Neutron production at the heavy ion research facility in Lanzhou

In this work, the neutron radiation field at Heavy Ion Research Facility in Lanzhou (HIRFL) was investigated. Total neutron yields, spectra and angular     

Neutron Yields and Neutron Emission Rate in the ForwardDirection for 50 MeV/u 18O-ion on Thick Be,Cu,Au Targets

The neutron yields and the neutron emission rates in the forward direction for 50MeV/u ¹⁸O-ion induced reactions on thick Be, Cu, Au targets have been measured using the threshold detector activation method. The measured results indicate that the neutron yield and the neutron emission rate depend on the atomic number of target nuclei; neutron yield for the lighter target is greater than that for the heavier one. The neutron yield for 50MeV/u ¹⁸O-ion on Cu is about four times as large as that for 50MeV/u ¹²C-ion on Cu when incident energies per nucleon are identical.     

Neutron dose measurement in carbon ion radiation therapy at HIRFL （IMP）

For radiation protection purposes, the neutron dose in carbon ion radiation therapy at the HIRFL （Heavy Ion Research Facility in Lanzhou） was investigated. The neutron dose from primary ^12C ions with a specific energy of 100 MeV/u delivered from SSC was roughly measured with a standard Anderson-Broun rem-meter using a polyethylene target at various distances. The result shows that a maximum neutron dose contribution of 19 mSv in a typically surface tumor treatment was obtained, which is less than 1% of the planed heavy ion dose and is in reasonable agreement with other reports. Also the T-ray dose was measured in this experiment using a thermo luminescent detector.     

Neutron dose measurement in carbon ion radiation therapy at HIRFL (IMP)

For radiation protection purposes, the neutron dose in carbon ion radiation therapy at the HIRFL (Heavy Ion Research Facility in Lanzhou) was investigated. The neutron dose from primary 12C ions with a specific energy of 100 MeV/u delivered from SSC was roughly measured with a standard Anderson-Broun rem-meter using a polyethylene target at various distances. The result shows that a maximum neutron dose contribution of 19 mSv in a typically surface tumor treatment was obtained, which is less than 1% of the planed heavy ion dose and is in reasonable agreement with other reports. Also the γ-ray dose was measured in this experiment using a thermo luminescent detector.     

60 MeV/u 18O离子同天然铀反应钡同位素截面的测定

通过60MeV/u18O离子照射天然铀靶产生Ba放射性同位素,使用BaCl2沉淀法从大量铀和其它反应产物混合物中分离出Ba.通过离线γ谱学方法测量了Ba样品的γ射线单谱,根据Ba同位素特征γ射线峰的强度及其它相关数据计算了Ba同位素的生成截面.发现在厚铀靶的情况下,缺中子Ba同位素仍有较高的截面. The radioactive Ba isotopes were produced by 60 MeV/u~(18)O ion bombardment of natural uranium. Ba was separated from U and the reaction product mixture by BaCl_(2) precipitation. The Ba fraction was measured by off-line γ-ray spectroscopy. The cross sections of the individual Ba isotope were calculation based on the intensities of the character γ-ray peaks of Ba isotopes and other relative information. It was found that the n-deficient Ba isotopes have higher cross sections using the thick uranium targets.     

并合不变中子质子产额比值角分布各向异性与对称能关系的研究

采用ImQMD05模型分析了非对称反应体系40Ar+197Au,124Sn在中低能区（E_beam=35~100 MeV/u）的半擦边反应的条件下的反应机制,并进一步探索了不同模型参数,如对称能斜率、碰撞参数等,对轻粒子并合不变中子质子产额之比角分布各向异性的影响。通过研究发现:对于出射动能大于每核子10 MeV的动力学出射的轻粒子而言,其并合不变的中子质子产额比值角分布各向异性与对称能的软硬具有明显的关联;碰撞参数对轻粒子动力学发射各向异性的影响最弱。By using the ImQMD05 code,we simulate the 40Ar+197Au,+124Sn at beam energy of 35,50 and 100 MeV/u and semi-peripheral collisions.The reaction mechanism,symmetry potential and Coulomb potential competition around the overlapped neck region and impact parameters effects are investigated for understanding the angular distribution of isospin contents of dynamical emitted light particles.Our results show that the angular anisotropy of the coalescence invariant neutron to proton yield ratios is sensitive to the stiffness of symmetry energy,especially for the dynamical emitted light particles with E_k>10 MeV.     

HIRFL辐照终端照射野均匀度与离子通量的关系

采用固体核径迹探测器聚碳酸脂膜,测定了兰州重离子研究装置提供的55MeV/u40Ar和80MeV/u20Ne离子束经辐照终端束流均匀化扫描装置后照射野均匀度与离子通量之间的关系.结果表明:对于40Ar和20Ne离子束,离子通量小于1×106和2×107ions/cm2时,横向照射野均匀度缓Ne离子束照射慢增加;当离子通量分别介于1×106—1×107和2×107—1×108ions/cm2时,40Ar和20野均匀度逐渐增加;离子通量达到1×107和1×108ions/cm2时,40Ar和20Ne离子束照射野均匀度分别约为58%和61%.从而说明,辐照终端束流扫描装置对束流的均匀化程度目前并不能满足辐照生物效应、辐射育种和重离子治癌等研究工作的需要,须对其性能做进一步的提高. Using 55 MeV/u 40Ar and 80 MeV/u20Ne ion beams delivered by the Heavy Ion Research Facility at Lanzhou (HIRFL), the relationships between the irradiation homogeneities in irradiation fields generated by the beam scanning device located at the irradiation terminal of the HIRFL and ion fluence were measured respectively with 100 μm polycarbonate films by means of nuclear track detection. The results show that the homogeneity increases when the ion fluence are lower than ........     

