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1.
《Radiation measurements》1995,25(1-4):257-260
The emission of fragments (A≥16) from reaction of 4He with 197Au has been studied at bombarding energy of 12.7 GeV. Policarbonate Makrofol in sandwich form was used as a detector. Fragments produced in the experiment were identified and an event by event model-free analysis was performed. The decay channels ending with one, two or more (three, four) fragments were detected. A classification scheme based on the multiplicity (MH) of heavy fragments (A≥40) was used in order to define multifragmentation (MH = 0), spallation (MH = 1) and fission (MH = 2) events. The various experimental features of the fragmentation process are discussed. 相似文献
2.
《Radiation measurements》1997,28(1-6):291-296
The processes of production of fragments Z 8 in the interactions of 12.7 GeV 4He with U, Pb, Au and Ag have been analyzed using the polycarbonate track detector Makrofol. A sandwich technique was used which enables direct evidence for multiple fragment emission by a single nucleus. The decay channels ending with one, two or more (three, four) fragments were detected. A classification scheme based on the multiplicity of heavy fragments MH (Z> 20) was used in order to identify events belonging to the different reaction channels. Cross sections, excitation energies and multiplicities of intermediate mass fragments (8 Z 20) have been evaluated for various reaction mechanisms. The experimental features of the fragmentation process have been analyzed as a function of the target mass. 相似文献
3.
《Radiation measurements》2003,36(1-6):313-316
The processes of production of heavy fragments in the fission mass region in the interaction of 0.65, 1.74, 5.1, 8.8 and 12.7 GeV 4He with 232Th have been analyzed using the polycarbonate track detector Makrofol in the form of a sandwich. The decay channels ending with one, two, or more (three, four) fragments were detected. We have analyzed the events in which at least one heavy fragment (Z>20) was registered. Fragments produced in the experiment were identified and an event-by-event model-free analysis was performed in order to separate different production mechanisms. We have identified the events produced in fission, deep spallation and fragmentation processes. The cross-sections and experimental features have been determined for the various reaction mechanisms, and their variation as a function of the incident energy has been investigated. 相似文献
4.
《Radiation measurements》2001,34(1-6):231-235
The fission processes from the interactions of 0.65, 1.74, 5.1, 8.8 and 12.7 GeV 4He with Pb have been analyzed using the polycarbonate track detector Makrofol in the form of a sandwich. The decay channels ending with one, two, or more (three, four) fragments were detected. We analyzed events in which only two heavy fragments (Z>20) are detected, irrespective of the existence of coincident intermediate mass fragments (8Z20). Using the correlation between the common observables which characterize fission events, we identified events originated from thermal (soft) fission and more violent processes. Cross sections, angular distributions and excitation energy have been determined for two fission mechanisms, and their variation as a function of the incident energy has been investigated. 相似文献
5.
Ž. Todorović S. Savović S. Jokić 《The European Physical Journal A - Hadrons and Nuclei》1998,2(3):295-300
The processes of production of fragments with Z≥ 8 in the interaction of 12.7 GeV 4He with U, Pb, Au and Ag have been analyzed using the polycarbonate track detector Makrofol. The sandwich technique was used
which enables direct observation of multiply charged fragment emission by a single nucleus. The decay channels ending with
one, two, or more (three, four) fragments were detected. A classification scheme based on the multiplicity of heavy fragments
with Z > 20 was used in order to identify the events belonging to the different reaction channels. The cross sections, excitation
energies and multiplicities of intermediate-mass fragments 8 ≤Z≤ 20 have been determined for the various reaction mechanisms, and their variation as a function of the target mass has been
investigated.
Received: 28 November 1997 / Revised version: 24 April 1998 相似文献
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S. Baba K. Hata S. Ichikawa T. Sekine Y. Nagame A. Yokoyama M. Shoji T. Saito N. Takahashi H. Baba I. Fujiwara 《Zeitschrift für Physik A Hadrons and Nuclei》1988,331(1):53-62
Evaporation-residue excitation functions for16O and12C+197Au reactions were measured by means of the activation technique. The competition between evaporation and fission of the compound nuclei was studied by comparing the observed evaporation-residue data with the published fission excitation functions. A newly devised analysis was applied in order to deduce a fission barrier height at a specified angular momentum and determine the relevant fissioning nucleus as well. We found the fission barriers to be 8.2 MeV for the211Fr nucleus at 16? and 8.2 MeV for the207At nucleus at 27?. 相似文献
8.
