Vol.26,

The BL08U1A beamline is established as a sophisticated platform at Shanghai Synchrotron Radiation Facility (SSRF), taking advantage of its high spatial resolution (<30 nm) and high energy resolving power (>10000), for studying properties of solid, liquid, gas, film and other forms of materials at sub-micron scale. In this paper, we present a review on newly implemented techniques, such as total electron yield (TEY), dual energy contrast imaging, nano-CT, soft X-ray excited optical luminance (SXEOL), and coherent diffraction imaging (CDI) under development. Several research cases in nanomaterials, environmental science and biology are presented to demonstrate capabilities of the beamline.

769

In this paper, we propose a two-mode polarizable deflecting structure, as a new concept for bunch measurement and beam control. With two modes of HEM11 and HEM12 operating in the same structure on horizontal and vertical directions, respectively, the operation status can be switched between the two polarization modes. They can be operated simultaneously with two independent input power sources. With two-mode deflecting structure, the bunch distortion caused by the geometric wake-fields in the accelerating structure can be measured by one structure.

470

A proton therapy system is a large medical device to treat tumors. Its gantry is of large structure and high precision. A new half-gantry was designed in the Shanghai Advanced Proton Therapy (SAPT) project. In this paper, the weight of gantry in design is reduced significantly by size and structure optimizations, to improve its cost-effectiveness, while guaranteeing the functions and precision. The processes of physics optimization, empirical design optimization, topological optimization and size optimization, together with factors of consideration, are described. The gantry weight is reduced by 30%, with the same precision.

697

In order to do alignment between the timing signal and the synchrotron X-ray pulse on the sample spot in the time domain, measuring time structure of the storage ring on the sample spot inside the experimental hutch is a foundational step during the time-resolved experiments using the pulsed synchrotron X-rays with the time structure defined by the storage ring. In this work, the method of time-resolved X-ray excited optical luminescence (TRXEOL) was designed and implemented to do the measurement. It is based on the principle of time-correlated single photon counting techniques. The measurement system consists of a spectrometer with a detector of photomultiplier tube, a timing system, a set of nuclear instrument modules and a luminescent material of zinc oxide. The measurement was performed on the X-ray absorbed fine structure spectrum beamline at Shanghai Synchrotron Radiation Facility. The results show that this method can be used to measure the time structure of the storage ring with a precision of less than 1 ns. The measurement system can also be used for the time-resolved research for the optical luminescent materials.

545

Graphene oxide (GO) nanosheets possess several advantages, such as a large surface, outstanding bio-compatibility, and straightforward chemical modification capability. They also have great potential as a drug-carrier. In this article, we radiolabeled GO nanosheets with ^99mTc, which satisfies the potential needs of micro-SPECT imaging probes in pre-clinical and clinical research. GO nanosheets were synthesized through the modified Hummers’ method, then GO nanosheets with azide group covalently functionalized in two steps were conjugated to DOTA (1,4,7,10-tetraazacyclododecane-N,N’,N",N" ’-tetraacetic acid) and functionalized with an alkynyl group by means of click chemistry. Then through the addition and reduction of technetium-99m, the ^99mTc-DOTA-GO were attained. DOTA-conjugated GOs with lateral dimensions of 500–600 nm were synthesized. Both atomic force microscopy (AFM) and FT-IR were performed to characterize the GO-DOTA. Labeling efficiency of GO-DOTA with ^99mTc was >90% and radiochemical purities were >96% with purification. We successfully synthesized graphene oxide derivatives, DOTA-conjugated GOs, via Click Chemistry, and it was labeled with ^99mTc for SPECT imaging. High radiolabeling efficiency makes GO nanosheets suitable platforms for future molecular imaging research.

391

Uranium removal efficacy of fullerence multi-macrocyclic polyamine derivatives (C₆₀-MMP), a novel chelating agent, was evaluated in mice. C₆₀-MMP was administrated intravenously into mice at 30 min after the uranium contamination. The molar ratio of chelating ligand/uranium was about 1:1. The results indicate that C₆₀-MMP can effectively prevent accumulation of uranium in liver at 8 h after C₆₀-MMP injection. At 48 h after the last injection, uranium deposition in liver of C₆₀-MMP treated mice is approximately 65% less than that of the control group. C₆₀-MMP reacted positively in promoting the removal of uranium from kidney, and the urinary uranium excretion increased significantly, compared with the control and DTPA-treated mice. However, repeated administration of C₆₀-MMP, and combined injection of DTPA and C₆₀-MMP, did not show desirable effects on uranium removal from mice. It implies that more investigations are needed for the treatment protocols and clinical applications of C₆₀-MMP.

