共查询到20条相似文献,搜索用时 581 毫秒
1.
G. G. Bunatian 《Physics of Particles and Nuclei》2012,43(6):867-881
We treat generic physical features of the production of neutrons from the high atomic number materials irradiated by the electron beam provided by linear electron accelerator. The bremsstrahlung of incident electrons inducing the photo-nuclear reactions is considered. The experimental data on photo-nuclear reactions are utilized to describe neutrons generating caused by the ??-radiation absorption. The generally received theoretical approaches are applied to explore the photo-neutrons energy distribution. The produced neutrons are primarily statistical, yet the direct neutrons share is noteworthy as well. The dependence of the neutron spectrum, mean neutron energy and total neutron yield on the energy and current of the electron beam and on the characteristics of irradiated samples is investigated. The analysis is plainly carried out in framework of the quantum electrodynamics and photo-nuclear physics, without having any recourse to the ??numerical Monte-Carlo simulations??. Our findings prove mainly to conform satisfactorily to the experimental measurements, so far as those are available for now. 相似文献
2.
G. Belovitsky E. Konobeevski A. Stepanov V. Zavarzina S. Zuyev N. Polukhina N. Starkov S. Lukyanov Yu. Sobolev 《The European physical journal. Special topics》2007,150(1):5-7
To estimate the probability of two-neutron
configurations in halo nuclei, we propose an experimental method
of studying neutron-neutron correlations at periphery of such
nuclei by measuring two-neutron transfer reaction. The
experimental study of 6He + A ↦ 4He + B for various targets
is performed using 6He beam of Flerov Laboratory of Nuclear
Reactions (JINR, Dubna) at energy of about 15 MeV/u and technique
of nuclear photoemulsions. Searching for events of two-nucleon
transfer reaction and their processing is performed using the
PAVICOM-setup at P.N. Lebedev Physical Institute. 相似文献
3.
V. L. Aksenov V. D. Ananiev G. G. Komyshev A. D. Rogov E. P. Shabalin 《Physics of Particles and Nuclei Letters》2017,14(5):788-797
The upper limit of the density of the thermal neutron flux from pulsed sources based on the fission reaction is established. Three types of sources for research on ejected beams are considered: a multiplying target of the proton accelerator (a booster), a booster with the reactivity modulation (a superbooster), and a pulsing reactor. Comparison with other high-flux sources is carried out. The investigation has been performed at the Frank Laboratory of Neutron Physics of JINR. 相似文献
4.
The neutron binding energy of137Xe has been deduced to be 4025.2±0.6 keV from a study of the136Xe(n, γ)137Xe reaction. The importance of a precise value for this quantity is due to the fact that an accurate determination of binding energies of delayed neutron emitters is possible only for87Kr and137Xe, neighbouring stable isotopes. Nuclear reaction.136Xe(n,γ), enriched target; measurede89-01, deduced neutron binding energy, Ge(Li) detector. 相似文献
5.
V. A. Andreev A. V. Vasiljev E. A. Ivanov D. S. Ilyin A. G. Krivshich A. P. Serebrov 《Technical Physics》2016,61(4):609-617
The gas-discharge detector is designed for the neutron lifetime spectrometer. The detector is intended for ultracold neutron flux monitoring in measurement cycles at the specrtometer (ILL, Grenoble, France). The detector has been successively tested with a Pu–Be neutron source under laboratory conditions and as a part of the spectrometer. 相似文献
6.
By means of X-γ andγ-γ coincidence measurements of the35Cl+58Ni reaction products, 38γ lines have been identified to be in coincidence with KX(Tc)-rays and assigned to the decay of90Ru. Its half-life of 11±3 s has been deduced from the 154.6 keVγ-decay. The result supports our previous identification of90Ru produced in the same reactions. 相似文献
7.
V. N. Tarasov K. A. Gridnev W. Greiner D. K. Gridnev V. I. Kuprikov D. V. Tarasov X. Viñas 《Physics of Atomic Nuclei》2012,75(1):17-26
On the basis of the Hartree-Fock method as implemented with Skyrme forces (Ska, SkM*, Sly4, and SkI2) and with allowance for an axial deformation and nucleon pairing in the Bardeen-Cooper-Schrieffer approximation, the properties
of extremely neutron-rich even-even nuclei were calculated beyond the neutron drip line known earlier from theoretical calculations.