Mass asymmetry relaxation as manifested in fission and heavy ion-induced binary reactions is reviewed. In fission, the dynamics
is characteristic of a fully damped case and is well described by a stochastic theory. In heavy ion deep inelastic collisions
and quasi-fission, on the other hand, the relaxation is incomplete giving rise to the possibility of studying its time evolution. 相似文献
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M. F. Rivet B. Gatty H. Guillemot B. Borderie R. Bimbot I. Forest J. Galin D. Gardes D. Guerreau M. Lefort X. Tarrago B. Tamain L. Novicki 《Zeitschrift für Physik A Hadrons and Nuclei》1982,307(4):365-373
rgy of light charged-particles has been measured in coincidence with one or two fission fragments in the reaction20Ne+197Au at a bombarding energy of 13 MeV/u. The fission cross section was found equal to 1,340±260 mb. Assuming that it represents the totality of the fusion cross section, the critical valuel c is deduced equal to 93±9?, higher thanl Bf=0=74 in the rotating liquid drop model. The main emission source for protons and alpha particles seems to be a thermally equilibrated composite system. The competition between fission and charged particle emission is unexpected in the frame of the statistical treatment. A high energy component is observed in the forward direction. These results correspond to the first step of a study programme on the evolution of nucleus-nucleus collisions between 10 and 100 MeV per nucleon. 相似文献
12.
The recoil energies of24Na produced in Cu, Ag and Au and of a series of fragments produced in Cu irradiated with 800 MeV bremsstrahlung have been measured in directions forward, backward and perpendicular to the beam using the thick target-thick catcher method. Comparison of the measured values with theoretical calculations indicates that24Na is produced through fission in Ag and Au and that fission is competing with spallation even in Cu. 相似文献
13.
Ralf P. Averbeck 《Czechoslovak Journal of Physics》1995,45(7-8):637-643
A systematic study of neutral meson production in heavy-ion reactions at 2 GeV/u was started with a12C+12C experiment using the photon spectrometer TAPS. Special emphasis is put on the possible observation of the-meson in a heavy-ion reaction exploiting the decay channel 0.Presented at the International School-Workshop Relativistic Heavy-Ion Physics, Prague (Czech Republic), 19–23 September 1994. 相似文献
14.
Intermediate mass fragments emitted in the reaction Ag+14N at 100, 160 and 250 MeV bombarding energy
L.G. Moretto S.K. Kataria R.C. Jared R. Schmitt S.G. Thompson 《Nuclear Physics A》1975,255(2):491-508
The fragments produced in the reaction between a 14N beam of various energies and a natural Ag target have been studied. The atomic numbers of the fragments have been identified up to Z = 17 by means of a E-ΔE counter telescope. The cross sections, the kinetic energy distributions as well as the angular distributions have been measured for each atomic number. The kinetic energy distributions show two components: a high-energy component (quasi-elastic), prevailing at angles close to the grazing angles and for atomic numbers close to Z = 7, and a low-energy component (relaxed), at energies close to the Coulomb repulsion energy, present at all angles and for all the Z. A detailed study of the relaxed components of the kinetic energy seems to account for both them means and the widths of these distributions on a purely statistical basis. The cross sections of the relaxed components appear to be quite large at low Z and to decrease rapidly to a fairly constant value in the region of 10 ≦ Z ≦ 17. A marked even-odd alternation in the cross sections is observed. The angular distributions are strongly forward peaked for Z < 7. For Z > 7 the forward peaking decreases rapidly until, for Z > 13, the limiting form 1/sinθ is attained. Evidence for the existence of a diffusion process along the mass asymmetry coordinate is discussed. 相似文献
15.
We present a systematic analysis on the helium projectile fragments produced from 10.6 A GeV197Auemulsion interactions in an experiment conducted at the Brookhaven AGS. Total charge changing and partial production cross-sections are measured experimentally on the basis of helium multiplicity. The multiplicity distribution of helium fragments which are produced collectively obey a KNO scaling. The transverse momentum distribution of these particles indicates that they are produced from two different independent sources.We are thankful to the BNL technical staff and specially to Dr. D. Beavis for his help in the exposure of emulsion stacks. Thanks are due to Profs. Y. Takahashi and G. Romano for their help in the preparation and development of the emulsion stacks. We appreciate the discussions with Prof. H. Stocker and J. Aichelin. This work was supported by D.O.E. under Grant No. DE-FGO2-90ER 40566. 相似文献
16.
