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Study of very heavy systems by means of INDRA: First evidence for a volume effect in the nuclear multifragmentation process; Etude de systemes tres lourds observes avec INDRA: Premiere mise en evidence d`un effet de volume dans le processus de multifragmentation nucleaire

Abstract

We present a study of Gd+U collisions at 36 AMeV measured with the INDRA multidetector, permitting almost complete detection (over 80%) of all the reaction products. We show that events exist which correspond to the multifragmentation of a single system comprising the majority of the nucleons for a cross-section of 2.6 mbarn, by isolating reactions for which the emitted fragments have lost all memory of the entrance channel. Such reactions correspond to neither the most central collisions nor the most isotropic events (in the fragments` momentum space), and therefore cannot be correctly distinguished from the dominant binary deeply-inelastic collisions using these criteria. An initial comparison of the selected data with a statistical code indicates that fragments are formed in a dilute, compact system, undergoing a self-similar expansion corresponding to a collective energy of between 1 and 1.5 MeV. Comparison with the same type of events observed in Xe+Sn collisions at 32 AMeV reveals the existence of a scaling law for the multifragmentation of systems of different mass at the same excitation energy per nucleon: fragment Z distributions are identical while their multiplicity increases proportionally to the mass of the multi-fragmenting system. This observation is interpreted as an experimental signal that  More>>
Authors:
Frankland, John David [1] 
  1. Inst. de Physique Nucleaire, Paris-11 Univ., 91 - Orsay (France)
Publication Date:
Dec 10, 1998
Product Type:
Thesis/Dissertation
Report Number:
IPNO-T-98-06
Reference Number:
SCA: 663450; PA: AIX-30:044663; EDB-99:104343; SN: 99002153185
Resource Relation:
Other Information: DN: 156 refs., 76 figs., 19 tabs.; TH: Theses (Ph.D); PBD: 10 Dec 1998
Subject:
66 PHYSICS; CHARGED PARTICLE DETECTION; FOUR-PI DETECTORS; GADOLINIUM 155 REACTIONS; MEV RANGE 10-100; MULTIPARTICLE SPECTROMETERS; NUCLEAR FRAGMENTATION; PARTICLE IDENTIFICATION; S CODES; URANIUM 238 TARGET
OSTI ID:
690197
Research Organizations:
Inst. de Physique Nucleaire, Paris-11 Univ., 91 - Orsay (France)
Country of Origin:
France
Language:
French
Other Identifying Numbers:
Other: ON: DE99635251; TRN: FR9903336044663
Availability:
INIS; OSTI as DE99635251
Submitting Site:
FRN
Size:
206 p.
Announcement Date:

Citation Formats

Frankland, John David. Study of very heavy systems by means of INDRA: First evidence for a volume effect in the nuclear multifragmentation process; Etude de systemes tres lourds observes avec INDRA: Premiere mise en evidence d`un effet de volume dans le processus de multifragmentation nucleaire. France: N. p., 1998. Web.
Frankland, John David. Study of very heavy systems by means of INDRA: First evidence for a volume effect in the nuclear multifragmentation process; Etude de systemes tres lourds observes avec INDRA: Premiere mise en evidence d`un effet de volume dans le processus de multifragmentation nucleaire. France.
Frankland, John David. 1998. "Study of very heavy systems by means of INDRA: First evidence for a volume effect in the nuclear multifragmentation process; Etude de systemes tres lourds observes avec INDRA: Premiere mise en evidence d`un effet de volume dans le processus de multifragmentation nucleaire." France.
@misc{etde_690197,
title = {Study of very heavy systems by means of INDRA: First evidence for a volume effect in the nuclear multifragmentation process; Etude de systemes tres lourds observes avec INDRA: Premiere mise en evidence d`un effet de volume dans le processus de multifragmentation nucleaire}
author = {Frankland, John David}
abstractNote = {We present a study of Gd+U collisions at 36 AMeV measured with the INDRA multidetector, permitting almost complete detection (over 80%) of all the reaction products. We show that events exist which correspond to the multifragmentation of a single system comprising the majority of the nucleons for a cross-section of 2.6 mbarn, by isolating reactions for which the emitted fragments have lost all memory of the entrance channel. Such reactions correspond to neither the most central collisions nor the most isotropic events (in the fragments` momentum space), and therefore cannot be correctly distinguished from the dominant binary deeply-inelastic collisions using these criteria. An initial comparison of the selected data with a statistical code indicates that fragments are formed in a dilute, compact system, undergoing a self-similar expansion corresponding to a collective energy of between 1 and 1.5 MeV. Comparison with the same type of events observed in Xe+Sn collisions at 32 AMeV reveals the existence of a scaling law for the multifragmentation of systems of different mass at the same excitation energy per nucleon: fragment Z distributions are identical while their multiplicity increases proportionally to the mass of the multi-fragmenting system. This observation is interpreted as an experimental signal that this multifragmentation originates in a bulk instability of low-density nuclear matter (spinodal region). A complete semi-classical microscopic calculation for the two reactions, including the formation and multifragmentation by spinodal decomposition of very heavy, low-density systems, reproduces very well not only the experimental fragment multiplicities and Z distributions but also their mean kinetic energies, as well as the size distributions of the largest fragments. (author) 156 refs., 76 figs., 19 tabs.}
place = {France}
year = {1998}
month = {Dec}
}