Vol.26,

New theoretical calculations are performed to investigate the Coulomb proximity and angular momentum effects on multifragmentation picture for ⁸⁴Kr+^112,124Sn collisions at an incident beam energy of 35 MeV/nucleon. Charge and isotopic distributions and the mean neutron-to-proton ratios of the fragments are reproduced within the microcanonical Markov chain calculations on the basis of Statistical Multifragmentation Model. It is shown that the Coulomb interactions and angular momentum effects are very important to reproduce isotopic composition of nuclear fragments in peripheral heavy-ion collisions at Fermi energies. Our results imply that it is possible to investigate in laboratories the modification of structure parameters of fragments, such as the symmetry energy coefficient, at subnuclear densities in dense environment of other species.

421

Nuclear double β^--decay with two neutrinos is an important decay mode for some unstable nuclei. Based on the available experimental data of nuclear double β^--decay, we propose that there is a law between the logarithm of double β^--decay half-lives and the reciprocal of the decay energy. The physics behind the law is discussed and it is found that this is associated with the universal properties of the weak interaction. This double β^--decay law is similar to the famous Geiger-Nuttall law of α-decay. The law is applied to predictions of the nuclear double β^--decay half-lives for six even-even nuclei from Z=84 to Z=98 and we found that ²³²Th is very interesting for future experiments. The branching ratios between double β^--decay and α-decay are also estimated for the six even-even nuclei and this is useful for future experimental search of new emitters of double β^--decay.

447

577

The experimental elastic cross section data of the projectile ¹¹Be on target ¹²C at 49.3 MeV/nucleon energy is analysed. The calculations for the elastic scattering are performed by the phenomenological optical model. The different optical potentials to include breakup effects into the calculations, which are neutron+¹²C, neutron+¹⁰Be and ¹⁰Be+¹²C, are described with the aid of the global potentials for neutron interactions and fitted to experimental data for the core and target interaction. Also, the first analysis of the optical model for ¹⁰Be on target ¹²C at 39.1 MeV is done for building the interaction potential of the core and the target for ¹¹Be. For investigating the effects of the spectroscopic factors, obtained factors from the direct capture process using the nuclear level density are compared with the previous cross section and spectroscopic factor results. Obtained results for the elastic cross section reproduce the experimental data very well and show the requirement of including spectroscopic properties such as, spectroscopic factors and density of the excited states, to explain this elastic cross section data.

425

We report our recent progress on the nuclear symmetry energy probe, which is called the isobaric yield ratio difference (IBD), and its application in neutron density determination in experiments. The results obtained by the IBD, from which the isobaric yields in the measured 140 A MeV ^{40, 48}Ca + ⁹Be and ^58,64Ni + ⁹Be reactions, and the calculated 80 A MeV ^38-52Ca + ¹²C reactions by using a modified statistical abrasion-ablation model, show the sensitivity of the IBD to the density differences between reactions.

444

Reaction dynamics in collisions of antiprotons on nuclei is investigated within the Lanzhou quantum molecular dynamics model. The reaction channels of elastic scattering, annihilation, charge exchange and inelastic collisions of antiprotons on nucleons have been included in the model. Dynamics on particle production, in particular pions, kaons, antikaons and hyperons, is investigated in collisions of p¯ on ¹²C, ²⁰Ne, ⁴⁰Ca and ¹⁸¹Ta from low to high incident momenta. It is found that the annihilations of p¯ on nucleons are of importance to the dynamics of particle production in phase space. Hyperons are mainly produced via meson induced reactions on nucleons and strangeness exchange collisions, which lead to delayed emission in antiproton-nucleus collisions.

