^12C离子与铜相互作用中的平均线性动量转移

使用离线γ能谱法和厚靶－厚收集箔技术测定了２０－４６ＭｅＶ／ｕ＾１２Ｃ离子和Ｃｕ相互作用中剩余核的前向平均反冲射程。根据这些数据得到了所有碰撞参数积分的平均线性动量转移和初始复合体系的平均激发能，实验结果与献值吻合较好。     

Production of cosmogenic nuclides in thick targets by alpha bombardment. Part I — short-lived radioisotopes

Production of short-lived cosmogenic nuclides in planetary surfaces and remote spacecraft detectors was simulated by bombarding “thick” C, Mg, Al, Si, SiO₂, Fe, Ni, and Ge targets with 60, 90 and 120 MeV alpha particles. Gold foils were used to monitor alpha particle fluence; product nuclides were measured by gamma ray spectroscopy. The results were used to calculate production yields for each alpha energy, as well as cross sections averaged over the energy ranges 60–90 and 90–120 MeV.     

Stopping power measurements of heavy ions (3 ? Z1 ? 14) in Mylar foil by time-of-flight spectrometry

Heavy ions elastic recoil detection analysis coupled with time of flight spectrometer (HIERDA_ToF-E) have been used to measure energy loss of charged particles in thin absorber. The stopping power of heavy ions has been determined in Mylar for ²⁸Si, ²⁷Al, ²⁴Mg, ¹⁹F, ¹⁶O, ¹²C and ⁷Li ions over a continuous range of energies 0.14-0.80 MeV/nucleon. The ions were recoils from the bombardment of different samples (Si, MgO, Al₂O₃, LiF and C) with a 27.5 MeV Kr⁺ beam. The energy loss of the recoil atoms is measured with and without additional foils placed in front of a Surface Barrier Detector (SBD). The energy of individual ions is determined from its ToF data; the exit energy after the stopping foil is measured using the SBD detector. We have compared our stopping values to those predicted by SRIM-2008 computer code, ICRU-73 stopping data tables, MSTAR calculations and to the published data from literature. The results show good agreement with limited existing data but indicate a large deviation among the predicted theoretical values at the low energy side of the stopping maximum peak.     

Stopping power measurements for O, F and Si ions in Mylar by a transmission technique

Electronic energy loss of charged particles in materials is a fundamental process responsible for the unique response of materials in applications of advanced nuclear power, radiation detectors and advanced processing of electronic devices. In this study, stopping powers of ¹⁶O, ¹⁹F and ²⁸Si heavy ions crossing thin Mylar foils have been determined in transmission geometry. The energy loss was measured over a continuous range of energies from 1.6 to 5.5 MeV/n (MeV per nucleon) using the data that was tagged by a surface barrier detector (SBD) with and without stopping foils. We have compared the obtained stopping values to those predicted by SRIM-2008 computer code, ICRU-73 stopping data tables and MSTAR calculations. The effective charge values of these heavy ions have been also deduced from the experimental set of data.     

Simulation experiments for the sputtering of niobium by 14 MeV neutrons

Simulation experiments for the sputtering of niobium by 14 MeV neutrons are conducted at the Berlin Cyclotron with protons of 11 to 20 MeV which pass through a sandwich of niobium target foils and silicon catcher disks. The stack is assembled in an UHV chamber and is irradiated to doses of 0.7 to 1.4 × 10¹⁸ p/cm². The sputtered material is detected by RBS, taking advantage of Si background reduction by the 〈111〉 channeling effect and by electronic pile-up rejection. The measured sputter ratios are in the forward direction (1.0–2.4) × 10^?4 for the first irradiation and (1.0–2.5) × 10^?5 for a second (subsequent) irradiation; in the backward direction sputter ratios are found to be considerably lower, between several 10^?6 (limit of detection) and 2.8 × 10^?5 (maximum). The emission of radioactive recoils is also observed through 7 spectrometry of targets and collectors.     

RIBLL大面积真空镀膜装置

描述了一台大面积双叠层阳极在 X、Y方向分条读出气体电离室而发展的大面积真空镀膜装置。镀膜腔体内体积为 990 mm× 780 mm× 780 mm。可镀膜面积最大为 960 mm× 750 mm。用该装置为RIBLL电离室镀阴极、X阳极、Y阳极和窗 ,镀膜面积 4 4 0 mm× 160 mm,Mylar膜厚 3.2 6μm,镀银 97.2 7nm,镀银厚度不均匀度为 18.91%。用它制作的 RIBLL电离室的阳极、阴极 ,当电离室工作气压2 5k Pa P10气体 ,阳极电压 2 2 0 V,阴极电压 - 160 0 V时 ,对 5.15Me Vα源测量能量分辨率为 4 .2 %。     

Stopping power of swift neon ions in dependence on the charge state in the non-equilibrium regime

We report on measurements of charge changing cross-sections and energy losses in dependence on the initial and final charge state of Ne ions at an incident energy of 2 MeV/u penetrating thin carbon foils. Different initial charge states could be separated in energy by applying a high voltage in front of the carbon foils; the final charges and their energy loss were measured with a high-resolution magnetic spectrometer. We derived a consistent evolution of the charge state distribution solving the corresponding rate equations for the measured cross-sections. Including the charge state dependent energy losses, ΔE(q_i,q_f), stopping power values for frozen charge states, S(q), could be extracted. The experimental data are compared with different theoretical predictions.     

