Gyrokinetic simulations based on the Gyrokinetic Toroidal Code are conducted to investigate the geodesic acoustic mode (GAM) physics in the pedestal of EAST H-mode discharge #74036 (Zhou et al 2018 Nucl. Fusion 58 106009). Linear simulations reveal that the instabilities are dominated by the collisionless trapped electron mode (CTEM) in the absence of collisions, and transit to the dissipative trapped electron mode (DTEM) when the collisions are considered. The frequency and propagation direction of DTEM align with those of the edge coherent mode (ECM) observed in the experiments after considering the Doppler shift correction due to the radial electric field on the frequency, indicating DTEM is the dominant component of ECM. In the nonlinear simulations, it is found that CTEM turbulence drives the continuum GAM, whose frequency increases with the ion temperature, aligning with the theoretical predictions. In comparison, DTEM turbulence excites the eigenmode GAM, whose frequency almost does not change with the ion temperature, consistent with the experimental observations. The properties of eigenmode GAM are further confirmed through antenna excitation. Both the continuum and eigenmode GAMs are found to strongly modulate the turbulent transport.

A class of Boris-like second-order volume-preserving algorithms (VPAs) for simulating charged particle motion in electromagnetic fields have been generalized to a rotating angle formulation by matrix notation. The phase stability of this class of VPAs has been analyzed by utilizing discrete Fourier transformations (DFT) technique. It is found that two prominent VPAs, namely the and the well-known Boris algorithm, exhibit optimal phase precision for high-frequency (gyro motion) and low-frequency dynamics (transit/bounce motion), respectively. These findings have been empirically verified through numerical experiments. The insights gained from this study enable the selection of an appropriate VPA for practical simulations based on the characteristic frequencies of specific physics problems, which can substantially enhance numerical accuracy and improve computational efficiency for long-term calculations.

A dedicated real-time detection system (NTM-RTDS) has also been developed to determine the radial position of neoclassical tearing mode (NTM) magnetic islands. Built upon the LabVIEW real-time framework and PXIe architecture, it adopts a distributed upper-lower computer structure that enables high-speed acquisition and real-time processing of signals from magnetic probes and electron cyclotron emission diagnostics. By analyzing perturbation frequencies associated with magnetic island rotation and electron temperature profile variations, the system achieves island localization within a 10 ms cycle. Validation on experimentally advanced superconducting tokamak confirms a detection accuracy of 80.25% in identifying magnetic islands, verifying the system's robustness. The NTM-RTDS thus represents a critical instrument for enabling active, real-time NTM control via electron cyclotron resonant heating, and provides a foundational platform for real-time disruption mitigation strategies in future large-scale fusion experiments, including the international thermonuclear experimental reactor.

An improved Boris algorithm for simulating the motion of charged particles in electromagnetic fields has been developed. This enhancement addresses the issue of inaccurate fast-scale cyclotron phase calculations present in the original Boris algorithm, while preserving its advantage in simulating slow-scale guiding center motion. As a result, it strikes a balance between low and high-frequency dynamics, overcoming the limitations of traditional second-order volume-preserving algorithms (VPAs) which are constrained to a single characteristic frequency. Test particle simulations indicate that, in most cases, the improved Boris algorithm achieves significantly higher accuracy than conventional VPAs when simulating cases involving various frequencies of electric field within a typical Tokamak magnetic field, highlighting its superior efficacy in handling problems across a wide range of characteristic frequencies.

A quasi-vertical Schottky diodes with high speed and high responsivity were demonstrated by epitaxially growing Ga(2)O(3 )on Pt. The research further investigated the impact of incorporating metal stripes in the photosensitive region to enhance both the responsivity and response speed of the device. Characterization of the photoresponses reveals that these devices exhibit high sensitivity to solar-blind ultraviolet light, peaking at approximately 260 nm. At the bias of -5V, the detector achieves a responsivity of 2998 A/W, an exceptional specific detectivity of 1.68 x 10(7) Jones and a high response speed about 0.1 ms. By applying these metrics demonstrate substantial improvements over existing technologies and suggest a promising avenue for developing high speed and high responsivity photodetectors.