427

The relation between the vector-isoscalar and vector-isovector interactions in the two-flavor Nambu-Jona-Lasinio (NJL) model is investigated under the different constraints from QCD. We demonstrate that the flavor-mixing can be induced by the mismatched vector-isoscalar and vector-isovector interactions at finite baryon chemical potential μ and isospin chemical potential μ_I. The effect of this non-anomaly flavor-mixing on the possible separate chiral transitions at nonzero μ_I is studied under the assumption of the effective restoration of U(1)_A symmetry. We find that for the weak isospin asymmetry, the two separate phase boundaries found previously can be converted into one only if the vector-isovector coupling gvv is significantly stronger than the vector-isoscalar one gvs without the axial anomaly.

510

Antiproton-induced reactions on nuclei at the beam energies from hundreds MeV up to several GeV provide an excellent opportunity to study interactions between the antiproton and secondary particles (mesons, baryons and antibaryons) with nucleons. The antiproton projectile is unique in the sense that most of the annihilation particles are relatively slow in the target nucleus frame. Hence, the prehadronic effects do not much influence their interactions with the nucleons of the nuclear residue. Moreover, the particles with momenta less than about 1 GeV/c are sensitive to nuclear mean field potentials. This paper discusses the microscopic transport calculations of the antiproton-nucleus reactions and is focused on three related problems: (i) antiproton potential determination, (ii) possible formation of strongly bound antiproton-nucleus systems, and (iii) strangeness production.

534

We discussed recent studies, within the framework of transport theories, on heavy ion reactions between charge asymmetric systems, from low up to Fermi energies. We concentrated on the analysis of ternary breakup events of dynamical origin occurring in semi-central reactions, where the formation of excited systems in various conditions of shape, excitation energy and spin is observed. At beam energies around 20A MeV, we showed how this fragmentation mode emerges from the combined action of surface (neck) instabilities and angular momentum effects, leading to the observation of three aligned massive fragments in the exit channel. At Fermi energies, a transition towards a prompt emission of small fragments from the neck region with larger relative velocity with respect to projectile and target remnants is observed. We also focus on isospin sensitive observables, aiming at extracting information on the density dependence of the isovector part of the nuclear effective interaction and of the nuclear symmetry energy.

496

404

Korea plans to build a new radioactive ion-beam accelerator RAON together with various experimental facilities. In particular, KOBRA (the Korea Broad Acceptance Recoil Spectrometer & Apparatus) and LAMPS (the Large-Acceptance Multi-Purpose Spectrometer) will be constructed for the nuclear physics experiments. The primary goal of KOBRA is to study the structure of exotic nuclei near drip lines and various astrophysical processes at low energies. On the other hand, LAMPS will investigate the density dependence of the nuclear symmetry energy in wide beam energy range up to 2 times normal nuclear densities. This paper provides an overview of RAON and the experimental setup for the nuclear physics program.

527

The X-ray diffraction beamline developed at Shanghai Synchrotron Radiation Facility (SSRF)is located at the BL14B1 bending magnet port of the 3.5 GeV storage ring. The beamline optics is based on a collimating mirror, a sagittally focused double crystal monochromator and a focusing mirror. Photon flux of 4.43×10¹¹ phs/s at 10 keV is obtained. The primary instrument equipped in the experimental end-station is a Huber 5021 six-cycle diffractometer. BL14B1 is a general purpose X-ray diffraction beamline and focused on material science, condensed matter physics and other relevant fields looking for structural information.

787

On May 6, 2009, the X-ray imaging and biomedical application beamline (BL13W1) at Shanghai Synchrotron Radiation Facility (SSRF) officially opened to users, with 8–72.5 keV X-rays. The experimental station is equipped with four sets of X-ray CCD detectors of different pixel size (0.19–24 μM) for on-line phase-contrast imaging and micro-CT imaging with 0.8 μm spatial resolution and 1 ms temporal resolution. An in vivo micro-CT experiment for a living insect was realized in 4 s. An X-ray fluorescence detector is equipped for X-ray fluorescence mapping imaging and X-ray fluorescence micro-CT imaging with 50 μm spatial resolution. In order to meet different requirements from the users, several experimental methods, such as X-ray spiral micro-CT, X-ray local micro-CT, X-ray fast micro-CT, X-ray grating-based differential micro-CT, X-ray fluorescence micro-CT and X-ray quantitative micro-CT have been developed, and nearly 60 papers related to those developments for this beamline have been published. Moreover, the beamline has realized the remote fast CT reconstruction, providing a great convenience for the users to process experimental data at their offices. As of August 2014, the beamline has offered the user beamtime of (23145 h), from which 232 user papers have been published, including 151 SCI papers and 55 papers with SCI impact factor >3. The quantity and quality of the user paper outcome keep a steady increase. Some typical user experimental results are introduced.

