共查询到20条相似文献,搜索用时 15 毫秒
1.
G. N. Lovchikova A. M. Trufanov M. I. Svirin V. A. Vinogradov 《Physics of Atomic Nuclei》2004,67(5):890-900
The energy distributions of neutrons accompanying the fission of 232Th are measured by the time-of-flight technique at the bombarding-neutron energies of E n=14.6 and 17.7 MeV. The data obtained in this way are compared with the results of previous investigations. An excess of soft neutrons that was observed in the experimental spectra of neutrons from 238U fission at E n=13.2, 14.7, 16.0, and 17.7 MeV in relation to the results of the calculations based on the model of two sources is also present in the spectra for 232Th. The discrepancy between the results of the calculations and experimental data disappears as soon as one assumes the presence of a third source that is related to neutron emission from nonaccelerated fragments. 相似文献
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J. Kaufmann W. Mollenkopf F. Gönnenwein P. Geltenbort A. Oed 《Zeitschrift für Physik A Hadrons and Nuclei》1992,341(3):319-326
Masses, charges and kinetic energies of light fission fragments from the reactions232U(n, f) and239Pu(n, f) induced by thermal neutrons have been measured on the Cosi fan tutte spectrometer of the Institut Laue-Langevin in Grenoble. Both at very high and very low kinetic energies marked fine structures in the mass yields and odd-even staggerings in the charge yields are observed. In the framework of a scission point model the results are shown to point to compact and deformed scission configurations, respectively, where at scission the fragments carry no intrinsic excitation energy. The two limiting processes may, therefore, be called cold compact fission (usually known as cold fission) and cold deformed fission. The latter process as a general phenomenon of low energy fission has come into focus only recently. 相似文献
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M. Djebara M. Asghar J.P. Bocquet R. Brissot M. Maurel H. Nifenecker CH. Ristori 《Nuclear Physics A》1984,425(1):120-140
A gas ΔE ? ER telescope has been used to measure charge yields and their correlations with kinetic energies for 229Th and 232U. Even-charge yields are enhanced compared with odd-charge yields for both fissioning systems; this enhancement increases for events with higher kinetic energy. The mean odd-even effect ; it is . The energy-integrated δp and δp for different energy windows, vary strongly as a function of charge (Z) due to the underlying shells. The δp averaged over Z increases fast with kinetic energy, contrary to the existing results for 233U and 235U, where δp flattens off at low energies. For both systems, the most probable kinetic energy ē shows a strong odd-even stagger; the mean odd-even effect on energy, the latter is about twice the value for . These results are discussed in terms of the existing models. 相似文献
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V. M. Maslov 《Zeitschrift für Physik A Hadrons and Nuclei》1994,348(3):211-215
A new method for the extraction of the neutron structure functions from the combined data on the deep inelastic lepton scattering off proton and deuteron targets is proposed. The principal advantages of the method are: (i) only analyticity of the structure functions is assumed, and (ii) the spin-dependent structure functions may be considered as well, whereas the smearing factor method does not work is this case. To make clear the capabilities of the new method, we consider its application to the real data on polarized and unpolarized deuteron. 相似文献
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R. Van de Vyver J. Devos H. Ferdinande R. Carchon E. Van Camp 《Zeitschrift für Physik A Hadrons and Nuclei》1978,284(1):91-93
The total photoneutron cross section of208Pb was measured between 8 and 13 MeV using the bremsstrahlung photon facility from a 35 MeV linac. Considerable resonance structure was observed in the cross section, of which the peak around 9 MeV, as well as the structure around 10.8 MeV may be due toE2 excitations. 相似文献
