ATLAS用于CARIBU项目的ECR离子剥离器

A new radioactive beam facility for ATLAS,the Californium Rare Ion Breeder Upgrade (CARIBU), is under construction.The facility will use fission fragments from a 1 Ci ~(252)Cf source;thermalized and collected into a low-energy beam by a helium gas catcher.In order to reaccelerate these beams,the existing ATLAS ECR-I ion source is being redesigned to function as a charge breeder source.The design and features of this charge breeder configuration is discussed and the project status described.     

裂变产物中短寿命核素138Cs的分离提取

本文研究了从裂变产物中分离提取短寿命核素138Cs的方法.通过两步沉淀和一步溶剂萃取,实现138Cs与其他裂片核素的分离.γ能谱分析表明,138Cs对其他裂片核素的去污系数＞103,138Cs的化学回收率为45.0%.     

248 Cm和252Cf自发裂变瞬发中子谱测量

在飞行时间方法测量 2 0 0keV— 1 2MeV能区内2 48Cm和2 5 2 Cf自发裂变瞬发中子谱 ,以国际原子能机构推荐的2 5 2 Cf自发裂变瞬发中子谱为标准 ,可以免去探测器效率刻度的问题并消除系统误差 ,提高测量精度 .实验用一个微型电离室作为裂变碎片探测器 ,两个芪晶体中子探测器测量中子及一套基于微机的距离分别为 3 2 ,50和 1 0 0cm ,经过对数据的处理和分析给出了 2 0 0keV— 1 2MeV的中子能区内的实验数据 .用Maxwell分布对实验数据进行拟合 ,得到的核温度为 (1 4 0 1± 0 0 0 6)MeV .     

Measurement of 248Cm/252Cf Cf Spontaneous Prompt Fission Neutron Spectrum

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.     

New data on the ternary fission of 252Cf from the Gammasphere facility

Ternary fission of ²⁵²Cf was studied at Gammasphere using eight ΔE×E particle telescopes. Helium, beryllium, boron, and carbon light charged particles (LCPs) emitted with kinetic energy more than 9, 21, 26, and 32 MeV, respectively, were identified. The 3368-keV γ transition from the first 2⁺ excited state in ¹⁰Be was found and the population probability ratio N(2⁺)/N(0⁺) = 0.160 ± 0.025 was estimated. No evidence was found for 3368-keV γ rays emitted from a triple molecular state. For the first time, charge distributions are obtained for ternary fission fragments emitted with helium, beryllium, and carbon LCPs.     

Statistical properties of deexcitation of fragments originating from the spontaneous fission of 252Cf

A method of parametrizing radiative strength functions for electric dipole transitions is used to calculate the spectra of photons emitted by fragments originating from the spontaneous fission of ²⁵²Cf nuclei. The LDPL-98 library of parameters, which contains data for 2000 nuclei, is composed for performing relevant calculations. It is shown that the use of this method leads to regular agreement with experimental data—that the structure and the energy dependence of the spectra are reproduced without varying parameters suggests a statistical character of fission-fragment deexcitation.     

Calculations of neutron evaporation from 252Cf fission 14 fragments based on the shell model

The average neutron kinetic energies and the residual total gamma ray energies as a function of fragment mass are calculated for the spontaneous fission of ²⁵²Cf on the basis of the Nilsson model and of the B.C.S. Hamiltonian.     

Mass spectrometric investigation of desorbed ions from a valine sample by252Cf fission fragments

Summary Spectra of positive and negative secondary ions desorbed from a valine sample by²⁵²Cf fission fragments were measured in a new time-of-flight mass spectrometer. The outstanding features of the obtained results, including fragmentation, cationization and clustering are discussed. To speed up publication, the authors of this paper have agreed to not receive the proofs for correction.     

Evaluation of the time of prompt-fission-neutron emission from 252Cf by measuring a two-particle correlation function

The time of prompt-fission-neutron emission from ²⁵²Cf is evaluated at τ₀≥(1?2)×10^?19 s by measuring a two-neutron correlation function. The final-state interaction of identical neutrons emitted by moving fission fragments is taken into account.     

