Kinetic equilibrium reconstruction with internal safety factor profile constraints on EAST tokamak

Reconstruction of plasma equilibrium plays an important role in the analysis and simulation of plasma experiments. The kinetic equilibrium reconstruction with pressure and edge current constraints has been employed on EAST tokamak. However, the internal safety factor(q) profile is not accurate. This paper proposes a new way of incorporating q profile constraints into kinetic equilibrium reconstruction. The q profile is yielded from the Polarimeter Interferometer(POINT)reconstruction. Virtual probes containing information on q profile constraints are added to inputs of the kinetic equilibrium reconstruction program to obtain the final equilibrium. The new equilibrium produces a more accurate internal q profile. This improved method would help analyze EAST experiments.

Observation of Doppler shift f_(D) modulated by the internal kink mode using conventional reflectometry in the EAST tokamak

In this paper we present a new experimental observation using a conventional reflectometry technique,poloidal correlation reflectometry(PCR),in the Experimental Advanced Superconducting Tokamak(EAST).The turbulence spectrum detected by the PCR system exhibits an asymmetry and induced Doppler shift f_(D)during the internal kink mode(IKM)rotation phase.This Doppler shift f_(D)is the target measurement of Doppler reflectometry,but captured by conventional reflectometry.Results show that the Doppler shift f_(D)is modulated by the periodic changes in the effective angle between the probing wave and cutoff layer normal,but not by plasma turbulence.The fishbone mode and saturated long-lived mode are typical IKMs,and this modulation phenomenon is observed in both cases.Moreover,the value of the Doppler shift f_(D)is positively correlated with the amplitude of the IKM,even when the latter is small.However,the positive and negative frequency components of the Doppler shift f_(D)can be asymmetric,which is related to the plasma configuration.A simulated analysis is performed by ray tracing to verify these observations.These results establish a clear link between f_(D)and IKM rotation,and are helpful for studying the characteristics of IKM and related physical phenomena.

Effect of chemical ordering annealing on superelasticity of Ni-Mn-Ga-Fe ferromagnetic shape memory alloy microwires

Ni50Mn25Ga20Fe5 ferromagnetic shape memory alloy microwires with diameters of^30-50μm and grain sizes of^2-5μm were prepared by melt-extraction technique.A step-wise chemical ordering annealing was carried out to improve the superelasticity strain and recovery ratio which were hampered by the internal stress,compositional inhomogeneity,and high-density defects in the as-extracted Ni50Mn25Ga20Fe5 microwires.The annealed microwires exhibited enhanced atomic ordering degree,narrow thermal hysteresis,and high saturation magnetization under a low magnetic field.As a result,the annealed microwire showed decreased superelastic critical stress,improved reversibility,and a high superelastic strain(1.9%)with a large recovery ratio(>96%).This kind of filamentous material with superior superelastic effects may be promising materials for minor-devices.

Magnetohydrodynamic effect of internal transport barrier on EAST tokamak

An internal transport barrier(ITB)can be formed on EAST in exploring high-parameter operation.Previous studies show that safety factor(q)profiles,Shafranov shift and magnetohydrodynamic behaviors could be helpful in ITB formation by suppressing anomalous transport.Recently,electron density evolution with high resolution demonstrates that fishbone could be dominant in electron density ITB formation and sustainment.The power threshold is low in the fishbone condition and the electron density profile is determined by traits of fishbone.Simulation shows that the low-k ion mode is suppressed by fishbone.Direct measurement of turbulence in the inner region shows that the internal kink mode could sustain an electron temperature ITB by suppressing the trapped electron mode.The multi-scale interaction between the kink mode and turbulence by current could be key in sustaining high-electron-temperature long-pulse operation.

Simulation studies of tungsten impurity behaviors during neon impurity seeding with tungsten bundled charge state model using SOLPS-ITER on EAST

An investigation into tungsten(W)impurity behaviors with the update of the EAST lower W divertor for H-mode has been carried out using SOLPS-ITER.This work aims to study the effect of external neon(Ne)impurity seeding on W impurity sputtering with the bundled charge state model.As the Ne seeding rate increases,plasma parameters,W concentration(C_(W)),and eroded W flux(Γ_(W)^(Ero))at both targets are compared and analyzed between the highly resolved bundled model‘jett’and the full W charge state model.The results indicate that‘jett’can produce divertor behaviors essentially in agreement with the full W charge state model.The bundled scheme with high resolution in low W charge states(<W^(20+))has no obvious effect on the Ne impurity distribution and thus little effect on W sputtering by Ne.Meanwhile,parametric scans of radial particle and thermal transport diffusivities(D_(⊥)andχ_(e,i))in the SOL are simulated using the‘jett’bundled model.The results indicate that the transport diffusivity variations have significant influences on the divertor parameters,especially for W impurity sputtering.

