Table of contents

The space-time characters of the pion-emitting sources produced in the heavy ion collisions at the Large Hadron Collider (LHC) energies are investigated in a granular source model of quark-gluon plasma droplets. The results of two-pion interferometry indicate that the longitudinal interferometry radius is sensitive to the initial breakup time of the system. For a larger breakup time the values of the longitudinal interferometry radius for the LHC source are larger than that of the source produced in the collisions at the Relativistic Heavy Ion Collider's (RHIC) top energy. However, the values of the longitudinal radius are smaller if the source fragments at a smaller breakup time with a higher initial temperature of the droplets. The values of the transverse interferometry radius in the "side" direction for the LHC sources are larger than those for the RHIC source. The imaging analyses for the characteristic quantities of the granular sources are consistent with the interferometry radii.

Azimuthal anisotropy, especially for the multi-strange hadrons, is expected to be sensitive to the dynamical evolution in the early stage of high energy nuclear collisions. In this paper we present the latest results of multi-strange hadron elliptic flow in Au + Au collisions at √S_NN = 200 GeV from the STAR experiment at RHIC. The number-of-quark scaling is evidenced with ϕ(s) and Ω(sss) with highly statistical data, which shows strange quark collectivity at RHIC. The ν₂ of ϕ meson is found to be consistent with that of proton within statistical error bars at p_T < 1 GeV/c.

The ¹³C(⁷Li, ⁶He)¹⁴N reaction is measured at E(⁷Li) = 34 MeV with the Q3D magnetic spectrometer of HI-13 tandem accelerator. Angular distributions at forward angles for proton transfer to the ground and the first excited states in ¹⁴N are obtained. In addition, angular distribution for ⁷Li + ¹³C elastic scattering is also measured. The optical potential parameters for the entrance and exit channels of the transfer reactions are derived by fitting the ⁷Li + ¹³C and ⁶Li + ¹⁴N elastic scattering experimental data, and their angular distributions are well reproduced by the distorted wave Born approximation calculations. A phase shift of about 2° between the calculations and the experiment data has been found in the earlier (⁷Li, ⁶He) study, whereas no such phase shift is observed in the present work.

The experimental data of the isotopic distribution for projectile-like fragments are presented for the ^17,18N + ¹⁹⁷Au reaction at 33 MeV/u. The width of the isotopic distributions for ¹⁸N projectile is significantly broader than that for ¹⁷N projectile, and the average N/Z ratio of the former shifts to higher neutron number side. As long as the realistic nucleon density distribution is used, the isotopic distribution for fragments is reproduced by the simple abrasion-ablation model calculation, which thus provides an independent way to determine the surface distribution of the nuclear matter density for neutron-rich nuclei.

An experiment for knockout reaction induced by ⁸He beam at 82.5 MeV/nucleon on CH₂ and C targets was carried out. The ⁶He and ⁴He core fragments at forward angles and the recoiled protons at large angles were detected coincidently. From this exclusive measurement the valence nucleon knockout mechanism and the core knockout mechanism are separated, which can be applied to the exclusive spectroscopic study on the structure of exotic nuclei.

Efficient calibration methods have been applied to a complex neutron detector array by using the cosmic-ray muons. Through a differential operation on the time difference spectrum, the two edges of this spectrum can be precisely determined, corresponding to the geometrical two ends of the bar, and therefore the relationship between the position and time difference spectrum can be deduced for each bar. The alignment between different bars is realized by choosing cosmic-rays which are perpendicular to the bars. The position resolutions are extracted through a track fitting procedure which uses all tracks detected coincidently by the whole system, together with a simulation analysis. A method is also developed to calibrate the deposited energy by using cosmic-rays at different incident angles.

This paper presents a conceptual design for the first tentative surface muon source based on the proton beam provided by China Spallation Neutron Source (CSNS). We have calculated the optimal parameters of solid muon target, in which the method of Monte Carlo simulation is used to obtain the optimal muon beam parameters, such as beam fluence rate, momentum spread and phase space distribution. A simple muon transport beamline system was also designed, which could transport the muons emitted from the muon target into the experimental area, where positrons from muon decay in a test sample are detected by a spectrometer. The beam optics of this new beam line is also described.

