Most ReadThe W-band constitutes a critical atmospheric window in the millimeter-wave spectrum, with significant importance for advanced applications such as high-capacity communications, high-resolution imaging, and high-precision sensing. As essential components within core millimeter-wave transmitter and receiver systems, filters fundamentally determine transceiver performance. However, conventional designs frequently face challenges in simultaneously achieving high electrical performance and favorable manufacturability, representing a key obstacle in contemporary W-band filter development.
This work aims to develop a low-loss, low-order, and readily fabricable waveguide quasi-elliptic bandpass filter for the W-band. The goal is to maximize structural simplicity while maintaining high performance, thereby addressing the requirements of next-generation highly integrated transceiver systems.
The proposed filter employs a novel H-plane offset magnetic coupling configuration, which simplifies the input–output coupling mechanism. Guided by quasi-elliptic filtering theory, transmission zeros are generated on both sides of the passband through the excitation of TE201/TE102 and TE301/TE102 hybrid modes in two respective resonant cavities, resulting in enhanced out-of-band suppression. The filter is implemented in a split-block architecture and fabricated via high-precision computer numerical control (CNC) milling.
Measured results demonstrate an operational passband from 91.5 GHz to 98 GHz, corresponding to a 3 dB fractional bandwidth of 7%, with an in-band insertion loss as low as 0.4 dB and a return loss greater than 15 dB. Except for a slight deviation observed at the upper band edge, the experimental data show strong agreement with simulation, confirming the design’s manufacturability, integration compatibility, and high-frequency performance.
A compact, low-loss W-band quasi-elliptic filter has been successfully realized using only two hybrid-mode cavities. The presented design exhibits notable advantages in terms of fabrication ease, integration suitability, and electrical performance, providing a viable solution for advanced millimeter-wave system applications.
The study of multi-scale turbulence and related anomalous transport under high-performance plasma operation remains an important topic in the research of magnetic confinement fusion. The parameter range of plasmas in the tokamak experiment determines that far-infrared laser collective scattering is the optimal diagnostic method for multi-scale turbulence diagnostics.
This paper discusses the overall design parameters of the diagnostic system and provide a detailed introduction to the design of the windows for the multi-scale turbulence collective scattering (MSTCS) diagnostic system on the HL-3 Tokamak.
The laser beam entrance window of the MSTCS diagnostic system is located in the mid-plane port #6 of the HL-3 tokamak, and the scattered light beams exit from the windows in the mid-plane port #12. The design aspects of the windows include the material selection, clear aperture calculation, window thickness design, mechanical design, and surface quality requirements. Several interrelated factors need to be considered in the design process. These include the diagnostic wavenumber range, wavenumber resolution, wavenumber purity of the scattering data, laser beam transmission coefficients, and the requirements for vacuum sealing and safety.
On the basis of these considerations, a corresponding design scheme was formulated. The technical details of the analysis and design process as well as the design results are presented.
The MSTCS diagnostic system has been successfully installed on HL-3, and preliminary experimental data confirm the vacuum safety and optical performance of the diagnostic windows, thereby validating the overall design.
High-power pulsed applications increasingly require power supplies capable of high-current bipolar output and flexible controllability. However, achieving high power density while maintaining pulse precision and current-sharing stability remains a significant challenge pulsed source design.
This work aims to design and implement a compact, integrated bipolar pulsed current supply system that utilizes a paralleled silicon carbide (SiC) MOSFET full-bridge architecture to meet the demands of medium-voltage, high-power pulsed applications.
The proposed system integrates the main power stage, isolated drivers, auxiliary power supplies, and protection module on a single printed circuit board (PCB), featuring both high power density and good scalability.
Experimental results demonstrate that, under DC bus voltages ranging from 50 V to 300 V, the peak output current exhibits excellent linear correlation with the bus voltage, while pulse-width adjustment enables continuously controllable peak current with a maximum enhancement of 37%. The system is capable of delivering bipolar pulse currents up to ±300 A, confirming the compatibility of high-current output with compact integration. In addition, at a 500$ \mathrm{\; ns} $ pulse width, the four-device paralleled branch achieves a current-sharing imbalance factor of 12.87%, validating the effectiveness of the cooperative gate-drive scheme and the use of independent gate resistors.
These findings indicate that the proposed compact integrated design successfully balances high-current bipolar pulsed output and parameter adjustability, providing experimental evidence and design guidance for the miniaturization and engineering implementation of medium-voltage and high-power pulse sources.
