Measurement of 4He-p recoil cross sections

The recoil cross sections of protons induced by ⁴He⁺ particles were experimentally determined in an energy range of 1.3–2.1 MeV at recoil angles of 20° and 30 ° . The angular dependence of the recoil cross section at 2.0 MeV was also measured. By using the principle of detailed balance, a calculation of ⁴He-p recoil cross sections were calculated from p-⁴He phase shift data. Good agreement between the experimental data and theoretical values was found. The results show that recoil cross sections at low energies are non-Rutherford and are larger than the Rutherford value by approximately a factor of 2 at 2.0 MeV.     

Scattering of protons by hydrogen atoms at low energies: Phase shifts and differential cross sections

Phase shifts and differential cross sections for spin exchange (charge transfer) and total elastic scattering of protons by hydrogen atoms are presented for 36 and 38 values, respectively, of the collisional kinetic energy in the range 0.0001 to 10 eV (center of mass). The phase shifts are tabulated with a precision of six decimal digits. Each cross section is presented as a graph covering the complete angular range from 0 to π radians (in center-of-mass coordinates). The phase shifts were obtained via partial wave analysis within a modified Perturbed-Stationary-States theory by calculations based upon very accurate (nonrelativistic) internuclear potential energies for the 1Sσ_g and 2Pσ_u electronic states of H₂⁺. The cross sections demonstrate a transition from purely quantum behavior at very low energies (<0.1 eV) to semicllssical behavior at higher energies (>1 eV) in which protons scattered by spin exchange are angularly separated from those scattered without exchange. Thus the in-principle unobservable charge-transfer cross section becomes physically measurable at energies greater than about 1 eV.     

Stopping cross sections of liquid water for MeV energy protons

Cross sections for the stopping of swift protons in liquid water have been measured for the first time by using a liquid water jet target of 50 μm in diameter. The energy loss spectra of incident 2.0 MeV protons were measured at scattering angles of 5.0-50 mrad. Experimental energy loss spectra have been successfully reproduced by Monte Carlo simulation calculations (GEANT4.9.1.p02 toolkit) by taking account of multiple scattering of projectile ions inside the liquid water target. The present stopping cross sections are found to be considerably smaller than other standard stopping power data, revealing e.g. about 11% deviation from those of SRIM2003.     

Differential cross sections for ejection of electrons from helium by protons

A compilation is presented of the results of several authors on experimental cross sections for ejection of electrons from helium gas by protons of 5 keV to 5 MeV energy. The data are given as a function of the angle and energy of ejection. Angles from 10° to 160° are surveyed and electron energies range from 1 to 8600 eV. The doubly differential cross sections are integrated in various ways to obtain cross sections differential only in energy or angle, total electron production cross sections, and mean energies of ejection.     

Differential cross sections for ejection of electrons from argon by protons

Measured cross sections for ejection of electrons from argon gas by protons of 5 keV to 5 MeV energy are given as a function of the angle and energy of ejection. These doubly differential cross sections are integrated to obtain cross sections differential in either angle or energy, total electron production cross sections, and mean energies of ejection.     

The role of projectile interactions in triply differential cross sections for excitation-ionization of helium

We report triply differential cross section (TDCS) for the simultaneous excitation-ionization of helium by electron impact for both coplanar and non-coplanar geometry. In the coplanar case, calculations have been performed for an incident energy of 500 eV and low ejection energies (3 and 10 eV), whereas in the noncoplanar case we have considered impact energies in the range 1240-4260 eV for a symmetric geometry. The present calculation is based on the eikonal approximation due to Glauber. We have incorporated the effect of post-collision interaction in the Glauber approximation. A comparison is made of the present calculations with the results of other theoretical methods and recent experiments. The Glauber results are in reasonably good agreement with the experiment for small scattering angles.     

Impact parameter method calculations for fully differential ionization cross sections

In this work, our previous fully differential ionization cross section calculations using the semiclassical, impact parameter method are improved by a new method suitable to calculate impact parameter values corresponding to different momentum transfers. This goal is achieved by two successive steps. First, using the transverse momentum balance different projectile scattering angles are calculated for the binary and recoil peak regions as a function of the transferred momentum. Then, by treating the projectile scattering as a classical potential scattering problem, impact parameters are assigned to these scattering angles. The new method, which no longer contains empirical considerations, is tested calculating by fully differential ionization cross sections for single ionization of helium produced by fast C⁶⁺ ions.     

1-2 MeV能区6Li(n,t)4He反应微分截面与截面的实验测量

利用屏栅电离室对1.05、1.54及2.25 MeV中子6Li(n,t)4He反应的微分截面与截面进行了实验测量.采用氚固体靶的T(p,n)3He反应产生准单能中子,用相对效率已知的BF3长中子管和238U裂变片相结合来测定绝对中子通量.将测量结果与已有数据进行了比较,1-2 MeV能区6Li(n,t)4He反应截面的分歧在一定程度上得到了澄清.     

MERCSF-N: A program for the calculation of fast neutron removal cross sections in composite shields

An approximate method for calculating the attenuation of fast neutrons can be achieved by using the “macroscopic effective removal cross-section” concept, usually denoted by Σ_R (cm⁻¹). The conventional method for the quantitative determination of Σ_R (cm⁻¹) for fast neutrons, which has been applied for several composites based on manual calculations, has a number of restrictions; a limited number of investigated samples, a lot of time, the possibility of random errors, etc. This work deals with the development, validation and application of the macroscopic effective removal cross-section of fast neutrons [MERCSF-N] computer program for calculating Σ_R (cm⁻¹) for fast neutrons transmitted through homogeneous mixtures, composites, concretes and compounds. The required physical data representing all periodic table elements have been compiled on the basis of the recommended published data and stored in a data base file. The validity of MERCSF-N has been confirmed by comparing its predictions with previously published results, both manually calculated and measured, where a good agreement was found. In addition, the code is used for calculating the macroscopic effective removal cross-sections of steel alloy, aluminum and magnetite concrete, which have previously been measured and reported. The calculated and measured results were compared and a good agreement was noticed.     

