Analyzing powers of heavy ion induced transfer reactions

A semiclassical model based on the DWBA formalism is used to discuss the analyzing powers of heavy ion transfer reactions in particular the dependence on the Q-value, l, j and on the asymptotic normalization constants. Good agreement is obtained for the cross section and iT₁₁ angular distribution data of the ⁵⁸Ni(⁷L$\text{i}$, ⁶Ni)⁵⁹Ni reaction at 20.3 MeV.     

Suppression of intrabeam scattering in cooled heavy ion beams

The properties of electron cooled heavy ion beams in the ESR storage ring are dominated by heating due to intrabeam scattering. For low intensity ion beams a sudden reduction of the longitudinal ion beam temperature has been detected by Schottky noise analysis. This can be interpreted as the disappearance of intrabeam scattering heating which could allow a longitudinal ordering of the ion beam.     

Formation of hollow heavy ion beams in plasma lens

Hollow cylindrical high-energy heavy ion beams are an efficient driver for target irradiation to achieve highly compressed matter. This paper is devoted to the study of how hollow beams form with the use of a plasma lens. Calculations and measurements were performed with a 200 MeV/amu C⁺⁶ beam.     

Electronic stopping power of polymers for heavy ions in the ion energy domain of LSS theory

LSS based computed electronic stopping power values have been compared with the corresponding measured values in polymers for heavy ions with Z = 5–29, in the reduced ion velocity region, v_red ≤ 1. Except for limited v_red  0.6–0.85, the formulation generally shows significantly large deviations with the measured values. The ζ factor, which was approximated to be Z₁^1/6, involved in LSS theory has been suitably modified in the light of the available experimental stopping power data. The calculated stopping power values after incorporating modified ζ in LSS formula have been found to be in close agreement with measured values in various polymers in the reduced ion velocity range 0.35 ≤ v_red ≤ 1.0.     

Effective stopping charges and stopping power calculations for heavy ions

In this study the model suggested by Sugiyama has been developed and applied for the calculation of the stopping powers for nonrelativistic heavy ions in various target materials. Sugiyama's model has been expanded to low and high energy regions in our work. Analytical expressions are obtained in the modified BB stopping power formula for the effective charge and effective mean excitation energies. In the modified LSS formula, a quasi-molecule criterion has been applied to both the projectiles and the target atoms. Electronic excitation contribution, S _e0, and quasi-molecule contribution, S _ei , to stopping power were found for a wide energy region. It is observed that in intermediate energy region both contributions have maxima. The stopping power due to excitation-ionization in the intermediate and higher energy region is found to be dominant, whereas quasi-molecule contribution is dominant in the lower energy region. The calculated results of stopping power are in good agreement with experimental data for various ions and targets within a few percent in a wide projectile energy range.     

Modification of Ti foils irradiated by intense heavy ion beams

ABSTRACT

Modification of Ti foils irradiated by intense energetic heavy ion (HI) beams in long-term experiments has been considered. The experiments on the synthesis of superheavy nuclei, which are carried out in Dubna with a gas-filled recoil separator (DGFRS), determine the conditions of such experiments. High intensities of HIs passing through a relatively small area and thickness of the foils, as well as their heating by a beam, are inherent in such experiments. The ability of the foils to withstand radiation damages, sputtering, and evaporation of atoms becomes questionable. All the processes seem to be dependent on temperature, and none of them is independent of the others, but they can be considered separately. In this work, sputtering yields are estimated on the grounds of available models and experimental data and compared with the results of measurements carried out to verify the estimates. The foil temperature, in turn, can be estimated in the conditions of pulse heating followed by subsequent cooling with radiation emitted from their surfaces. These conditions correspond to the rotating Ti entrance window irradiated by a continuous HI beam in the DGFRS experiments.     

Laser-cooled and trapped atoms as a precision target for heavy ion beams

We report on the development of a novel precision target for atomic physics with heavy ion beams, which consists of extremely cold and well localized, laser-cooled lithium atoms in a magneto-optical trap. First experiments are in preparation to study the collisional losses from the trap caused by the ion beam. The experimental set-up and the laser system, using exclusively 670 nm diode lasers, are described.     

