Vol.27,

The presence of sulfonamide antibiotics in aquatic environments has received increasing attention in recent years. Sulfadiazine (SD), a widely used heterocyclic sulfonamide pharmaceutical, has entered into the receiving water body. In this paper, gamma-rays are used to irradiate samples of sulfadiazine antibiotics-containing wastewater. The results demonstrate that SD can be effectively degraded by irradiation, but the mineralization degree of SD (in terms of TOC) is not as efficient as the SD degradation. The addition of Fe²⁺ can significantly enhance the SD degradation and mineralization through the generation of hydroxyl radical by catalytic decomposition of H₂O₂ from water radiolysis. Ion chromatography analysis indicates that sulfate ions (SO₄²⁻) and formate (HCOO⁻) are the main intermediate products. Gamma irradiation is a promising technology for removing low-concentration antibiotics from water and wastewater.

332

In an attempt to elucidate the biological effects and underlying mutations involving flower color in ornamental plants following carbon ion beam radiation, shoots of geranium were exposed at dosages of 0 Gy, 10 Gy, 15 Gy, 30 Gy, and 40 Gy, and one flower color mutant was obtained. The morphological characteristics, physiological aspects, and DNA polymorphisms between wild-type and flower color mutants were analyzed. The colors of petal, peduncle, pistil, and stamen of the mutant displayed significant differences compared to those of the wild-type. Compared to the original plants, the total anthocyanin content in the petals of the mutant significantly decreased, resulting in a light pink petal phenotype. DNA polymorphisms detected by random amplified polymorphic DNA analysis showed that the ratio of different bands between the wild-type and mutant reached up to 13.2%. The present study demonstrates that carbon ion beam irradiation is effective in inducing genomic variations, resulting in flower-color geranium mutants within a relatively short period of time. Meanwhile, the developed flower-color mutants may be potentially used in future mutational research studies involving ornamental plants.

316

We used density functional theory (DFT) calculations at the B3LYP/6-311G** level for a theoretical study on the complex formed when uranium(IV) coordinates with N, N'-bis-allyl salicylaldehyde ally-o-phenylene-diamine (BSAPDA), i.e., U(BSAPDA)_2. The results indicated that the coordination complex of U(BSAPDA)₂ could form two different structures with a ratio of 1:2. One was a parallel dislocation structure (PDS-U), in which the two BSAPDAs’ middle benzene rings adopted a parallel dislocation with an angle of 56.64°, and the other was a staggered finger "+" structure (SFS-U), in which the two BSAPDA employed the staggered finger "+" shape. The binding energies, charge distribution, spectral properties, thermodynamic properties, molecular orbitals, and wiberg bond indices for both PDS-U and the SFS-U were calculated and compared to each other.

499

X-ray scattering is widely used in material structural characterizations. The weak scattering nature, however, makes it susceptible to background noise and can consequently render the final results unreliable. In this paper, we report an iterative method to determine X-ray scattering background and demonstrate its feasibility by small angle X-ray scattering on gold nanoparticles. This method solely relies on the correct structural modeling of the sample to separate scattering signal from background in data fitting processes, which allows them to be immune from experimental uncertainties. The importance of accurate determination of the scaling factor for background subtraction is also illustrated.

510

In high-energy flash radiography, scattered photons degrade the acquiring image, which limits the resolving power of interfaces and density of dense object. The application of large anti-scatter grid can reduce the scattered photons remarkably, but this requires a stable source position in order to reduce the loss of signal photons in the grid structure. The pinhole imaging technique is applied to observe spatial jitters of a triple-pulse radiographic source of a linear induction accelerator. Numerical simulations are conducted to analyze the imaging performance with the same or close parameters of the pinhole object and experimental alignment. Experiments are carried out to observe spatial jitters of the source between different measurements. Deviations of the source position between different pulses are measured in each experiment.

455

In X-ray absorption fine structure (XAFS) experiments, Soller slits are widely used as filter devices in order to improve the signal-to-noise ratio. Performing high accuracy manual focusing operations is a time-consuming process; therefore, this work introduces an automatic focusing method for Soller slits in multi-element fluorescence detectors. This method establishes a relation model between the fluorescence intensity distribution and the coordinates of the fluorescence excitation point. According to this relation model, the actual coordinates of the fluorescence excitation point can be deduced from the detected fluorescence intensity distribution and used in focusing operations. This method has proven to be feasible in an XAFS experiment at the BL14W1 beamline of the Shanghai Synchrotron Radiation Facility (SSRF).