Experimental data analysis and simulation calculations were performed in order to evaluate the cross-talk rejection performance of a typical neutron detection array. For very closely packed scintillation bars, the CT rejection may rely on the position relation between the two signals. The criteria |Δx| ≦ 15 cm and |Δ_y| ≦ 12 cm are currently proposed for a rejection rate higher than 90%. For signals coming from distanced bars, the energy conservation relationship can be applied to reject the CT events with a similar performance. In both cases the results of simulation agree very well with the experimental data, assuring their applicability to other detection systems and physics problems.

LPT (Lanzhou Penning Trap) is an ion-trap facility in Lanzhou, China. As ions can be cooled to an extremely small phase space and can be stored for a very long time, ion traps are a perfect instrument for high precision mass measurements. A system with specialized electronics for LPT is under construction now. This system could be used for voltage and timing control to make ions moving in a special mode, and the data acquisition and analysis online/offline could be achieved in the mean time. The requirements of control system, the distribution of hardware, the overview of software, and the latest progress of LPTCtrlSys (Lanzhou Penning Trap Control System) are presented.

Usually, there are several methods, e.g. experiment, interpolation experiment-based, analytic function, and Monte-Carlo simulation, to calculate the response functions in LaBr₃(Ce) detectors. In logging applications, the experiment-based methods cannot be adopted because of their limitations. Analytic function has the advantage of fast calculating speed, but it is very difficult to take into account many effects that occur in practical applications. On the contrary, Monte-Carlo simulation can deal with physical and geometric configurations very tactfully. It has a distinct advantage for calculating the functions with complex configurations in borehole. A new application of LaBr₃(Ce) detector is in natural gamma-rays borehole spectrometer for uranium well logging. Calculation of response functions must consider a series of physical and geometric factors under complex logging conditions, including earth formations and its relevant parameters, different energies, material and thickness of the casings, the fluid between the two tubes, and relative position of the LaBr₃(Ce) crystal to steel ingot at the front of logging tube. The present work establishes Monte-Carlo simulation models for the above-mentioned situations, and then performs calculations for main gamma-rays from natural radio-elements series. The response functions can offer experimental directions for the design of borehole detection system, and provide technique basis and basic data for spectral analysis of natural gamma-rays, and for sourceless calibration in uranium quantitative interpretation.

The radiative capture reaction plays an important role in nuclear astrophysics. We have indirectly measured the astrophysical S(E) factors for some proton capture reactions and reaction rates for several neutron capture reactions with one nucleon transfer reactions at HI-13 tandem accelerator in recent years. Some of them are compiled into IAEA EXFOR database and JINA REACLIB project, and used in the network calculations of Big Bang nucleosynthesis and type-I X-ray bursts.

This paper reports on two nuclear astrophysics experiments performed in collaboration with Ruhr University. In a ¹²C+¹²C fusion reaction, the ¹²C(¹²C, α)²⁰Ne and ¹²C(¹²C, p)²³Na reactions were studied in the energy range of E = 2.10 MeV to 4.75 MeV using γ-ray spectroscopy. The deduced astrophysical S(E)* factor exhibited a new, strong resonance at E = 2.14 MeV, which lay at the high-energy tail of the Gamow peak. The resonance increased the reaction rate of the α-channel by a factor of five near T = 8 × 10⁸ K. The electron screening in d(d, p)t was studied for a series of deuterated metal, insulator and semiconductor targets. Compared with the measurements performed with a gaseous D₂ target, a large effect was observed in most metals, while a comparatively small effect was found in the insulators and semiconductors. Subsequently the temperature dependence of the electron screening in the d(d, p)t reaction was studied for the deuterated metals Pt and Co. Enhanced electron screening decreased with increasing temperature. These data represent the first observations of the temperature dependence of a nuclear cross section.

