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Macroscopic description of the interaction between two complex nuclei

Description: Assuming that the particle number is large, and using the leptodermous idealization that the ratio of the surface thickness to the cube root of nuclear volume is very small, an attempt is made to give an account of the time evolution of the shape of a nuclear system. It is suggested that a one-body, dissipation dominated approach to nuclear dynamics should be a reasonable starting point. (SDF)
Date: September 1, 1975
Creator: Swiatecki, W.J.
Partner: UNT Libraries Government Documents Department

Strangeness production in relativistic nuclear collisions

Description: A review of strange particle production in heavy ion collisions from AGS to SPS energies is presented. Implications of the newest developments in understanding the collision dynamics and the role of strange particle production in the search for a new phase of matter, in both experimental and theoretical sectors, are discussed.
Date: January 1, 1998
Creator: Odyniec, G.J.
Partner: UNT Libraries Government Documents Department

New <sup>88</sup>Sr(n,<font face="symbol">g</font>)Astrophysical Reaction Rate from Resonance Analysis of New High-Resolution Neutron Capture and Transmission Data

Description: Because of its small cross section, the <sup>88</sup>Sr(n,<font face="symbol">g</font>) reaction is an important bottleneck during <i>s</i>-process nucleosynthesis. Hence, an accurate determination of this rate is needed to better constrain the neutron exposure in <i>s</i>-process models and to more fully exploit the recently discovered isotopic anomalies in certain meteorites. We have completed the resonance analysis of our new and improved measurements of the neutron capture and total cross sections for <sup>88</sup>Sr made at the Oak Ridge Electron Linear Accelerator (ORELA). We describe our experimental procedures and resonance analysis, compare our results to previous data, and discuss their astrophysical impact.
Date: August 30, 1999
Creator: Koehler, P.E.
Partner: UNT Libraries Government Documents Department

Multifragmentation at intermediate energy: Dynamics or statistics

Description: In this report the authors consider two contradictory claims that have been advanced recently: (1) the claim for a predominantly dynamical fragment production mechanism; and (2) the claim for a dominant statistical and thermal process. They present a new analysis in terms of Poissonian reducibility and thermal scaling, which addresses some of the criticisms of the binomial analysis.
Date: January 1, 1998
Creator: Beaulieu, L.; Phair, L.; Moretto, L.G. & Wozniak, G.J.
Partner: UNT Libraries Government Documents Department

Reducible emission probabilities and thermal scaling in multifragmentation

Description: Intermediate-mass-fragment multiplicity distributions for a variety of reactions at intermediate energies are shown to be binomial and thus reducible at all measured transverse energies. From these distributions a single binary event probability can be extracted that has a thermal dependence. A strong thermal signature is also found in the charge distributions. The {eta}-fold charge distributions are reducible to the {eta}-fold charge distributions through a simple scaling that is dictated by fold number and charge conservation.
Date: August 1, 1995
Creator: Moretto, L.G.; Phair, L. & Tso, K.
Partner: UNT Libraries Government Documents Department

Proposed solution to the {open_quotes}k{sub eff} of the world{close_quotes} problem

Description: In 1971 Whitesides posed a Monte Carlo (MC) problem which he called {open_quotes}computing the k{sub eff} of the world.{close_quotes} This problem is still troublesome today. The problem arose in MC studies of a 9 x 9 x 9 configuration of weakly coupled Pu spheres, initially identical, with the whole array surrounded by water. The MC eigenvalue for this array was .93. When the central sphere was replaced by another, just critical in isolation, the MC eigenvalue was still .93. Here we consider a model problem somewhat analogous to Whitesides`, and use it (1) to illustrate the difficulties in the simplest traditional MC approach, and (2) to explore an alternative approach.
Date: December 31, 1995
Creator: Gelbard, E.M. & Roussel, B.
Partner: UNT Libraries Government Documents Department

The equivalent fundamental-mode source

Description: In 1960, Hansen analyzed the problem of assembling fissionable material in the presence of a weak neutron source. Using point kinetics, he defined the weak source condition and analyzed the consequences of delayed initiation during ramp reactivity additions. Although not clearly stated in Hansen`s work, the neutron source strength that appears in the weak source condition corresponds to the equivalent fundamental-mode source. In this work, we describe the concept of an equivalent fundamental-mode source and we derive a deterministic expression for a factor, g*, that converts any arbitrary source distribution to an equivalent fundamental-mode source. We also demonstrate a simplified method for calculating g* in subcritical systems. And finally, we present a new experimental method that can be employed to measure the equivalent fundamental-mode source strength in a multiplying assembly. We demonstrate the method on the zero-power, XIX-1 assembly at the Fast Critical Assembly (FCA) Facility, Japan Atomic Energy Research Institute (JAERI).
Date: February 1, 1997
Creator: Spriggs, G.D.; Busch, R.D.; Sakurai, Takeshi & Okajima, Shigeaki
Partner: UNT Libraries Government Documents Department