426

The micro-CT imaging of vasculature is a powerful tool for evaluation of angiogenesis, a prominent characteristic of hepatic fibrosis. The segment or bifurcation density, which is usually adopted to evaluate the degree of hepatic fibrosis, does not always work and may lead to incorrect assessment, especially when the three dimensional vasculature obtained is imperfect in sample preparation or image collection. In this paper, we propose a new parameter to solve this problem. The experimental results demonstrate that the method is robust and reliable, and is practical for angiogenesis evaluation, despite of image data imperfections. This quantitative analysis method can be extended to investigate other kinds of diseases in which vasculature change is a key indicator.

319

As one candidate of tritium storage materials, palladium subjects to the damage from helium atoms introduced by the β-decay of tritium atoms. The mechanical properties of palladium will be greatly degraded deriving from the accumulation of helium atoms. A set of interatomic potentials has been fitted based on ab initio calculation according to the Morse formula. Molecular dynamic methods are utilized to investigate the existence of H atoms on the release of helium atoms from palladium with the present fitted potentials. It is found that hydrogen atoms play significant roles in the diffusion and release of helium atoms. The presence of hydrogen atoms tends to obstacle the diffusion and release of helium atoms in palladium.

465

To obtain multiple monoenergetic neutron sources and realize the on-site calibration of radiation monitoring equipment for nuclear-involved places, the structural characteristics and neutron source features of D-T neutron tube was analyzed; Monte Carlo method was adopted to simulate the effect of interaction between typical materials and different energy neutrons; multi-layered shielding materials were combined and optimized to acquire the optimal scheme to shield the neutron sources from the neutron tube. On the base, a tapered alignment filtration construction was designed and Monte Carlo method was employed to simulate the effect of alignment construction. The result showed that the tapered alignment filtration construction can create monoenergetic neutrons including 14.1 MeV, 0.18 MeV and thermal neutrons and demonstrated good monochrome performance which provides multiple monoenergetic sources for the on-site calibration.

427

Molten-salt pump is applied to pump high temperature molten-salt as the primary coolant of a molten-salt reactor. The pump, generally a vertical rotor system, suffers from radial force generated by the liquid seal component, and the rotordynamic characteristics of the pump are affected considerably. In this paper, the rotordynamic coefficients of the tooth-on-stator liquid seal in molten-salt pump are studied. The flow in the seal region is simulated using computational fluid dynamics technique. Parameters of the inlet loss and the pre-swirl at the inlet region of the seal are calculated. The coefficients of resistance and the wall parameters are obtained from the simulation results by data fitting method. The rotordynamic coefficients are analyzed based on the bulk-flow model of liquid seal. The rotordynamic characteristics, with and without the liquid seal, of the objective molten-salt pump are inspected. The first critical speed of the rotor is found to increase. Harmonic analysis shows that the pump, being sensitive to unbalance force though, can operate safely under its design specifications.

556

The Lead-Bismuth-Eutectic (LBE) spallation target has been considered as one of the two alternatives for the spallation target for China Initiative Accelerator Driven Sub-critical (CIADS) system. This paper reports the preliminary study on physical feasibility of a U-type LBE target with window. The simulation results based on Monte Carlo transport code MCNPX indicate that the spallation neutron yield is about 2.5 per proton. The maximum spallation neutron flux is observed at about 3 cm below the lowest part of the window. When the LBE target is coupled with the reactor, the reactor neutrons come from the fission reaction increased the neutron field significantly. The energy deposition of high-energy protons is the main heat source, the spallation neutrons and reactor neutrons contribute only a small fraction. The maximum energy deposition in the LBE is about 590 W/cm³ and that in the target window is about 319 W/cm³. To estimate the lifetime of the target window, we have calculated the radiation damages. The maximum displacement production rate in the target window is about 10 dpa/FPY. The hydrogen and helium production rates generated during normal operation were also evaluated. By analyzing the residual nucleus in the target during the steady operation, we estimated the accumulated quantities of the extreme radioactivity toxicant ²¹⁰Po in the LBE target loop. The results would be helpful for the evaluation of the target behavior, and will be beneficial to the optimization of the target design work of the experimental facilities.