This work reports a high-performance enhancement-mode $\beta-\text{Ga}_{2} \mathrm{O}_{3}$ multi-fin field-effect transistor (FinFET). Utilizing a non-metal mask etching and self-aligned process based on photoresist planarization. The $\beta-\text{Ga}_{2} \mathrm{O}_{3}$ FinFET exhibited a maximum output current density of $361.5 \mathrm{A} / \text{cm}^{2}$, a peak transconductance of $127 \mathrm{S} / \text{cm}^{2}$, a specific on-resistance of $4.3 \mathrm{m} \Omega \cdot \text{cm}^{2}$, a breakdown voltage of 975 V, and a power figure of merit (PFOM) of $0.22 \text{GW} / \text{cm}^{2}$. These results demonstrate the feasibility of $\beta-\text{Ga}_{2} \mathrm{O}_{3}$ power transistors for large-area applications.

An Improved Boris algorithm for simulating charged particle motion in electromagnetic fields has been derived. It addresses the issue of inaccurate fast-scale cyclotron phase calculations in the original Boris algorithm, while still maintaining its advantage in simulating slow-scale guiding center motion, hence achieves a balance between low and high-frequency dynamics, overcoming the limitation of traditional second-order volume-preserving algorithms(VPAs) that are constrained to a single characteristic frequency. Test particle simulations indicate that, in most cases, the improved Boris algorithm achieves an exceedingly higher accuracy than conventional VPAs when simulating cases involving various frequencies of electric field within a typical Tokamak magnetic field, highlighting its superior efficacy in handling problems over a large range of characteristic frequencies.

The stability and dependability of the cryostat will be impacted by its thermal expansion and contraction. We first examined the heat transfer, alignment, and monitoring technique in a cryo-environment from a theoretical perspective to supply the appropriate quantity of pre-compensation and guarantee alignment of the cryostat with bottom-supported at 2 K in the HighIntensity heavy-ion Accelerator Facility (HIAF). The continuous monitoring of cryo-deformation based on a Wire Position Monitor (WPM) and Micro-Alignment Telescope (MAT) was taken out respectively. We have shown by comparing the results that both WPM and MAT monitoring are accurate. At 2 K, the bottom-supported cryostat exhibited less vertical low-temperature deformation than the top-suspended one. The pre-compensation of cryo-deformation under operating conditions, such as mechanical and thermal loads on the cryostat, will benefit from the analytical results. An optimization for the design of future cryostats will also benefit from the data.

Second-order Volume-preserving algorithms (VPAs) for simulating charged particle motion in electromagnetic fields have been generalized to a rotating angle formulation by using the matrix decomposition methods. Based on this method, the phase stability of this class of VPAs has been analyzed by using the Discrete Fourier Transformations (DFT) technique. It is found that two prominent VPAs, namely the $G_h^2$ and the Boris algorithm, exhibit optimal phase precision for high-frequency (gyro motion) and low-frequency dynamics (transit/bounce motion), respectively. These findings have been empirically verified through numerical experiments. The insights gained from this study enable the selection of an appropriate VPA for practical simulations based on the characteristic frequencies of specific physics problems, which can substantially enhance numerical accuracy and improve computational efficiency for long-term simulations.

β-phase gallium oxide (β-Ga2O3)/aluminum nitride (AlN) heterojunctions hold significant potential for high-power and microwave device applications. In this study, we systematically investigated the properties of the β-Ga2O3/AlN heterostructure grown via metal-organic chemical vapor deposition (MOCVD). High-resolution X-ray diffraction (HRXRD) and Raman spectroscopy revealed the crystal structures and demonstrated the high-crystalline quality of both films. Atomic force microscopy (AFM) scans displayed a smooth β-Ga2O3 surface with a root-mean-square (RMS) roughness of 3.6 nm. Scanning electron microscopy (SEM) images showed a flat surface with distinct heterostructure boundaries. Elemental distributions across the interface were mapped by using energy-dispersive spectroscopy (EDS). X-ray photoelectron spectroscopy (XPS) analysis characterized the chemical components of the sample and confirmed a type-II band alignment in the heterojunction, which facilitates electron accumulation. Furthermore, the thermal conductivity of β-Ga2O3 was measured at 4.2 W/(m·K), and the thermal boundary conductivity at the β-Ga2O3/AlN interface was determined to be 118.6 MW/(m2·K) using the time-domain thermoreflectance (TDTR) method. Temperature-dependent electrical performance of the β-Ga2O3/AlN SBD, including a low turn-on voltage of 0.1 V, ideality factor of 4.22, modified Richardson constant of 48.5 A/cm2 K2, and high breakdown voltage of 1260 V, was obtained. All of these values are competitive among β-Ga2O3-based heterostructures. The findings highlight the excellent interface quality, superior heat dissipation capability, and decent SBD performance of the β-Ga2O3/AlN integration, offering a promising platform for developing β-Ga2O3-based power devices capable of operating at high temperatures.