561

A monochromator is important to a beamline for desired monochromatic light. There are three water-cooled double crystal monochromators (DCMs) commissioned in the phase-I beamlines of Shanghai Synchrotron Radiation Facility (SSRF). In this paper, the mechanical principle of the DCMs is introduced. A control system for the monochromator based on the standard architecture for SSRF beamlines is described. To achieve the control requirement precisely, the hardware includes VME (Versa Module Eurocard)-based controller for stepper motors, RS-232-based controllers for micropositioning and piezoelectric actuators. The software is developed with EPICS (Experimental Physics and Industrial Control System) package. Test results have revealed the stability and reliability of the system.

633

A biaxial rotational technique is proposed to improve the neutron irradiation uniformity for a large sample, and the theoretical method is established to predict and design the main parameters. The technique used a device to rotate the target sample around two perpendicular axes simultaneously. Numerical calculations found that the lowest common multiple of the two angular speeds should be large enough to improve the uniformity, and the minimal experimental time should be no less than 600 s. For a three-dimensional sample with a size of 20 cm×12 cm×14 cm, the maximal non-uniform neutron irradiation factor of the sample is mainly determined by the distance between the center of the sample and of the point neutron source. It was computed to be less than 10% when the distance was no less than 34 cm. Experiments were carried out on the CFBR-II reactor and the experimental results were in good accordance with the theoretical analysis. As a result, the theoretical conclusions given above are reasonable and of reference value for the design of future irradiation experiments.

608

Reversible addition-fragmentation chain transfer (RAFT) mediated grafting of acrylonitrile onto Polyethylene/Poly(ethylene terephthalate) (PE/PET) composite fibers was performed using γ-irradiation as the initial source at ambient temperature. Different initial concentrations of 2-cyanoprop-2-yl dithiobenzonate were used as the chain transfer agent. The kinetics of graft polymerization is in accordance with the living RAFT polymerization. The successful grafting of acrylonitrile is proved by Fourier transform infrared spectroscopy analysis. The results of monofilament tensile test show that mechanical properties of the fibers change slightly after grafting. Scanning electronic microscopy images of the fibers show that the surface of RAFT grafted fibers is smoother than that of fibers grafted conventionally.

423

It was learned that 99 % degradation rate of carbamazepine (CBZ) (75 mg L^-1) in solutions was got under 10 kGy by EB (electron beam) irradiation while 15.74% and 96.02% CBZ (2 mg L^-1) degradation rate was got by UV and UV/H₂O₂ process in 180 min. EB-radiolysis was thought to be an efficient and energy-saving method to decompose CBZ in comparison of energy consumption between EB irradiation and UV/H₂O₂. Alkali metal cations which existed in surface water have little inhibition on the degradation of CBZ under EB and UV/H₂O₂ process. The anions usually existed in surface water had little suppression on EB-radiolysis of CBZ, while have an inhibition on UV-photodegradation of CBZ. Fe³⁺ promoted the degradation under EB irradiation and UV (ultraviolet) irradiation because of being the OH. promoter. In addition, Fe²⁺ hugely enhanced the degradation of CBZ under UV irradiation. On the basis of the intermediates’ appearance during the radiolysis, the main degradation pathway for the mineralization of CBZ was proposed under EB irradiation. It came to a conclusion that EB-radiolysis was an efficient and energy-saving method to completely mineralize CBZ.

