Baolong Ma

Water-cooled tungsten targets may remain in contact with stagnant deionized water during accelerator shutdown, creating a beam-off corrosion condition distinct from irradiation-assisted service. Untreated tungsten (W), laser-ablated tungsten (LA-W), and a 500 nm tantalum-coated laser-ablated tungsten surface (Ta-LA-W) were therefore immersed in deionized water for up to 28 days. Laser ablation replaced the machined surface with a hierarchical micro/nanostructure and increased the areal roughness Sa from 0.22 ± 0.01 to 1.75 ± 0.07 μm; after Ta deposition, Sa was 1.62 μm. LA-W exhibited the largest topographic attenuation and the highest dissolved W concentration, reaching 7.915 mg·L⁻¹ at 21 days. Ta-LA-W maintained Sa within the range from 1.60 ± 0.06 to 1.66 ± 0.07 μm and limited dissolved W to 1.118–1.601 mg·L⁻¹. X-ray photoelectron spectroscopy showed increased WOx-related intensity and disappearance of the metallic-W loss feature only for untreated W. The W 4f envelopes of LA-W and Ta-LA-W remained broadly similar before and after immersion, but for different reasons: sustained W dissolution for LA-W and suppression of W oxidation and release by the Ta-containing barrier for Ta-LA-W. The dissolution-based corrosion sequence was LA-W > W > Ta-LA-W. Laser texturing therefore acted as an interfacial-engineering treatment rather than an intrinsically corrosion-resistant modification.

Optical MOS solid-state relays provide electrical isolation and favorable switching performance, making them suitable as isolated switching interfaces for optoelectronic sensors used in radiation monitoring systems, high-energy physics accelerator monitoring systems, and aerospace electronic equipment. However, to the best of our knowledge, the reliability of this device under atmospheric-like neutron irradiation has not been systematically investigated. In this study, the neutron-induced degradation characteristics and potential physical mechanisms of a commercial optical MOS solid-state relay were systematically investigated through electrical characterization, Sentaurus TCAD mixed-mode simulation, and post-irradiation annealing experiments. Particular attention was paid to the possible internal coupling relationship between degradation of the internal photoelectric conversion unit and the increase in the off-state leakage current of the output-side power MOSFET.

The design of a high-performance Beam Shaping Assembly (BSA) for accelerator-based BNCT is a complex multi-objective optimization problem. We present an automated framework integrating the NSGA-III algorithm with Monte Carlo simulations to optimize the material and geometry of a multi-layered BSA for a 2.8 MeV RFQ neutron source. An entropy-weighted TOPSIS method objectively selects the optimal compromise from the Pareto set. The optimized BSA delivers an epithermal flux of 2.024 × 10 ⁹ n·cm ^-2 ·s ^-1 at 20 mA, while reducing fast-neutron contamination by ∼ 44% below the IAEA limit. Dosimetry in a head phantom demonstrates promising therapeutic potential, with an 8.6 cm advantage depth and a 4.78 advantage ratio. This work provides a robust, intelligent design framework for supporting the preliminary evaluation of AB-BNCT facilities.

The design and simulation of an inductive coupler with an integrated DC bias function are reported. A choke structure is implemented to reduce the electric-field on the ceramic window, lowering sparking risk. Particle-in-cell simulations reveal the power-dependent behavior of multipacting, showing electron cloud migration towards the ceramic at high power, which is correlated with increased thermal deposition in thermal analysis. To enable multipacting suppression via DC bias, a blocking structure featuring a Kapton-film and ceramic-copper composite insulator is introduced between the coupler's inner and outer conductors. This study provides a validated design approach for stabilizing high-power CW inductive couplers against multipacting, forming the basis for subsequent prototyping and conditioning.