The high-spin states of ¹⁴¹Pm nucleus have been studied by using in-beam γ-ray spectroscopy technology through the¹²⁶Te(¹⁹F, 4n) reaction at a beam energy of 90 MeV. The previous level scheme has been extended with spin up to 49/2 ℏ. Many new levels and transitions are identified. Five collective band structures are observed. Based on systematic comparison with the neighboring nuclei, two bands with strong ΔI = 1 M1 transitions inside the bands are proposed as the oblate bands with γ∼−60°, and three bands with large signature splitting have been suggested as the oblate-triaxial deformation with γ∼−90°. The characteristics for these bands have been discussed.

A set of new global phenomenological optical model potential parameters has been obtained in the mass range of target nuclei 220≤A≤260 with incident energies below 300 MeV, by simultaneously fitting the experimental data of ²³²Th and ²³⁸U, and these potential parameters are analyzed and used to calculate the reaction cross sections, energy spectra and double differential cross sections for p+²³²Th reaction. Comparison of calculated results using these potential parameters with available experimental data shows that the present form of global optical model potential could reproduce experimental data for both the neutron and the proton.

A knockout reaction experiment was carried out by using the ⁶He beam at 82.5 MeV/nucleon impinging on CH₂ and C targets. The α core fragments at forward angles were detected in coincidence with the recoiled protons at larger angles. From this exclusive measurement the valence nucleon knockout mechanism and the core knockout mechanism are separated. This study provides a basis for the exclusive spectroscopic investigation of the exotic nuclei.

High-spin states in ¹⁵⁷Yb have been populated in the ¹⁴⁴Sm(¹⁶O, 3n)¹⁵⁷Yb fusion-evaporation reaction at a beam energy of 85 MeV, and two rotational bands have been established for the first time. Within the framework of the triaxial particle-rotor model, the energy spectra and single-particle configurations of ¹⁵⁷Yb are investigated. The calculated energy spectra agree well with the experimental data. The newly observed νf_7/2 band, and the previously known νi_13/2 band in ¹⁵⁷Yb, are also discussed by means of Total-Routhian-Surface methods. The structural characters observed in ¹⁵⁷Yb provide evidence for the shape coexistence of three distinct shapes: prolate, triaxial and oblate. At higher spins, both the νf_7/2 band and the νi_13/2 band in ¹⁵⁷Yb undergo a shape evolution with sizable alignments occurring.

An angular momentum projected potential-energy-surface (PES) calculation, which takes both rotational symmetry restoration and multi-quasiparticle excitation into account, is developed by using the macroscopic-microscopic model and the projected shell model (PSM). Within this method, it may become possible to modify the excitation spectra which are influenced by shape-softness of nuclei, including high-K states. As our first example, this method is adopted to study the collective and multi-quasiparticle excitations of ¹⁷⁸Hf, and the results are in good agreement with the existing experimental data. In addition, as for the dominant structure of non-collective 6⁺ bands, the conflict between experimental result and the previous PSM calculation is clarified.

High spin states in ¹⁰⁷Ag have been studied via the ¹⁰⁰Mo(¹¹B, 4n)¹⁰⁷Ag reaction at a beam energy of 60 MeV on the HI-13 tandem accelerator at the China Institute of Atomic Energy. By analyzing the gamma-gamma coincidence and their DCO ratios, a new level scheme of ¹⁰⁷Ag is presented. The structures for the newly constructed bands are briefly discussed and tentatively assigned to be chiral doublet bands.

An attempt is made to improve the evaluation of the prompt fission neutron emission from ²³³U(n, f) reaction for incident neutron energies below 6 MeV. The multi-modal fission approach is applied to the improved version of Los Alamos model and the point by point model. The prompt fission neutron spectra and the prompt fission neutron as a function of fragment mass (usually named "sawtooth" data) υ(A) are calculated independently for the three most dominant fission modes (standard I, standard II and superlong), and the total spectra and υ(A) are synthesized. The multi-modal parameters are determined on the basis of experimental data of fission fragment mass distributions. The present calculation results can describe the experimental data very well, and the proposed treatment is thus a useful tool for prompt fission neutron emission prediction.

