查看更多>>摘要：The recognition of residual cores in aero-engine blades is a crucial task in ensuring the safety and reliability of aircraft. Compared to techniques such as borescope and X-ray radiography, neutron radiography, with its strong penetration ability and high sensitivity to light elements, can detect residual cores as thin as 2 mm within complex cavities. This significantly enhances the detection rate of residual cores in aero-engine blades. However, the recognition of residual cores in neutron images currently relies heavily on manual inspection by professionals, which is subjective and inefficient. To address this issue, an improved residual core recognition method based on a patch-level support vector data description (Patch SVDD) algorithm is proposed for neutron images. This study employs an improved gamma transformation to enhance the quality of neutron images and highlight the features of aero-engine blades. A fusion of dilated residual network (DRN) and efficient channel attention (ECA) serves as the feature extraction network in Patch SVDD, improving the capability of feature extraction. Additionally, a residual core grading module is designed to improve core leaching efficiency in production. Neutron images of aero-engine blades were acquired through the reactor-based cold neutron radiography facility (CNRF) to construct a dataset. The results demonstrate that this improved method achieves areas under the receiver operating characteristic curves (AUCs) of 94.8% at the image level and 95.6% at the pixel level, indicating its favorable recognition efficacy. This study provides an intelligent method for quality monitoring in aero-engine blades.
查看更多>>摘要：The dilation pulse (DP) is a critical factor influencing the temporal performance of a magnetic focusing pulse-dilation framing camera (PDFC). As the DP propagates along the photocathode (PC), it not only induces variations in acceleration voltage but also results in different drift times, dilated ratios, and motion radii for the electron pulse (EP) at various PC positions. This significantly affects spatiotemporal dispersion (STD) of the dynamic space charge effect (SCE) during the EP drift process. To address the issue, the drift step recovery diodes (DSRDs) are employed to design the DP. By establishing a connection with the dynamic spatiotemporal characteristics of the EP, the impact on the dynamic SCE is analyzed. Research results indicate that the DSRD circuit can generate four DPs with peak voltages ranging from −3.508 to −1.819 kV, rise times between 236 and 288 ps, average amplitude change rates from 22.36% to 35.0%, and slope change rates from 40.07% to 62.80%. When a specific DP is applied to the 50 mm PC, the transient temporal dispersion (TTD) of the SCE during the EP drift process is inversely proportional to the electron density and drift velocity. The transient spatial dispersion (TSD) is significantly influenced by the EP’s radius and its ratio to the axial width, decreasing as both factors increase. When the four DPs are individually applied to the PC, during the EP drift process, the DP with the smallest amplitude change rate and the largest slope change rate reduces the average temporal dispersion (TD) along the PC from 0.764 to 0.590 ps and decreases non-uniformity from 40.69% to 27.73%. The average spatial dispersion (SD) is reduced from 21.87 to $15.21~\mu $ m, and non-uniformity drops from 39.94% to 26.13%. These findings provide the basis for analyzing and improving the STD and uniformity of the dynamic SCE. Additionally, they offer research insights into integrating high-power pulse technology into ultrafast diagnostic applications.
Nguyen V. H. VietAlaa Al MasriMasaharu NomachiMarc-André Tétrault...
1680-1685页
查看更多>>摘要：The Light-only Liquid Xenon (LoLX) experiment is a prototype detector aimed at studying liquid xenon (LXe) light properties and various photodetection technologies. LoLX is also aimed to quantify LXe’s time resolution as a potential scintillator for 10-ps time-of-flight positron emission tomography (TOF-PET). Another key goal of LoLX is to perform a time-based separation of Cerenkov and scintillation photons for new background rejection methods in LXe experiments. To achieve this separation, LoLX is set to be equipped with photon-to-digital converters (PDCs), a photosensor type that can provide a timestamp for each observed photon. To guide the PDC design, we explore the requirements and potential outcomes for time-based Cerenkov separation. We use a PDC simulator, whose input is the light information from the Geant4-based LoLX simulation model, and evaluate the separation quality against time-to-digital converter (TDC) parameters of the PDCs. Compared with the current filter-based approach, the simulations predict a few different configurations that offer a Cerenkov separation level increase from 50% to 66% when using PDCs and time-based separation. A separation of 65% is also achievable with just 16 TDCs for 14 400 micro-cells per PDC, or one TDC per 2.25 mm2. These simulation results will lead to a specification guide for the upcoming PDC design as well as expected results to compare against future PDC-based experimental measurements. In the longer term, the overall LoLX results will assist large LXe-based experiments and motivate the assembly of an LXe-based TOF-PET demonstrator system.
Jens GregorMatthew R. HeathTimothy DellerMatthew A. Blackston...
1686-1697页
查看更多>>摘要：We describe a unified framework for model-based iterative 3-D reconstruction of multimodal neutron transmission, hydrogen-scatter, and induced-fission images from low resolution data recorded using $\mathrm {14.1~\!\!\text {-}\text{MeV} }$ neutrons and the associated-particle imaging (API) technique. The framework, which was developed to facilitate use in challenging field-deployment scenarios, is centered around physics-based system models and a total variation (TV) constrained implementation of the simultaneous iterative reconstruction technique (SIRT). Modified to solve a statistically weighted least squares (WLS) problem, the SIRT algorithm is accelerated using ordered subsets and Nesterov’s momentum for which we derive a near-optimal value of the governing Lipschitz constant. The approach enables the reconstruction of images that are high resolution compared to the acquired data and is robust to both limited statistics and a limited number of projection angles. Moreover, the framework is fast enough to be practical. Example images are provided that demonstrate both the ability to perform fast-neutron imaging of high-atomic-number materials with low radiation dose and the benefit of multimodal neutron imaging to identify key materials.
查看更多>>摘要：This work investigates the radiation-induced attenuation (RIA) performance of F-doped silica core single-mode fibers (Si-SMFs) under high ionizing radiation exposure. The Si-SMFs were fabricated using plasma chemical vapor deposition (PCVD) with a triple-cladding design to minimize internal stress. Throughout two distinct types of radiation exposure experiments, the spatial distribution and temporal evolution of RIA at telecommunication wavelengths of 1310 and 1550 nm were monitored in real-time using an optical time-domain reflectometer (OTDR). Upon completion of the initial irradiation cycle, characterized by a dose rate of 1.25 Gy(SiO2)/s and a total dose of 1 MGy(SiO2) at room temperature (RT), the RIA values for the sample fibers reached approximately 14.43 dB/km at 1310 nm and 22.81 dB/km at 1550 nm. Notably, the F-doped fibers exhibited superior RIA performance at the shorter wavelength (1310 nm) when the accumulated dose exceeded 40.5 kGy(SiO2) ( $\gamma $ -rays, at RT). After the second irradiation phase, the RIA values decreased to approximately 7.27 dB/km at 1310 nm and 14.38 dB/km at 1550 nm. This study sheds light on the attenuation characteristics of F-doped silica fibers under high ionizing radiation and their variation with radiation dose, providing valuable insights for the application of optical fibers in radiation environments.
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IEEE