Equilibrium reconstruction method for self-organized plasmas on reversed field pinches with polarimeter-interferometer

In the reversed field pinch(RFP),plasmas exhibit various self-organized states.Among these,the three-dimensional(3D)helical state known as the“quasi-single-helical”(QSH)state enhances RFP confinement.However,accurately describing the equilibrium is challenging due to the presence of 3D structures,magnetic islands,and chaotic regions.It is difficult to obtain a balance between the available diagnostic and the real equilibrium structure.To address this issue,we introduce KTX3DFit,a new 3D equilibrium reconstruction code specifically designed for the Keda Torus eXperiment(KTX)RFP.KTX3DFit utilizes the stepped-pressure equilibrium code(SPEC)to compute 3D equilibria and uses polarimetric interferometer signals from experiments.KTX3DFit is able to reconstruct equilibria in various states,including axisymmetric,doubleaxis helical(DAx),and single-helical-axis(SHAx)states.Notably,this study marks the first integration of the SPEC code with internal magnetic field data for equilibrium reconstruction and could be used for other 3D configurations.

Effects of vacuum magnetic field region on the compact torus trajectory in a tokamak plasma

The trajectory of the compact torus(CT)within a tokamak discharge is crucial to fueling.In this study,we developed a penetration model with a vacuum magnetic field region to accurately determine CT trajectories in tokamak discharges.This model was used to calculate the trajectory and penetration parameters of CT injections by applying both perpendicular and tangential injection schemes in both HL-2A and ITER tokamaks.For perpendicular injection along the tokamak's major radius direction from the outboard,CTs with the same injection parameters exhibited a 0.08 reduction in relative penetration depth when injected into HL-2A and a 0.13reduction when injected into ITER geometry when considering the vacuum magnetic field region compared with cases where this region was not considered.In addition,we proposed an optimization method for determining the CT's initial injection velocity to accurately calculate the initial injection velocity of CTs for central fueling in tokamaks.Furthermore,this paper discusses schemes for the tangential injection of CT into tokamak discharges.The optimal injection angle and CT magnetic moment direction for injection into both HL-2A and ITER were determined through numerical simulations.Finally,the kinetic energy loss occurring when the CT penetrated the vacuum magnetic field region in ITER was reduced byΔEk=975.08 J by optimizing the injection angle for the CT injected into ITER.These results provide valuable insights for optimizing injection angles in fusion experiments.Our model closely represents actual experimental scenarios and can assist the design of CT parameters.

Polarimeter–interferometer diagnostic using terahertz solid-state sources for fluctuation measurements on Keda Torus e Xperiment(KTX)

A multi-channel polarimeter-interferometer has been developed on the Keda Torus eXperiment(KTX)for the study of equilibrium dynamics and internal magnetic fluctuations.A three-wave technique based on terahertz solid-state sources(-650 GHz)is applied for simultaneous measurements of electron density and Faraday rotation angle.The output power of the microwave source is 2 mW.Faraday rotation effect using a rotating wave plate is tested with phase noise less than 0.8°,and the density phase noise is less than 0.9°.Measurement of Faraday rotation angle and density for discharges on KTX have demonstrated high sensitivity to internal MHD activities.

The impact of toroidal mode coupling on high-density discharges in J-TEXT

Density limit has long been a widely studied issue influencing the operating range of tokamaks.The rapid growth of the m/n=2/1(where m and n are poloidal and toroidal mode numbers,respectively)tearing mode is generally regarded as a primary precursor to the density limit disruption.In this experiment,the coupling of the m/n=1/1 mode and the m/n=2/1 mode in highdensity plasma was observed.During a sawtooth cycle,the frequencies of the two modes gradually converge until they become equal.After that,toroidal coupling occurs between the 1/1 and 2/1 modes,resulting in a mutually fixed phase relationship.With the occurrence of toroidal coupling,the 2/1 mode is stabilized.Prior to the disruption,the cessation of the 1/1 and 2/1 mode coupling,along with the rapid growth in the amplitude of the 2/1 mode,can be observed.Additionally,under the same parameters,comparing discharges with or without the 1/1 mode,it is found that the presence of the 1/1 mode leads to higher plasma density and temperature parameters.