This paper focuses on the element doping technology of low-density polymer foams for inertial confinement fusion (ICF) experiments and summarizes their research status and development trends. As key target materials for ICF, low-density polymer foams can optimize radiation transport, suppress hydrodynamic instability, and achieve diagnostic functions by introducing doping elements such as chlorine, argon, and germanium. The paper systematically analyzes the principles, advantages, disadvantages, and application bottlenecks of two major types of doping technologies: physical doping (particle dispersion, physical vapor deposition) and chemical doping (copolymerization, monomer functionalization, polymer substitution), with an emphasis on core issues such as uniformity control and doping precision. Finally, it discusses cutting-edge directions including composite doping, two-photon polymerization, and ion implantation, providing technical references for the high-performance and precise preparation of ICF target materials and facilitating the development of high-repetition-rate ICF experiments.
In indirect-drive laser inertial confinement fusion (ICF), the precise calculation of X-ray drive intensity at the capsule is crucial for accurately predicting the implosion performance of deuterium-tritium fuel capsules. Achieving this requires detailed radiation-hydrodynamic simulations that accurately capture processes such as laser-to-X-ray conversion and X-ray absorption losses at the hohlraum walls. However, since the inception of the National Ignition Campaign at the National Ignition Facility (NIF), radiation-hydrodynamic simulations have consistently overestimated the experimentally measured X-ray drive flux intensity at the capsule, reflecting the widespread presence of hohlraum energy deficits. Although extensive experimental studies have been conducted at NIF along with continuous optimization of its radiation-hydrodynamic simulation models, the challenging issue of hohlraum energy deficit remains unresolved, constituting one of the critical barriers to achieving high-gain inertial confinement fusion. This paper systematically reviews the critical research developments regarding hohlraum energy deficit at NIF and introduces the methods adopted by NIF and China for characterizing the X-ray radiation flux intensity at the capsule.
Pinhole cameras based on the principle of pinhole imaging are widely used in high-energy-density physics experiments to monitor laser-target interaction regions. However, traditional pinhole cameras often suffer from signal acquisition failures due to the lack of online aiming capability, especially for small targets such as wire targets in facilities like the Xingguang-Ⅲ laser system.
This study aims to develop an X-ray online-aiming pinhole camera for the Xingguang-Ⅲ laser facility to address the challenge of precise target alignment under vacuum conditions and enhance the reliability of signal acquisition.
An integrated design combining a visible-light CCD and an X-ray CCD was implemented. A revolver-type pinhole adjustment device was developed to switch between aiming apertures and imaging pinholes with a concentricity error below 3.5 µm. High-precision two-dimensional pointing adjustments (pitch and tilt) were achieved using a motorized stage, with a targeting accuracy of 15 µm. The visible-light CCD enabled real-time target imaging, while different aperture sizes on a precision adjustment disk facilitated coarse-to-fine aiming.
The camera was tested on the Xingguang-Ⅲ laser facility using a Cu planar target irradiated by a picosecond laser. Clear X-ray spot images were obtained, with a peak intensity of 52 040 and a background noise of approximately 2 500. The full width at half maximum of the spot was 43 µm horizontally and 38 µm vertically, confirming successful online aiming and imaging performance.
The developed X-ray online-aiming pinhole camera fulfills the operational requirements of the Xingguang-Ⅲ laser facility. It enables real-time, high-precision target alignment under vacuum, significantly improving the success rate of signal acquisition in high-energy-density physics experiments.
The projection sequence of Hadamard speckle patterns directly influences the image reconstruction quality and efficiency of computational ghost imaging under undersampled conditions. Optimizing the speckle sorting strategy is an effective approach to achieving high-quality imaging at low sampling rates.
This study aims to address the oscillation of quality metrics observed during the sampling process of traditional sorting strategies and to further enhance the signal-to-noise ratio and convergence stability within the low-sampling-rate regime.
A recursive cross (RC) sorting strategy based on the Hadamard basis is proposed. By inversely deconstructing hierarchical subspaces and utilizing an even-index mapping mechanism, this method interleaves and reorganizes speckles with orthogonal texture features, thereby disrupting the continuous accumulation of unidirectional features in the sampling sequence. Numerical simulations under both ideal and Gaussian noise environments, along with optical experiments, were conducted to validate the proposed method.