Nuclear structure and reactions with stored nuclei

Description: The use of ion-storage rings is discussed for studies of nuclear reactions and structure, with emphasis on energetic beams of short- lived, radioactive nuclei. Aspects of internal versus external luminosity are considered as well as other issues connected with the inverse kinematics of reactions induced by a circulating beam of complex nuclei. Some of the physics motivation that is driving studies with radioactive beams is described.
Date: December 31, 1996
Creator: Henning, W.
Partner: UNT Libraries Government Documents Department

Event generator overview

Description: Due to their ability to provide detailed and quantitative predictions, the event generators have become an important part of studying relativistic heavy ion physics and of designing future experiments. In this talk, the author will briefly summarize recent progress in developing event generators for the relativistic heavy ion collisions.
Date: December 1, 1997
Creator: Pang, Y.
Partner: UNT Libraries Government Documents Department

Prompt muon-induced fission: A probe for nuclear friction in large-amplitude collective motion

Description: Excited muonic atoms in the actinide region may induce prompt fission by inverse internal conversion, i.e. the excitation energy of the muonic atom is transferred to the nucleus. The authors solve the time dependent Dirac equation for the muonic spinor wave function in the Coulomb field of the fissioning nucleus on a 3-dimensional lattice and demonstrate that the muon attachment probability to the light fission fragment is a measure of the nuclear energy dissipation between the outer fission barrier and the scission point.
Date: January 1, 1998
Creator: Oberacker, V.E.; Umar, A.S.; Wells, J.C.; Strayer, M.R.; Maruhn, J.A. & Reinhard, P.G.
Partner: UNT Libraries Government Documents Department

A threshold for dissipative fission

Description: The empirical domain of validity of statistical theory is examined as applied to fission data on pre-fission data on pre-fission neutron, charged particle, and {gamma}-ray multiplicities. Systematics are found of the threshold excitation energy for the appearance of nonstatistical fission. From the data on systems with not too high fissility, the relevant phenomenological parameter is the ratio of the threshold temperature T{sub thresh} to the (temperature-dependent) fission barrier height E{sub Bar}(T). The statistical model reproduces the data for T{sub thresh}/E{sub Bar}(T) < 0.26 {plus_minus} 0.05, but underpredicts the multiplicities at higher T{sub thresh}/E{sub Bar}(T) independent of mass and fissility of the systems.
Date: September 21, 1993
Creator: Thoennessen, M. & Bertsch, G. F.
Partner: UNT Libraries Government Documents Department

Source dimensions in ultrarelativistic heavy ion collisions

Description: Recent experiments on pion correlations, interpreted as interferometric measurements of the collision zone, are compared with models that distinguish a prehadronic phase and a hadronic phase. The models include prehadronic longitudinal expansion, conversion to hadrons in local kinetic equilibrium, and rescattering of the produced hadrons. The longitudinal radius measured in collisions of 200 GeV/u sulfur nuclei on a heavy target require the existence of a prehadronic phase which converts to the hadronic phase at densities around 0.8 GeV/fm{sup 3}. The transverse radii cannot be reproduced without introducing more complex dynamics into the transverse expansion.
Date: May 16, 1994
Creator: Herrmann, M. & Bertsch, G. F.
Partner: UNT Libraries Government Documents Department

Measuring sticking and stripping in muon catalyzed dt fusion with multilayer thin films

Description: The authors propose a direct measurement of muon sticking to alpha particles in muon catalyzed dt fusion at a high density. Exploiting the features of a multilayer thin film target developed at TRIUMF, the sticking is determined directly by detection of charged fusion products. Experimental separation of initial ticking and stripping may become possible for the first time. Monte Carlo simulations, as well as preliminary results of test measurements are described.
Date: December 1, 1995
Creator: Fujiwara, M.C.; Bailey, J.M. & Beer, G.A.
Partner: UNT Libraries Government Documents Department

CNI polarimetry and the hadronic spin dependence of pp scattering

Description: Methods for limiting the size of hadronic spin-flip in the Coulomb- Nuclear Interference. region are critically assessed. This work was presented at the High Energy Polarimetry Workshop in Amsterdam, Sept. 9, 1996 and the RHIC Spin Collaboration meeting in Marseille, Sept. 17, 1996.
Date: November 22, 1996
Creator: Trueman, T.L.
Partner: UNT Libraries Government Documents Department