共查询到20条相似文献,搜索用时 31 毫秒
1.
2.
Temperatures and Excitation Energies of Hot Nuclei in Reactions of 40Ar+natAg,209Bi at MeV/u 下载免费PDF全文
Yin Shuzhi Jin Weiyang Zhang Chun Jin Genming Zheng Jiwen Wu Enjiu Tan Jilian Li Zuyu Wang Sufang Song Mingtao Wu Heyu He Zhiyong Jiang Dongxing Qian Xing 《中国物理C(英文版)》1997,21(8):680-685
Coincidence measurements of fission fragment and light charged particle have been perfotrmed for the reactions of 40Ar+natAg,209Bi at E/A=25MeV using 4 PPAC and 11 sets of ΔE-E telescopes.Angular correlations of fission fragment were ploted as a function of the folding angle between the two detected fission fragments.The linear momentum transfer distributions were derived by measuring angular correlations.The backward spectra of light particles detected in coincidence with fission fragments having different average〈LMT〉are analyzed with Maxwell distribution.After some corrections the initial temperatures of the hot nuclei are determined from the energy spectra.The excitation energies corresponding to the different average〈LMT〉are obtained considering the reaction Q values and pre-equilibrum emission.In the central collision of the 40Ar+natAg,209Bi reactions,excitation energies are measured to be about 4.2MeV/u,2.4MeV/u and temperatures about 6.1MeV,5.5MeV,respecdvely.In semi-central collision,excitaionen energies are measured to be about 3.5MeV/u,1.9MeV/u and temperatures about 5.8MeV,4.8MeV respectively. 相似文献
3.
Light Particle and Complex Fragments Emission from 12C Induced Reactions on 58Ni,64Ni at E/A=46.2MeV 下载免费PDF全文
YIN Shu-Zhi ZHAN Wen-Long ZHU Yong-Tai GUO Zhong-Yan FENG En-Pu XI Hong-Fei ZHOU Jian-Qun LIU Guan-Hua 《中国物理C(英文版)》1992,16(4):364-369
Energy spectra of light charged particles and complex fragments emitted in the interaction of 46.2MeV/u 12C with different target 58Ni,64Ni,12C,197Au and 209Bi have been measured by telescopes,consisting of CsI(Tl) and surface barrier detector stacks.These telescopes for light charged particles and complex fragments have good energy resolution and mass identification.The inclusive data have been analysed within a moving source parametrization.The complex fragment yields from different targets have been compared at several angles.The systematic variation of deduced isotope yields ratios with different reaction systems is used to detemine the N/Z degree of freedom equilibration of the system achieved. 相似文献
4.
He Zhiyong Li Zuyu Duan Limin Zhang Baoguo Dai Guangxi Jin Genming Fu Yanbiao Wang Hongwei 《中国物理C(英文版)》1998,22(1):13-19
Light charged particles and complex fragments have been measured at forward angles in coincidence with two fission fragments for 40Ar+159Tb reaction at 25MeV/u. These three-body coincident events were sorted as a function of the impact parameter using linear momentum transfer and total transverse momenta methods. Equilibrium statistical emissions of complex fragments from quasi-target residues accompanied by non-equilibrium mid-rapidity components were found to dominate in central collisions, while projectile fragmentations were found to dominate in peripheral collision. Three components of complex-fragments from quasi-target, quasi-projectile and mid-rapidity soures were found in mid-central collision. 相似文献
5.