389

In helical cone-beam computed tomography (CT), Feldkamp-Davis-Kress (FDK) based image reconstruction algorithms are by far the most popular. However, artifacts are commonly met in the presence of lateral projection truncation. The reason is that the ramp filter is global. To restrain the truncation artifacts, an approximate reconstruction formula is proposed based on the Derivative-Hilbert-Backprojection (DHB) framework. In the method, the first order derivative filter is followed by the Hilbert transform. Since the filtered projection values are almost zero by the first order derivative filter, the following Hilbert transform has little influence on the projection values, even though the projections are laterally truncated. The proposed method has two main advantages. First, it has comparable computational efficiency and image quality as well as the conventional helical FDK algorithm for non-truncated projections. The second advantage is that images can be reconstructed with acceptable quality and much lower computational cost in comparison to the Laplace operator based algorithm in cases with truncated projections. To point out the advantages of our method, simulations on the computer and real data experiments on our laboratory industrial cone-beam CT are conducted. The simulated and experimental results demonstrate that the method is feasible for image reconstruction in the case of projection truncation.

423

Passive neutron multiplicity counting is widely used as a nondestructive assay technique to quantify mass of plutonium material. One goal of this technique is to achieve good precision in a short measurement time. In this paper, we describe a procedure to derive mass assay variance for multiplicity counting based on the three-parameter model, and analytical equations are established using the measured neutron multiplicity distribution. Monte Carlo simulations are performed to evaluate precision versus plutonium mass under a fixed measurement time with the equations. Experimental data of seven weapons-grade plutonium samples are presented to test the expected performance. This variance analysis has been used for the counter design and optimal gate-width setting at Institute of Nuclear Physics and Chemistry.

374

The safety analysis code SCTRAN for SCWR (Super Critical Water Reactor) is modified to own the capability to assess the radiation heat transfer with developing a two-dimensional heat conduction solution scheme and incorporating a radiation heat transfer model. The verification of the developed radiation heat transfer model is conducted through code-to-code comparison with CATHENA. The results show that the modified SCTRAN code is successful for that the maximum absolute error and relative error of the surface temperature between results of SCTRAN and CATHENA are 6.1 ℃ and 0.9%, which are acceptable in temperature prediction. Then, with the modified SCTRAN code, the loss of coolant accident with a total loss of emergency core cooling system (LOCA/LOECC) of Canadian-SCWR is carried out to evaluate its "no-core-melt" concept. The following conclusions are achieved: 1) in the process of LOCA, the decay heat can be totally removed by the radiation heat transfer and the natural convection of the high-temperature coolant, even without an intervention of ECCS (Emergency Core Cooling System); 2) The peak cladding temperature of the fuel pins in the inner and outer rings of the high power group are 1236 ℃ and 1177 ℃ respectively, which are much lower than the melting point of the fuel sheath. It indicates that the Canadian-SCWR can achieve "no-core-melt" concept under LOCA/LOECC.

355

Tritium real-time measurement in glovebox or workplace is important to ensure safe operation of tritium. A novel tritium monitor system including an open-walled ionization chamber, an electrometer and an IPC (Industrial Personal Computer) has been developed to measure tritium in gaseous form. Using mesh walls, instead of sealed wall, the open-walled ionization chamber has less tritium absorption and lower memory effect. In addition, tritium gas can diffuse into the chamber’s sensitive region without the assistant of sampling system and ion trap, which are installed at the front-end of commonly used flow-through ionization chambers. Background signal of this monitor system is about 3.7×10⁵ Bq/m³, and after exposed to tritium concentration at about 10¹¹ Bq/m³ for 4h, background of the monitor can recover after purging it several times with dry air. It is suitable for longtime tritium measurements in both glovebox and workplace.

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