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Fission throughout the periodic table

Description: The dualistic view of fission and evaporation as two distinct compound nucleus processes is substituted with a unified view in which fission, complex fragment emission, and light particle evaporation are seen as different aspects of a single process. 47 refs., 22 figs.
Date: April 1, 1989
Creator: Moretto, L.G. & Wozniak, G.J.
Partner: UNT Libraries Government Documents Department

The decay of hot nuclei

Description: The formation of hot compound nuclei in intermediate-energy heavy ion reactions is discussed. The statistical decay of such compound nuclei is responsible for the abundant emission of complex fragments and high energy gamma rays. 43 refs., 23 figs.
Date: November 1, 1988
Creator: Moretto, L.G. & Wozniak, G.J.
Partner: UNT Libraries Government Documents Department

Proceedings of the 8th high energy heavy ion study

Description: This was the eighth in a series of conferences jointly sponsored by the Nuclear Science Division of LBL and the Gesellschaft fuer Schwerionenforschung in West Germany. Sixty papers on current research at both relativistic and intermediate energies are included in this report. Topics covered consisted of: Equation of State of Nuclear Matter, Pion and High Energy Gamma Emission, Theory of Multifragmentation, Intermediate Energies, Fragmentation, Atomic Physics, Nuclear Structure, Electromagnetic Processes, and New Facilities planned for SIS-ESR. The latest design parameters of the Bevalac Upgrade Proposal were reviewed for the user community. Also, the design of a new electronic 4..pi.. detector, a time projection chamber which would be placed at the HISS facility, was presented.
Date: January 1, 1988
Creator: Harris, J.W. (ed.) & Wozniak, G.J. (ed.)
Partner: UNT Libraries Government Documents Department

Quad time-to-amplitude converter (LBL No. 21X9191 P-1)

Description: Four Time-to-Amplitude Converters (TACs) have been designed and packaged in a single-width NIM module. These moderate-resolution units (/approximately/0.1/percent/ full scale) are ideal for applications where large numbers of TACs are required because of the high packing density provided by the quad configuration. Full-scale ranges of 100 ns, 300 ns, 1 ..mu..s, and 3 ..mu..s are switch selectable. Read out of each unit may be either internally or externally controlled. All units may be read out at the same time via a common /open quotes/group readout/close quotes/. The readout time is adjustable between 2 and 20 ..mu..s. An LED indicates a valid event. 4 figs.
Date: February 1, 1988
Creator: McDonald, R.J.; Landis, D.A. & Wozniak, G.J.
Partner: UNT Libraries Government Documents Department

Angular-momentum-bearing modes in fission

Description: The angular-momentum-bearing degrees of freedom involved in the fission process are identified and their influence on experimental observables is discussed. The excitation of these modes is treated in the ''thermal'' limit, and the resulting distributions of observables are calculated. Experiments demonstrating the role of these modes are presented and discussed. 61 refs., 12 figs.
Date: March 1, 1989
Creator: Moretto, L.G.; Peaslee, G.F. & Wozniak, G.J.
Partner: UNT Libraries Government Documents Department

Businaro-Gallone transition as observed in complete charge distributions from compound nucleus decay

Description: The compound nucleus emission of fragments covering the entire mass range has been observed in reactions exploiting both ordinary and reverse kinematics. The compound nucleus mechanism has been inferred from full momentum transfer, angular independence of the fragment center of mass kinetic energies and excitation functions. The drastic change in the observed charge distributions as one crosses A approx. = 100 illustrates the effect of the Businaro-Gallone point.
Date: August 1, 1984
Creator: Moretto, L.G.; Wozniak, G.J. & Sobotka, L.G.
Partner: UNT Libraries Government Documents Department

Quad nanosecond delay module

Description: Four nanosecond (ns) delay units have been designed to fit in a single-width NIM module. This module is particularly suited for use in conjunction with quad constant fraction timing discriminators (CFTDs) since it has four delay units that can be placed adjacent to the four units of the CFTD. A series of different length cables connected via DIP toggle switches provide delays of 0.60 ns in 4 ns increments. Thus, the CFTD delay can be optimized for pulses of different rise times from approx.10-100 ns. Design work for the PC board and silkscreening of the front panel were done with the MacDraw program on the Apple Mackintosh computer and printed with the Lasewriter printer. 6 refs.
Date: April 1, 1986
Creator: McDonald, R.J.; Hunter, J.B. & Wozniak, G.J.
Partner: UNT Libraries Government Documents Department

TIME-WALK CHARACTERISTICS OF AN IMPROVED CONSTANT FRACTION DISCRIMINATOR

Description: A modification to a constant fraction discriminator design published earlier makes the observed time walk less than 30 ps over an input voltage range of 0.15 to 2.5 V. This performance makes time-walk corrections unnecessary in many situations.
Date: September 1, 1980
Creator: Wozniak, G. J.; Richardson, L. W. & Maier, M. R.
Partner: UNT Libraries Government Documents Department

Do phase transitions survive binomial reducibility and thermal scaling?

