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Articles in press have been peer-reviewed and accepted, which are not yet assigned to volumes/issues, but are citable by Digital Object Identifier (DOI).
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, Available online , doi: 10.11884/HPLPB202638.250166
Abstract:
Background Purpose Methods Results Conclusions
System-generated electromagnetic pulse (SGEMP) arises from electromagnetic fields produced by photoelectrons emitted from spacecraft surfaces under intense X-ray or γ -ray irradiation. Cavity SGEMP, a critical subset of SGEMP, involves complex interactions within enclosed structures. While scaling laws have been established for external SGEMP, their applicability to cavity SGEMP remains debated due to photon spectrum distortion caused by variations in cavity wall thickness and other factors.
This study aims to validate the applicability of SGEMP scaling laws to cavity SGEMP by proposing a canonical transformation method that maintains constant wall thickness. The goal is to provide a theoretical basis for analyzing cavity SGEMP mechanisms and designing laboratory-scale experiments.
A cylindrical cavity model with an aluminum wall was irradiated by a laser-produced plasma X-ray source. Numerical simulations were performed using a 3D particle-in-cell (PIC) code under two conditions: an original model and a 10×scaled-up model. Key parameters, including grid size and time steps, were scaled according to the derived laws. The wall thickness was kept constant to avoid photon spectrum distortion. Simulations compared electric fields, magnetic fields, charge densities, and current distributions between the two models.
The original and scaled-up models exhibited identical spatial distributions of electromagnetic fields and charge densities. Specific validation results include: Peak electric fields decreased from 2.0 MV/m (original) to 200 kV/m (scaled-up); peak magnetic fields reduced from 0.8×10−3 T (original) to 0.8×10−4 T (scaled-up); and charge densities maxima dropped from 6.0×10−3 /m3 to 6.0×10−5 /m3. Waveform shapes for currents and fields remained unchanged across models. These results all adhere to the scaling laws.
The scaling laws for SGEMP are validated for cavity SGEMP when wall thickness remains unchanged. This work provides a universal theoretical tool for cavity SGEMP studies and reliable scaling criteria for laboratory experiments.
, Available online , doi: 10.11884/HPLPB202638.250185
Abstract:
Background Purpose Methods Results Conclusions
Gyrotron traveling-wave tubes (gyro-TWTs), based on the electron cyclotron maser mechanism, are extensively utilized in critical military domains such as high-resolution millimeter-wave imaging radar, communications, and electronic countermeasures. Experimental observations indicate that when the cathode magnetic field exceeds a specific range, the electron beam bombardment of the tube wall occurs.
This study aims to reduce damage risks to the electron gun during experiments, provide guidance for identifying optimal operating points in experimental testing of Ka-band second-harmonic large-orbit gyrotron traveling wave tube (gyro-TWT).
This paper introduces the formation theory of large-orbit electron guns and analyzes the motion of electron beams in non-ideal CUSP magnetic fields. Using CST Particle Studio and E-Gun software modeled and simulated the electron gun. The effects of magnetic fields, operating voltage, and beam current on the quality and trajectories of large-orbit electron beams were investigated.
As the absolute value of the cathode magnetic field increases, both the velocity ratio and the Larmor radius increase, while the velocity spread decreases. With an increase in voltage, the velocity ratio decreases, and the Larmor radius drops to a minimum at a certain point before rising again. Variations in current have limited impact on the Larmor radius and the transverse-to-longitudinal velocity ratio; however, the electron-wave interaction efficiency reaches its maximum at the optimal operating current.
The study demonstrates that excessively low operating voltage leads to high transverse-to-longitudinal velocity ratios and electron back-bombardment phenomena, which detrimentally affect the cathode. Therefore, within this voltage range (20–40 kV), the power supply voltage should be increased promptly. Conversely, excessively high reverse magnetic fields at the cathode result in an oversized electron cyclotron radius, causing beam-wall bombardment and gun damage. To prevent electron beam bombardment of the tube wall, the cathode magnetic field should not exceed 0.0085 T.