Simulation results demonstrate that the RC strategy effectively eliminates the oscillation of evaluation metrics observed in Russian Dolls sorting as the sampling rate increases across the full 0–100% range, achieving a smooth evolution and robust convergence of imaging quality. Particularly in the low-sampling-rate range of 0–10%, the peak signal-to-noise ratio of the reconstructed images shows a maximum improvement of approximately 101.7% compared to Hadamard natural sorting and 11.4% compared to laser model speckle sorting, with a maximum gain of about 3.4 dB.
By optimizing the sampling path of spectral energy, the RC sorting strategy improves the data acquisition efficiency of ghost imaging, potentially offering an effective technical pathway for realizing rapid and real-time ghost imaging applications.
Titanium and its alloys are the predominant base materials for oral implants. However, challenges such as prolonged osseointegration periods and limited success rates persist due to their inherent low surface bioactivity. Femtosecond laser processing has emerged as an innovative, non-thermal, and high-precision surface modification technique, offering a novel approach to precisely tailor the micro-nano topography, chemical composition, and biological performance of implant surfaces. This review summarizes research advances in femtosecond laser surface treatment of titanium implants over the past five years. It systematically elaborates on methods for constructing specific surface architectures by regulating parameters such as laser power, wavelength, scanning strategies, and pulse patterns. Furthermore, it introduces hybrid processing strategies that combine femtosecond laser with techniques like hydroxyapatite deposition, sandblasting, and 3D printing, highlighting their synergistic effects. By comparing femtosecond laser processing with conventional surface treatment technologies (e.g., sandblasting and acid etching, electrochemical deposition, plasma sputtering), this paper analyzes its unique advantages in terms of processing precision, heat-affected zone, biocompatibility, and long-term stability. Finally, current challenges (e.g., equipment cost, processing efficiency) are summarized, and future development directions are proposed, including personalized implant manufacturing, multifunctional surface construction, and integration with other advanced technologies.
The China Institute of Atomic Energy has designed of a 9.5 MeV ultra-compact cyclotron to support the independence of Positron Emission Tomography (PET) cyclotrons. A high-performance control system is critical for the equipment, as the stability of the acceleration field directly impacts beam quality.
In order to ensure the stable acceleration of the accelerator beam, this study aims to develop a Low-Level Radio Frequency (LLRF) control algorithm based on a fully digital hardware platform.
To enhance control precision and increase the feedback rate, a high-speed Digital Down-Conversion (DDC) demodulation system was designed. Addressing the issue where the IQ sequence after digital down-conversion may be distributed in arbitrary quadrants, an innovative quadrant preprocessing module was developed to extend applicability across the Cartesian plane. A position-type Proportion-Integral-Derivative (PID) tuning loop was implemented for automatic frequency compensation, integrating adaptive protection, timed detection, and one-click startup. Furthermore, a robust cross-clock-domain data path was constructed to ensure accurate and stable amplitude regulation.
Closed-loop tests verified the reliability of the demodulation system. During the joint commissioning with the accelerator, a stable internal target beam current of 100 μA was successfully extracted. The system achieved a cavity voltage amplitude stability of 0.047% (RMSE) and maintained a detuning angle of 0.46°(RMSE).
The experimental results demonstrate that the proposed LLRF system fully meets the control requirements of the accelerator. The design ensures high stability and precision, providing reliable technical support for the operation of the 9.5 MeV ultra-compact cyclotron.
Although quartz exhibits excellent light transmittance, the significant difference in thermal expansion coefficients between quartz and metal sealing materials has long been a critical technical bottleneck, leading to interface stress concentration and vacuum sealing failures in low-leakage quartz windows.
This study addresses the urgent demand for ultra-high vacuum precision optical systems by conducting systematic research on sealing technologies for high-performance quartz vacuum windows.
To overcome this challenge, this paper innovatively proposes using magnetron sputtering technology to sequentially deposit a Ti/Mo/Cu/Ag multilayer film system on the quartz welding surface, thereby creating a gradient functional metallization layer with thermal stress buffering capability that achieves effective surface metallization.
Scanning electron microscopy observations revealed continuous, dense, and structurally uniform film layers. Nanoindentation experiments further demonstrated a bonding strength of approximately 3.83 N between the metallized layer and quartz substrate, indicating robust adhesion. Experimental results show that vacuum window components fabricated using this metallization scheme achieve leakage rates below 10−12 Pa·L/s.
This achievement has broad applications in synchrotron radiation, quantum measurement, and space exploration, providing crucial technical support for the development of high-performance vacuum devices.
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