Excitation of RSAEs during Sawteeth-Like Oscillation in EAST

The excitation condition of reversed shear Alfven eigenmodes(RSAEs)has been investigated during sawtoothlike oscillation in the EAST tokamak.The sawtooth-like phenomena can be reproduced in the configuration of reversed magnetic shear,and the threshold gradient of electron temperature is formed accordingly,together with the increasing of the confinement of thermal particles.The distribution function of energetic ions density is altered dramatically when the neutral beam is switched from NBI1 L(tangent)to NBI1 R(perpendicular),which can be captured by the measurement of radial neutron camera.The RSAEs are excited easily in the vicinity of q_(min)(1.99 m≤R≤2.06 m)for the injection of neutral beam with perpendicular direction,which should be excited by the steep gradient of energetic ions density.Furthermore,the excitation of RSAEs and the formation of threshold gradient of electron temperature can take place concurrently,which means that the neutral beam with perpendicular injection is beneficial for the establishment of internal transport barrier.

Numerical Simulation of Unidirectional Infiltration of Silicon Carbide Preforms

Mathematical model of unidirectional infiltration was set up and metal infiltration velocity and temperature fields of the metal, preform, and composites were calculated using the finite difference method. The metal infiltration velocity has a close relationship with infiltration time. It is very large after the infiltration begins in a few seconds, then the velocity keeps almost constant. The temperature field of the composite proves that metal matrix composites (M MCs) after unidirectional pressure infiltration can solidify from the entrance of the preform to the infiltration front, which is useful for obtaining the MMCS with low porosity and high properties.

Ultra-high strength GNP/2024Al composite via thermomechanical treatment

The 5.0 vol.%GNP/2024Al composites were prepared by accumulated shear deformation combined with heat treatment,i.e.the thermomechanical treatment(TMT).The results showed that homogeneous distributed GNPs that aligned along the plastic deformation direction were obtained by six-pass drawing in the solution heat treatment state.The introducing of high-density dislocations in Al matrix by multiple drawing resulted in enhanced nucleation of precipitates and subsequent uniform growth during ageing.Consequently,ultra-strength GNP/2024Al composites,with yield and ultimate tensile strength 482 and571 MPa,respectively,were achieved.The high strength was attributed to homogeneous dispersion of undamaged GNPs,fine and dispersed precipitations and work-hardening effect.This work demonstrated that TMT could act as a feasible strategy for preparing high-performance GNP/Al composites.

DCX and CRABP2 are candidate genes for differential diagnosis between pre-chemotherapy embryonic and alveolar rhabdomyosarcoma in pediatric patients

Importance Rhabdomyosarcoma(RMS)is the most common soft tissue sarcoma in children.More than 90%of cases are classified as embryonic RMS(ERMS)or alveolar RMS(ARMS).ERMS has a worse prognosis than ARMS.Early differential diagnosis is of paramount importance for optimization of treatment.Objective To identify genes that are differentially expressed between ARMS and ERMS,which can be used for accurate rhabdomyosarcoma classification.Methods Three Gene Expression Omnibus datasets composed of ARMS and ERMS samples were screened and 35 differentially expressed genes(DEGs)were identified.Receiver operating characteristic curve analysis and area under the curve analysis was performed for these 35 DEGs and seven candidate genes with the best differential expression scores between ARMS and ERMS were determined.The expression of these seven candidate genes was validated by immunohistochemical analysis of pre-chemotherapy ARMS and ERMS specimens.Results The levels of DCX and CRABP2 were confirmed to be remarkably different between paraffin-embedded ARMS and ERMS tissues,while EGFR abundance was only marginally different between these two RMS subtypes.Interpretation DCX and CRABP2 are potential biomarkers for distinguishing ARMS from ERMS in pre-chemotherapy pediatric patients.