Ultrafine platinum (Pt)-based nanowires (NWs) have emerged as a highly promising type of materials for multifunctional electrocatalysts. However, to achieve their synthesis presents significant challenges via relatively facile strategies, especially for multicomponent Pt-based NWs, due to the substantial variation in reduction potentials among different precursors and the tough coordination required for nanocrystal nucleation and growth. Herein, ultrathin NWs composed by Pt, Se, and Cd were realized via a facile one-pot synthesis where only involving precursors, reducing agent and solvent. Moreover, the prepared NWs embed the joint advantages of multicomponent, partial amorphous, ultrafine size, abundant grain boundaries and surface-defect-sites meanwhile. Thus, the ultrahigh methanol oxidation reaction (MOR) activity of 2.94 A mgPt-1 and superior catalytic stability were achieved for Pt-Se-Cd NWs, transcending the most of Pt-based catalysts. Density functional theory calculation suggests that the outstanding MOR activity was attributed to the weakened CO poisoning and optimized adsorption of *CH3OH. Apart from MOR, Pt-Se-Cd NWs are also with remarkable activities for ethanol oxidation reaction (EOR) and hydrogen evolution reaction (HER). Se precursor plays a key role on NWs formation and amorphous regulation, based on which more Pt-Se-M NWs (M = Zn, In, CdZn, ZnIn, CdInZn) were fabricated successfully, revealing a superior generalization in NW synthesis. The work may not only highlight a facile synthesis for ultrafine Pt-based NWs with abundant catalytic advantages, but also explore their potential applications in electrocatalysis and beyond.

The fast ions and electrons generated by neutral beam injection (NBI) can induce charge separation, resulting in radial electric fields. Employing beamlet injection of small cross-section may effectively generate radial electric field, and adjusting beamlet parameters allows active control over their distribution. A new NBI injection geometry system has been developed in the NEOE code to explore the potential for vertical beamlets injection in future fusion reactor scenarios. Both high-field side and low-field side beamlet vertical injections can establish radial electric fields. In scenarios dominated by collision effects, the direction of the radial electric field is influenced by the toroidal angle of the beamlet. Adjusting the poloidal angle can alter the location of the electric field shear. Injecting particles into the trapped region using broader banana orbits can establish electric fields within the plasma core. Alternatively, injecting particles into the passing region can yield higher electric fields. Under future reactor conditions, conservative estimates of the electric field shear may even surpass critical velocities, potentially contributing to instability suppression.

The stabilization of the m/n= 2/1 neoclassical tearing mode (NTM) by electron cyclotron current drive (ECCD) has been carried out in EAST H-mode discharges, where m/n is the poloidal/toroidal mode number. The experimental results are reported for the first time in this paper. To facilitate the experimental study, the magnetic island (NTM) is generated by a sufficiently large amplitude of the externally applied resonant magnetic perturbation (RMP). After switching off the RMP, the NTM exists due to the bootstrap current perturbation, with the magnetic island width being about 5 cm for the local equilibrium bootstrap current fraction being larger than 10%. By applying the localized ECCD later, the NTM is fully suppressed if the radial misalignment between the magnetic island and the ECCD location is sufficiently small. The stabilizing effect depends on both the radial misalignment and the applied electron cyclotron wave power. More importantly, it is found that the NTM can be avoided when applying ECCD earlier during the ramp-up phase of the RMP amplitude, if ECCD is localized around the O-point of the magnetic island, indicating an efficient way for avoiding locked modes that can lead to the major disruptions of tokamak plasmas.

In 2021, EAST was equipped with a full-ring divertor coil to facilitate research on the fish tail divertor concept. Initially, it was observed that the coil current had a negligible ability to sweep the strike point. Conversely, when the amplitude and frequency of the alternating current were marginally increased, there was a significant interruption to plasma control. This perturbation was attributed to the poloidal control field's limited response rate to the coil's fluctuations. To address this issue, novel control methodologies were devised to ensure stable and effective sweeping of the strike point using the divertor coil. The devised methods are twofold: For high-frequency strike point control, a low-pass filter decoupling technique based on ISOFLUX control strategy enabled achieving a sweeping frequency of 100 Hz. This strategy allowed for consistent plasma management without compromising average stored energy or density regulation. Resulting from this proficient manipulation of the strike point, a reduction in the peak temperature of the divertor plate was observed. For low-frequency sweeping, a static multi-input multi-output decoupling approach was developed, facilitating concurrent sweeping of both the outer and inner strike points.