The safe immobilization of high-level waste (as actinide) remains a critical bottleneck in the disposal of high-level radioactive waste worldwide. Moreover, the higher specific surface area and surface energy of nano-scale powders enable the production of ceramic materials featuring denser crystal structures and superior strength, hardness, and toughness. Therefore, in this study, Gd³⁺ was used as a surrogate for actinides, and Nb⁵⁺ was introduced as a high-valence charge-compensating cation. Nano-scale powders of CaCO₃, ZrO₂, Gd₂O₃, TiO₂, and Nb₂O₅ were employed to prepare a series of defect-fluorite-derived ceramics, CaZr_1-xGd_xTi_2-xNb_xO₇ (x = 0.1–1.0), via a high-temperature solid-state reaction method, aiming to investigate the atomic substitution mechanisms, phase evolution, and chemical stability under high-valence charge compensation. Laboratory X-ray diffraction (XRD), synchrotron X-ray diffraction (SXRD), and backscattered scanning electron microscopy with energy-dispersive X-ray spectroscopy (BSEM-EDX) confirmed a phase evolution sequence from zirconolite-2M to zirconolite-4M and finally to pyrochlore. This behavior is consistent with that reported for other Ln³⁺-Nb⁵⁺ co-doped zirconolite systems. Rietveld refinement of the SXRD data further revealed, for the first time, the site-occupancy mechanism of Gd and Nb in zirconolite-4M. In both zirconolite-2M and zirconolite-4M, Gd preferentially occupies the Ca sites, whereas Nb substitutes at the Ti sites. In the pyrochlore structure, Ca, Zr, and Gd occupy the 16d sites, while Ti and Nb occupy the 16c sites. Static leaching tests following the MCC-1 protocol showed that pyrochlore exhibits the highest leaching resistance, whereas zirconolite-2M shows the lowest. After 28 days, the highest Gd leaching rate was 1.92(1) × 10⁻⁵ g m⁻² d⁻¹. These results provide new insights into actinide immobilization behavior and compositional design in zirconolite-based waste forms.

To suppress the Secondary Electron Yield (SEY) of Al₂O₃ ceramic surfaces for accelerator ceramic windows, a synergistic strategy integrating TiN film deposition and laser surface texturing was developed. TiN films were first deposited on Al₂O₃ substrates by pulsed DC magnetron sputtering, and the sputtering power was optimized through systematic characterization of the film morphology and chemical states, with 300 W identified as the optimal deposition condition. Laser surface texturing was then introduced to construct micro-structured Al₂O₃ surfaces with different geometrical features. Among the investigated laser powers, the 12 W-treated surface exhibited the most developed surface morphology and the highest roughness, indicating the most favorable topography for electron trapping. SEY measurements showed that the maximum SEY decreased from 8.2 for the as-received Al₂O₃ to 5.5 after deposition of a 10 nm TiN film, and was further reduced to 2.1, 1.0, and 1.7 for the textured TiN/Al₂O₃ surfaces prepared at 6, 12, and 18 W, respectively, with the best suppression for the 12 W textured TiN/Al₂O₃. The enhanced performance is attributed to the synergistic effect of low-SEY TiN surface chemistry and geometrical electron trapping induced by laser texturing. This work provides an effective route for constructing low-SEY Al₂O₃ ceramic surfaces for beam-window-related applications.

The therapeutic efficacy of Boron Neutron Capture Therapy (BNCT) relies on the radiation dose delivered to tumor regions via the ¹⁰ B(n, α ) ⁷ Li reaction. Real-time monitoring of boron concentration distribution enables dynamic adjustment of thermal neutron fluence during treatment. Prompt Gamma Single-Photon Emission Computed Tomography (PG-SPECT) serves as a powerful tool for quantifying boron concentration by detecting the 478 keV prompt gamma rays emitted during this process. This study proposes a half-ring pinhole PG-SPECT system comprising seven independent pinhole modules integrated with CZT detector arrays. The system geometry was optimized to achieve high spatial resolution and detection sensitivity. Reconstruction results of two spherical tumors demonstrate that the TV + bisection algorithm achieves a Structural Similarity Index Measure (SSIM) of 0.8249 and a Root Mean Squared Error (RMSE) of 0.1497, indicating excellent image quality. Evaluations under varying boron concentrations and measurement times show that satisfactory image quality is achieved at a boron concentration of 650 ppm with a measurement time of 5.2 minutes. This work provides a valuable system design for boron concentration monitoring, supporting the ongoing development of BNCT at Xi'an Jiaotong University.