中能重离子碰撞中同位旋效应和晕核结构

本论文主要包括两部分内容，一部分是关于中能重离子碰撞中的同位旋效应和同位旋非对称核物质状态方程，第二部分是改进的Glauber理论和晕核核结构的研究．利用同位旋相关的量子分子动力学模型（IQ＼MD）系统而仔细的研究了同位旋相关的平均场和介质中核子核子碰撞截面对中能重离子碰撞中碎裂和耗散的同位旋效应．研究在国际上首次发现原子核阻止，中等质量碎片多重性和质子（中子）发射数都敏感的依赖于介质中核子一核子碰撞截面的同位旋效应，而对于同位旋相关的平均场（又寸称势）很不灵敏．故这些物理量可以作为提取相对高能范围缺中子系统同位旋相关介质中核子一核子碰撞故面的灵敏探针．另一方而，与前三种物理观测量相反，研究发现在相对较低能区前平衡核子发射中质比和同位旋分馏强度灵敏的依赖于对称势，而对于同位旋相关介质中核子一核子碰撞截面很不灵敏，可以用来提取同位旋相关平均场的知识．在此基础上分别研究了动量相关作用，核介质效应和库仑作用分别对提取上述知识动力学过程的机理和影响，研究发现这三种动力学因素对中能重离子碰撞过程中的同位旋效应有重要影响．例如研究发现核子一核子碰撞的介质效应明显增加了中等质量碎片多重性和核子发射数对于核子一核子碰撞截面的灵敏性．库仑作用降低了同位旋分馏和原子核阻止．但不影响它们分别对平均场和两体碰撞同位旋效应的灵敏性．动量相关作用明显增加了各种物理观测量对于平均场或两体碰撞截面同位旋效应的灵敏性．以上的研究结果对建立同位旋非对称核物质状态方程具有重要的参考价值和学术意义．在考虑量子修正、库仑修正、核子一核子碰撞同位旋效应和假定有效原子核密度分布后将仅适用于计算高能核子对原子核反应总截面的Glouber理论推广到能适用于中低能情况下核一核反应的Glaube理论．研究发现在应用推广的Glauber理论计算中、低能核一核反应截面时，量子修正是重要的．利用修正了的Glauber理论，系统计算了从低能到较高能大量稳定线附近30个核一核反应总截面，在没有可调参数的情况下，都与实验结果较好地符合．在计算晕核与稳定核反应总截面时，发现对于"Be，"Be和" Li等入射晕核，必须考虑它们的晕核结构才能得到与实验符合的反应截面，并可依据反应总截面来提取晕核的密度分布和均方半径等信息，以此来判定晕核的存在。

HIRFL剥离器后切束线物理设计

HIRFL is a tandem cyclotron complex for heavy ion. On the beam line between SFC and SSC, there is a stripper. Behind it, the distribution of charge states of beam is a Gauss distribution. The equilibrium charge state Q_0 is selected by 1BO2(a 50° dipole behind the stripper) and delivered to SSC. One of two new small beam line (named SLAS) after 1B02 will be builded in or der to split and deliver the unused ions of charge states (Q_0 ± n) to aspecific experimental area. Q_0 ± n ions are septumed and separated from initial(Q_0) ion beam by two septum magnets SM1, SM2. The charge state selected by SM1 will be Q_0 ± 1(6 ≤ Q_0 < 17), Q_0 ± 2(17 ≤ Q_0 < 33) and Q_0 ± 3 (Q_0 ≥ 33) forming a beam in one of the two possine new beam line with the stripping energy of (0.2 to 9.83 Mev/A), an emittance of 10π mm.mrad in the two transverse planes and an intensity ranging from 10~(11) pps for z ≤ 10 to some 10~5 pps for the heaviest element. Behind SM2, a few transport elements (three dipoles and seven qudrupoles) tra nsport Q_0 ± n beam to target positions T1, T2 (see fig. 1) and generate small beam spots (φ ≤ 4mm, φ ≤ 6mm). The optics design of the beam line has been done based on SLAC-75 (a first and second - order matrix theory). beam optics calculation has been worked out with the TRANSPORT program. The design is a very economical thinking, because without building a new accelerator we can obtain a lower energy heavy ion beam to provide for a lot of atomic and solid state physical experiments

Nuclear stopping and compression in heavy-ion collisions at intermediate energies

The nuclear stopping and the radial flow are investigated with an isospin-dependent quantum molecular dynamics (IQMD) model for Ni + Ni and Pb + Pb from 0.4 to and 1.2 GeV/u. The expansion velocity as well as the degree of nuclear stopping are higher in the heavier system at all energies. The ratio between the flow energy and the total available energy in center of mass of the colliding systems exhibits a positive correlation to the degree of nuclear stopping. The maximum density (rho(max)) achieved in the compression is comparable to the hydrodynamics prediction only if the non-zero collision time effect is taken into account in the later. Due to the partial transparency, the growing of the maximum density achieved in the central region of the fireball with the increase of beam energy becomes gradually flat in the 1 GeV/u energy regime. (C) 2008 Elsevier B.V. All rights reserved.

Effects of elastic and inelastic NN scattering cross sections on pi(-)/pi(+) ratios in heavy-ion collisions at intermediate energies

Based on the isospin-dependent Boltzmann-Uehling-Uhlenbeck transport model and the scaling model according to nucleon effective mass, effects of elastic and inelastic NN scattering cross sections on pi(-)/pi(+) in the neutron-rich reaction of Ca-48 + Ca-48 at a beam energy of 400 MeV/nucleon are studied. It is found that cross-section effects of both NN elastic and inelastic scatterings affect Delta(1232), pi(-) and pi(+) production, as well as the value of pi(-)/pi(+).

