Vol.26,

Beamline BL16B1 at Shanghai Synchrotron Radiation Facility (SSRF) is dedicated to small angle X-ray scattering (SAXS) study. It aims at probing microstructure and dynamic processes of polymers, nanomaterials, mesoporous materials, colloids, liquid crystals, metal materials, etc. At present, SAXS, wide angle X-ray scattering (WAXS), simultaneous SAXS/WAXS, grazing incident SAXS, and anomalous SAXS techniques are available. The sample-to-detector distance is adjustable from 0.2 m to 5 m. For conventional SAXS, the practicable q-range is from 0.03–3.6 nm^-1 at incident X-ray of 10 keV. A continuous q-region of 0.06–33 nm^-1 can be achieved in simultaneous SAXS/WAXS mode. Time-resolved SAXS measurements in sub-second level can be performed. Detailed descriptions about status, performance and application of the SAXS beamline are given in this paper.

559

Conditioning an accelerating structure is important, and its performance is limited by breakdown and vacuum degradation, hence the necessity of finding problem in the conditioning. In order to save time, a judging process built in the firmware layer is applied in this paper. The system using the embedded algorithm in the Field Programmable Gate Array (FPGA) locates the position of breakdown and displays the result in the user interface. Also, the system has the functions of automatic conditioning and interlock protection, which are useful during the conditioning process of an S-band accelerating structure.

802

A beam dynamics design of 352.2 MHz radio-frequency quadrupole (RFQ) of Turkish Accelerator Center (TAC) project which accelerates continuous wave (CW) proton beam with 30 mA current from 50 keV to 3 MeV kinetic energy has been performed in this study. Also, it includes error analysis of the RFQ, in which some fluctuations have been introduced to input beam parameters to see how the output beam parameters are affected, two-dimensional (2-D) and three-dimensional (3-D) electromagnetic structural design of the RFQ to obtain optimum cavity paramaters that agree with the ones of the beam dynamics. The beam dynamics and error analysis of the RFQ have been done by using LIDOS.RFQ. Electromagnetic design parameters have been obtained by using SUPERFISH for 2-D cavity geometry and CST Microwave Studio for 3-D cavity geometry.

491

Simulating charged particle motion through the elements is necessary to understand modern particle accelerators. The particle numbers and the circling turns in a synchrotron are huge, and a simulation can be time-consuming. Open multi-processing (OpenMP) is a convenient method to speed up the computing of multi-cores for computers based on share memory model. Using message passing interface (MPI) which is based on non-uniform memory access architecture, a coarse grain parallel algorithm is set up for the Accelerator Toolbox (AT) for dynamic tracking processes. The computing speedup of the tracking process is 3.77 times with a quad-core CPU computer and the speed almost grows linearly with the number of CPU.

625

A novel high-frequency and high power density planar insulated core transformer (PICT) applied to high voltage direct current (DC) generator is introduced. PICT’s operating principle and fundamental configuration are described, and preliminary experimental results in self-designed PICT apparatus are presented. Emphatically, magnetic leakage flux (MFL) giving rise to the output voltage drop is analyzed in detail both theoretically and by finite element method (FEM). Showing good consistency with experimental result, FEM simulation is considered to be practicable in physical design of PICT. To cancel out leakage inductance and improve the voltage uniformity, compensation capacitor is adopted and experimental verification is also presented. All shows satisfactory results.

596

The low level radio frequency (LLRF) system for booster accelerator at Shanghai Synchrotron Radiation Facility (SSRF) was upgraded by a digital controller based on field programmable gate array (FPGA) technology. Parameters of voltage, frequency and field flatness in the two 5-cell cavities are controlled to meet the requirements of booster. In this article, the ramping curve of cavity voltage, amplitude and phase control loop with vector sum of the two 5-cell cavities, tuning loop and field flatness loop are analyzed and discussed in detail. A different method in tuning loop is adopted due to the limitations of ADC channels. The function realizes energy ramping of electron beam from 150 MeV to 3.5 GeV with a repetition rate of 2 Hz. With the new LLRF controller, the phase stability at ramping mode in 10 hours long operation is improved from ± 1.5° (RMS) with open loop to ± 0.15° (RMS) with close loop, while the detuning phase and field flatness are maintained to within ± 2°and ± 1%, respectively.