Flux and dose transmission through concrete of neutrons from proton induced reactions on various target elements

Simple empirical expressions for transmission of flux and dose through concrete are presented for neutrons from proton induced reactions. For this purpose the neutron emission from different targets in proton induced reactions in the energy range 25–200 MeV have been considered. The calculated effective dose outside a concrete shield shows overall good agreement with the effective dose estimated from measured neutron flux in the framework of the Moyer model. The calculated effective attenuation length shows a rising trend with incident proton energy and shield thickness.     

Stopping power of Mylar for heavy ions up to copper

The stopping powers of Mylar for several heavy ions covering Z=11 to 29 in the energy range 0.3 to 2.3 MeV/n have been measured using the elastic recoil detection technique and twin detector system. The technique provided a unique method to generate a variety of variable energy ion species utilizing a fixed energy 140 MeV Ag¹³⁺ primary beam from the Pelletron accelerator facility at Nuclear Science Center, New Delhi, India. Most of these measurements are new. The experimentally measured stopping power values have been compared with those calculated using LSS theory, Ziegler et al. formulation and Northcliffe and Schilling tabulations. Merits and demerits of these formulations are highlighted. Stopping power calculations using the Hubert et al. formulation have been extended successfully beyond its recommended range of validity, i.e. 2.5–500 MeV/n down to energies as low as 0.5 MeV/n.     

Mylar膜衬底上的镀膜技术

本文系统地研究了在Mylar膜上通过真空蒸发沉积各种不同材料薄膜的技术,详细讨论了真空蒸发沉积薄膜时使衬底温度升高的蒸发源的辐射热和沉积时的冷凝热,介绍了一种精确控制厚度的方法,分析了静止衬底和转动衬底沉积薄膜的均匀性,探索和总结了在Mylar膜衬底上镀膜过程中防止衬底软化的方法。在12.5 μm厚的Mylar膜上成功沉积了厚度为1 μg/cm²和20 μg/cm²的Sc、Ti等24种物理实验需要的薄膜。最后用X射线荧光分析方法测量了沉积在Mylar膜上的Cu膜和Cr膜的均匀性。结果显示,均匀性优于5%,完全满足物理实验的要求。     

Development of a TOF-ERDA measurement system for analysis of light elements using a He beam

A time-of-flight ERDA (TOF-ERDA) measurement system has been developed for the analysis of light elements. He ions are used for the incident beam, and recoil light ions are detected with the system. The system consists of a time detector and a silicon detector, and energy and velocity of recoil ion are measured simultaneously. The depth resolution of 21.6 ± 2.2 nm (FWHM) has been obtained by an ERDA measurement of a thin carbon layer onto a silicon wafer using a 5.7 MeV He beam. The mass resolution is better than 1 for elements up to oxygen. Maximum detectable depth of carbon in a PET film is about 650 nm. An ERDA measurement of implanted carbon in a silicon wafer has been demonstrated.     

Fusion neutron induced radioactive emissions from surfaces

Neutron induced direct nuclear recoil sputtering ratios have been measured for a variety of 14.8 MeV (d, t) neutron induced reactions in Nb, Mo, V and 316 SS. Absolute recoil sputtering ratios for forward and backward sputtering are reported. Forward sputtering ratios are typically in the range of 10^?9–10^?7 recoil atoms per (d, t) neutron while backward sputtering ratios are usually several orders of magnitude lower. Some of the implications of radioactive particle ejection in the first wall region of fusion reactors are discussed. It is shown that radioactivity ejected into the fusion reactor coolant channels by direct nuclear recoil and by lattice dynamic neutron sputtering, may have a significant effect on the design and maintenance of fusion reactors.     

Neutron sputtering yields from Nb,Au and Co

Employing a neutron source based on the ⁹Be (d, n) reaction, high energy neutron sputtering yields have been determined for Nb, Au and Co. Two experiments have been conducted. In the first, graphite catcher foils were used and in the second, polished Si wafers. From data collected in the first experiment the neutron sputtering yields of Nb, Au and Co were determined to be in the range of 10^?5 to 10^?4 particles per incident neutron. Examination of the collector foils from the second experiment did not show any evidence of large particle (> 1 μm) ejection from the Nb targets.     