Description: First order phase transitions are described in terms of the microcanonical and canonical ensemble, with special attention to finite size effects. Difficulties in interpreting a `caloric curve` are discussed. A robust parameter indicating phase coexistence (univariance) or single phase (bivariance) is extracted for charge distributions. 9 refs., 4 figs.
Date: May 1, 1996
Creator: Moretto, L.G.; Phair, L. & Wozniak, G.J.
Partner: UNT Libraries Government Documents Department

Phase transitions in nuclear physics

Description: A critical overview of the low energy phase transitions in nuclei is presented with particular attention to the 2nd (1st) order pairing phase transitions, and to the 1st order liquid-vapor phase transition. The role of fluctuations in washing out these transitions is discussed and illustrated with examples. A robust indicator of phase coexistence in multifragmentation is presented.
Date: August 1, 1997
Creator: Moretto, L.G.; Phair, L. & Wozniak, G.J.
Partner: UNT Libraries Government Documents Department

Surface instabilities and nuclear multifragmentation

Description: Central heavy-ion collisions, as described by a Boltzman-Nordheim-Vlasov calculation, form nuclear disks that break up into several fragments due to surface instabilities of the Rayleigh-Taylor kind. We demonstrate that a sheet of liquid, nuclear or otherwise, stable in the limit of infinitely sharp surfaces, becomes unstable due to surface-surface interactions. The onset of this instability is determined analytically. The relevance of these instabilities to nuclear multifragmentation is discussed.
Date: March 1, 1992
Creator: Moretto, L.G.; Tso, K.; Colonna, N. & Wozniak, G.J.
Partner: UNT Libraries Government Documents Department

Complex fragment emission in binary and multifragment decay of very hot nuclear systems

Description: Low-energy compound nucleus emission of complex fragments in the reaction {sup 63}Cu + {sup 12}C is used to infer the associated ridge-line potential. Compound binary emission of complex fragments at higher energies is illustrated for a variety of reactions. Complex fragment emission from 35 and 40 MeV/N {sup 139}La + {sup 12}C, {sup 27}Al, {sup 40}Ca and {sup 51}V reactions has been studied. Multifragment events from these reactions were assigned to sources characterized by their energy and mass through the incomplete-fusion-model kinematics. Excitation functions for the various multifragment channels appear to be nearly independent of the system and bombarding energy. Preliminary comparisons of the data with sequential-statistical-decay calculations are discussed.
Date: July 1, 1990
Creator: Moretto, L.G.; Blumenfeld, Y.; Delis, D. & Wozniak, G.J.
Partner: UNT Libraries Government Documents Department

Binary and multifragment decay of very hot nuclei

Description: Compound binary emission of complex fragments is illustrated for a variety of reactions. Complex fragment emission from 35 and 40 MeV/N {sup 139}La + {sup 12}C, {sup 27}Al, {sup 40}Ca and {sup 51}V reactions has been studied. Multifragment events from these reactions were assigned to sources characterized by their energy and mass through the incomplete-fusion-model kinematics. Excitation functions for the various multifragment channels appear to be nearly independent of the system and bombarding energy. Preliminary comparisons of the data with sequential-statistical-decay calculations are discussed. 14 refs., 7 figs.
Date: May 1, 1990
Creator: Moretto, L.G.; Blumenfeld, Y.; Charity, R.J. & Wozniak, G.J.
Partner: UNT Libraries Government Documents Department

Complex fragment production in 50 MeV/A sup 197 Au + sup 12 C, sup 27 Al, and @Cu reactions

Description: Complex fragment (Z>6) production was studied in three reverse- kinematic reactions: 50 MeV/A {sup 197}Au + {sup 12}C, {sup 27}Al, and {sup nat}Cu. Typical inclusive cross sections are shown, as well as exclusive results for 2- , 3-, and higher-fold events. Reconstructing the source velocity of these fragments and using a simple incomplete fusion model gives a reliable measure of the impact parameter and excitation energy of the reactions producing these fragments. A clear progression from peripheral (cold) events to more central (very hot) events is seen as function of source velocity. The primary production of fragments in the {sup 197}Au + {sup 12}C and {sup 27}Al reactions is consistent with statistical emission from a thermalized source, up to approximately 5 MeV/A of excitation energy. For the {sup nat}Cu target, another significant source of fragment emission is observed. 20 refs., 15 figs.
Date: April 1, 1990
Creator: Peaslee, G.F.; Moretto, L.G. & Wozniak, G.J.
Partner: UNT Libraries Government Documents Department

Quad delay gate generator (LBL No. 21X6691 P-2)