The level lifetimes in partner bands of ¹³⁰Cs have been measured using the Doppler Shift Attenuation method (DSAM). The high-spin states of ¹³⁰Cs were populated via fusion evaporation reaction ¹²⁴Sn(¹¹B; 5n)¹³⁰Cs at a beam energy of 65 MeV. The absolute M1 and E2 transition probabilities have been deduced. The results indicate that the partner bands of ¹³⁰Cs indeed manifest chiral properties.

Configuration-constrained potential energy surface calculations have been performed to investigate four-quasiparticle high-K configurations in neutron-deficient lead and polonium isotopes. A good agreement between the calculations and the experimental data has been found for the excitation energy of the observed K^π = 19⁻ state in ¹⁸⁸Pb. Several lowly excited high-K states are predicted, and the large oblate deformation and low energy indicate high-K isomerism in these nuclei.

The high spin states of ¹⁰⁶Pd have been populated through the ¹⁰⁰Mo(¹¹B, 1p4n)¹⁰⁶Pd reaction using a beam energy of 60 MeV provided by the Beijing HI-13 tandem accelerator at China Institute of Atomic Energy. By analyzing the γ-γ coincidence relation and DCO raios of transitions, 3 rotational bands with 13 new states and 22 new γ transitions belonging to ¹⁰⁶Pd were constructed. Bands 2 and 3 with negative parity were supposed to build on the νh_11/2g_7/2 and νh_11/2d_5/2 configuration, respectively.

In this work, the ground-state properties of Pt, Hg, Pb, and Po isotopes have been systematically investigated in the deformed relativistic mean field (RMF) theory with the new parameter set FSUGold. The calculated results show that FSUGold is as successful as NL3 in reproducing the ground-state binding energies of the nuclei in this region. The calculated two-neutron separation energies, quadrupole deformations, and root-mean-square charge radii are in agreement with the experimental data. The parameter set FSUGold can successfully describe the shell effect of the neutron magic number N = 126 and give smaller neutron skin thicknesses than NL3 for all the nuclei considered.

A neutron detector array was used in a breakup reaction experiment at RIKEN with an 82.5 MeV/u ⁸He beam impinging on the CH₂ and C targets. The array was calibrated using the cosmic ray, the γ ray from the ⁶He+Pb reaction and the mono-energetic neutrons from the ⁷Li(p, n)⁷Be(g.s.+0.43 MeV) reaction. The position resolution, timing resolution and neutron detection efficiency were obtained accordingly. Cross-talk rejection conditions were developed based on analysis of the data taken from the ⁷Li(p, n)⁷Be(g.s.+0.43 MeV) test experiment, and finally a preliminary two-neutron correlation function for the ⁸He breakup reaction was investigated.

The ratio of ³⁶Cl/Cl can determine the exposure age of surface rocks and monitor the secular equilibrium of ³⁶Cl of sedimentary and igneous rock in groundwater. Due to the uncertainty effects of different chemical separation processes for removing ³⁶S, there is a high degree of uncertainty in ³⁶Cl accelerator mass spectrometry (AMS) measurements if the ratio of ³⁶Cl/Cl is lower than 10⁻¹⁴. A ³⁶Cl AMS higher sensitivity measurement has been set up by using a ΔE-Q3D method at the China Institute of Atomic Energy (CIAE). The performances of ΔE-Q3D method for ³⁶Cl-AMS measurement had been systemically studied. The experimental results show that the ΔE-Q3D method has a higher isobar suppression factor. Taking advantage of direct removing ³⁶S, the sample preparation can be simplified and the uncertainty effects of different chemical separation processes can be reduced in ³⁶Cl AMS measurements.