639

Microstructure and oxidation behavior of modified Ni-16Mo-7Cr-4Fe alloys by yttrium microalloying were investigated by scanning electron microscopy, transmission electron microscopy, grazing incident X-ray diffraction and synchrotron radiation X-ray fluorescence. M₆C and Ni₁₇Y₂ phases were observed and the amount of Ni₁₇Y₂ increased with yttrium concentration. When the yttrium concentration increased to 0.43wt.%, some Ni₁₇Y₂ chains and multi phase regions containing Ni₁₇Y₂, M₆C and γ phase appeared, which is harmful for the oxidation resistance. The alloy containing 0.05wt.% yttrium showed the best oxidation resistance, which derives its oxidation resistance from the adequate concentration of yttrium in the solid-solution (γ phase), the formation of the protective layer of YCrO₃ and chromia oxide and the strengthening effect of yttrium on oxide boundaries.

550

A macroporous silica-based silver loaded adsorbent was synthesized by grafting the silver complexes of thiourea (Ag(tu)₃NO₃) into a silica-based copolymer support (SiO₂-P). The adsorbent was used to uptake iodide anions (I^-) by batch and column techniques. The kinetic and saturated adsorption experiments were carried out by varying the shaking times and initial concentration of I^-. The experiments found that the kinetic adsorption of I^- was controlled by a pseudo second order model and the saturated adsorption of I^- was controlled by the chemisorption mechanism, which followed a Langmuir adsorption equation. The breakthrough curve of I^- had a S-shaped profile. The column efficiency was estimated to be over 90%.

663

615

The average absorbed dose in glandular tissue is the most appropriate parameter for the assessment of the radiation-induced risk during breast imaging. The aims of this work concern: (1) the investigation of the variation effect of any related update to photon cross-section data-bases on the computation of the normalized glandular dose (DgN) for mammography quality control tests and (2) the proposition of a parameterization method leading to provide DgN values function of the breast thickness (T) and the particle energy (E) instead of E alone, as normally known. We analyzed the change effect of the photon cross-section data-bases on the computation of DgN. Those coefficients, generated using the Geant4 Monte Carlo toolkit, were studied over a range of compressed breast thickness of 2–8 cm for monoenergetic (1–120 keV by 1 keV intervals) and polyenergetic (23–35 kVp by 2 kVp intervals) X-ray beams. Moreover, breast tissue composition ranging from about 0% glandular (about 100% adipose) to 100% glandular (0% adipose) was also covered. The successful parameterization of DgN look-up table function of the breast thickness and energy, will compact its analytical form without loss of accuracy. All parameterization fits resulted in r² values of 0.999 or better.

458

Poly[bis(phenoxyphosphazene)] (PBPP) and magnesium hydroxide (MH) are used as a flame retardant blend with low-density polyethylene (LDPE) for the nuclear cable. This study aims to investigate the effects of PBPP in MH-LDPE blend composites on flame retardance and electron beam irradiation. The structure, morphology, and properties of the blend composites irradiated by an electron beam to different absorbed doses were characterized. The results indicated that PBPP provides lubrication during processing. As the PBPP content in the blend increases the melt flow rate at 20 phr MH, meaning the material is easier to process. The higher the PBPP content, the higher the limiting-oxygen index. The elongation at the break of the PBPP containing composites (at 50 phr MH) was evidently higher than the non-PBPP ones at different absorbed doses by electron beam irradiation. The thermogravimetric analysis results indicated that the improved mechanical property, resulting from electron-beam irradiation, could be attributed to the consumption of PBPP.

463

Single event effects (SEEs) induced by radiations become a significant reliability challenge for modern electronic systems. To evaluate SEEs susceptibility for microelectronic devices and integrated circuits (ICs), an SEE testing system with flexibility and robustness was developed at Heavy Ion Research Facility in Lanzhou (HIRFL). The system is compatible with various types of microelectronic devices and ICs, and supports plenty of complex and high-speed test schemes and plans for the irradiated devices under test (DUTs). Thanks to the combination of meticulous circuit design and the hardened logic design, the system has additional performances to avoid an overheated situation and irradiations by stray radiations. The system has been tested and verified by experiments for irradiating devices at HIRFL.

