Vol.31,

Aromatic copolysulfonamide (co-PSA) fiber produced via wet spinning exhibits poor mechanical properties. Hence, dry jet-wet spinning was introduced to prepare the co-PSA fiber. Dry jet-wet spinning exhibits the advantage of positive stretching to the extruded fiber before coagulation. The fibers were spun at different jet draw ratios and second draw ratios and were examined for scanning electron microscopy (SEM), mechanical properties, sound velocity, small-angle X-ray scattering (SAXS), and wide-angle X-ray scattering (WAXS). The results revealed that all the fibers exhibited a uniform and dense structure and nearly round cross-section at different drawing conditions. The strength and orientation of the fiber increased slightly as the jet draw ratio was increased to the second draw ratio of 2.0. Furthermore, the fibers formed a periodic ordered structure along the fiber axis. However, the strength of the fibers decreased significantly when the jet draw ratio continued to increase and the second draw ratio decreased year-on-year to maintain the total draw ratio at 11.0. Additionally, the fibers exhibited lower orientation because the molecular chain segments could not continue to extend and orient even at larger jet draw ratios, and thus they could not be further well-stretched at subsequent lower stretching ratios. Meanwhile, the periodic ordered structure disappeared and more content of entanglement structure existed in the fibers. During the heat drawing process, the results of SAXS and WAXS indicated that the better ordered molecular chain segments within the fiber were easier to arrange and reconstruct to significantly improve the content of crystalline and mesophase structures in the fibers. Hence, after the heat drawing process, the strengths of co-PSA-H2 and co-PSA-H3 fibers increased to more than 620 MPa, which is significantly higher than those of commercialized fibers and fibers reported in extant studies.

311

A compact room-temperature inter-digital H-mode (IH) drift tube linac (DTL) with Kombinierte Null Grad Struktur beam dynamics is proposed in this paper. The proposed IH-DTL, which operates at 325 MHz, accelerates 18 mA proton particles from 3.0 to 7.0 MeV as part of a proton synchrotron-based therapy system. It is composed of two main sections, namely a bunching section (−30°) and accelerating section (0°). There is no transverse focusing element inside the cavity, which increases the acceleration gradient and reduces the cavity length and power consumption. In our physical designs, LORASR code is utilized for beam dynamics design and multi-particle simulations. The synchronous particle energy, injection phase, and acceleration voltage of each gap are optimized carefully to increase transmission efficiency while minimizing beam emittance growth and beam loss. The total length of the cavity is 0.82 m and the acceleration gradient reaches 4.88 MV/m, resulting in a transmission efficiency of 100% and beam emittance growth less than 10%. The details of the specific work undertaken in this study are presented in this paper.

415

We present a lattice design and beam dynamic analysis for a 4 GeV low-emittance, high-brilliance synchrotron light source. The lattice consisted of 26 six-bend achromats with 26 long and 26 short straight sections. We present the design results for a hybrid multi-bend achromat (HMBA) lattice with a natural emittance of 168 pm and circumference of 729.3 m. Each cell had 4 longitudinal gradient bendings, 2 combined bendings, 14 quadrupoles, and 2 families of sextupoles. The lattice was designed to be flexible to provide both non-zero- and zero-dispersion functions in the long straight section. The two straight sections in each cell had lengths of 5.6 and 1.2 m.To ensure sufficient injection, we optimized the design lattice and dynamic aperture. We investigated the dynamic aperture in the lattice with machine errors, and the results showed that the lattice design provides sufficient dynamic aperture after COD correction for beam injection. We present the results of an injection scheme that demonstrates the space in the injection section and the particle motions of the injected beam. We also present the results of beam tracking after the beam injection to examine the characteristics of the beam injection. The designed HMBA lattice was well optimized in terms of the beam parameters and brilliance as an intermediate light source at 4 GeV and a circumference of 729.3 m.

345

The Shanghai High-repetition-rate XFEL and Extreme Light Facility (SHINE) under construction is designed to be one of the most advanced free electron laser (FEL) facilities in the world. The main part of the SHINE facility is an 8 GeV superconducting Linac operating in continuous wave (CW) mode. The Linac consists of seventy-five 1.3 GHz and two 3.9 GHz cryomodules. Based on the design and experience of 3.9 GHz cavities in the European X-ray Free Electron Laser (E-XFEL) and the Linac Coherent Light Source-II (LCLS-II) projects, we optimize the SHINE 3.9 GHz cavity design to adapt it for CW mode operation. In this paper, we present a particular redesign of the end-group for the SHINE 3.9 GHz superconducting cavity that includes a redesign of the end-cell and beam pipe to shift away the potentially troublesome lowest high order modes(HOMs), a modification of the main coupler antenna, and a tuning of the HOM notch filter to meet the cavity requirements. RF losses calculations on the HOM coupler antennas show that the overheating on the inner conductor at the operating mode is diminished significantly. Furthermore, we have also studied the HOMs to ensure there are no dangerously trapped modes in the optimized cavity design.

601

The limited availability of studies on the natural convection heat transfer characteristics of fluoride salt has hindered progress in the design of passive residual heat removal systems (PRHRS) for molten salt reactors. This paper presents results from a numerical investigation of natural convection heat transfer characteristics of fluoride salt and heat pipes in the drain tank of a PRHRS. Simulation results are compared with experimental data, demonstrating the accuracy of the calculation methodology. Temperature distribution of fluoride salt and heat transfer characteristics are obtained and analyzed. The radial temperature of liquid fluoride salt in the drain tank shows a uniform distribution, while temperatures increase with increasing axial height from the bottom to the top of the drain tank. In addition, natural convection intensity increases with increasing height of the heat pipes in the tank. Spacing between heat pipes has no obvious effect on the natural convection heat transfer coefficient. This study will contribute to the design of passive heat removal systems for advanced nuclear reactors.