High energy heavy ion tracks in bubble detectors

Bubble detectors which are commonly used as neutron detectors have been demonstrated through this study to be good detectors for registration of high energy heavy ion tracks. Large size bubble detectors made in China Institute of Atomic Energy were irradiated to heavy ions Ar and C up to 650 MeV/u and 400 MeV/u, respectively. Very clear features of stringy tracks of high energy heavy ions and their fragmentations are manifested and distinguishable. A single track created by a specific high energy heavy ion is composed of a line of bubbles, which is visible by naked eyes and retained for months wihhout reduction in size. The creation of heavy ion tracks in bubble detectors is governed by a threshold whose essence is approximately a critical value of energy loss rate (dE/dX)_c similar to that of etch track detectors. Ranges of heavy ions in bubble detectors are apparent and predictable by existing formulas. Identification of high energy heavy ions and the applications to heavy ion physics, cosmic rays, exotic particles and cancer therapy monitoring are obviously promising. The experimental and theoretical aspects of high energy heavy ion tracks in bubble detectors as well as the expectable applications are presented and discussed.     

Emission von Spallationsprodukten aus metallischen Targets

Emission of spoliation products with mass numbers A = 147 ? 173 from tantalum targets irradiated by 660 MeV protons has been investigated. Cascade-evaporation model calculations are compared to experimental results and data for smaller energies and various targets. Calculations are in agreement with experiments. Relations allowing to estimate the “practical range” of neutron deficient nuclides in thick targets have been obtained.     

28.7MeV/u的 14，16，18 O+7，9Be反应中的同位素分布研究

用同位旋相关的Boltzmann-Langevin方程研究了在入射能量为28.7MeV/u下,不同弹核^14O,^16O和^18O轰击不同靶核^7Be和^9Be的反应,计算了生成碎片的产生截面,发现用丰中子（缺中子）炮弹或丰中子（缺中子）靶进行反应,所得到的产物均有丰中子（缺中子）的碎片出现。同位素分布宽度和峰位与入射体系密切相关,产生碎片的电荷数越接近入射弹核的电荷数,则同位素分布的宽度越大,峰位偏离β稳定线值越远,其同位旋效应越明显。。     

HIRFL-CSR commissioning in 2006 and 2007

HIRFL-CSR, a new heavy ion cooler-storage-ring system at IMP, had been in commissioning since the beginning of 2006. In the two years of 2006 and 2007 the CSR commissioning was finished, including the stripping injection (STI), electron-cooling with hollow electron beam, C-beam stacking with the combination of STI and e-cooling, the wide energy-range synchrotron ramping from 7 MeV/u to 1000 MeV/u by changing the RF harmonic-number at mid-energy, the multiple multi-turn injection (MMI), the beam accumulation with MMI and e-cooling for heavy-ion beams of Ar, Kr and Xe, the fast extraction from CSRm and single-turn injection to CSRe, beam stacking in CSRe and the RIBs mass-spectrometer test with the isochronous mode in CSRe by using the time-of-flight method.     

展宽重离子束的Bragg峰

介绍了自行设计加工的用于对重离子束Bragg峰进行展宽的旋转式射程调制器. 实验上运用双电离室法测定了75MeV/u ¹²C离子束的Bragg曲线以及经该射程调制器调制的75MeV/u ¹⁶O及¹²C离子束的Bragg曲线,调制的离子束展示出明显展宽的Bragg峰,并将测量结果同计算结果进行了比较.     

Photoproduction of high-energy neutrons in thick targets by electrons in the energy range 150 to 270 MeV

Photoneutron spectra with energies greater than 12 MeV produced by electrons incident on a thick lead target have been measured for primary electron energies between 150 and 266 MeV and at a fixed angle of 90 ° to the beam axis. Measurements of the neutron yield have furthermore been performed at a primary energy of 234 MeV as a function of target depth for the same lead target and as a function of the mass number for C, Al, Cu, Cd and Pb targets. The results were obtained with three independent neutron detectors: two proton recoil counters and one time-of-flight set-up. The high-energy regions of the spectra are compared with the predictions of the phenomenological quasi-deuteron model and a satisfactory agreement in shape and scale of the spectra is found. Additional high-energy neutrons from pion reabsorption processes were observed at electron energies of 234 and 266 MeV.     