511

A fully digital beam position monitoring system (DBPM) has been designed for SSRF (Shanghai Synchrotron Radiation Facility). As analog-to-digital converter (ADC) is a crucial part in the DBPM system, the sampling methods should be studied to achieve optimum performance. Different sampling modes were used and compared through tests. Long term variation among four sampling channels, which would introduce errors in beam position measurement, is studied, too. An interleaved distribution scheme was designed to address this issue. To evaluate the sampling methods, in-beam tests were conducted in SSRF. Test results indicate that with proper sampling methods, a turn-by-turn (TBT) position resolution better than 1 μm is achieved, and the slow-acquisition (SA) position resolution is improved from 4.28 μm to 0.17 μm.

432

Angle-resolved photoemission spectra (ARPES) are calculated in the Hubbard model by using cluster perturbation method. It is found that in a cluster of 12 sites, the local density of states displays the phase transition from normal conductor to Mott insulator with the increase of the electron-electron coupling. We show that a pseudogap develops from the metallic phase to the insulating phase. Evidence of spin-charge separation is also verified in the calculated single particle spectral functions.

689

A Neutron Time-Of-Flight (NTOF) spectrometer, based at the Heavy Ion Research Facility in Lanzhou (HIRFL) was developed for studies of neutron production of proton induced spallation reactions related to the ADS project. After the presentation of comparisons between calculated spallation neutron production double-differential cross sections and the available experimental data, a detailed description of the NTOF spectrometer is given. Test beam results show that the spectrometer works well and data analysis procedures are established. The comparisons of the test beam neutron spectra with those of GEANT4 simulations are presented.

463

In radiotherapy, the energy of the γ rays used could be larger than 10 MeV, which would potentially activate stable nucleus into a radioactive one. The γ induced reactions on some of the human essential elements are studied to show the probability of changes of nuclei. The Talys1.4 toolkit was adopted as the theoretical model for calculation. The reactions investigated include the (γ, n) and (γ, p) channels for the stable Na, Mg, Cl, K, Ca, and Fe isotopes, with the incident energy of γ ranging from 1 to 30 MeV. It was found that the cross sections for the reactions are very low, and the maximum cross section is no larger than 100 mb. By considering the threshold energy of the channel, the half-life time of the residue nucleus, and the percentage of the element accounting for the weight and its importance in the body, it is suggested to track the radioactive nuclei ²²Na, ⁴¹Ca, and ^42,43K after γ therapy. The results might be useful for medical diagnosis and disease treatment.

520

The theoretical model and the numerical analyses on the Gibbs-free-energy of the association states of amphiphilic molecules in nanoconfined aqueous solutions are presented in detail. We exhibit the continuous change of the Gibbs-free-energy trend, which plays a critical role in the association states of the system transforming from the dispersion state, through the "reversible state", and finally to the aggregation state in amphiphilic molecule solutions. Furthermore, for the "reversible state", we present the difference in the free-energy barrier heights of the dispersion state and aggregation state, resulting from the competition between the entropy, which makes the solute molecules evenly disperse in the solution and the energy contribution driving the amphiphilic molecules to aggregate into a larger cluster. These findings provide a comprehensive understanding of confinement effects on the solute association processes in aqueous solutions and may further improve the techniques of material fabrication.

542

Fluorescence spectroscopy was employed to investigate the interaction between fluorophore fluoresceinamine (FA) and bovine serum albumin (BSA) under physiological conditions. In the mechanism discussion, it was proved that the fluorescence quenching of BSA by FA is a result of the formation of a BSA-FA complex. Fluorescence quenching constants were determined using the modified Stern-Volmer equation to provide a measure of the binding affinity between FA and BSA. The results of the thermodynamic parameters ΔG, ΔH, and ΔS at different temperatures indicated that several kinds of interactions, except for the electrostatic interactions play cooperative roles in BSA-FA association. Furthermore, the conformation of BSA upon interaction with FA was also studied by synchrotron fluorescence spectroscopy.

