Vol.28,

In this work, linear and mass attenuation coefficients, half and tenth value layers, effective atomic number and electron density of different types of concretes were determined at 316.51, 468.07, 511, 662, 1173 and 1332 keV using MCNP-4C code and WinXCom program. The MCNP-4C and WinXCom results agreed well with each other, with differences of < ±1.9%. The results agreed with available experimental data, too, with differences of <±6%. The MCNP-4C results showed better agreement with the experimental data than the WinXCom results. Also it was found that the effective electron density of studied concretes varies in the range of (2.83–3.2) ×10²³ electron/g.

458

The magnetic lens (Zumbro lens) is a critical part in proton radiography. Traditionally the matched beam for Zumbro lens in proton radiography is a virtual-point source beam, which is not suitable for some cases, such as cylindrical samples. In these cases, a parallel beam is more appropriate. In this paper, a method, which uses quadrupole beamline, is proposed for designing a magnetic lens with parallel beam matched. Theoretical analysis is given. The results show that the matched beam for this lens is indeed parallel beam, while the major merits of Zumbro lens are inherited. Following this method, a theoretical design based on the 11-MeV cyclotron is presented.

424

Grating-based X-ray imaging can make use of conventional tube sources to provide absorption, refraction and scattering contrast images from a single set of projection images efficiently. In this paper, a fresh cherry tomato and a dried umeboshi are imaged by using X-ray Talbot-Lau interferometer. The seed distribution in the scattering image of the cherry tomato, and the wrinkles of epicarp in the refraction image of the umeboshi, are shown distinctly. The refraction and scattering images provide more information on subtle features than the absorption image. Also, the contrast-to-noise ratio values show distinguishing capacity of the three kinds of imaging techniques. The results confirm that grating-based X-ray imaging is of great potential in non-destructive fruit testing.

581

Thermal aging effects on surface of 2.5 MeV Fe ion irradiated Fe-0.6%Cu alloy were investigated using positron annihilation techniques. The samples were irradiated at 573 K to a dose of 0.1 dpa. Their thermal aging was performed at 573 K for 5, 50, and 100 h. From the results of Doppler broadening measurement, an obvious trough could be seen in near surface region from the S parameters and inflection point form at S-W curves. This indicates changes in the annihilation mechanism of positrons in surface region after thermal aging. Coincident Doppler broadening indicates that the density of Cu precipitates in the thermal aged samples decreased, due to recovery of the vacancies.

502

Natural radioactivity radionuclides in building materials, such as ²²⁶Ra, ²³²Th and ⁴⁰K, cause indoor exposure due to their gamma rays. In this research, in a standard dwelling room (5.0 m×4.0 m×2.8 m), with the floor covered by various granite stones, was set up to simulate the dose rates from the radionuclides using MCNP4C code. Using samples of granite building products in Iran, activities of the ²²⁶Ra, ²³²Th and ⁴⁰K were measured at 3.8–94.2, 6.5–172.2 and 556.9–1529.2 Bq·kg⁻¹, respectively. The simulated dose rates were 26.31–184.36 nGy·h⁻¹, while the measured dose rates were 27.70–204.17 nGy·h⁻¹. With the results in good agreement, the simulation is suitable for any kind of dwelling places.

455

Isotopic fragment yields of projectile fragmentation in peripheral collisions of ⁸⁶Kr on ^124,112Sn and the mean neutron to proton ratios of the fragments are calculated, theoretically, within the ensemble approach of statistical multifragmentation model. Obtained data are compared to the experimental cross section measurements for the projectile-like fragmentation in the reaction of 25 MeV/nucleon ⁸⁶Kr+^124,112Sn at Texas A&M University. We show the enhancement in the production of neutron-rich isotopes close to the projectile as observed in the experiments. We also demonstrate the universality of the limitation of the excitation energy induced in the projectile residues.

