Allowance for multiple scattering in proton energy spectra

The energy spectra of 6.3 MeV energy protons backscattered by a thick Au target are studied experimentally for a broad range of varying backscattering angle. It has been shown in what manner the deviations of the forms of the energy spectra from the spectral forms calculated in the single-scattering approximation increase with decreasing scattering angle. It has been shown also that at not too high proton energy loss in the target the deviations may be described by a correction function which takes into account the contribution to the energy spectra of multiple particle scattering in the target.     

Search for d' in pion inclusive spectra from pp-interactions

We report on our measurement of the inclusive spectrum of positive pions from the reaction pp→π⁺+X on a CH ₂ internal target of the ITEP proton synchrotron at 1.5 GeV/c with a missing mass resolution of about 1 MeV/c². The goal of our experiment was the search for the hypothetical narrow πNN resonance (0.5\ MeV/c² width and a mass of 2.06\ GeV/c²) with I(J ^P P)=even(0⁻), called d′. We do not see any statistically significant d′-signal. The upper limit for d′ production cross-section in pp-interactions is near 2μb at 84%C.L. Received: 5 November 1997     

Search for very light lambda hypernuclei in proton induced reactions

Proton-induced associated strangeness production of bound hypernuclei is accompanied by large momentum transfers. Therefore, the hyperon sticking probability is low and strongly depends on short range correlations. The most favourite reactions D(p,K⁺)_Λ³H, ³He(p,K⁺)_Λ⁴He and ⁴He(p,K⁺)_Λ⁵He were studied at LNS Saclay using the high resolution spectrometer SPES4 at ϑ_lab ≈ 7°. Background pions and protons were eliminated by aerogel veto-counters and several TOF cuts, respectively. The tracking of remaining kaon-like events through four horizontally and two vertically resolving drift chambers showed no evidence for respective g.s. transitions above background. Upper limits of the order of nb/sr (CMS) are deduced.     

Rise of proton proton total cross section and inclusive spectra

The origin of the rise of p-p total cross section (σ_t(pp)) is investigated by making use of the inclusive sum rule. The contribution to the rise of σ_t(pp) from the development of sharp peak near the kinematical boundary in the process p+p→p+ “anything” is almost completely canceled out by the decrease of the cross section in other x-region between s=45 (GeV/c)² and s=2820 (GeV/c)². Then the net contribution to the rise of σ_t(pp) from the process p+p→p+ “anything” is very likely to be zero. The true origin of the rise of σ_t(pp) is found to be the increase of inclusive cross sections at x ? 0 between PS and ISR energies. The contribution from the process p+p→π+ “anything” at x ? 0 to the rise of σ_t(pp) is estimated to be 3.2 mb, that from the process p+p→K + “anything”, 0.71 mb and that from the process p+p→$\text{p}$ “anything”, 0.62 mb. According to our conclusion we expect that all total cross sections will rise with energy at high energy.     

内爆初级质子能谱直接测量方法

基于单能质子对CR39的标定实验,利用获取的响应曲线,设计了一种内爆初级质子的直接测量方法。在内爆初级质子产额较低的情况下,该方法可获得更多的计数。对实验中的噪声信号排除做出了说明,并对其背景噪声来源进行了分析,以提高实验数据的精确性。利用标定数据,对CR39上观察到的径迹进行鉴别,确定质子径迹并测量其径迹参数,从而确定质子能量。在随机扫描的约300个显微镜视场中获得了200个质子径迹数据,并通过与标定数据比对,获得了它们各自的能量,再利用蒙特卡罗程序Geant4修正铝膜的岐离,最终确认本次内爆实验初级质子的能谱峰值应该在2.4~2.6 MeV之间,据此换算到靶丸面密度为7~8 mg/cm2,为实验结果的进一步后续分析提供了依据。     

Gaussian parametrization of a meson-theoreticalN-N potential for microscopic nuclear-structure calculations

The radial dependencies of anr-space version of the meson-theoretical nucleon-nucleon potential of the Bonn group (OBEPR) are expressed through a set of Gaussians. First results for the three-nucleon system are given.Partly supported by the BMFT under contract 06 ER 771     

Search for beta-delayed proton emission from $$^{11}$$Be

The European Physical Journal A - A deterministic treatment of sequential neutron emission, based on recursive equations of the residual temperatures, was applied to numerous fission cases (i.e. 49...     