362

To prevent radioactive iodides from releasing into the environment in an accident of a nuclear power plant, silver-impregnated alumina (Ag/Al₂O₃) was fabricated, and its performance of radioactive iodine adsorption from high-temperature gas was tested. The silver loadings on alumina were obtained by ICP-OES and the texture properties of Ag/Al₂O₃ were characterized by N₂ adsorption-desorption. The Ag/Al₂O₃ was of reduced specific surface (107.2 m²/g at 650 ℃). Crystalline phases of Ag/Al₂O₃ were confirmed through XRD characterization. After calcination at 650 ℃ for 2 h, the crystalline phase of Ag/Al₂O₃ changed. The ¹³¹I- removal efficiency of Ag/Al₂O₃ was tested at 100, 250, 350, 450 and 650 ℃, with good decontamination factor values for the radioactive iodine. Silver-impregnated alumina can be applied as adsorbents to remove radioactive iodine at high temperatures in nuclear accident.

355

Instrumental neutron activation analysis (INAA) has been used to determine some chemical element contents (K, Ca, Na, Fe, Zn, Co, Eu, Sb, and Sc) in Traganum nudatum Del (Chenopodiaceae family) consumed in North African rangelands by sheep livestock. Samples were collected from the area of Djelfa in an arid steppe of Algeria. Results show that pasture halophyte had sufficient levels of K, Ca, Zn, and Co to meet the requirements of ruminants. However, it seems that this halophyte shrub had substantial amounts of Na, higher than the critical level established by the National Research Council (NRC). Eu, Sb, and Sc were within the safety baseline of all the assayed elements recommended by the NRC. The high Na content (∼ 10 g/kg) in this halophytic species requires elevated intake of water by livestock.

320

Wire position monitor (WPM) is designed to monitor contraction of the cold masses during the cooling-down operation in an accelerator driven system. Because of material difference, machining error, assembly error, etc., each WPM has to be calibrated. The sensing voltage and wire position are of a nonlinear relationship, which is expressed by high order polynomial. Root mean square (RMS) of the polynomial fitting error were 3.8 μm and 7.4 μm at x and y directions, respectively. The alignment test was carried out on the beta cryostat. Optical instruments were used to verify the WPM measuring results. The differences between WPM measuring results and optical measurements were 0.044 and 0.05 mm in x and y direction, respectively. A significant asymmetric contraction was detected, and asymmetry of material was taken as the main reason through analysis.

347

A digital three-detector positron lifetime spectrometer was developed. It consists of a DRS4 waveform digitizing board and three LaBr₃ scintillation detectors coupled to XP2020Q photomultiplier tubes. DRS4 waveform digitizing allows data sampling at up to 5 GSPS with high amplitude resolution, with good time scale linearity and stability. In the triple-coincidence, the new system could reach a 195 ps time resolution, which is better than the conventional analog apparatus with the same detectors. This spectrometer can be applied to the other scintillation timing measurements with picoseconds accuracy.

447

The Dragon-I linear induction accelerator (LIA) at China Academy of Engineering Physics generates 20 MeV flash X-rays mainly for radiography applications in fluid dynamics. Its spectral information is quite important for diagnostic X-ray imaging applications, but because of its short pulse and great radiation intensity, direct measurement is impossible. In this work, we propose a new method based on transmission measurements to obtain the flash X-ray spectrum. Pure iron cylinders were used as attenuation material, and alanine dosimeters were attached on their rear bottom to record the dose after different degrees of attenuation. Iterative least square method was used to unfold the spectrum, while Geant4 Monte Carlo code was used to simulate the X-ray spectrum. The unfolded spectrum and the simulated spectrum have a high degree of consistency, with the reduced chi-square value of 0.044. This shows that the method is reliable in estimating megavoltage high-intensity X-ray spectrum.

490

The ²⁵²Cf source-driven verification system (SDVS) can recognize the enrichment of fissile material with the enrichment-sensitive autocorrelation functions of a detector signal in ²⁵²Cf source-driven noise-analysis (SDNA) measurements. We propose a parallel and optimized genetic Elman network (POGEN) to identify the enrichment of ²³⁵U based on the physical properties of the measured autocorrelation functions. Theoretical analysis and experimental results indicate that, for 4 different enrichment fissile materials, due to higher information utilization, more efficient network architecture, and optimized parameters, the POGEN-based algorithm can obtain identification results with higher recognition accuracy, compared to the integrated autocorrelation function (IAF) method.

