An ab initio calculation of the electric-field gradient(EFG)at the site of a phosphorous impurity substituting an Al atom in α-Al_(3)O_(2) is carried out using the WIEN2k code with the full-potential linearized augme...An ab initio calculation of the electric-field gradient(EFG)at the site of a phosphorous impurity substituting an Al atom in α-Al_(3)O_(2) is carried out using the WIEN2k code with the full-potential linearized augmented plane wave plus local orbital method(LAPW+lo)in the frame of density functional theory.The atomic lattice relaxations caused by the implanted impurities were calculated for two different charged states to well describe the electronic structure of the doped system.The EFG at the site of the phosphorous impurity in the charged supercell calculated with the exchange-correlation potential of the Wu-Cohen generalized gradient approximation(WC-GGA)is 0.573×10^(21) V/m^(2).Then,the nuclear quadrupole moment of the I=3 state in ^(28)P is deduced to be 137 mb from the quadrupole interaction frequency of 190 kHz measured recently by theβ-NQR method.展开更多
To explore the medical use of a radioactive 9C-ion beam in tumor treatment, which is a double radiation source coming from the external beam itself and the delayed particles emitted internally, some physical experimen...To explore the medical use of a radioactive 9C-ion beam in tumor treatment, which is a double radiation source coming from the external beam itself and the delayed particles emitted internally, some physical experiments are performed at the Secondary Beam Line (SBL) of Heavy Ion Medical Accelerator, Chiba (HIMAC) in Japan be- fore radiobiological research for exhibiting therapeutic value of the 9C beam. Intention of the experiments is for pro- ducing a radioactive 9C-ion beam with higher production rate and purity by means of optimizing the beam line pa- rameters. Finally, a produced 9C beam with the production rate of 9.07×10-6 and purity of 82.88% at full momentum acceptance has been obtained under the optimal conditions of 40 mm-thick beryllium target and 10 mm-thick alumi- num degrader. Both momentum distribution and contaminations for the produced 9C beam under the optimal condi- tions are measured. In order to execute further biological experiments of the 9C beam project, a uniform irradiation field is made with the wobbling magnets and its homogeneity is up to 93.8% inside central area of 20mm in diameter.展开更多
The distinguishing feature and current technique progress of tumor treatment with heavy-ion beams is introduced in the paper. Additional superiority to tumor treatment from a radioactive ion beam (RIB) is emphatically...The distinguishing feature and current technique progress of tumor treatment with heavy-ion beams is introduced in the paper. Additional superiority to tumor treatment from a radioactive ion beam (RIB) is emphatically discussed. The experimental research of the radioactive 9C-ion beams aimed at tumor treatment at Heavy Ion Medical Accelerator in Chiba (HIMAC), National Institute of Radiological Sciences (NIRS), Japan is described in detail, La-eluding production of the beams, optimization of parameters, distribution of depth dose, survival effect of cell and comparison of RBE between 9C- and 12C-beams. Results show that under 40 mm thick Beryllium target and 10 mm thick aluminum degrader at full (5%) momentum acceptance, the production rate and purity of the produced 9C-beams are 9.07×10-6 and 82.88% respectively with the primary 12C-beams of 430 MeV/u and 1.8×109 pps. A uniform irradiation field with homogeneity up to 89.6% inside central area 10 mm in diameter is obtained by using spot scanning. In this case, the dose rate at the entrance is 0.5 Gy/h. In survival experiment of cells, the average relative biological effectiveness (RBE) of 9C-beams is 5.28 and 2.93 for 12C-beams in the region around Bragg peak. The RBE of 9C-beams is 1.8 times higher than that of 12C-beams. It indicates that cell-killing efficiency of 9C-beams is stronger than that of 12C-beams. 9C-beams are more efficacious for tumor treatment than 12C-beams.展开更多
With the prototype ECR ion source for the next carbon therapy facility in Japan a new series of measurements has been performed in order（a）to find the highest beam currents of C<sup>4+</sup> ions,and（b...With the prototype ECR ion source for the next carbon therapy facility in Japan a new series of measurements has been performed in order（a）to find the highest beam currents of C<sup>4+</sup> ions,and（b）to study the effect of"special"gas-mixing by using a chemical compound as a feed gas.An isotopic effect has been found in a previous experiment:with deuterated methane（CD<sub>4</sub> gas） the C<sup>5+</sup> beam currents are about 10% higher than with regular methane（CH<sub>4</sub> gas）.For butane gases(C<sub>4</sub>D<sub>10</sub> and C<sub>4</sub>H<sub>10</sub> respectively)the isotopic effect for C<sup>5+</sup> production is even stronger（】15%）.For production of C<sup>4+</sup> ions the isotopic effect appears to be absent.It turns out that the relative amount of carbon is much more important:acetylene gives 15% higher C<sup>4+</sup> current than butane,which in turn gives about 10% higher C<sup>4+</sup> ion currents than methane.展开更多
Four ECR ion sources have been operated in National Institute of Radiological Sciences（NIRS）. Two ECR ion sources supply various ion species for the Heavy Ion Medical Accelerator in Chiba（HIMAC）. The 10GHz NIRS-EC...Four ECR ion sources have been operated in National Institute of Radiological Sciences（NIRS）. Two ECR ion sources supply various ion species for the Heavy Ion Medical Accelerator in Chiba（HIMAC）. The 10GHz NIRS-ECR ion source mainly produces C<sup>2+</sup> ions for the heavy-ion therapy.Ions of Si,Ar,Fe,Kr and Xe are usually produced by the 18GHz NIRS-HEC ion source for physical and biological experiments.The other two compact ECR ion sources with all permanent magnet configuration have been developed for the new generation carbon therapy facility.One of these,the Kei-source,is a prototype which has been installed to the NIRS-930 cyclotron for axial injection.The other source,Kei2-source,is a demonstration source and utilized for the new generation Linac.In addition,both Kei sources have been used to study fundamental properties. In this paper,present status of the ion sources and recent developments are reported.展开更多
基金Supported by National Natural Science Foundation of China under Grant Nos 10975189 and 91126002.