615

Based on the newest experimentally extracted nuclear density distributions for double-magic nucleus ²⁰⁸Pb [C. M. Tarbert et al., Phys. Rev. Lett. 112, 242502 (2014)], the sensitivity of α-decay half-life to nuclear skin thickness is explored in the vicinity of the shell closure region around ²⁰⁸Pb, i.e., isotopes of Z=82 and isotones of N=126. With the two-parameter Fermi (2PF) density distributions and an analytically derived formula, the α-decay half-life is found to be closely related to the magnitude of nuclear skin thickness. For α decays to the Z=82 isotopes, the α-decay half-life is found to decrease with the increasing neutron skin thickness, while the opposite behavior is found for α decays to the N=126 isotones. Therefore, it could be a possible way to extract the nuclear skin thickness from measured α-decay half-lives.

507

In this paper, we propose a new method for position-sensitive measurement of beta surface contamination. With a position-sensitive detector of enlarged sensitive detection area, accurate information of the contamination distribution can be obtained. The position-sensitive detection is based on a large-area plastic scintillator and the wavelength shifting (WLS) fibers, and adopts the "light center of gravity" method. Optical transmission of the detector is simulated with a preliminary detector model, and feasibility of the detector design and measurement method are evaluated using an experiment system. The simulation and experiment results at different beta-ray incident points on the scintillator surface show that there is a polynomial relationship between the average amplitude ratio of the output pulses from the two parallel WLS fibers in the same fiber layer and the relative distance from the incident point to the WLS fiber.

489

We report in this paper the alignment calibration of the STAR pixel detector (PXL) prototype for the RHIC 2013 run and performance study of the full PXL detector installed and commissioned in the RHIC 2014 run. PXL detector is the innermost two silicon layers of the STAR heavy flavor tracker (HFT) aiming at high precision reconstruction of secondary decay vertex of heavy flavor particles. To achieve the physics goals, the calibration work was done on the detector with high precision. A histogram-based method was successfully applied for the alignment calibration, and the detector efficiency after alignment was studied using both p+p collision data and cosmic-ray data.

600

The relativistic heavy-ion collisions create both hot quark-gluon matter and strong magnetic fields, and provide an arena to study the interplay between quantum chromodynamics (QCD) and quantum electrodynamics (QED). In recent years, it has been shown that such an interplay can generate a number of interesting quantum phenomena in hadronic and quark-gluon matter. In this short review, we first discuss some properties of the magnetic fields in heavy-ion collisions and then give an overview of the magnetic-field induced novel quantum effects. In particular, we focus on the magnetic effect on the heavy-flavor mesons, the heavy quark transports, and the phenomena closely related to chiral anomaly.

529

Four FPGA-based α/γ pulse shape discrimination algorithms for BaF₂ detector are investigated and compared in this paper. A 2 Gsps fast waveform sampling board based on DRS4 chip is employed to sample the pulses. The test results with a ²²Na γ-source and the natural radioactivity of BaF₂ show good discrimination performance of the algorithms, with false rates around 1%. Small logical resource occupancy and short dead time are achieved. About 4400 slices are used in FPGA for pulse sampling and real-time discrimination altogether.

615

In-situ quick X-ray absorption spectroscopy (QXAFS) at the Cu and Zn K-edge under operando conditions has been used to unravel the Cu/Zn interaction and identify possible active site of CuO/ZnO/Al₂O₃ catalyst for methanol synthesis. In this work, the catalyst, whose activity increases with the reaction temperature and pressure, were studied at calcined, reduced and reacted conditions. TEM and EDX images for the calcined and reduced catalysts showed that copper was distributed uniformly at both conditions. TPR profile revealed two reduction peaks at 165°C and 195°C for copper species in the calcined catalyst. QXAFS results demonstrated that the calcined form consisted mainly of a mixed CuO and ZnO, and it was progressively transformed into Cu metal particles and dispersed ZnO species as the reduction treatment. It was demonstrated that activation of the catalyst precursor occurred via a Cu+ intermediate, and the active catalyst predominantly consisted of metallic Cu and ZnO even under higher pressures. Structure of the active catalyst did not change with temperature or pressure, indicating that the role of the Zn was mainly to improve Cu dispersion. This indicates the potential of QXAFS method in operate structure evolutions for catalysts in methanol synthesis.

453