[en] Results of survey experiments in which the neutron multiplicity distributions have been measured for a wide variety of systems using a 4π neutron detector are presented. Using both light and heavy ion projectiles, systems have been prepared with expected excitation energies ranging from about 100 MeV to more than 1000 MeV. After a brief of the techniques involved, the results of some of the experiments are described. Comparisons with statistical model calculations indicate that the energy deposition can be significantly below that estimated from linear momentum systematics. (authors). 9 refs., 3 figs

[en] Aspects of the recent reactor accelerator coupled experiments (RACE) carried out at University of Texas Nuclear Engineering Teaching Laboratory will be discussed. In particular, a compact instrument that allowed a continuous non-invasive means of determining the relative electron beam position was developed. The operation of the instrument is similar to an inductive current pick up toroid except that the core is sectioned radially, which allows spatial information to be derived from the induced voltages. Results of initial tests, both in beam and with a pulser, will be presented along with plans to optimize future designs

[en] Isotopically resolved intermediate-mass fragments and light charged particles have been detected from the reactions ⁴⁰Ar and ⁴⁰Ca with ⁵⁸Fe and ⁵⁸Ni at E_beam=33 and 45 MeV/nucleon. There is an angular dependence to the isotopic ratios. A moving source analysis shows that fragments emitted at Θ_lab=40 degree can be attributed primarily to a composite source while the fragments emitted at backward angles are primarily from a targetlike source. The results are compared to predictions of QMD, BUU, and GEMINI. QMD generally reproduces the charge distribution and energy spectra and has partial success with the isobaric ratios when the system is chemically equilibrated. All of the models have difficulty reproducing the isotopic ratios when the system is not chemically equilibrated. copyright 1997 The American Physical Society

[en] We modify the method of Albergo et al. for determining the temperature of an excited nucleus from double ratios of isotope yields and present a statistical model which accounts for the population and decay of excited states of the emitted fragments. Nuclear temperatures are extracted using experimental ratios of isotopic yields of fragments from helium through carbon for the reactions ⁴⁰Ca + ⁵⁸Ni, ⁴⁰Ar + ⁵⁸Ni, ⁴⁰Ca + ⁵⁸Fe, and ⁴⁰Ar + ⁵⁸Fe at 33 MeV/nucleon projectile energy. Using the model we obtain consistent values for the temperature from various isotope combinations within the experimental error when accounting for the population and decay of the excited fragments. copyright 1996 The American Physical Society

[en] Short communication

[en] The breakup reactions of 30 MeV per nucleon ¹⁶ O and ²⁰ Ne projectiles on a number of targets from ¹² C to ²⁰⁸ Pb using high resolution magnetic spectrograph are investigated. The experimental methods and reaction mechanisms are discussed. For all systems sequential breakup is the dominant reaction mechanism at least at small relative energies. A preliminary analysis of excited states population in the projectile-like fragment is given. 21 refs., 6 refs

No abstract available

[en] Inclusive neutron multiplicity distributions have been measured for 30 A MeV ¹⁴N, ²⁰Ne, ⁶³Cu and 55 A MeV ⁴He beams incident on targets ranging from ¹²C to ²³⁸U. For the lightest targets, the distributions decrease approximately exponentially with increasing multiplicity. The heavier targets display an additional Gaussian component peaked at higher multiplicities, which is attributable to central collisions. In the latter cases, the most probable multiplicities, M_n^*, have been extracted by fitting the data with a simple functional form. These multiplicities are compared to the predictions of the statistical model codes GEMINI and CASCADE using a massive transfer scenario to define the initial conditions. Reasonable agreement is obtained for systems with estimated excitation energies ∼100 MeV, but the calculations consistently overpredict the most probable multiplicities for more highly excited systems. Good agreement is observed between the experimental M_n^* values and the predictions of the code EUGENE. However, this code gives M_n^* values that are consistently lower than those predicted by other statistical model calculations. An alternative procedure is utilized to extract the amount of excitation energy of the composite system. In this approach, the input excitation energy in a standard model code is varied until the predicted M_n^* value matches the experimental value. The resulting excitation energies follow systematic trends with the estimated momentum transfer and the N/Z of the system. These patterns are also observed in reactions induced with other projectiles. (orig.)

[en] The author reports on hadroproduction of charm based on a sample of ∼ 750 D mesons. Charmed particles, produced in a thin segmented target of Si and W by a 340 GeV/c π beam and selected by a novel trigger with an enrichment factor of ∼ 15, are identified by the invariant mass of secondary vertices. Data were collected with the Ω' spectrometer at the CERN SPS supplemented by a silicon microstrip vertex detector. Assuming the parameterization σ(π^- N → DX) ∼ A^α where A is the atomic number, they find α = 0.89 ± 0.05 ± 0.05 for a data sample with an average x_P of 0.2. The x_F p perpendicular distributions of the charged D mesons are also described and the possibility of a leading effect is investigated. 10 refs., 7 figs

[en] We study the anisotropy effects measured with INDRA at GSI in central collisions of ¹²⁹Xe+^natSn at 50 A MeV and ¹⁹⁷Au+¹⁹⁷Au at 60, 80, 100 A MeV incident energy. The microcanonical multifragmentation model with non-spherical sources is used to simulate an incomplete shape relaxation of the multifragmenting system. This model is employed to interpret observed anisotropic distributions in the fragment size and mean kinetic energy. The data can be well reproduced if an expanding prolate source aligned along the beam direction is assumed. An either non-Hubblean or non-isotropic radial expansion is required to describe the fragment kinetic energies and their anisotropy. The qualitative similarity of the results for the studied reactions suggests that the concept of a longitudinally elongated freeze-out configuration is generally applicable for central collisions of heavy systems. The deformation decreases slightly with increasing beam energy