related to the radioresistance of cells to highLET radiation in previous work. In this study,action mechanisms of survivin gene in apoptosis induced by high LET radiation were investigated. We found that inhibiting survivin by siRNA had no notable influence on Bcl-2 and Bax expressions induced by carbon ions. Survivin depressed cell apoptosis through the inhibition of the activities of caspase-3 and -9 possibly in cell apoptosis induced by highLET radiation.
It has been proven that over expression of survivin in cancerous cell lines is related to the radioresistance of cells to highLET radiation in previous work. In this study,action mechanisms of survivin gene in apoptosis induced by high LET radiation were investigated. We found that inhibiting survivin by siRNA had no notable influence on Bcl-2 and Bax expressions induced by carbon ions. Survivin depressed cell apoptosis through the inhibition of the activities of caspase-3 and -9 possibly in cell apoptosis induced by highLET radiation.
2010, 27(2): 206-211.
doi: 10.11804/NuclPhysRev.27.02.206
Abstract:
Space radiation, particularly induced by the highenergy charged particles, may cause serious injury on living organisms. So it is one critical restriction factor in Manned Spaceflight. Studies have shown that the biological effects of charged particles were associated with their quality, the dose and the different biological end points. In addition, the microgravity conditions may affect the biological effects of space radiation. In this paper we give a review on the biological damage effects of space radiation and the combined biological effects of the space radiation coupled with the microgravity from the results of space flight and ground simulation experiments.
Space radiation, particularly induced by the highenergy charged particles, may cause serious injury on living organisms. So it is one critical restriction factor in Manned Spaceflight. Studies have shown that the biological effects of charged particles were associated with their quality, the dose and the different biological end points. In addition, the microgravity conditions may affect the biological effects of space radiation. In this paper we give a review on the biological damage effects of space radiation and the combined biological effects of the space radiation coupled with the microgravity from the results of space flight and ground simulation experiments.
2010, 27(2): 212-217.
doi: 10.11804/NuclPhysRev.27.02.212
Abstract:
The beam intensity map optimization of Intensity Modulated Radiation Treatment(IMRT) is a large scale optimization problem because of thousands of parameters involved. A fast and efficient approach was studied in the paper according to the clinical requirement for high speed and good results. Firstly, the clinical prescribed dose of Planning Target Volume(PTV) and dosevolume constraints of Normal Tissue and Organ at Risk(OAR) were transformed into a quadratic objective function. And then Conjugate Gradient(CG) was adopted to optimize the objective function. At last, a simulated case and a clinical case were used to test the approach. The results showed that the optimization process need 40 s while satisfied results could be obtained in 10 s for simulated case and the optimization process need 1 min and 20 s while optimized results could be obtained in 20 s for the clinical prostate case. So it can be found that the approach of proposed in this paper is valid and efficient, and can be used to the accurate radiation therapy system.
The beam intensity map optimization of Intensity Modulated Radiation Treatment(IMRT) is a large scale optimization problem because of thousands of parameters involved. A fast and efficient approach was studied in the paper according to the clinical requirement for high speed and good results. Firstly, the clinical prescribed dose of Planning Target Volume(PTV) and dosevolume constraints of Normal Tissue and Organ at Risk(OAR) were transformed into a quadratic objective function. And then Conjugate Gradient(CG) was adopted to optimize the objective function. At last, a simulated case and a clinical case were used to test the approach. The results showed that the optimization process need 40 s while satisfied results could be obtained in 10 s for simulated case and the optimization process need 1 min and 20 s while optimized results could be obtained in 20 s for the clinical prostate case. So it can be found that the approach of proposed in this paper is valid and efficient, and can be used to the accurate radiation therapy system.
2010, 27(2): 218-222.
doi: 10.11804/NuclPhysRev.27.02.218
Abstract:
In the treatment planning for arcintensitymodulated radiation therapy, because many irradiation directions are involved, the computing time and storage space needed for calculating beamlet dose matrices in optimization is quite heavy. In order to improve the computation efficiency, the simplified dose calculation is often used for the calculation of the dose matrices. Thus, it is deserved to study how this simplification could influence the quality of the treatment plan. In this paper, a simulation and a clinical case are adopted. Using the primary dose calculation model without taking into account the scattering effect to generate the dose matrices of beamlets, the optimization for beam intensity profile are firstly carried out. Then, based on the obtained intensity profile, the dose distributions are recalculated by using the primary dose calculation model and the differential convolution superposition dose calculation model which is more accurate but more time consuming. By comparing dose distributions obtained by this two models, the influence of using simplified model for dose matrix calculation on beam profile optimization is studied. The results demonstrate that when the beam number is large(corresponding to the arcmodulated radiation), using the simplified model for the calculation of dose matrix of beamlets will reduce the quality of dose distribution greatly comparing with the expected dose distribution quality. Thus it is very necessary to correctly take into account the scattering effect in beam profile optimization for the arcintensitymodulated radiation therapy.
In the treatment planning for arcintensitymodulated radiation therapy, because many irradiation directions are involved, the computing time and storage space needed for calculating beamlet dose matrices in optimization is quite heavy. In order to improve the computation efficiency, the simplified dose calculation is often used for the calculation of the dose matrices. Thus, it is deserved to study how this simplification could influence the quality of the treatment plan. In this paper, a simulation and a clinical case are adopted. Using the primary dose calculation model without taking into account the scattering effect to generate the dose matrices of beamlets, the optimization for beam intensity profile are firstly carried out. Then, based on the obtained intensity profile, the dose distributions are recalculated by using the primary dose calculation model and the differential convolution superposition dose calculation model which is more accurate but more time consuming. By comparing dose distributions obtained by this two models, the influence of using simplified model for dose matrix calculation on beam profile optimization is studied. The results demonstrate that when the beam number is large(corresponding to the arcmodulated radiation), using the simplified model for the calculation of dose matrix of beamlets will reduce the quality of dose distribution greatly comparing with the expected dose distribution quality. Thus it is very necessary to correctly take into account the scattering effect in beam profile optimization for the arcintensitymodulated radiation therapy.
2010, 27(2): 223-227.
doi: 10.11804/NuclPhysRev.27.02.223
Abstract:
In order to investigate the potential effect in the C60 films induced by slow highlycharged ion(SHCI), the irradiation experiments of C60 films were performed by using Xen+ ions(n=3, 10, 13, 15, 17, 20, 22, 23). The irradiated C60 films were analyzed by means of AFM and Raman scattering. The analysis results indicated that the surface roughness of C60 films irradiated is decreasing with the increase of the charge state of Xen+ ions(potential energy stored in Xen+ ions).This reveals the existing of the potential effect. The results of the Raman spectra showed that in despite of existing influence of potential effect, the damage process of C60 films in the area for analysis depth of Raman is dominated by the elastic collisions, because the deposited potential energy of Xen+ ion in C60 films is much less than its kinetic energy.
In order to investigate the potential effect in the C60 films induced by slow highlycharged ion(SHCI), the irradiation experiments of C60 films were performed by using Xen+ ions(n=3, 10, 13, 15, 17, 20, 22, 23). The irradiated C60 films were analyzed by means of AFM and Raman scattering. The analysis results indicated that the surface roughness of C60 films irradiated is decreasing with the increase of the charge state of Xen+ ions(potential energy stored in Xen+ ions).This reveals the existing of the potential effect. The results of the Raman spectra showed that in despite of existing influence of potential effect, the damage process of C60 films in the area for analysis depth of Raman is dominated by the elastic collisions, because the deposited potential energy of Xen+ ion in C60 films is much less than its kinetic energy.