Measurement of the Ratio of Cumulative Spectra of Beta Particles from $${}^{{235}}$$ U and $${}^{{239}}$$ Pu Fission Products for Solving Problems of Reactor-Antineutrino Physics

Physics of Atomic Nuclei - The first cycle of measurements of the ratio of cumulative spectra of beta particles originating from the isotopes $${}^{235}$$ U and $${}^{239}$$ Pu undergoing...     

Investigation of Ternary Fission of <Stack><Subscript>98</Subscript><Superscript>252</Superscript></Stack>Cf Using Three-Cluster and Unified Ternary Fission Models

Using three-cluster and unified ternary fission models, the ternary fission of ₉₈²⁵²Cf is studied. We applied collinear and equatorial configurations to study the ternary fission of ₉₈²⁵²Cf when the third fragment is ₃¹⁰Li. The nuclear potential energy in the three-cluster model and unified ternary fission model is calculated respectively, using Yukawa plus exponential and proximity formalisms. The relative yields of different fragmentation channels are calculated. Our results reveal that the ternary fragmentation potential of the three fragments and the relative yields depend on the configuration of three fragments and usedmodel. Two models predict that the lowest driving potential and highest relative yield take place for the fragment combination ₅₁¹³²Sb + ₄₄¹¹⁰Ru + ₃¹⁰Li. Also, the values of driving potential and relative yield are not equal in the three-clustermodel and unified ternary fission model. For fragment combination ₅₁¹³²Sb + ₄₄¹¹⁰Ru + ₃¹⁰Li, the relative yield based on the three-cluster model in collinear configuration is maximum, whereas the unified ternary fission model in equatorial configuration predicts the lowest relative yield.     

The collinear cluster tri-partition (CCT) of 252Cf (sf): New aspects from neutron gated data

Results of two different experiments for the study of fission of ²⁵²Cf (sf) events in coincidence with neutrons are reported. Two time-of-flight-energy (TOF-E detectors systems have been used. The fission fragment masses were obtained in a double arm coincidence set-up, where the missing mass in the binary decay is used to characterise ternary fission as a collinear cluster tri-partition (CCT). The ³He filled neutron counters have been arranged so as to detect principally neutrons emitted from an isotropic source in the laboratory frame. The fission events connected to the larger experimental neutron multiplicities show a wide range in the missing-mass spectrum, down to $ \alpha$ -particles, carbon and oxygen isotopes. These are linked with magic nuclei in the binary mass-mass correlations of the fission fragments. These neutron gated data are virtually free from background events from scattered binary fission fragments. The ungated spectra are compared to those of the previous data from our previous article (Eur. Phys. J. A. 45, 29 (2010)), the observed structures agree well with the manifestations of the collinear cluster tri-partition of ²⁵²Cf (sf) observed earlier. Several new families of the CCT modes are observed.     

Calculation of Radii and Density of ^7-19B Isotopes Using Effective Skyrme Force

Abstract In this study, the proton and neutron densities, charge densities, rms nuclear charge radii, rms nuclear mass radii, rms nuclear proton, neutron radii, and neutron skin thickness are calculated by using Harfree-Fock method with an effective nucleon-nucleon Skyrme interactions with SⅠ, SⅡ, SⅣ, T3, SKM, and SKM^＊ parameters. These nuclear properties for the neutron-rich isotopes of B （Boron） are presented. The calculated results are compared with the experimental and theoretical results of other researchers.     

Clusterization of Heavy Nuclei from the Microscopic Point of View: Application of the U(3) Selection Rule to 252Cf

Microscopic aspects of the fission channels of ²⁵²Cf are studied using the U(3) selection rule. Effective U(3) symmetry labels, which are consistent with deformation, are used to characterize the parent and daughter nuclei. Our study shows a non-uniform structural dependence of the relative preference for different fission channels.     

Detailed investigation of the β-decay of the 9/2+ ground state of 99Nb to levels in 99Mo

The decay of ⁹⁹Nb to ⁹⁹Mo has been investigated. The use of the ion-guide technique for on-line mass separation and of a Ge-array for γ-ray detection have allowed the observation of decay branchings lower than 10^?3. Mediumspin levels, some already known from reaction studies and new ones at high energy, are populated. The β-feeding patterns of the decays of the 9/2⁺ states in ⁹⁹Nb and in its isotones ⁹⁷Y, and ¹⁰¹Tc are qualitatively reproduced by QRPA calculations.