, Available online , doi: 10.11884/HPLPB202638.250194
Abstract:
The Low Energy High Intensity High Charge State Heavy Ion Accelerator Facility (LEAF) is a national scientific instrument developed by the Institute of Modern Physics, Chinese Academy of Sciences, to provide high-current, high-charge-state, full-spectrum low-energy heavy ion beams for interdisciplinary studies. To meet research needs in nuclear astrophysics, atomic and molecular physics, and nuclear materials, LEAF offers tunable energies from 0.3 to 0.7 MeV/u and supports continuous-wave acceleration for ions with with a mass-to-charge ratio ranging from 2−7. This paper presents an overview of the construction progress, key design parameters, and operational performance of the facility, summarizing recent achievements and outlining future development goals. The paper introduces the system architecture—comprising the 45 GHz superconducting ECR ion source FECR, RFQ, IH-DTL, and terminal beamlines—and describes beam commissioning and diagnostic approaches. LEAF has successfully achieved stable acceleration of multi-species, high-charge-state heavy ion beams with intensities up to 1 emA. It has delivered more than13000 h of beam time, realized efficient operation of “cocktail”multi-ion beams, and established a high-current, low-energy-spread 12C2+ beamline for precise reaction measurements in the Gamow window. These results verify LEAF’s excellent beam quality and operational reliability. Planned upgrades—including an extended energy tuning range and triple-ion beam capability—will further enhance its role as a frontier platform for experimental studies in nuclear astrophysics and radiation effects in advanced materials.
The Low Energy High Intensity High Charge State Heavy Ion Accelerator Facility (LEAF) is a national scientific instrument developed by the Institute of Modern Physics, Chinese Academy of Sciences, to provide high-current, high-charge-state, full-spectrum low-energy heavy ion beams for interdisciplinary studies. To meet research needs in nuclear astrophysics, atomic and molecular physics, and nuclear materials, LEAF offers tunable energies from 0.3 to 0.7 MeV/u and supports continuous-wave acceleration for ions with with a mass-to-charge ratio ranging from 2−7. This paper presents an overview of the construction progress, key design parameters, and operational performance of the facility, summarizing recent achievements and outlining future development goals. The paper introduces the system architecture—comprising the 45 GHz superconducting ECR ion source FECR, RFQ, IH-DTL, and terminal beamlines—and describes beam commissioning and diagnostic approaches. LEAF has successfully achieved stable acceleration of multi-species, high-charge-state heavy ion beams with intensities up to 1 emA. It has delivered more than
, Available online , doi: 10.11884/HPLPB202638.250148
Abstract:
Background Purpose Methods Results Conclusions
Backward stimulated Raman scattering (SRS) and backward stimulated Brillouin scattering (SBS) are two major laser-plasma instabilities that influence the laser-target energy coupling efficiency in inertial confinement fusion (ICF). Hot electrons excited by SRS can preheat the fuel. Their nonlinear competition determines the effectiveness of laser-plasma coupling and thus the performance of laser-driven fusion. In realistic laser fusion conditions, the electron distribution often deviates from a Maxwellian due to strong laser heating, leading to nonthermal effects such as the Langdon effect. Additionally, ion-ion collisions in multispecies plasmas such as CH can alter the damping and dispersion of ion acoustic waves.
This study aims to investigate the impact of the Langdon effect and ion-ion collisions on the competition between SRS and SBS in CH plasma, particularly focusing on their respective reflectivities under varying plasma conditions.
Five-wave coupling equations describing the nonlinear interactions among the pump laser, scattered light, Langmuir wave, and ion acoustic wave were numerically solved. A super-Gaussian electron distribution function was employed to incorporate the Langdon effect, while ion-ion collision effects were included through modifications to the ion susceptibility. The dispersion relations and damping characteristics of both electron plasma waves (EPWs) and ion acoustic waves (IAWs) were analyzed in detail.