Medium effects on pi(-)/pi(+) in heavy-ion collisions at intermediate energies

Based on the isospin-dependent transport model IBUU and on the scaling model according to nucleon effective mass, effects of elastic and inelastic NN scattering cross-sections on pi(-)/pi(+) in the neutron-rich reaction Ca-48 + Ca-48 at a beam energy of 400MeV/nucleon are studied. It is found that cross-section effects of both NN elastic and inelastic scatterings affect Delta(1232), pi(-) and pi(+) productions as well as the value of pi(-)/pi(+).

DETERMINING THE DENSITY DEPENDENCE OF THE NUCLEAR SYMMETRY ENERGY USING HEAVY-ION REACTIONS

We review recent progress in the determination of the subsaturation density behavior of the nuclear symmetry energy from heavy-ion collisions as well as the theoretical progress in probing the high density behavior of the symmetry energy in heavy-ion reactions induced by high energy radioactive beams. We further discuss the implications of these results for the nuclear effective interactions and the neutron skin thickness of heavy nuclei.

Single and double pi(-)/pi(+) ratios in heavy-ion reactions as probes of the high-density behavior of the nuclear symmetry energy

Based on the isospin- and momentum-dependent hadronic transport model IBUU04, effects of the nuclear symmetry energy on the single and double pi(-)/pi(+) ratios in central reactions of Sn-132+Sn-124 and Sn-112+Sn-112 at a beam energy of 400 MeV/nucleon are studied. It is found that around the Coulomb peak of the single pi(-)/pi(+) ratio the double pi(-)/pi(+) ratio taken from the two isotopic reactions retains about the same sensitivity to the density dependence of nuclear symmetry energy. Because the double pi(-)/pi(+) ratio can significantly reduce the systematic errors, it is thus a more effective probe for the high-density behavior of the nuclear symmetry energy.

Ultra peripheral heavy ion collisions and the energy dependence of the nuclear radius

To estimate realistic cross sections in ultra peripheral heavy ion collisions we must remove effects of strong absorption. One method to eliminate these effects make use of a Glauber model calculation, where the nucleon-nucleon energy dependent cross sections at small impact parameter are suppressed. In another method we impose a geometrical cut on the minimal impact parameter of the nuclear collision ((b)min > R-1 + R-2, where R-i is the radius of ion 'i'). In this last case the effect of a possible nuclear radius dependence with the energy has not been considered in detail up to now. Here we introduce this effect showing that for final states with small invariant mass the effect is negligible. However when the final state has a relatively large invariant mass, e.g., an intermediate mass Higgs boson, the cross section can decrease up to 50%. (C) 2003 Published by Elsevier B.V.

Latent track radius of PTFE irradiated with high energy ion beam

PTFE foils were irradiated with different ion beams (Xe, Au and U) with energies up to 1.5 GeV and fluences between 1 x 10(8) and 1 x 10(13) ions/cm(2) at room temperature. The induced modifications in the polymer were analyzed by FTIR, UV-Vis spectroscopy, and XRD. In the FTIR spectra, the CF2 degradation accompanied by the formation of CF3 terminal and side groups were observed. In the UV-Vis spectra, the observed increase in the absorption at UV wavelengths is an indication of polymer carbonization. From XRD, the amorphization of the material was evidenced by the decrease in the intensity of the main diffraction peak. An exponential fit of the intensity of the IR absorption peaks resulted in the following values: 2.9 +/- 0.8; 4.5 +/- 0.9 and 5.6 +/- 0.8 nm for the latent track radius after irradiation with Xe, Au and U beams, respectively. (C) 2011 Elsevier B.V. All rights reserved.

Single - and double energy swift and slow heavy ion irradiated optical waveguides in Er: Tungstene-Tellurite glass and BGO for telecom applications

The fabrication of broadband amplifiers in wavelength division multiplexing (WDM) around 1.55 m, as they exhibit large stimulated cross sections and broad emission bandwidth. Bi4Ge3O12 (eultine type BGO) - well known scintillator material, also a rare-earth host material, photorefractive waveguides produced in it only using light ions in the past. Recently: MeV N+ ions and swift O5+ and C5+ ions, too*. Bi12GeO20 (sillenite type BGO) - high photoconductivity and photorefractive sensitivity in the visible and NIR good candidate for real-time holography and optical phase conjugation, photorefractive waveguides produced in it only using light ions. No previous attempts of ion beam fabrication of waveguides in it.

Ion-beam damage induced in SiO2: Excitonic mechanisms under heavy electronic excitation

The Centro de Micro-Análisis de Materiales (CMAM) in the Universidad Autónoma de Madrid is carrying out an extensive research program on the processes induced by high energy heavy mass ions (SHI) on dielectric materials and their photonic applications [1?21]. A significant part of this activity constitutes a relevant contribution to the scientific program associated to the TECHNOFUSION project. It is performed in collaboration with the Instituto de Fusion Nuclear at the UPM, the CIEMAT, the Departamento de Física de Materiales at UAM and several other national institutions (INTA) and international laboratories (GANIL, France), Legnaro Italy, Grenoble?. The program has led to a large number of publications in reputed international journals.