Double differential neutron scattering cross sections of materials for ultra high temperature reactors

The five materials with the highest melting point are hafnium, tantalum, niobium and zirconium (ZrC) carbides and graphite (that sublimes). Graphite is the material of choice for very high temperature reactors (VHTR); ultra high temperature reactors (UHTR), like the thermal nuclear propulsion reactor NERVA use a dispersion of ZrC and UC in graphite as the material in the reactor core. Presently there are neither inelastic nor elastic double differential scattering data available that describe the thermalization process in ZrC. We therefore, calculated coherent elastic and incoherent inelastic cross sections for the ZrC crystal which has a face centered cubic (fcc) lattice. The phonon spectrum for the ZrC lattice was calculated with the computer code PHONON using the Hellman–Feynman forces computed with ab-initio methods [Jochyn, P.T., Parlinski, K., 2000. Ab initio lattice dynamics and elastic constants of ZrC. Eur. Phys. J. B 15, 265–268]. This phonon spectrum was then used to compute the S(α, β, T) matrices for the inelastic scattering cross sections for C and Zr in the ZrC lattice using modified versions of the computer codes GASKET, HEXSCAT and NJOY. The results were applied to calculate, with the proper S(α, β, T), criticality and reactivity coefficients of temperate of reactor systems containing ZrC and UC. For comparisons, these parameters were also calculated with approximations of S(α, β, T), i.e. the gas or the graphite scattering kernels. Depending on the degree of thermalization, k_eff is underestimated between 0.6% and 1%, and the values and the shape of the reactivity coefficients as a function of temperature change by substantial amounts.     

0.96-2.74MeV质子在铝上的160°散射截面测量

采用薄靶对能量0.962.74MeV质子在纯度为99.99%铝上的160非卢瑟福弹性背散射截面进行了测量。质子束由21.7MV串列加速器提供,测量仪器采用金硅面垒探测能谱仪。实验中最低能区进入卢瑟福弹性散射能区,测量结果用图表形式给出,并与以前发表的结果进行了比较。所测量数据可供从事背散射分析技术的有关人员参考。     

质子在天然硼上的非卢瑟福弹性背散射截面测量

采用相对测量法对能量为0.15-2.00MeV的质子在天然硼上的非卢瑟福弹性背散射截面(160     

Depth resolution and recoil cross section for analyzing hydrogen in solids using elastic recoil detection with 4He beam

Two aspects of the elastic recoil detection technique for analyzing H and D are described; i) experimental factors which effectively limit the depth resolution in Al film, and ii) determination of the recoil cross section for H(⁴He, ⁴He)H and D(⁴He, ⁴He)D reactions in the range of 1.5–3.0 MeV energy of ⁴He. Both experimental and theoretical estimates of the depth resolution are presented and are in good agreement each other. The theoretical estimate therefore provides a reliable guide to find optimum resolution conditions. The recoil cross section for H is more than double the theoretical Rutherford scattering value and that for D becomes greater than 30 times Rutherford near the resonance energy of 2.1 MeV ⁴He.     

Differential elastic scattering cross sections of protons from Al in 2.4–4.8 MeV energy range

Measurement of differential elastic cross section of protons from aluminum was taken at 165° degree in the2.4–4.8 Me V energy range. The results and measured energy resonances were compared with reported measurements.These data will improve the reliability of backscattering analysis of Al with protons in this energy region.     

The calculation of radial dose from heavy ions: predictions of biological action cross sections

The track structure model of heavy ion cross sections was developed by Katz and co-workers in the 1960s. In this model the action cross section is evaluated by mapping the dose-response of a detector to gamma rays (modeled from biological target theory) onto the radial dose distribution from delta rays about the path of the ion. This is taken to yield the radial distribution of probability for a "hit" (an interaction leading to an observable end-point). Radial integration of the probability yields the cross section. When different response from ions of different Z having the same stopping power is observed this model may be indicated. Since the 1960s there have been several developments in the computation of the radial dose distribution, in the measurement of these distributions, and in new radiobiological data against which to test the model. The earliest model, by Butts and Katz made use of simplified delta ray distribution functions, of simplified electron range-energy relations, and neglected angular distributions. Nevertheless it made possible the calculation of cross sections for the inactivation of enzymes and viruses, and allowed extension to tracks in nuclear emulsions and other detectors and to biological cells. It set the pattern for models of observable effects in the matter through which the ion passed. Here we outline subsequent calculations of radial dose which make use of improved knowledge of the electron emission spectrum, the electron range-energy relation, the angular distribution, and some considerations of molecular excitation, of particular interest both close to the path of the ion and the outer limits of electron penetration. These are applied to the modeling of action cross sections for the inactivation of several strains of E-coli and B. subtilis spores where extensive measurements in the "thin-down" region have been made with heavy ion beams. Such calculations serve to test the radial dose calculations at the outer limit of electron penetration. We lack data from which to test these calculations in regions close to the path of the ion aside from our earliest work on latent tracks in plastics, though it appears that the criterion then suggested for the threshold of track formation, of a minimal dose at a minimal distance (of about 20 angstroms, in plastics), remains valid.