Energy Correlations between Fragments and Light Charged Particles in Reaction of 25MeV/u 40Ar+115In 下载免费PDF全文
WANG Jin-Chuan ZHAN Wen-Long GUO Zhong-Yan XI Hong-Fei ZHOU Jian-Qun ZHAO You-Xiong 《中国物理C(英文版)》2001,25(2):115-120
The correlations between the emitted fragments at θlab=15°and the light charged particles(LCPs) at the close geometry configuration in the reaction of 25MeV/u 40Ar+115In were measured. The energy correlations between fragments (4≤Zf≤14) and the LCPs including proton, deuterium, tritium and a particle as well as the energy spectra of the LCPs were obtained. The result shows the existence of sequential decay mechanism. It is found that the peak position of angular correlation is at the small angles and the most probable correlation angle is at 2°or so; The peak positions of the two components in the energy spectra of LCPs increase gradually with the mass of correlated partner; The lighter primaly products are more easier to be excited and decay to IMFs and the LCPs. In the Sequential decay, the yield of the LCPs with more heavier mass is higher than that of the lighter LCPs. The result reveals that the total correlation yield ratios summed over the fragments of Zf=4—14 are 1: 1. 3: 1. 78: 7. 57 for proton, deuterium, tritium and a particles, respectively. 相似文献
6.
Angular distributions of light charged particles from 252Cf fission in the ranges 0–46° and 134–180°
A.J. Kordyasz E. Piasecki L. Nowicki P. Koczoń J. Sobolewski M. Kisieliński W. Czarnackif 《Nuclear Physics A》1985,439(1):28-44
Alpha particles, tritons, deuterons and protons accompanying 252Cf fission were registered in coincidence with both fission fragments by means of a system containing two-dimensional position-sensitive silicon detectors. Angular distributions, kinetic energy spectra of light charged particles as well as mass distributions of fission fragments in coincidence with light charged particles were measured. The experimental results are compared with some theoretical models. 相似文献
7.
RADIOCHEMICAL INVESTIGATION OF MASS DISTRIBUTIONS IN 12C-INDUCED FISSION OF 209Bi AND 238U 下载免费PDF全文
The yields of 15 and 17 fission, products have been obtained by radiochemical determinations in 12C-induced fission of 209Bi and 238U respectively. From these data, the mass distributions of fission fragments are calculated based on three different hypotheses for the charge distribution. The results seem to indicate that the hypothesis of equal charge displacement gives the best fit to the Gaussian distribution for the masses of the fission fragments. By comparison with the mass distributions for 209Bi (12C, f), 238U(12C, f) and 197Au(12C, f) in our early measurement, we find that for fission parameter Z2/A>37, the width of the mass distributions increases with Z2/A rapidly. 相似文献
8.
Azimuthal Correlations of Fragments with Light Charged Particles in Reaction of 25MeV/u 40Ar+115In 下载免费PDF全文
WANG Jin-Chuan ZHAN Wen-Long GUO Zhong-Yan XI Hong-Fei ZHOU Jian-Qun ZHAO You-Xiong 《中国物理C(英文版)》2001,25(1):16-22
The large angle correlations for in-plane and out-of-plane have been measured for the pairs of the fragments and light charged particles (LCPs) in the reaction of 25MeV/u 40Ar+115In. The azimuthal correlation functions and the azimuthal asymmetry factors were obtained. The azimuthal correlation functions of all pairs between fragments and a particles are of minimum value in φ=90°plane. It indicates that the LCPs and fragments formed in the reaction exhibit an enhanced emission in the reaction plane due to collective rotation-like effect induced by attractive mean field. The more heavier the masses of the coincident LCPs and fragments are, the more stronger the left-right asymmetries of the coincident particles with respect to the beam direction in the reaction plane are, the more preferential the particle emission to the direction opposite to the coincident reaction products is. Along with the increase of the mass of the coincident LCPs and fragments, the influences of the sequential decay and particle final state interactions on the azimuthal correlation functions of the correlated pairs in the φ=0° plane decrease and vanish at last, the collective rotation-like effect is enhanced, and the azimuthal asymmetries increase. 相似文献
9.
WU He-Yu DAI Guang-Xi CAI Wei QI Yu-Jin YAN De-Hong ZHANG Bao-Guo DANG Bing-Rong LUO Qin-Zheng QIAN Xing WEN Wan-Xin 《中国物理C(英文版)》1993,17(8):680-684
Alternative layers of target material,which were prepared by evaporating 209Bi on the surface of mica foils,were irradiated with 12C ions.Ternary fission events in which three fragments of comparable mass were produced in 2525-47.5MeV/A 12C+209Bi reaction,were recorded by the mica detectors with 2π geometry.The observed probability ratio of ternary fission relative to binary fission in 2π geometry was modified to 4π geometry spatial in terms of the Monte Carlo method.The values of ratioes increase with the bombarding energy,and are compared with the calculation result of the cascade fission model. 相似文献
10.