The results reveal that the Langdon effect notably reduces Landau damping of EPWs and modifies the dispersion relation of SRS, enhancing its growth rate. Simultaneously, ion-ion collisions increase IAW damping and shift the SBS dispersion curve, weakening its instability. These combined effects lead to a dominance of SRS over SBS at lower electron densities, altering the overall backscattering reflectivity spectrum in laser fusion plasma.
Both the Langdon effect and ion-ion collisions play crucial roles in reshaping the nonlinear dynamics of SRS and SBS. Their influence must be considered in predictive models of laser-plasma interactions. These findings provide insight into optimizing plasma parameters for improved control of backscatter instabilities in inertial confinement fusion experiments.
, Available online , doi: 10.11884/HPLPB202638.250271
Abstract:
Background Purpose Methods Results Conclusions
In recent years, reflectarray antennas have received significant attention and research in the high-power microwave field due to their low profile, conformability, and spatial feed characteristics. Multi-frequency reflectarray antennas can share the same antenna plane while providing differentiated beam steering at different frequencies, resulting in greater system platform adaptability. However, these antennas commonly face the challenges of limited power handling capacity and low aperture efficiency.
This paper aims to propose a phase synthesis method for high-power, dual-band reflectarray antennas, which enhances their power handling capacity and aperture efficiency. This approach is universally applicable to the design of multi-frequency reflectarray antennas.
The proposed phase synthesis method incorporates reference phase optimization and screening threshold techniques. It takes into account the reflected phase and electric field intensity of the antenna elements under different incident wave conditions. This approach effectively increases power capacity and aperture efficiency.
We designed an improved reflectarray antenna element and applied the proposed phase synthesis method to a dual-band reflectarray antenna design. A 27×27 array operating at 4.3 GHz and 10.0 GHz achieved aperture efficiencies of 67.37% and 48.69%, respectively, with a power capacity of hundreds of megawatts in a vacuum environment.
The proposed phase synthesis method has been successfully validated, proving its effectiveness in designing high-performance, high-power, dual-frequency, and multi-frequency reflectarray antennas.
, Available online , doi: 10.11884/HPLPB202537.250138
Abstract:
Background Purpose Methods Results Conclusions
High-power microwave (HPM) pulses, which can interfere with or damage electronic components and circuits, have attracted considerable research interest in recent years. Aperture coupling represents a primary mechanism for such pulses to penetrate shielded metallic enclosures, significantly affecting the electromagnetic compatibility and resilience of electronic systems. Although substantial studies have focused on shielding effectiveness and resonant behaviors, the spatial distribution of coupling parameters—particularly the extent of strongly coupled regions within the cavity—remains inadequately investigated. This paper proposes a quantitative metric termed “the coverage rate of strong-coupled region” to better evaluate HPM backdoor coupling effects.
The objective is to systematically examine the influence of key HPM waveform parameters on this coverage rate within a representative metallic cavity.
A three-dimensional simulation model of a rectangular metallic cavity with an aperture was developed using the finite-difference time-domain (FDTD) method. The internal field distribution was monitored via an array of electric field probes. Numerical simulations were performed to assess the effects of various HPM parameters, including frequency, pulse width, the pulse rise time, and polarization angle, on the coverage of strongly coupled regions.
The coverage rate was markedly higher at the cavity’s inherent resonant frequencies than at non-resonant frequencies. Increasing the pulse width led to a saturation of coverage beyond a specific threshold. Variations in polarization angle from horizontal to vertical considerably enhanced the coverage, with vertical polarization yielding the maximum value. Superimposing multiple resonant frequencies effectively compensated for weakly coupled areas, further increasing the overall coverage. In contrast, the pulse rise time had a negligible effect on the coverage rate. The proposed the coverage rate of strong-coupled region effectively addresses the practical dilemma wherein strong local coupling does not necessarily lead to significant system-level effects.
This metric provides a quantitative basis for optimizing the alignment between sensitive components and highly coupled zones. Frequency and polarization are identified as decisive parameters for enhancing coupling effectiveness, while pulse width and multi-frequency excitation can be utilized to achieve more uniform and robust coupling coverage. These findings offer valuable guidance for the design and assessment of HPM protection measures and electromagnetic compatibility analysis.