HIRFL-CSR commissioning in 2006 and 2007

HIRFL-CSR, a new heavy ion cooler-storage-ring system at IMP, had been in commissioning since the beginning of 2006. In the two years of 2006 and 2007 the CSR commissioning was finished, including the stripping injection (STI), electron-cooling with hollow electron beam, C-beam stacking with the combination of STI and e-cooling, the wide energy-range synchrotron ramping from 7 MeV/u to 1000 MeV/u by changing the RF harmonic-number at mid-energy, the multiple multi-turn injection (MMI), the beam accumulation with MMI and e-cooling for heavy-ion beams of Ar, Kr and Xe, the fast extraction from CSRm and single-turn injection to CSRe, beam stacking in CSRe and the RIBs mass-spectrometer test with the isochronous mode in CSRe by using the time-of-flight method.     

208Hg β衰变新γ射线的初步观察

利用８．４ＭｅＶ／ｕ的１８Ｏ束轰击天然铅靶，分离出汞元素产物，并以此研究２０８Ｈｇβ衰变的新γ射线．除已报道的γ射线以外，观察到对应于２０８Ｔｌ已知能级间跃迁的９条新γ射线.The Hg products produced in the bombardment of natural lead targets by 18 O beam of 8.4 MeV/u were separated by means of an off line gas thermochromategraphic device. The coincident gamma spectra and time successive single γ ray spectra were measured. Except the already known γ rays, nine new γ rays assigned to the transitions between the known levels of 208 Tl were observed.     

H2O分子在不同电荷态的重离子作用下的离化

利用含时密度泛函理论和局域密度近似方法，计算了H2O分子在速度为12．5α0／fs的重离子C^＋和C^2＋作用下产生的各种电荷态的H2O分子离子的几率、平均逃逸电子数和偶极矩的变化随时间的演化。计算结果表明，在重离子势最大时，电偶极矩的变化最大，重离子的电荷态越高，得到高电荷态H2O分子的几率越大；重离子远离分子时，电偶极矩的变化趋于平缓。The time-dependent density functional theory （TDDFT） and local density approximation （LDA） are used to calculate the dipole moment changes, the ionization probabilities of the H20 molecule and the time-dependent probabilities of escaped electrons in the process of excitation of H2O molecule by C^＋ , C^2＋ with energy of 2.3 MeV/u. It is shown that the dipole moment changes of H2O are the greatest and the higher the charge staate of heavy ion, the bigger the probabilities of the high charge state of H2O molecule at maximal heavy ion potential. The dipole moment changes slightly when heavy ion leaved far from molecule.     

Neutron yields upon irradiation of thick targets by ions with energies below 1.75 MeV/Nucleon

The yields of neutrons produced in thick LiF, Be, C, Al, Al₂O₃, and Cu targets irradiated by Li, C, and N ions with energies below 1.75 MeV/nucleon are measured on the DC-60 cyclotron at the Institute of Nuclear Physics, Astana Branch, Kazakhstan. The experimental angular distributions of the neutron yields from the targets are measured and an empirical equation to describe the distributions is proposed. The measured neutron yields are compared with the figures calculated by the LISE++ program. The measured and predicted neutron yields in the reactions coincide to within a factor of 2.     

Study of neutron dose equivalent at the HIRFL deep tumor therapy terminal

The secondary neutron fields at the deep tumor therapy terminal at HIRFL(Heavy Ion Research Facility in Lanzhou) were investigated. The distributions of neutron ambient dose equivalent were measured with a FHT762Wendi-II neutron ambient dose equivalent meter as ~(12)C ions with energies of 165, 207, 270, and 350 Me V/u were bombarded on thick tissue-like targets. The thickness of targets used in the experiments was larger than the range of the carbon ions. The neutron spectra and dose equivalent were simulated by using FLUKA code, and the results agree well with the experimental data. The experiment results showed that the neutron dose produced by fragmentation reactions in tissue can be neglected in carbon-ion therapy, even considering their enhanced biological effectiveness.These results are also valuable for radiation protection, especially in the shielding design of high energy heavy ion medical machines.     

Fragment distribution in ~(78,86)Kr+~(181)Ta reactions

Within the framework of the isospin-dependent quantum molecular dynamics model, along with the GEMINI model, the ~(86)Kr+~(181)Ta reaction at 80, 120 and 160 MeV/nucleon and the ~(78)Kr+~(181)Ta reaction at 160 MeV/nucleon are studied, and the production cross sections of the generated fragments are calculated. More intermediate and large mass fragments can be produced in the reactions with a large range of impact parameter. The production cross sections of nuclei such as the isotopes of Si and P generally decrease with increasing incident energy.Isotopes near the neutron drip line are produced more in the neutron-rich system ~(86)Kr+~(181)Ta.     

Ground-state, β and K = 11/2? γ bands in 163, 165Er

Neutron production by stopping 55 MeV deuterons in thick carbon and heavy-water targets has been measured by the activation method. The geometry was close to the one defined for the SPIRAL2 uranium-carbide target in the initial phase. A comparative method for obtaining the neutron flux has been used and is presented in detail. The neutron flux generated by 55 MeV deuterons on carbon is 2.3 times the flux at the deuteron energy of 40 MeV. The flux further increases by a factor 1.4 when using a heavy-water target. These results are discussed in the context of an energy upgrade of the SPIRAL2 driver accelerator.