Energy loss of 450–2400 kev protons in Havar,Kapton and aluminized Mylar foils

The energy loss of 450–2400 keV protons in common exit foils used in external beam setups has been determined. The measured foils consisted of 2.4 μm Havar, 9.9 μm Kapton and 3.5 μm and 6.6 μm aluminized (40 nm Al) Mylar. Good agreement with the calculations by using Bragg's rule and the Andersen and Ziegler parameters was found in the higher energy region. At energies ? 1000 keV, the results are higher ( ? 6%) than the calculated values. A rapid decrease of the energy loss in the Mylar foils under proton exposure was detected.     

~(107)Ag(d,2n)~(107)Cd和~(109)Ag(d,2n)~(109)Cd反应的激发函数

用13.4MeV的氘束轰击天然银迭靶,银箔前后用铝箔作捕集减能膜。实验确定了~(107)Ag(d,2n)~(107)Cd和~(109)Ag(d,2n)~(109)Cd反应的激发函数,同时作了理论计算。由结果可见,实验值与理论值吻合得很好。     

A new technique for measuring sputtering yields at high energies

The use of thin, self-supporting carbon catcher foils allows one to measure sputtering yields in a broad range of materials with high sensitivity. Analyzing the foils with Rutherford forward scattering, we have measured sputtered A1, Si and P surface densities down to 5 × $\text{10}{}^{13}\text{cm}{}^2$ with uncertainties of about 20%.     

Verification of Monte Carlo transport codes FLUKA, GEANT4 and SHIELD for radiation protection purposes at relativistic heavy ion accelerators

The crucial problem for radiation shielding design at heavy ion accelerator facilities with beam energies of several GeV/n is the source term problem. Experimental data on double differential neutron yields from thick targets irradiated with high-energy uranium nuclei are lacking. At present there are not many Monte Carlo multipurpose codes that can work with primary high-energy uranium nuclei. These codes use different physical models for simulating nucleus–nucleus reactions. Therefore, verification of the codes with available experimental data is very important for selection of the most reliable code for practical tasks. This paper presents comparisons of the FLUKA, GEANT4 and SHIELD code simulations with experimental data on neutron production at 1 GeV/n ²³⁸U beam interaction with a thick Fe target.     

Determination of (n,2n) Reaction Cross Sections for Some Nuclei with Asymmetry Parameter

The (n,2n) reaction cross sections for targets of ^203,205Tl, ^{204,206,207,208}Pb, ²⁰⁹Bi, ²³²Th and ²³⁸U were calculated both theoretically and semi-empirically. Theoretical calculations were done using two different computer codes: PCROSS computer code for the full exciton model and ALICE/ASH-2006 computer code for the geometry dependent hybrid (GDH) model with the incident neutron energy up to 25 MeV. Semi-empirical calculations were done using formulas derived by several researchers. The obtained results have been discussed and compared with the available experimental data taken from the literature. The different nuclear reaction program codes used in the present study show considerable differences depending upon the selected energy range. Especially PCROSS calculation results show a disagreement above the incident energy of about 16 MeV for all the studied nuclei. Moreover, even though the graphs qualitatively agree in shape, they differ in magnitude below 15 MeV.     

Study of the excitation functions for K, Sc and Ti by proton irradiation on Sc up to 37 MeV

The excitation functions of proton induced reactions on Sc targets (100% ⁴⁵Sc), leading to the formation isotopes ⁴³K, ⁴³Sc, ^44mSc, ^44gSc and ⁴⁴Ti were studied by the stacked foil activation technique up to 37 MeV. High-resolution gamma-spectrometry measurements were performed on an HPGe detector in order to determine the activity of the irradiated Sc₂O₃ pellets and Ti monitor foils. The reaction cross-sections were measured from their respective thresholds up to E_p = 36.4 MeV and were compared with previous values reported in literature. Possible batch yields and optimal irradiation parameters for generator ⁴⁴Ti -^44gSc in high current accelerators are discussed.     

Excitation Functions of Some Neutron Production Targets on (d,2n) Reactions

Deuterons are weakly bound nuclei which easily undergo break up reactions. This is well known at low energies, around 10 MeV, where deuteron beams have been used to produce neutrons very efficiently. These neutrons have a widely application field such as fission energy production and hybrid reactor systems. In this study, neutron emission cross sections produced by (d,2n) reactions for spallation neutron targets such as ⁵²Cr, ⁵⁶Fe, ^60,62,64Ni, ^63,65Cu, ^{182,183,184,186}W, ²³²Th, ²³⁵U and ²³⁸U have been investigated. Hybrid model and geometry dependent hybrid model were used to calculate the pre-equilibrium neutron-emission cross sections. For the reaction equilibrium process, Weisskopf–Ewing model calculations were selected. The obtained results have been discussed and compared with the available experimental data and found agreement with each other.