The radial electric field plays an important role in plasma confinement in tokamaks and can be generated through neutral beam injection. In this study, we propose a model for calculating the radial electric field resulting from tangential local neutral beamlet injection, aiming to externally control and improve plasma confinement. The Neutral beamlet ion and Energetic particles Orbit mover and Electric field solver code has been developed to analyze this issue, and its simulation results have been validated against results from other codes as well as measurements from correlation reflectometers. The charge separation is primarily caused by the redistribution and loss of beam ions due to magnetic gradient and curvature drift as well as collision effects, and it is maintained through continuous beamlet injection. The electric field is calculated using Poisson's equation, taking into account both classical and neoclassical polarization effects. The results demonstrate that despite the high losses and low heating efficiency associated with localized beamlets, they are capable of generating a significant radial electric field characterized by a steep gradient. This presents opportunities for external control of the electric field, potentially enhancing plasma confinement.

The alpha particle distribution in the full energy region is studied in this work. The Fokker-Planck equation near the equilibrium state is analytically solved using an iteration method for alpha particles. The resulting distribution includes the Maxwellian part, the modified slowing down part, and the high energy tail part. The analytical results align with the conventional slowing down distribution in the high energy region v(alpha) > 02v(b) and the Maxwellian distribution in the low energy region v(alpha) < 01v(b), where v(alpha) is the alpha particle velocity and v(b) is the birth velocity of alpha particles. In the range of 0.1v(b )< v(alpha) < 02v(b), the distribution is described by the sum of the Maxwellian part and modified slowing down part. Turbulent transport effects on the alpha particle distribution are studied through introducing a local sink term. A simplified analytical solution is provided, and the bump-on-tail distribution is observed under appropriate parameters. In both cases with and without transport effects, the Fokker-Planck equation is numerically solved. It is shown that the full temporal evolution of the system can be divided into three stages: the slowing down stage, thermalization stage, and quasi-steady state stage. The numerically obtained alpha particle distribution in the quasi-steady state stage agrees well with the theoretical results. (C) 2024 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

ep-level defects in beta-Ga2O3 that worsen the response speed and dark current (I-d) of photodetectors (PDs) have been a long-standing issue for its application. Herein, an insitu grown single-crystal Ga2O3 nanoparticle seed layer (NPSL) was used to shorten the response time and reduce the I-d of metal-semiconductor-metal (MSM) PDs. With the NPSL, the I-d was reduced by 4 magnitudes from 0.389 mu A to 81.03 pA, and the decay time (tau(d1)/tau(d2)) decreased from 258/1690 to 62/142 mu s at -5 V. In addition, the PDs with the NPSL also exhibit a high responsivity (43.5 A W-1), high specific detectivity (2.81 x 10(14) Jones), and large linear dynamic range (61 dB) under 254 nm illumination. The mechanism behind the performance improvement can be attributed to the suppression of the deep-level defects (i.e., self-trapped holes) and increase of the Schottky barrier. The barrier height extracted is increased by 0.18 eV compared with the case without the NPSL. Our work contributes to understanding the relationship between defects and the performance of PDs based on heteroepitaxial beta-Ga2O3 thin films and provides an important reference for the development of high-speed and ultrasensitive deep ultraviolet PDs.

Neutron diffraction is a widely utilized technique in detecting microstructures and residual strains in large-scale engineering components. In this study, we present the final physical design of an upcoming neutron diffractometer for engineering materials at the China Spallation Neutron Source. Our primary objective is to minimize the experimental time required for precise diffraction peak determination. To achieve this, the design includes a neutron transport system, a neutron wavelength selection system, a diffracted neutron optical system, and a resolution and intensity regulation system. Notably, we optimized the wavelength bandwidth specifically for scientific experiments, while the neutron flux or integrated peak intensity were optimized through careful considerations of neutron transport. Additionally, we placed great emphasis on ensuring the uniformity of the neutron phase space to enhance measurement accuracy. Moreover, we optimized the combinations of resolution and integrated peak intensity based on the best figure of merit. Consequently, we successfully developed an advanced diffractometer that is poised to offer new capabilities for engineering material studies.