Description: A quad delay gate generator has been designed and packaged in a single-width NIM module. Both delay times and gate widths may be set continuously from 25 ns to 120 ..mu..sec. In normal operation, the gate follows the delay time unless a ''stop'' pulse cuts it short. Alternatively, the module may be operated in a bipolar mode, where the delay time is set by the input ''start'' pulse and reset by the input ''stop'' pulse. Modes and coarse time ranges are set via an octal DIP switch on the front panel. Fine adjustments of the delay and gate width are made via two twenty-turn potentiometers. Stability over a several day period was measured at approx. 250 ps on the 120 ns full scale range. LEDs gives a visual indication of both the input rate and the dead time.
Date: August 1, 1986
Creator: McDonald, R.J.; Maier, M.R.; Landis, D.A. & Wozniak, G.J.
Partner: UNT Libraries Government Documents Department

The end of incomplete fusion and the decoupling of the fireball as seen from complex fragment emission

Description: The incomplete fusion process is affected by the entrance channel asymmetry as well as by the bombarding energy. In the first part of the paper, the role of entrance channel mass asymmetry is explored by characterizing the resulting complex fragment sources in terms of their velocity, charge and excitation energy. In the second part evidence is given about the possible demise of incomplete fusion and the onset of the fireball regime from the anomalous charge and angular distributions of the emitted complex fragments. Complete ternary events are analyzed and discussed in terms of sequential binary decay. 14 refs., 8 figs.
Date: April 1, 1989
Creator: Moretto, L.B.; Bowman, D.R.; Colonna, N. & Wozniak, G.J.
Partner: UNT Libraries Government Documents Department

Angular momentum and linear momentum transfer in intermediate-energy heavy-ion reactions

Description: In order to explore the changing role of angular momentum transfer to the heavy target-like fragment in heavy-ion reactions, the gamma-ray multiplicities associated with projectile residues were measured in the reaction of /sup 20/Ne with /sup 181/Ta in the energy range of 7.5 to 42 MeV/nucleon. From the gamma-ray multiplicities, the intrinsic spin of the target-like nucleus was determined and corrected for the spin removed by evaporated particles. Comparisons of the measured intrinsic spin with that expected from the missing linear momentum were found to be good at low energies but failed around a bombarding energy of 17 MeV/nucleon. From the results of these studies we infer that angular momentum and therefore linear momentum is being carried away in significant amounts by particles which were not detected.
Date: November 1, 1981
Creator: Wozniak, G.J.; Hsu, C.C.; Morrissey, D.J.; Richardson, L.W. & Moretto, L.G.
Partner: UNT Libraries Government Documents Department

Binary complex fragment emission and multifragmentation from very hot nuclei

Description: Complex fragments at low and intermediate energies originate mostly from the binary decay of a compound nucleus formed in either complete or incomplete fusion. With increasing bombarding energy incomplete fusion should terminate. Evidence of this occurrence is given. As the excitation energy increases, multifragment decay becomes prevalent. The sources of ternary and quaternary events, characterized in terms of their velocity and total charge, do not seem to differ from that of binary events. 9 refs., 13 figs.
Date: October 1, 1989
Creator: Moretto, L.G. & Wozniak, G.J.
Partner: UNT Libraries Government Documents Department

Thermal and statistical properties of nuclei and nuclear systems

Description: The term statistical decay, statistical or thermodynamic equilibrium, thermalization, temperature, etc., have been used in nuclear physics since the introduction of the compound nucleus (CN) concept, and they are still used, perhaps even more frequently, in the context of intermediate- and high-energy heavy-ion reactions. Unfortunately, the increased popularity of these terms has not made them any clearer, and more often than not one encounters sweeping statements about the alleged statisticity of a nuclear process where the statistical'' connotation is a more apt description of the state of the speaker's mind than of the nuclear reaction. It is our goal, in this short set of lectures, to set at least some ideas straight on this broad and beautiful subject, on the one hand by clarifying some fundamental concepts, on the other by presenting some interesting applications to actual physical cases. 74 refs., 38 figs.
Date: July 1, 1989
Creator: Moretto, L.G. & Wozniak, G.J.
Partner: UNT Libraries Government Documents Department

Fission along the mass asymmetry coordinate: an experimental evaluation of the conditional saddle masses and of the Businaro-Gallone point

Description: The importance of empirically determining the ridge line of conditional saddle points is discussed in view of the recent liquid drop model refinements, like diffuseness and finite range. Two series of experiments are presented. The first series involves the complex fragment emission from compound nuclei resulting from the /sup 3/He + Ag reaction. Kinetic energy distributions and excitation functions are shown, and the conditional barriers are obtained over a range of atomic numbers. In the second series, reverse kinematic reactions like Ge, Nb, La + Be, C are studied. The fragments emitted cover the entire Z range, from Z = 1 to symmetric splitting. Their origin from a full momentum transfer intermediate is shown. From the complete charge distributions it is possible to conclude that the Businaro-Gallone transition is observed. 15 references.
Date: December 1, 1984
Creator: Moretto, L.G.; McMahan, M.A.; Sobotka, L.G. & Wozniak, G.J.
Partner: UNT Libraries Government Documents Department