F. Laue I. Böttcher M. Debowski A. Förster E. Grosse P. Koczoń B. Kohlmeyer M. Mang M. Menzel L. Naumann H. Oeschler F. Pühlhofer E. Schwab P. Senger Y. Shin J. Speer H. Ströbele C. Sturm G. Surówka F. Uhlig A. Wagner W. Waluś 《The European Physical Journal A - Hadrons and Nuclei》2000,9(3):397-410
Production cross-sections of charged pions, kaons and antikaons have been measured in C+C and C+Au collisions at beam energies
of 1.0 and 1.8 AGeV for different polar emission angles. The kaon and antikaon energy spectra can be described by Boltzmann
distributions whereas the pion spectra exhibit an additional enhancement at low energies. The pion multiplicity per participating
nucleon M(π+)/<A
part> is a factor of about 3 smaller in C+Au than in C+C collisions at 1.0 AGeV whereas it differs only little for the C and the
Au target at a beam energy of 1.8 AGeV. The K+ multiplicities per participating nucleon M(K+)/ <A
part> are independent of the target size at 1 AGeV and at 1.8 AGeV. The K- multiplicity per participating nucleon M(K-)/ <A
part> is reduced by a factor of about 2 in C+Au as compared to C+C collisions at 1.8 AGeV. This effect might be caused by the
absorption of antikaons in the heavy target nucleus. Transport model calculations underestimate the K-/K+ ratio for C+C collisions at 1.8 AGeV by a factor of about 4 if in-medium modifications of K-mesons are neglected.
Received: 10 December 1999 / Accepted: 14 November 2000 相似文献
17.
Akiba Y Beavis D Beery P Britt HC Budick B Chasman C Chen Z Chi CY Chu YY Cianciolo V Cole BA Costales JB Crawford HJ Cumming JB Debbe R Engelage J Fung SY Gonin M Gushue S Hamagaki H Hansen O Hayano RS Hayashi S Homma S Kaneko H Kang J Kaufman S Kehoe WL Kurita K Ledoux RJ Levine MJ Miake Y Morrison DP Morse RJ Moskowitz B Nagamiya S Namboodiri MN Nayak TK Olness J Parsons CG Remsberg LP Roehrich D Rothschild P Sakurai H Sangster TC Seto R Soltz R Stankus P Steadman SG Stephans GS Sung T 《Physical review letters》1996,76(12):2021-2024
18.
S.P. Avdeyev V.A. Karnaukhov W.D. Kuznetsov L.A. Petrov V.K. Rodionov A.S. Zubkevich H. Oeschler O.V. Bochkarev L.V. Chulkov E.A. Kuzmin A. Budzanovski W. Karcz M. Janicki E. Norbeck A.S. Botvina W.A. Friedman W. Nörenberg G. Papp 《The European Physical Journal A - Hadrons and Nuclei》1998,3(1):75-83
Multiple emission of intermediate-mass fragments has been studied for the collisions p + Au at 2.16, 3.6 and 8.1 GeV with
the FASA setup. The mean IMF multiplicities for events with at least one IMF are equal to 1.7, 1.9 and 2.1 (±0.2) respectively.
The multiplicity, charge distributions and kinetic energy spectra of IMF are described in the framework of a intranuclear
cascade model followed by the statistical multifragmentation model. However, between the two parts of the calculation the
excitation energies and the residual masses and charges are modified to take into account the losses during expansion. The
results support a scenario of true thermal multifragmentation of a hot and expanded target spectator.
Received: 15 December 1997 / Revised version: 24 April 1998 相似文献
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R. Tenzer N. Grün W. Scheid 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,11(3):347-353
Total and differential cross-sections for the production of free electron-positron pairs are calculated for the reactions
Au79+ (10.8 GeV/u) on Cu29+, Ag47+ and Au79+. The methods used are the semiclassical approach and the solution of the time-dependent Dirac equation by a coupled channel
method with free wavepakets describing the created fermions. The obtained total cross-sections are in good agreement with
the experimental data. The differential cross-sections give informations about the correlation between the electron and positron.
Received 21 December 1999 and Received in final form 6 March 2000 相似文献