432

In order to study the effect of tensor force, we plan to perform a (p,d) reaction with a 400–1600 MeV proton beam on the RIBLL2 at Lanzhou. Based on the experimental conditions of RIBLL2, a Monte Carlo method is used to simulate (p,d) reaction process. The distributions of primary beam and scattered deuterons are given on the target and at the F₁, F₂, F₃, and F₄ positions. Considering the yield of the deuteron, to separate the produced deuteron from the background particles, the target thickness is optimized. To obtain a clear particle identification spectrum by time of flight (TOF) and energy loss (ΔE), the distance between the two detectors, as well as the energy and timing resolution of detectors are simulated. As a result, the distance between F₂ and F₄ is fit for that of TOF. After taking into account the particle distribution at F₄, both sizes of Multi-Wire Drift Chamber, namely MWDC2 and MWDC3, are selected to be 50 mm×50 mm.

477

The influence of the α-decay radionuclide layer (the energy of α-particles are 5.45 MeV) on the radar cross section (RCS) of sphere objects was calculated under different radioactivities, frequencies, and sphere radii. When the sphere radius is smaller than 50 cm, the tendency of the electron densities of the plasma slab is to ascend first and then descend, and the typical maximum electron densities with a radioactivity of 10 Ci/cm² raises from 7.02×10¹⁰ to 1.76×10¹¹ when the sphere radii increases from 10 to 300 cm. The average data of a normalized RCS of a sphere with radius of 12.5 cm, which is coated with a radionuclide layer with different radioactivities are -0.35, -0.50, -0.79 and -1.13 dB when the radioactivity is, per-mode=symbol 1, 2, 5 and 10 Ci/cm², respectively.

502

The properties of color-flavor locked strange quark matter in an external strong magnetic field are investigated in a quark model with density-dependent quark masses. Parameters are determined by stability arguments. It is found that the minimum energy per baryon of the color-flavor locked (MCFL) matter decreases with increasing magnetic-field strength in a certain range, which makes MCFL matter more stable than other phases within a proper magnitude of the external magnetic field. However, if the energy of the field itself is added, the total energy per baryon will increase.

413

Aluminium is widely used as an antimicrobial coagulant, food additive, and cookware. However, many reports indicate that aluminium may be a critical factor in many amyloid diseases, such as Alzheimer’s disease and Parkinson’s disease. Unfortunately, the underlying mechanism is still poorly understood, which limits efforts to prevent and treat these diseases. In this paper, using an ab initio method, we studied the interaction of Al-backbone ring structure with the π-electron-rich sidechains of His, Phe, Trp, and Tyr. We found that in the absence of water, the Al-backbone ring can stably bind with those sidechains. In the presence of water, the Al-backbone ring can bind to the His sidechain and cannot bind to the other sidechains. As revealed by further investigations, this could be attributed to the fact that there was a coordinate bond of the Al-backbone ring with the His sidechain, while there were the π-π stacking and cation-π-like interactions with the other sidechains. These findings potentially provide a molecular understanding of Al-related toxicity, and may be helpful in designing drugs for those aforementioned aluminum-linked diseases and encourage treatment of Al-polluted water.

395

The present study is to develop a new user-defined function using artificial neural networks intent Computational Fluid Dynamics (CFD) simulation for the prediction of water-vapor multiphase flows through fuel assemblies of nuclear reactor. Indeed, the provision of accurate material data especially for water and steam over a wider range of temperatures and pressures is an essential requirement for conducting CFD simulations in nuclear engineering thermal hydraulics. Contrary to the commercial CFD solver ANSYS-CFX, where the industrial standard IAPWS-IF97 (International Association for the Properties of Water and Steam-Industrial Formulation 1997) is implemented in the ANSYS-CFX internal material database, the solver ANSYS-FLUENT provides only the possibility to use equation of state (EOS), like ideal gas law, Redlich-Kwong EOS and piecewise polynomial interpolations. For that purpose, new approach is used to implement the thermophysical properties of water and steam for subcooled water in CFD solver ANSYS-FLUENT. The technique is based on artificial neural networks of multi-layer type to accurately predict 10 thermodynamic and transport properties of the density, specific heat, dynamic viscosity, thermal conductivity and speed of sound on saturated liquid and saturated vapor. Temperature is used as single input parameter, the maximum absolute error predicted by the artificial neural networks ANNs, was around 3%. Thus, the numerical investigation under CFD solver ANSYS-FLUENT becomes competitive with other CFD codes of which ANSYS-CFX in this area. In fact, the coupling of the Rensselaer Polytechnical Institute (RPI) wall boiling model and the developed Neural-UDF (User Defined Function) was found to be useful in predicting the vapor volume fraction in subcooled boiling flow.