402

Precise point reactor kinetic parameters are essential in the study of reactor dynamics. Point reactor kinetic parameters include the effective delayed neutron fraction and prompt neutron lifetime. In this work, effective point reactor kinetic parameters, which can be applied to unstructured grids, were calculated based on the Galerkin finite element method. First, two-dimensional and three-dimensional benchmarks were used to verify the calculation of steady-state neutronics parameters. Then, the Tehran research reactor core was divided into hexahedral meshes, and the forward flux and adjoint flux were calculated. Finally, the effective point reactor kinetic parameters of the Tehran research reactor were obtained by comprehensively processing the steady-state neutronics parameters.

336

The photophysics and photochemistry of pefloxacin (PEF), a 1-ethyl-substituted fluoroquinolone (FQ) antibiotic, were studied using transient, steady-state experimental methods and computational methods. The fundamental photoproperties of PEF and its phototoxicity toward lysozyme, a single-chain protein, were compared with those of a 1-fluorophenyl-substituted FQ antibiotic, difloxacin (DIF). The results showed that the phototoxicity was significantly decreased by the insertion of the bulky 1-fluorophenyl substituent (the phototoxicity of DIF was approximately one-quarter of that observed for PEF). This trend was attributed to the lowest lying singlet state with sizeable oscillator strength (f ≥ 0.1) being shifted from 319 nm in PEF to 266 nm in DIF upon the insertion of the bulky substituent at the 1-position, as investigated by using computational methods. In addition, 95% of the solar UV irradiation that reaches the earth’s surface has wavelength >315 nm. Therefore, reducing the most effective excitation wavelength by optimizing the substituent at the 1-position may be a promising strategy to alleviate the phototoxicity of FQ antibiotics. These findings may be applied to other FQ antibiotics because a large number of phototoxicity studies on FQ antibiotics with different substituents at the 1-position can prove these finding’s effectiveness. Delafloxacin, an FQ antibiotic bearing a chlorine and bulky substituent at the 8- and 1-positions, respectively, exhibits no phototoxicity is the most recent example reported to date. To the best of our knowledge, this is the first transient and steady-state study of the effect of the N-1 substituent on the photochemistry and phototoxicity of FQ antibiotics. These findings will be beneficial to the development of novel FQ antibiotics without phototoxicity.

486

Irradiation breeding is an important technique in the effort to solve food shortages and improve the quality of agricultural products. In this study, a field test was implemented on the M₃ generation of two mutant pea plants gained from previous neutron radiation of pea seeds. The relationship between agronomic characteristics and yields of the mutants was investigated. Moreover, differences in physiological and biochemical properties and seed nutrients were analyzed. The results demonstrated that the plant height, effective pods per plant, and yield per plant of mutant Leaf-M1 were 45.0%, 43.2%, and 50.9% higher than those of the control group. Further analysis attributed the increase in yield per plant to the increased branching number. The yield per plant of mutant Leaf-M2 was 7.8% higher than that of the control group, which could be related with the increased chlorophyll content in the leaves. There was a significant difference between the two mutants in the increase of yield per plant owing to morphological variation between the two mutants. There were significant differences in SOD activity and MDA content between the two mutants and the control, indicating that the physiological regulation of the two mutants also changed. In addition, the iron element content of seeds of the two mutants were about 10.9% lower than in the seeds of the control group, a significant difference. These findings indicate that the mutants Leaf-M1 and Leaf-M2 have breeding value and material value for molecular biological studies.

382

A 476 MHz resonant stripline beam position monitor (BPM) is planned to be installed in an infrared free electron laser (IR-FEL) machine at National Synchrotron Radiation Laboratory (NSRL). This type of BPM was developed based on a standard stripline BPM by moving the coupling feedthrough closer to the short end downstream, which introduces a resonance and therefore, a capability for higher resolution compared with broadband BPMs. The design and offline measurement results of the prototype are shown in this paper. The design goal is the optimization of the central frequencies and corresponding quality factors of the three intrinsic transverse electromagnetic (TEM) modes to roughly 476 MHz and 30, respectively, the fulfilment of which are demonstrated by a transmission parameter test via a network analyzer. Induced voltage signal modeling and an estimation of the position resolution of the designed BPM are shown in detail. Furthermore, a calibration test of the prototype using the stretched wire method is presented, including a description of the test stand and the evaluation of position sensitivities.

384

Within a transport model using nucleon momentum profiles as the input from a parameterized isospin-dependent single-nucleon momentum distribution, with a high momentum tail induced by short-range correlations, we employ ¹⁹⁷Au + ¹⁹⁷Au collisions at 400 MeV/nucleon to examine the effects of the short-range correlations on the pion and flow observables in probing the nuclear symmetry energy. We investigate how reliable this isospin-dependent single-nucleon momentum distribution is and determine the corresponding parameter settings. Apart from the significant effects of the short-range correlations on the pion and flow observables that are observed, we also find that the theoretical simulations of the ¹⁹⁷Au + ¹⁹⁷Au collisions with this momentum distribution using two sets of parameters, extracted from the experimental analysis and the self-consistent Green’s function prediction, can reproduce the neutron elliptic flows of the FOPI-LAND experiment and the π^-/π⁺ ratios of the FOPI experiment, respectively, under the symmetry energy setting in a particular range. Therefore, we conclude that this parameterized isospin-dependent single-nucleon momentum distribution is reliable for isospin-asymmetric nuclear matter. Correspondingly, two sets of parameters extracted from both the experimental analysis and the self-consistent Green’s function prediction cannot be excluded according to the available experimental information at present.

327