It was shown that the chains of isotopes beyond the neutron drip line that contain N = 32, 58, 82, 126, and 184 neutrons form peninsulas of nuclei stable against the emission of one neutron and, in some cases,
peninsulas of nuclei stable against the emission of two neutrons. The neutron- and proton-density distributions in nuclei
forming stability peninsulas were found to be spherically symmetric. A mechanism via which the stability of nuclei might be
restored beyond the neutron drip line was discussed. A comparison with the results of calculations by the Hartree-Fock-Bogolyubov
method was performed for long chains of sulfur and gadolinium isotopes up to the neutron drip line. 相似文献
8.
A. Ioffe P. Lukas P. Mikula M. Vrana V. Zabijakin 《Zeitschrift für Physik A Hadrons and Nuclei》1994,348(4):243-244
The coherent scattering length of208Pb was measured by means of the neutron interferometry method and the value ofb c =9.494(29) fm was obtained. 相似文献
9.
J. Piekarewicz 《The European Physical Journal A - Hadrons and Nuclei》2007,32(4):537-541
The neutron radius of a heavy nucleus is a fundamental nuclear-structure observable that remains elusive. Progress in this
arena has been limited by the exclusive use of hadronic probes that are hindered by large and controversial uncertainties
in the reaction mechanism. The parity radius experiment at the Jefferson Laboratory offers an attractive electro-weak alternative
to the hadronic program and promises to measure the neutron radius of 208Pb accurately and model independently via parity-violating electron scattering. In this contribution we examine the far-reaching
implications that such a determination will have in areas as diverse as nuclear structure, atomic parity violation, and astrophysics. 相似文献
10.
A precise determination of the coherent scattering length of 3He with a neutron interferometer yields a value ac = 4.29 ± 0.04 fm. A comparison with varoous theoretical perdictions is made and its relation to the few-body problem is discussed. A combination with other experimental results yield as most probable values for the free singlet- and triplet scattering length as = 8.0 ± fm and at = 3.05 ± 0.07 fm, respectively. 相似文献
11.
W. Ketter W. Heil G. Badurek M. Baron E. Jericha R. Loidl H. Rauch 《The European Physical Journal A - Hadrons and Nuclei》2006,27(2):243-256
Improved knowledge of the real part of the neutron scattering length of 3He is important for further development of nuclear few-body theory, as well as for a thorough understanding of neutron scattering
off quantum liquids. The real part of the bound incoherent neutron scattering length bi' has recently been measured directly with an experimental uncertainty of better than 1% by means of spin echo spectrometry.
The uncertainty of the more fundamental bound multiplet scattering lengths b±' is thus limited by today's 1.2% uncertainty of the spin-independent coherent part bc'. Employing the skew-symmetric perfect crystal Si-interferometer at the S18 experimental site at ILL, Grenoble, we have re-measured
the real part of the bound coherent neutron scattering length bc' of 3He. Our result bc' = 6.010(21)fm exhibits a significant deviation compared to the latest accepted value bc' = 5.74(7)fm (H. Kaiser, H. Rauch, G. Badurek, W. Bauspiess, U. Bonse, Z. Phys. A 291, 231 (1979)). Including the known value of the incoherent neutron scattering length, we obtain new values for the real parts
of the free singlet and triplet scattering lengths, a-' = 7.573(30)fm and a+' = 3.480(18)fm. Our result contravenes by more than 7 standard deviations the measurement of the same physical quantity that
has recently been performed by a group at NIST in a very similar experiment (P.R. Huffman, D.L. Jacobson, K. Schoen, M. Arif,
T.C. Black, W.M. Snow, S.A. Werner, Phys. Rev. C 70, 014004 (2004)) which yielded bc' = 5.853(7)fm. 相似文献
12.