文摘An ab initio calculation of the electric-field gradient(EFG)at the site of a phosphorous impurity substituting an Al atom in α-Al_(3)O_(2) is carried out using the WIEN2k code with the full-potential linearized augmented plane wave plus local orbital method(LAPW+lo)in the frame of density functional theory.The atomic lattice relaxations caused by the implanted impurities were calculated for two different charged states to well describe the electronic structure of the doped system.The EFG at the site of the phosphorous impurity in the charged supercell calculated with the exchange-correlation potential of the Wu-Cohen generalized gradient approximation(WC-GGA)is 0.573×10^(21) V/m^(2).Then,the nuclear quadrupole moment of the I=3 state in ^(28)P is deduced to be 137 mb from the quadrupole interaction frequency of 190 kHz measured recently by theβ-NQR method.
文摘To explore the medical use of a radioactive 9C-ion beam in tumor treatment, which is a double radiation source coming from the external beam itself and the delayed particles emitted internally, some physical experiments are performed at the Secondary Beam Line (SBL) of Heavy Ion Medical Accelerator, Chiba (HIMAC) in Japan be- fore radiobiological research for exhibiting therapeutic value of the 9C beam. Intention of the experiments is for pro- ducing a radioactive 9C-ion beam with higher production rate and purity by means of optimizing the beam line pa- rameters. Finally, a produced 9C beam with the production rate of 9.07×10-6 and purity of 82.88% at full momentum acceptance has been obtained under the optimal conditions of 40 mm-thick beryllium target and 10 mm-thick alumi- num degrader. Both momentum distribution and contaminations for the produced 9C beam under the optimal condi- tions are measured. In order to execute further biological experiments of the 9C beam project, a uniform irradiation field is made with the wobbling magnets and its homogeneity is up to 93.8% inside central area of 20mm in diameter.
文摘The distinguishing feature and current technique progress of tumor treatment with heavy-ion beams is introduced in the paper. Additional superiority to tumor treatment from a radioactive ion beam (RIB) is emphatically discussed. The experimental research of the radioactive 9C-ion beams aimed at tumor treatment at Heavy Ion Medical Accelerator in Chiba (HIMAC), National Institute of Radiological Sciences (NIRS), Japan is described in detail, La-eluding production of the beams, optimization of parameters, distribution of depth dose, survival effect of cell and comparison of RBE between 9C- and 12C-beams. Results show that under 40 mm thick Beryllium target and 10 mm thick aluminum degrader at full (5%) momentum acceptance, the production rate and purity of the produced 9C-beams are 9.07×10-6 and 82.88% respectively with the primary 12C-beams of 430 MeV/u and 1.8×109 pps. A uniform irradiation field with homogeneity up to 89.6% inside central area 10 mm in diameter is obtained by using spot scanning. In this case, the dose rate at the entrance is 0.5 Gy/h. In survival experiment of cells, the average relative biological effectiveness (RBE) of 9C-beams is 5.28 and 2.93 for 12C-beams in the region around Bragg peak. The RBE of 9C-beams is 1.8 times higher than that of 12C-beams. It indicates that cell-killing efficiency of 9C-beams is stronger than that of 12C-beams. 9C-beams are more efficacious for tumor treatment than 12C-beams.
文摘With the prototype ECR ion source for the next carbon therapy facility in Japan a new series of measurements has been performed in order（a）to find the highest beam currents of C<sup>4+</sup> ions,and（b）to study the effect of"special"gas-mixing by using a chemical compound as a feed gas.An isotopic effect has been found in a previous experiment:with deuterated methane（CD<sub>4</sub> gas） the C<sup>5+</sup> beam currents are about 10% higher than with regular methane（CH<sub>4</sub> gas）.For butane gases(C<sub>4</sub>D<sub>10</sub> and C<sub>4</sub>H<sub>10</sub> respectively)the isotopic effect for C<sup>5+</sup> production is even stronger（】15%）.For production of C<sup>4+</sup> ions the isotopic effect appears to be absent.It turns out that the relative amount of carbon is much more important:acetylene gives 15% higher C<sup>4+</sup> current than butane,which in turn gives about 10% higher C<sup>4+</sup> ion currents than methane.
文摘Four ECR ion sources have been operated in National Institute of Radiological Sciences（NIRS）. Two ECR ion sources supply various ion species for the Heavy Ion Medical Accelerator in Chiba（HIMAC）. The 10GHz NIRS-ECR ion source mainly produces C<sup>2+</sup> ions for the heavy-ion therapy.Ions of Si,Ar,Fe,Kr and Xe are usually produced by the 18GHz NIRS-HEC ion source for physical and biological experiments.The other two compact ECR ion sources with all permanent magnet configuration have been developed for the new generation carbon therapy facility.One of these,the Kei-source,is a prototype which has been installed to the NIRS-930 cyclotron for axial injection.The other source,Kei2-source,is a demonstration source and utilized for the new generation Linac.In addition,both Kei sources have been used to study fundamental properties. In this paper,present status of the ion sources and recent developments are reported.