476

Safety system testing is one of the most rigorous and time-consuming requirements in the verification and validation process for reactor protection systems (RPSs). This paper presents the development of a test system for the fully digital and field-programmable gate array based RPS of the solid fuel (SF) thorium-breeding molten-salt pebble bed fluoride salt-cooled reactor (TMSR), denoted as the TMSR-SF1 project, developed by the Chinese Academy of Sciences. The test system is applied to the RPS to ensure that it fully meets its designed functions and system specifications. We first introduce the testing principles and methods. Then, the hardware component designs and the software program development of the test system are discussed. Finally, the test process and test results are discussed and summarized.

477

Bismuth vanadate (BiVO₄) is a promising semiconductor material for solar energy conversion via photoelectrochemical (PEC) water splitting, whereas its performance is limited by surface recombination due to trapping states. Herein, we developed a new method to passivate the trapping states on BiVO₄ surface using ultrathin aluminium oxide (Al₂O₃) overlayer by atomic layer deposition (ALD). The coated ultrathin Al₂O₃ film on BiVO₄ significantly enhanced photocurrent densities of the BiVO₄ anodes under standard illumination of AM 1.5 G (100 mW/cm²). The electrochemical impedances and photoluminescence spectra were studied to confirm that the improved PEC water splitting performance of BiVO₄ was due to the decreased surface recombination state on BiVO₄, which effectively enhanced the charge separation.

478

It is significant to quantify the intermolecular physisorption extent in biomedical field. By taking the advantage of a significant difference from either sizes or weights, we introduced a combination of Scatchard equation and either ultracentrifugation or size exclusion chromatography to obtain both the binding constant and the number of binding sites by using bovine serum albumin and eosin B as models. Compared to the photoluminescence quenching-based methods like Stern-Volmer and Hill equations, the introduced method is not only more precise but also simpler and more straightforward for the operation. Moreover, the protein conformational changes and the corresponding theoretical binding mode with an atomic resolution were also studied by using three-dimensional fluorescence spectroscopy and molecular docking method, respectively. These comparative results could help scientists select right methods to study any interactions between two molecules with significant differences from either sizes or weights.

409

The primary fragments in ⁴⁰Ca + ⁴⁰Ca reactions at 35, 50, 80, 100, 140 and 300 MeV/u were simulated using the anti-symmetrized molecular dynamics model, in the phase space at t = 300 fm/c with a coalescence radius R_c = 5 fm. The standard Gogny interactions g0, g0as, and g0ass were adopted in simulating the collisions at an impact parameter of b = 0 fm. It was found, using an isobaric yield ratio method, that temperature of the primary fragment depends on the incident energy and hardness of the interaction potential. The temperature obtained in this work agrees with the results by the self-consistent fitting method.

353

For simulating more accurately neutron or proton production from photonuclear reactions, a data-based photonuclear reaction simulation algorithm has been developed. Reliable photonuclear cross-sections from evaluated or experimental database are chosen as input data. For checking the validity of the use of the data-based photonuclear algorithm, benchmarking simulations are presented in detail. We calculate photonuclear cross-sections or reaction yield for ⁹Be, ⁴⁸Ti, ¹³³Cs, and ¹⁹⁷Au and compare them with experimental data in the region of incident photon energy below ∼30 MeV. While Geant4 can hardly reproduce photonuclear experimental data, results obtained from the data-based photonuclear algorithm are found in good agreement with experimental measurements. Potential application in estimation of specific activity of radioisotopes is further discussed. We conclude that the developed data-based photonuclear algorithm is suitable for an accurate prediction of photon-induced neutron or proton productions.

458

Nuclear level density (NLD) is a characteristic property of many-body quantum mechanical systems. NLDs are of special importance to make statistical calculations in reactor studies and various theoretical and experimental nuclear physics and engineering applications. In this study, we have investigated a set of particle states in distinct rotational and vibrational bands to calculate nuclear level density parameters and the NLDs of accessible states of some deformed Dy radionuclides using a collective model approach, which included different excitation bands of the observed nuclear spectra. The method used assumes equidistant spacing of collective coupled state bands of the considered nuclei. The results of the calculated NLD have been compared with the experimental and compiled data obtained by the Oslo group, shell model Monte Carlo, Hartree-Fock-Bogoliubov+combinatorial approach, Bardeen-Cooper-Schrieffer approach, and are in a good agreement.