Emission Time Measurements of Light Particles from 40Ar+197Au Collisions in Intermediate Energies 下载免费PDF全文
He Zhiyong Duan Limin Li Zuyu Jin Genming Luo Qingzheng Wu Heyu Zhang Baoguo Wen Wanxin Qi Yujin Dang Bingrong Dai Guangxi 《中国物理C(英文版)》1996,20(1):8-12
Particle-particle correlation functions have been measured for 40Ar+197Au collisions at E=25 MeV/u.Emission time of light particles has been extracted from correlation functions using the three-body trajectory model.The average emission time varies with the energy of particles. It decreases from about 300 fm/c for low energy particles to about 100fm/c for energetic particles. 相似文献
11.
Ternary fission in ^197Au+^197Au collisions at 15 A MeV is investigated by using the improved quantum molecular dynamical (ImQMD) model. The experimental mass distributions for each of the three fragments are reproduced for the first time without any freely adjusting parameters. The mechanisms of ternary fission in central and semicentral collisions are dynamically studied. In direct prolate ternary fission, two necks are found to be formed almost simultaneously and rupture sequentially in a very short time interval. Direct oblate ternary fission is a very rare fission event, in which three necks are formed and rupture simultaneously, forming three equally sized fragments along space-symmetric directions in the reaction plane. In sequential ternary fission a binary division is followed by another binary fission event after hundreds of fm/c. 相似文献
12.
ANGULAR DISTRIBUTIONS OF FISSION FRAGMENTS IN INTERACTIONS OF 12C IONS WITH VARIOUS TARGETS 下载免费PDF全文
Angular distributions of fission fragments were measured for a series of compound nuclei formed in the bombardment of 169Tm,175Lu,181Ta,W,Re,Pt,197Au,Pb and 209Bi by 12C ions with mica track detectors and gold surface barrier silicon detectors.All the measured angular distributions can be fitted satisfactorily by the theoretical formula based on saddle point model.The variation trend for K2 with the excitation energy increasing was given at various ranges of the fission parameter Z2/A. 相似文献
13.
THE MEASUREMENT OF COMPLETE FUSION CROSS-SECTIONS FOR THE REACTIONS 12C+27Al, 12C+209Bi AND 14N+Pb 下载免费PDF全文
Mica track detectors were used for the measurement of evaporation residues and fission fragments of compound nuclei formed in 12C+27Al, 12C+209Bi and 14N+Pb reactions. The complete fusion cross-sections and excitation functions were then obtained. By using the sharp cut-off model approximation, the values of the critical angular momenta were extracted from the complete fusion cross-sections. The results obtained were compared with the calculations based on current theories for critical angular momentum; they were found to agree within experimental uncertainties. 相似文献
14.
Some experimental results measured for light emission particles with Z≤2 from 12C+64Ni reaction at E(12C)=69, 56MeV are reported. A comparison between moving source model calculation and proton's spectra have been performed. Extracted parameters of the source with faster velocity are agreement with the systematic values found before. The composite particle energy spectra of α, 3He and D were analyzed by coalescence model. 相似文献
15.
In order to treat the waste material of nuclear power and develop new type of clean nuclear power,it is necessary to measure the neutron adta of long half life nuclei existed in the waste material.The prompt spontaneous neutron spectrum is one of the most important unclear data for new type nuclear power facilities as well as for understanding the mechanism of fission neutron emission.The measurements of 248Cm/252Cf spontaneous prompt fission neutron spectrum in the neutron energy range form 200keV to 12MeV wer performed by using TOF method.A micro-ionization chamber aws used as fission fragment detector and stibene crystal as neutron detector.The flying paths of neutrons for the measurements were 30cm,50cm and 100cm respectively.The spontaneous prompt fission neutron spectrum of 248Cm was fitted by the Maxwellian distribution and the temperature was determined as (1.401±0.006)MeV in the corresponding neutron energy range. 相似文献
16.