The irradiation damage in nickel-base alloy C-276 irradiated with 115 keV Ar ions from low to very high doses was investigated. Structural characterization was performed using transmission electron microscopy (TEM), grazing incident X-ray diffraction (GIXRD) and atomic force microscopy (AFM). High density of interstitial type dislocation loops could be observed at a dose level of around 2.75 displacements per atom (dpa). With the irradiation dose increased to 27.5 dpa, the average size of loops increased from 5 nm to 16 nm, while the density of the loops decreased from 1.4 × 10¹¹/cm² to 4.6 × 10¹⁰/cm². When the irradiation dose reached 82.5 dpa, original grains were transformed into subgrains whose sizes observed from TEM were about 20∼60 nm. The fragmentation of grains was confirmed by GIXRD. The mean subgrain size was 40 nm, which was obtained from the full width at half maximum (FWHM) of the X-ray diffraction lines using the Scherrer formula and Williamson formula. AFM micrographs showed that nanometer-sized hillocks formed at the dose of 82.5 dpa, which provided further evidence of grain fragmentation at a high irradiation dose.

An accurate energy calibration of a 5'' × 2'' BC501A liquid scintillator-based neutron detector by means of photon sources and the unfolding of pulse height spectra are described. The photon responses were measured with ²²Na, ¹³⁷Cs and ⁵⁴Mn photon sources and simulated using the GRESP code, which was developed at the Physikalisch Technische Bundesanstalt in Germany. Pulse height spectra produced by three different photon sources were employed to investigate the effects of the unfolding techniques. It was found that the four unfolding codes of the HEPRO and UMG3.3 packages, including GRAVEL, UNFANA, MIEKE and MAXED, performed well with the test spectra and produced generally consistent results. They could therefore be used to obtain neutron energy spectra in tokamak experiments.

The effect of the size of radiotherapy photon beams on the absorbed dose to an Al₂O₃ dosimeter was investigated using the Monte Carlo method. The EGSnrc/DOSRZnrc program code was used to simulate the absorbed dose to the Al₂O₃ dosimeter, as well as the absorbed dose to water at the corresponding position in the absence of the dosimeter. The incident beams were ⁶⁰Co γ and 6 MV with a different beam radius ranging from 0.1 cm to 2 cm. Results revealed that the absorbed dose ratio factor depends on the size of the incident photon beam. When the radius of the incident beam is smaller than that of the dosimeter, the absorbed dose ratio factor decreases as the incident beam size increases. The absorbed dose ratio factor reaches its minimum when the radius of the incident beam is almost the same as that of the dosimeter. When the radius of the incident beam is larger than that of the dosimeter, the absorbed dose ratio factor increases as the incident beam size increases. The maximum difference among these absorbed dose ratio factors can be up to 14% in ⁶⁰Co γ beams and 23% in 6 MV beams. However, when the size of the incident beam is much larger than that of the dosimeter, the effect of the incident beam size on the absorbed dose ratio factor becomes quite small. The maximum discrepancy between the absorbed dose ratio factors and the average value is not more than 1%.

Intensity modulated radiation therapy (IMRT) requires the determination of the appropriate multileaf collimator settings to deliver an intensity map. The purpose of this work was to attempt to regulate the shape between adjacent multileaf collimator apertures by a leaf sequencing algorithm. To qualify and validate this algorithm, the integral test for the segment of the multileaf collimator of ARTS was performed with clinical intensity map experiments. By comparisons and analyses of the total number of monitor units and number of segments with benchmark results, the proposed algorithm performed well while the segment shape constraint produced segments with more compact shapes when delivering the planned intensity maps, which may help to reduce the multileaf collimator's specific effects.

Neutral beam injection (NBI) system with two neutral beam injections will be constructed on the Experimental Advanced Superconducting Tokamak (EAST) in two stages for high power auxiliary plasmas heating and non-inductive current drive. Each NBI can deliver 2∼4 MW beam power with 50∼80 keV beam energy in 10∼100 s pulse length. Each elements of the NBI system are presented in this contribution.