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Nassar H Paul M Ahmad I Berkovits D Bettan M Collon P Dababneh S Ghelberg S Greene JP Heger A Heil M Henderson DJ Jiang CL Käppeler F Koivisto H O'Brien S Pardo RC Patronis N Pennington T Plag R Rehm KE Reifarth R Scott R Sinha S Tang X Vondrasek R 《Physical review letters》2005,94(9):092504
The 62Ni(n,gamma)63Ni(t(1/2)=100+/-2 yr) reaction plays an important role in the control of the flow path of the slow neutron-capture (s) nucleosynthesis process. We have measured for the first time the total cross section of this reaction for a quasi-Maxwellian (kT=25 keV) neutron flux. The measurement was performed by fast-neutron activation, combined with accelerator mass spectrometry to detect directly the 63Ni product nuclei. The experimental value of 28.4+/-2.8 mb, fairly consistent with a recent calculation, affects the calculated net yield of 62Ni itself and the whole distribution of nuclei with 62相似文献
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The excitation function for the fission of 230Th induced by neutrons has an unusual maximum for neutron energies in the vicinity of 700KeV,It has been suggested that this maximum may be associated with the vibrational-mode resonance states,The unusual peak in the excitation function is interpreted in terms of a vibrational-model resonance state in a two-humpted fission barrier.From theoretical fits to the fission cross sections and angular distributions,it is shown that the resonance has K=1/2. 相似文献
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J. Adam Chitra Bhatia K. Katovsky V. Kumar M. Majerle V. S. Pronskikh A. M. Khilmanovich B. A. Martsynkevich I. V. Zhuk V. M. Golovatiouk W. Westmeier A. A. Solnyshkin V. M. Tsoupko-Sitnikov A. S. Potapenko 《The European Physical Journal A - Hadrons and Nuclei》2011,47(7):1-18
Spallation neutrons produced in the collision of a 2.33GeV deuteron beam with a large lead target are moderated by a thick graphite block surrounding the target and used to activate the radioactive samples of natU and Th put at three different positions, identified as holes “a”, “b” and “c” in the graphite block. Rates of the (n, f), (n, $ \gamma$ and (n, 2n) reactions in the two samples are determined using the gamma spectrometry. The ratios of the experimental reaction rates, R (n, 2n)/R (n, f), for 232Th and natU are estimated in order to understand the role of the (n, x n) kind of reactions in Accelerator-Driven Sub-critical Systems. For the Th-sample, the ratio is ~ 54 (10)% in the case of hole “a” and ~ 95 (57)% in the case of hole “b” compared to 1.73(20)% for hole “a” and 0.710(9)% for hole “b” in the case of the natU sample. Also the ratio of fission rates in uranium to thorium, natU (n, f)/ 232Th (n, f), is ~ 11.2 (17) in the case of hole “a” and 26.8(85) in hole “b”. Similarly, the ratio 238U (n, 2n)/ 232Th (n, 2n) is 0.36(4) for hole “a” and 0.20(10) for hole “b” showing that 232Th is more prone to the (n, x n) reaction than 238U . All the experimental reaction rates are compared with the simulated ones by generating neutron fluxes at the three holes from MCNPX 2.6c and making use of the LA150 library of cross-sections. The experimental and calculated reaction rates of all the three reactions are in reasonably good agreement. The transmutation power, P norm as well as P norm/P beam of the set-up is estimated using the reaction rates of the (n, $ \gamma$ and (n, 2n) reactions for both the samples in the three holes and compared with some of the results of the “Energy plus Transmutation” set-up and TARC experiment. 相似文献
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用3He球形4中子探测器,通过直接反应法可以对核素的(n,2n)反应截面进行测量。在此类实验中,要求对中子束进行很好的准直。好的准直器设计要求能够提高样品处的中子注量率的均匀性,同时保证中子束流边缘处的下降幅度,能够降低低能中子所占份额。本工作采用FLUKA和MCNPX对圆柱形准直器、单锥形准直器及三种不同斜率的双锥形准直器对中子注量率的均匀性和低能中子所占份额进行了对比研究,结果表明,低斜率的双锥形准直器可以满足实验对这两方面的要求。同时,在有样品和无样品两种条件下,对探测系统经由这五种不同准直器准直后的中子束流的响应做了对比,结果显示,经过低斜率的双锥形准直器准直的中子束流,探测系统在有样品时表现为较高的计数率,在无样品时表现为较低的本底。除此之外,对准直器出口处的斜率对准直效果的影响也做了比较。最终中子准直器选用为这种低斜率的双锥形准直器,材料选用为紫铜、不锈钢、聚乙烯和铅。准直孔开口处直径为2.64 cm,长度为137 cm,经准直后样品处的中子束斑直径为3.2 cm。 相似文献
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SADHANA MUKERJI H NAIK S V SURYANARAYANA S CHACHARA B S SHIVASHANKAR V MULIK RITA CRASTA SUDIPTA SAMANTA B K NAYAK A SAXENA S C SHARMA P V BHAGWAT K K RASHEED R N JINDAL S GANESAN A K MOHANTY A GOSWAMI P D KRISHNANI 《Pramana》2012,79(2):249-262