E. Klemt P. Bopp L. Hornig J. Last S. J. Freedman D. Dubbers O. Schärpf 《Zeitschrift fur Physik C Particles and Fields》1988,37(2):179-189
The beta-decay asymmetry of the free neutron is measured with polarized neutrons and a long solenoidal beta-spectrometer with 4π electron-detection solid angle. The asymmetry parameter corrected for recoil and weak magnetism isA 0=?0.1146±0.0019, implyingg A /g v =1.262±0.005 for the ratio of the axial-vector to the vector weak coupling constants. 相似文献
13.
The current status of the measurements of the neutron lifetime has been analyzed. The problem of experimental data discrepancy
has been analyzed and systematic errors of some experiments have been found out. The corrected table of measurements is given
and a new world average value of neutron lifetime 879.9 ± 0.9 s is presented. 相似文献
14.
15.
A simple correlation based on the gross theory ofβ-decay is derived between the neutron emission probabilitiesP n of delayed neutron precursors, theirβ-decay energies and the neutron binding energies of the daughter nuclei. The correlation is shown to be valid for delayed neutron precursors among the fission products. TheP n-values of several expected but still unidentified neutron precursors are estimated together with their contributions to the delayed neutron groups in thermal-neutron induced fission of235U. Some aspects of theβ-strength function for transitions into highly excited states are discussed. 相似文献
16.
以SiC二极管和中子转换材料6LiF为基础,研制了SiC基中子探测器,并用241Am源与临界装置分别研究了SiC基中子探测器的粒子响应、热中子响应。结果表明:SiC基中子探测器能够满足241Am源粒子的计数测量,但由于SiC二极管灵敏区薄,故不能用于5.48 MeV的粒子能谱测量;SiC基中子探测器对热中子响应良好,不同功率下,脉冲幅度谱中可清晰看到由6Li(n,)3H的反应产物粒子、3H粒子形成的双峰;脉冲幅度甄别法可将射线及电子学噪声甄别掉;在直接测量与符合测量中,SiC基中子探测器的计数率均与临界装置功率成线性关系,且直接测量的线性度比符合测量的线性度好,最好可达0.999 97。研究表明:降低肖特基接触金属的厚度、增加其外延层厚度、提高其外延层品质,可将SiC二极管用于带电粒子能谱测量。 相似文献
17.
Charge neutrality, a spin 1/2 and an associated magnetic moment of the neutron make it an ideal probe of quantal spinor evolutions.
Polarized neutron interferometry in magnetic field Hamiltonians has thus scored several firsts such as direct verification
of Pauli anticommutation, experimental separation of geometric and dynamical phases and observation of non-cyclic amplitudes
and phases. This paper provides a flavour of the physics learnt from such experiments. 相似文献
18.
R. U. Khafizov N. Severijns O. Zimmer H. -F. Wirth D. Rich S. V. Tolokonnikov V. A. Solovei M. R. Kolhidashvili 《JETP Letters》2006,83(1):5-9
The aim of this work is the experimental observation of and research into a rare neutron mode, the radiative beta decay, where
a new particle, the radiative gamma quantum, is formed along with the expected decay products: a beta electron, a recoil proton,
and an antineutrino. The discovery of this rare neutron decay mode was conducted through identification of triple-coincidence
events: simultaneous registration of a beta electron, a proton, and a radiative gamma quantum. The ordinary neutron decay
was registered by double coincidences of a beta electron and a recoil proton. The statistics collected allow one to deduce
the branching ratio (BR) BR = (3.2 ± 1.6) × 10−3 (90% C.L.) in the gamma energy region greater than 35 keV. This value of BR is consistent with standard electroweak theory.
The text was submitted by the authors in English.
An erratum to this article is available at . 相似文献
19.
Neutron spectrometry provides many branches of science and technology with the necessary data. Usually the main part of the
data is supplied by powerful neutron time-of-flight spectrometers. Nevertheless there are many other very effective but simpler
and cheaper neutron spectroscopy methods on accelerators, suitable for solution of plenty of scientific and applied problems
(for example, in astrophysics and radioactive waste transmutation). The methods of slowing-down spectrometry in lead and graphite,
generating of neutron spectra, characteristic for nucleosynthesis in the stars, and neutron spectrometry by means of primary
γ-transition shift are discussed in the report. 相似文献