351

Nuclear single-proton resonances are sensitive to the Coulomb field, while the exchange term of Coulomb field is usually neglected due to its nonlocality. By combining the complex scaling method with the relativistic mean-field model, the influence of the Coulomb exchange term on the single-proton resonances is investigated by taking Sn isotopes and N=82 isotones as examples. It is found that the Coulomb exchange term reduces the single-proton resonance energy within the range of 0.4-0.6 MeV, and lead to similar isotopic and isotonic trends of the resonance energy as those without the Coulomb exchange term. Moreover, the single-proton resonance width is also reduced by the Coulomb exchange term, whose influence generally decreases with the increasing neutron number and increases with the increasing proton number. However, the influence of the Coulomb exchange term cannot change the trend of the resonance width with respect to the neutron number and proton number. Furthermore, the influence of the Coulomb exchange term on the resonance width is investigated for the doubly magic nuclei ⁴⁰Ca, ^56,78Ni, ^100,132Sn, and ²⁰⁸Pb. It is found that the Coulomb exchange term reduces the proton resonance width within 0.2 MeV, whose magnitude depends on the specific nucleus and the quantum numbers of resonant states.

542

The monitors used to measure radon concentration must be calibrated, and the calibration factor of each measurement cycle should be determined. Thus, the determination time of calibration factors of NRL-II radon monitors should be reduced. In this study, a method is proposed to determine the calibration factors of radon monitors rapidly. In the proposed method, the calibration factor is initially determined in the 60-min measurement cycle; the calibration factor is then identified in the other measurement cycle on the basis of the principle that the calibration factor of the same radon monitor in different measurement cycles is inversely proportional to the number of α particles produced by ²¹⁸Po decay in this cycle. Results demonstrate that the calculated calibration factor of the different measurement cycles is consistent with the experimental calibration factor. Therefore, this method is reliable and can be used to determine the calibration factor of radon monitors rapidly.

628

This work researched the impact of total dose irradiation on the threshold voltage of N-type metal oxide semiconductor field effect transistors (NMOSFETs) in Silicon on Insulator (SOI) technology. Using the sub-threshold separation technology, the factor causing the threshold voltage shift was divided into two parts: trapped oxide charges and interface states, the effects of which are presented under irradiation. Furthermore, by analyzing the data, the threshold voltage shows a negative shift at first, then turns to positive shift when irradiation dose is lower. Additionally, the influence of the dose rate effects on threshold voltage is discussed. The research results show that the threshold voltage shift is more significant in low dose rate conditions, even for a low dose of 100 krad(Si). The degeneration value of threshold voltage is 23.4% and 58.0% for the front-gate and the back-gate at the low dose rate.

542

In the Low Level RF control field, ADC acquisition accuracy and noise sets the boundary of our control ability, making it important to develop low noise acquisition systems. From the design to test stage, all the noise terms should be understood and characterized . The specific need addressed here is the precision acquisition system for the second Linac Coherent Light Source (LCLS-II), led by SLAC National Accelerator Laboratory. Test circuit boards for the LTC2174 and AD9268 ADCs are designed and fabricated by LBNL. An ADC test framework based on FPGA evaluation board to assess performance has been developed. The ADC test framework includes both DSP (Digital Signal Processing) firmware and processing software. It is useful for Low Level RF control and other synchronization projects. Investigating the clock jitter between two channels give us an understanding of that noise source. Working with the test framework, the raw ADC data is transferred to a computer through a Gigabit Ethernet interface. Then short term error signal can be calculated based on a sine wave fit. By changing low pass filter bandwidth, relative long term performance can also be obtained. Amplitude jitter and differential phase jitter are the key issues for ADCs. This paper will report the test results for LTC2174 and AD9268 chips. The integral amplitude jitter is smaller than 0.003%, and the integral phase noise is smaller than 0.0015 (measured at 47 MHz RF, 100 MHz clock, bandwidth 1 Hz to 100 kHz) for both ADC chips.

507

A new signal readout method for position-sensitive multi-output detectors, such as those in high energy spectroscopy measurement and nuclear imaging, was developed by combining the charge division circuit, summing circuit and charge-to-time conversion (QTC) circuit. The 64 outputs of a Hamamatsu H8500 position-sensitive photomultiplier tube (PSPMT) were processed and three digital pulses were generated. The widths of digital pulses were determined using the time-to-digital converter (TDC) in an FPGA (Field Programmable Gate Array). The energy and position information of incident γ-rays is estimated based on the proportionality between the width of digital pulses and input charge created by γ photons. A prototype was built using discrete components and tested, and the energy and position resolutions were improved compared with that obtained with standard ADCs. This method greatly simplifies the front-end electronics and the digital interface. It enables a compact electronics system and an easy integration into an ASIC.

346