Calculation of helium stopping powers in the intermdiate energy region

A model for calculation of helium stopping powers is developed which takes into account different charge fraction contributions. The neutral part contribution is treated according to the ordinary Firsov theory, whereas for the charged part of the ion beam earlier classical stopping power calculations for point charges by Kührt and Wedell are used.     

Fixed target project AFTER at the LHC beams for heavy ion and hadron physics

High intensity proton and lead ion beams at the LHC collider allow one to use the beam halo by placing a fixed target or a bent crystal for beam extraction. The particle energy in this case is just half that at the RHIC collider, but the luminosity exceeds the collider luminosity many times. It is also possible to install a polarized target in the extracted beam. The project AFTER is aimed at investigation of rare processes, polarization phenomena, determination of the parameters required for analysis of cosmic rays and neutrino astrophysics, detailed investigation of quarkonia production and suppression depending on the phase transition of matter to the quark-gluon phase.     

Comparative study of various stopping power formulations for heavy ions in solids

A comparative study of different energy loss formulations viz. Benton and Henke, Mukherjee and Nayak, Zieglar et al. and Hubert et al. has been done at lower energies (0.5 to 5 MeV/n) with the aim to identify their relative validity in this energy range. Calculated results using these formulations have been compared with experimental results available in literature.     

New aspect in transient magnetic fields using heavy ion beams

Transient field precessions have been measured with the first excited 2 ₁ ⁺ -state as probe for ions of²⁸Si traversing Fe at v_ion?1v₀ and 13v₀(v₀=c/137) and⁶²Ni being stopped in Fe. The degree of polarization deduced for the Si ions, p_1s=0.19(6), is consistent with low-velocity data. There is clear evidence that the field strength is attenuated by heavy ion beams. For the⁶²Ni(2 ₁ ⁺ ) state at 1.173 MeV a g-factor value of g=0.34(7) was obtained in good agreement with a previous result.     

Observation of a gas-solid difference in the stopping powers of (1–10) MeV/u heavy ions

The stopping powers of (1–10) MeV/u Kr, Xe, Pb, and U ions were measured to be smaller in gases than in solids. This gas-solid difference which is probably caused by smaller ionic charges of the projectiles in gases was found to increase with energy and atomic number of the projectile.     

Binary stopping theory for swift heavy ions

The Bohr theory treats charged-particle stopping as a sequence of interactions with classical target electrons bound harmonically to their equilibrium positions. We demonstrate that equivalent results can be derived on the assumption of free binary collisions governed by a suitable effective potential. This kind of mapping is rigorous in the limits of distant and close collisions and therefore provides a tool to evaluate energy losses via binary-scattering theory. This model was developed with the aim of calculating stopping forces for heavy ions at moderately high velocities, where a classical-orbital calculation is typically superior to the Born approximation. The effective potential employed holds equally well for dressed as for stripped ions. Unlike the Bohr theory, the present evaluation avoids a formal division into regimes of close and distant collisions that do not necessarily join smoothly. Moreover, no perturbation expansion is necessary. For these reasons the overall accuracy as well as the range of validity of the Bohr model are significantly enhanced. Extensive tests have been performed, including comparisons with rigorous evaluations of the Z ₁ ³ effect, with excellent agreement even where such was not necessarily expected. Moreover, credible results have been obtained under conditions where the perturbation expansion shows poor convergence. A comparison with experimental data on O–Al is encouraging, even though shell corrections and projectile excitation/ionization have not yet been incorporated and input has not yet been optimized. Received 21 April 2000 and Received in final form 16 June 2000 An erratum to this article is available at .     

Nuclear stopping as a probe for in-medium nucleon-nucleon cross sections in intermediate energy heavy ion collisions

Using an isospin-dependent quantum molecular dynamics, nuclear stopping in intermediate heavy ion collisions has been studied. The calculation has been done for colliding systems with different neutron-proton ratios in beam energy ranging from 15 MeV/ u to 150 MeV/ u. It is found that, in the energy region from above Fermi energy to 150 MeV/ u, nuclear stopping is very sensitive to the isospin dependence of in-medium nucleon-nucleon cross section, but insensitive to symmetry potential. From this investigation, we propose that nuclear stopping can be used as a new probe to extract the information on the isospin dependence of in-medium nucleon-nucleon cross section in intermediate energy heavy ion collisions.