Search for proton radioactivity in65As,69Br and77Y

A search for proton radioactivity in⁶⁵As,⁶⁹Br and⁷⁷Y, produced as residues of fusion reactions, was carried out at the Orsay Tandem accelerator. The residues were collected at the image point of the spectrometer Soleno and implanted into the gaseous medium of an ionization chamber which was also used to detect the radioactivity protons. No such protons have been observed in the energy range of 250–600 keV and in the half-life interval of 10 μs-100 ms, within a production cross section sensitivity of 1 μb.     

The proton resonance spectra of metal bis-cyclopentadienyls

The signs of the chemical shifts of the proton resonance frequencies in paramagnetic metallocenes are discussed.     

Modeling evaporation effects in conditional moment closure for spray autoignition

Simulations of an n-heptane spray autoigniting under conditions relevant to a diesel engine are performed using two-dimensional, first-order conditional moment closure (CMC) with full treatment of spray terms in the mixture fraction variance and CMC equations. The conditional evaporation term in the CMC equations is closed assuming interphase exchange to occur at the droplet saturation mixture fraction values only. Modeling of the unclosed terms in the mixture fraction variance equation is done accordingly. Comparison with experimental data for a range of ambient oxygen concentrations shows that the ignition delay is overpredicted. The trend of increasing ignition delay with decreasing oxygen concentration, however, is correctly captured. Good agreement is found between the computed and measured flame lift-off height for all conditions investigated. Analysis of source terms in the CMC temperature equation reveals that a convective–reactive balance sets in at the flame base, with spatial diffusion terms being important, but not as important as in lifted jet flames in cold air. Inclusion of droplet terms in the governing equations is found to affect the mixture fraction variance field in the region where evaporation is the strongest, and to slightly increase the ignition delay time due to the cooling associated with the evaporation. Both flame propagation and stabilization mechanisms, however, remain unaffected.     

Photoacoustic and laser-induced evaporation effects in liquids

It is shown experimentally that the photoacoustic pressure response in absorbing condensed matter to laser pulses with high frequency modulation of intensity can be used to monitor displacement of the irradiated surface. Some aspects of the processes under investigation are also discussed, including acoustic diffraction effects, features of acoustic reflection from liquid–air and liquid–solid boundaries, explosive boiling, and interference between thermoacoustic and vaporization pressure signals.     

Raman spectra of ZnSe nanoparticles synthesized by thermal evaporation method

ZnSe nanoparticles were synthesized by using a thermal evaporation method for a vapour phase reaction of zinc and selenium sources. The sample was characterized by XRD, TEM, HRTEM and Raman spectroscopy. Raman spectra of longitudinal-optical (LO) like mode was analysed by a macroscopic continuum dielectric model. Large broadening of LO-mode is homogeneous and comes from the relaxation of the phonons at the interface and contribution of defects. Surface modes give the main contribution to the asymmetry of the lineshape.     

Non-statistical effects for inelastic proton amplitudes in49V

The magnitudes and relative signs of inelastic proton-channel amplitudes have been measured for 71 3/2^? resonances in⁴⁹V. The measured quantitiesγ _c ² ,γ _c′ ² , andγ _c γ _c′ provide distributions of reduced widths, distribution of the relative sign between reduced width amplitudes, and correlations between reduced widthsρ(γ _c ² ,γ _c′ ² ) and between amplitudesρ(γ _c ,γ _c′ ). A variety of non-statistical effects are observed, including one case in which the effect occurs only in the signs, and not in the magnitudes of the amplitudes.     

质子照相中成像磁透镜系统对次级质子的消除

为了解成像磁透镜系统使用对提高质子照相品质的作用,研究了成像磁透镜系统对核反应产生的次级质子的消除作用。利用MCNPX模拟了次级质子的能谱,结果表明：次级质子的平均能量不足照相质子束的50%。从次级质子的能量特性和成像系统质子运动学方面的分析表明：成像磁透镜系统可消除次级质子的影响。利用程序MCNPX对含成像磁透镜系统的质子照相进行了模拟,结果显示：成像磁透镜系统将次级质子对光程的影响减小到2%以下,显著提高了图像品质。