445

The contents and distributions of metal elements in the brain are closely related to neurodegenerative diseases. In this study, we examined Fe, Cu and Zn contents in the brain section associated with Parkinson's disease (PD) using synchrotron radiation X-ray fluorescence (SRXRF). PD mouse model induced by 1-methyl-4-phenyl-1,2,3,6-terahydropyridine (MPTP) was used for the elemental analysis (e.g., Fe, Cu and Zn) in the substantia nigra pars compacta (SNpc) region of mice brain tissue samples. We found that mice in the MPTP group had higher contents of Fe, Cu and Zn in the SNpc than the control group. After treating the PD mice with rapamycin, the contents of Fe, Cu and Zn were reduced, the dopamine neurons and motor function were rescued correspondingly. The results prompted that the SRXRF provided an ideal method for tracing and analyzing the metal elements in the brain section to assess the pathological changes of PD model and the therapeutic effect of drugs.

453

TiO₂ nanofilms on surface of fused silica were fabricated by Ti ion implantation and subsequent thermal annealing in oxygen ambience. The silica glasses were implanted by 20 kV Ti ions to 1.5×10¹⁷ ions/cm² on an implanter of metal vapor vacuum arc (MEVVA) ion source. Effects of annealing parameters on formation, growth and phase transformation of the TiO₂ nanofilms were studied in detail. Optical absorption spectroscopy, Raman scattering spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy measurements were done to figure out formation mechanism of the TiO₂ nanofilms. The formation of TiO₂ nanofilms was due to out-diffusion of the implanted Ti ions to the substrate surface, where they were oxidized into TiO₂ nanoparticles. Formation, phase, and thickness of the TiO₂ nanofilms can be well tailored by controlling annealing parameters.

773

The rapid development of nuclear technology has led to more liquid organic radioactive wastes. Different from the regular aqueous radioactive wastes, these liquids possess a higher hazard potential and cannot be disposed through the conventional methods due to their radioactivity and chemical nature. Spent extraction solvent is a kind of common liquid organic radioactive wastes. In this work, tri-butyl phosphate (TBP), which is more difficult to degrade in the spent extraction solvent, was used as the model compound. Influences of reaction conditions on total organic carbon (TOC) removal and the volume percentage of each gas component under supercritical water oxidation (SCWO) were studied. The SCWO behaviors of spent extraction solvent simulants were studied under the optimal conditions derived from the TBP experiment. The SCWO experiments were studied at 400–550 ℃, oxidant stoichiometric ratio of 0–200%, feed concentration of 1.5%–4% and pressure of 25 MPa for 15–75 s. The results show that the TOC removal of the simulants was greater than 99.7% and CH₄, H₂ and CO were not detected at 550 ℃, 25 MPa, oxidant stoichiometric ratio of 150%, feed concentration of 3%, and residence time of 30 s.

518

In atmospheric dispersion models of nuclear accident, the dispersion coefficients were usually obtained by tracer experiment, which are constant in different atmospheric stability classifications. In fact, the atmospheric wind field is complex and unstable. The dispersion coefficients change even in the same atmospheric stability, hence the great errors brought in. According to the regulation, the air concentration of nuclides around nuclear power plant should be monitored during an accident. The monitoring data can be used to correct dispersion coefficients dynamically. The error can be minimized by correcting the coefficients. This reverse problem is nonlinear and sensitive to initial value. The property of searching the optimal solution of Genetic Algorithm (GA) is suitable for complex high-dimensional situation. In this paper, coupling with Lagrange dispersion model, GA is used to estimate the coefficients. The simulation results show that GA scheme performs well when the error is big. When the correcting process is used in the experiment data, the GA-estimated results are numerical instable. The success rate of estimation is 5% lower than the one without correction. Taking into account the continuity of the dispersion coefficient, Savitzky-Golay filter is used to smooth the estimated parameters. The success rate of estimation increases to 75.86%. This method can improve the accuracy of atmospheric dispersion simulation.

594