Fission Fragment Angular Correlation in the Reaction Induced by 84.0MeV 16O Bombarded 238U 下载免费PDF全文
QIAN Xing ZHANG Huan-Qiao LIU Zu-Hua XU Jin-Cheng CHEN Shao-Lin XU Kan LU Li-Xin 《中国物理C(英文版)》1993,17(2):173-178
Fission fragment angular distribution and angular correlation in the reaction induced by 84.0MeV 16O bombarded 238U have been measured by using two position-sensitive PPAC with large area.Transfer fission has been removed from total fission using fission fragment angular correlation technique.The contribution to the total fission cross section arising from transfer is about 10%.The anisotropy of fission fragment for transfer-fission is rather small,thus the removal of the transfer fission has little effect on the total fragment angular distribution.Indeed the anisotropy becomes larger by about 5% and anomalously anisotropies still persist. 相似文献
17.
S.C.L. Sharma G.K. Mehta R.K. Choudhury D.M. Nadkarni S.S. Kapoor 《Nuclear Physics A》1981,355(1):13-24
The emission probabilities per fission of α-particles, tritons and protons have been measured in fast neutron induced fission of 235U. The measurements were carried out at neutron energies of 120, 180, 230 and 550 keV. AΔE-E semiconductor detector telescope was used to identify different light charged particles and the fission fragments were detected with an ionization chamber. The three-parameter data corresponding to the pulse heights from the ΔE-E detectors and the ion-chamber were recorded event by event on magnetic tape and were analyzed off-line by computer. No significant variation in the most probable energy () and the standard deviation (σE) of the energy spectra of different light charged particles with incident neutron energy was observed, although was seen to have a slightly higher value beyond En = 230 keV. The yield of α-particles in fission induced by neutrons of En ~ 200 keV was found to be higher by about 20 % than that in thermal neutron induced fission. The yields of tritons and protons were found to increase significantly with neutron energy. 相似文献
18.
On the basis of the cluster shell model of double well,a new method for subs-tracting the kinetic energy of the relative motion of the fission fragments has beenproposed,and in this way the potential energy curve for spontaneous fission of 8Be-has been calculated.In the calculation,the effects of the coulomb potential and thespurious states of the motion of the center of mass have been considered properly.The results can qualitatively explain the metastable property of 8Be.It seems that the method proposed in this paper might serve as a way to describe the fisson processin microscopic study. 相似文献
19.
Analysis of the Energy Autocorrelation Functions in Dissipative Heavy Ion Collision of 27Al+27Al 下载免费PDF全文
The excitation functions of the dissipative fragments emitted from the reaction of 27Al+27Al have been measured in the energy region from 114MeV to 127MeV in steps of 200keV. The detection system covered continuous angles from 10° to 57° in laboratory system. The energy autocorrelation functions of the dissipative fragments have been analyzed by using different approaches,especially using the statistical nuclear reaction model with memory. The results indicate that the intermediate dinuclear system formed in the dissipative process is set in a damped coherent nuclear rotation which causes the nonself averaging oscillation structure in the excitation functions and originates from a typical quantum chaotic motion. 相似文献
20.
The behaviour of prompt γ-ray emission in the cold fission of 252Cf was investigated experimentally using a four-parameter correlation technique. A twin gridded ionization chamber was employed to detect the fission signals and to determine the fragment emission angles, and a φ10cm×10cm NaI(T1) detector was used to record the γ-ray energies. The result shows that the angular distribution coefficient of γ-rays emitted in cold fission is twice as large as that in the normal fission.The fact that in the cold fission the number of γ-rays emitted from the light fragments is approximately three times as large as that from the heavy ones can not be explained satisfactorily so far. 相似文献