The 232Th(n, ??) reaction cross-section at average neutron energies of 13.5, 15.5 and 17.28?MeV from the 7Li(p, n) reaction has been determined for the first time using activation and off-line ??-ray spectrometric technique. The 232Th(n, 2n) cross-section at 17.28?MeV neutron energy has also been determined using the same technique. The experimentally determined 232Th(n, ??) and 232Th(n, 2n) reaction cross-sections from the present work were compared with the evaluated data of ENDF/BVII and JENDL-4.0 and were found to be in good agreement. The present data, along with literature data in a wide range of neutron energies, were interpreted in terms of competition between 232Th(n, ??), (n, f), (n, nf) and (n, xn) reaction channels. The 232Th(n, ??) and 232Th(n, 2n) reaction cross-sections were also calculated theoretically using the TALYS 1.2 computer code and were found to be in good agreement with the experimental data from the present work but were slightly higher than the literature data at lower neutron energies. 相似文献
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K. Sagara T. Sugimoto S. Kuroita Y. Maeda T. Sueta H. Shimoda 《Few-Body Systems》2008,44(1-4):203-205
Systematic measurement of the D(p, pp)n cross section at E p = 13 MeV at star configurations at various inclined angle α is in progress at Kyushu University tandem accelerator laboratory (KUTL). The measured cross section at space star (α = 90°) is about 12% below the recent pd calculation. The next measurement is being made at 0° < α < 90° to see if the large anomaly of about 25% found by the Köln group (2006) at backward α exists also at forward α. 相似文献
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W. P. Poenitz 《Zeitschrift für Physik A Hadrons and Nuclei》1974,268(4):359-364
The6Li(n, α) cross section was measured in the 90–1500 keV energy range with uncertainties of 3–5%. A lithium glass scintillation detector was used for the measurement of the (n, α)-reaction rate. Flat response neutron detectors were used to monitor the neutron flux. A calibrated vanadium bath was employed to obtain absolute values. The results were analysed in terms of the single-level multi-channelR-matrix theory. 相似文献
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Reaction110Pd(n, 2n)109Pd has been investigated at 14.7 MeV neutrons. Cross sections for the formation of109m Pd and109g Pd were measured. Experimental value of the isomeric cross section ratio has been compared with the theoretical calculation performed with the Huizenga and Vandenbosch method. 相似文献
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Y. M. Gledenov V. I. Salatski P. V. Sedyshev 《Zeitschrift für Physik A Hadrons and Nuclei》1993,346(4):307-308
The14N(n,p)14C reaction cross section has been measured for thermal neutrons, making use of the neutron beam of the IBR-30 pulsed booster of the JINR, Dubna. Thermal neutrons were identified by a time-offlight method. Solid adenin targets were utilized. An ionization chamber was used for detecting the charged particles. The cross section was found to beσ np th =(1.83±0.07)b. 相似文献
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A theoretical analysis of the most detailed experimental data on the subbarrier fission of 232Th is performed. The energy dependences of the components of the cross sections for photofission through specific channels characterized by the quantum numbers J π K are obtained on the basis of previously measured total photofission cross sections and angular distributions of fission fragments. A theoretical analysis of the subbarrier photofission of 232Th is performed on the basis of the results obtained for these components. This analysis relies on the one-dimensional fission model within which one assumes a three-humped structure of the fission barrier and introduces damping in the second and third wells by including an imaginary part in the potential used. Values are selected for the parameters of the fission barriers and are compared with similar data from other studies. It is shown that the energy dependences of the photofission cross sections in question can be described adequately. 相似文献
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