520

Neutron-TPC (nTPC) is a fast neutron spectrometer based on GEM-TPC (Gas Electron Multiplier-Time Projection Chamber) and expected to be used in nuclear physics, nuclear reactor operation monitoring, and thermo-nuclear fusion plasma diagnostics. By measuring the recoiled proton energy and slopes of the proton tracks, the incident neutron energy can be deduced. It has higher n/γ separation ability and higher detection efficiency than conventional neutron spectrometers. In this paper, neutron energy resolution of nTPC is studied using the analytical method. It is found that the neutron energy resolution is determined by 1) the proton energy resolution (σ_Ep/E_p), and 2) standard deviation of slopes of the proton tracks caused by multiple Coulomb scattering (σ_{k(scattering)}) and by the track fitting accuracy (σ_k(fit)). Suggestions are made for optimizing energy resolution of nTPC. Proper choices of the cut parameters of reconstructed proton scattering angles (θ_cut), the number of fitting track points (N), and the working gas help to improve the neutron energy resolution.

369

The Chinese Academy of Science has launched a thorium-based molten-salt reactor (TMSR) research project with a mission to research and develop a fission energy system of the fourth generation. The TMSR project intends to construct a liquid fuel molten-salt reactor (TMSR-LF), which uses fluoride salt as both the fuel and coolant, and a solid fuel molten-salt reactor (TMSR-SF), which uses fluoride salt as coolant and TRISO fuel. An optimized 2 MWth TMSR-LF has been designed to solve major technological challenges in the Th-U fuel cycle. Preliminary conceptual shielding design has also been performed to develop bulk shielding. In this study, the radiation dose and temperature distribution of the shielding bulk due to the core were simulated and analyzed by performing Monte Carlo simulations and computational fluid dynamics (CFD) analysis. The MCNP calculated dose rate and neutron and gamma spectra indicate that the total dose rate due to the core at the external surface of the concrete wall was 1.91 μSv/h in the radial direction, 1.16 μSv/h above and 1.33 μSv/h below the bulk shielding. All the radiation dose rates due to the core were below the design criteria. Thermal analysis results show that the temperature at the outermost surface of the bulk shielding was 333.86 K, which was below the required limit value. The results indicate that the designed bulk shielding satisfies the radiation shielding requirements for the 2 MWth TMSR-LF.

407

After the Fukushima Dai-ichi nuclear power plant accident on March 11, 2011, the radioactivity released from the accident was transported around the globe by atmospheric processes. The radioactivity monitoring program on atmospheric particulate in Lanzhou, China was activated by GSCDC to detect the input radionuclides through atmospheric transport. Several artificial radionuclides were detected and measured in aerosol samples from March 26 to May 2, 2011. The peaked activity concentrations (in mBq/m³) were: 1.194 (¹³¹I), 0.231 (¹³⁷Cs), 0.173 (¹³⁴Cs) and 0.008 (¹³⁶Cs), detected on April 6, 2011. The average activity ratio of ¹³¹I/¹³⁷Cs and ¹³⁴Cs/¹³⁷Cs in air were 13.5 and 0.78. The significant increase of ¹³⁷Cs activity concentration, one order of magnitude higher than pre-Fukushima accident levels, in ground level aerosol was observed in 2013, as its resuspension from soil. The back-trajectory analysis simulated by NOAA-ARL HYSPLIT shows a direct transfer of the air masses released from Fukushima to Lanzhou across the Pacific Ocean, North America and Europe at the height close to 9000 m AGL. The value of effective dose for inhalation is close to one millionth of the annual limit for the general public.

504

The reduction stripping behavior of Pu(IV) from 30%TBP/OK with hydroxysemicarbazide (HSC) was investigated, and the separation efficiency of HSC and DMHAN-MMH for U/Pu partitioning in Purex process was compared. The results show that HSC can effectively realize the separation of Pu from U; using mixer-settlers to simulate U/Pu separation in 1B bank of PUREX, from 16-stage counter current extraction experiment (in which 6 stages for supplemental extraction, 10 stages for stripping) with flow rate ratio (1BF:1BX:1BS) =4:1:1 in 1B contactor, good result was achieved that the yields are both more than 99.99% for uranium and Pu, the separation factor of plutonium from uranium (SF_Pu/U) is 2.8×10⁴, and separation factor of uranium from plutonium (SF_U/Pu) is 5.9×10⁴. As a stripping reductant, HSC can effectively achieve the separation of Pu from U and the separation effect is nearly the same with DMHAN-MMH, which contributed to replace enough the latter with HSC in the U/Pu separation in Advanced Purex Process Based on Organic Reagent (APOR) process.

496