Comparison of transport coefficients before and after density pump-out induced by resonant magnetic perturbation using a BOUT++ six-field model on the EAST tokamak

Many experiments have demonstrated that resonant magnetic perturbation(RMP) can affect the turbulent transport at the edge of the tokamak. Through the Experimental Advanced Superconducting Tokamak(EAST) density modulation experiment, the particle transport coefficients were calculated using the experimental data, and the result shows that the particle transport coefficients increase with RMP. In this study, the six-field two-fluid model in BOUT++ is used to simulate the transport before and after density pump-out induced by RMP,respectively referred as the case without RMP and the case with RMP. In the linear simulations,the instabilities generally decreases for cases with RMP. In the nonlinear simulation, ELM only appears in the case without RMP. Additionally, the particle transport coefficient was analyzed,and the result shows that the particle transport coefficient becomes larger for the case with RMP,which is consistent with the experimental conclusion. Moreover, its magnitude is comparable to the results calculated from experimental data.

Investigation of phase modulation and propagation-route effect from unmatched large-scale structures for Doppler reflectometry measurement through 2D full-wave modeling

To interpret the common symmetric peaks caused by the large-scale structure in the complex S(f)spectrum from the heterodyne Doppler reflectometry(DR)measurement in EAST,a 2D circular-shaped O-mode full-wave model based on the finite-difference time-domain method is built.The scattering characteristics and the influences on the DR signal from various scales are investigated.When the structure is located around the cutoff layer,a moving radial or poloidal large-scale structure k_(θ)k_(θ),match(k_(θ),match is the theoretic wavenumber of Bragg scattering)could both generate an oscillation phase term called‘phase modulation’,and symmetrical peaks in the complex S(f)spectrum.It was found that the image-rejection ratio A_(−1)/A_(+1)(A_(±1)represents the amplitudes of±1 order modulation peaks)could be a feasible indicator for experiment comparison.In the case when the structure is near the cutoff layer with the same arrangement as the experiment for the edge DR channel,the curve of A_(−1)/A_(+1)versus kθcan be divided into three regions,weak asymmetrical range with k_(θ)/k_(0)0.15(k_(0)is the vacuum wavenumber),harmonics range with 0.15k_(θ)/k_(0)0.4,and Bragg scattering range of 0.4k_(θ)/k_(0)0.7.In the case when the structure is located away from the cutoff layer,the final complex S(f)spectrum is the simple superimposing of modulation and Bragg scattering,and the modulation peaks have an amplitude response nearly proportional to the local density fluctuation,called the‘propagationroute effect’.Under the H-mode experiment arrangement for the core DR,a critical fluctuation amplitude Amp(n_(e,Mod.@route))/Amp(n_(e,Tur.@MSA)∼1.3–4.1(Amp(n_(e,Mod.@route))refers to the pedestal large-scale structure amplitude and Amp(ne,Tur.@MSA)refers to turbulence amplitude at the main scattering area)is needed for the structure in the pedestal to be observed by the core DR measurement.The simulations are well consistent with the experimental results.These effects need to be carefully considered during the DR signal analyses as the injecting beam passes through the plasma region with large-scale structures.

Comparison of methods for turbulence Doppler frequency shift calculation in Doppler reflectometer

The Doppler reflectometer(DR),a powerful diagnostic for the plasma perpendicular velocity(u⊥)and turbulence measurement,has been widely used in various fusion devices.Many efforts have been put into extracting the Doppler shift from the DR signal.There are several commonly used methods for Doppler shift extraction,such as the phase derivative,the center of gravity,and symmetric fitting(SFIT).However,the strong zero-order reflection component around 0 kHz may interfere with the calculation of the Doppler shift.To avoid the influence of the zerofrequency peak,the asymmetric fitting(AFIT)method was designed to calculate the Doppler shift.Nevertheless,the AFIT method may lead to an unacceptable error when the Doppler shift is relatively small compared to the half width at half maximum(HWHM).Therefore,an improved method,which can remove the zero-frequency peak and fit the remaining Doppler peak with a Gaussian function,is devised to extract the Doppler shift.This method can still work reliably whether the HWHM is larger than the Doppler shift or not.

NLR、PLR与乳腺癌前哨淋巴结转移及临床病理特征之间的关系

目的探讨术前外周血中性粒细胞与淋巴细胞比值(NLR)、血小板与淋巴细胞比值(PLR)与乳腺癌前哨淋巴结(SLN)转移之间的关系,并分析其与乳腺癌临床病理特征的相关性。方法回顾分析我院2016年—2019年收治的100例乳腺癌患者的病历资料,将32例未出现SLN转移的患者作为对照组,68例出现SLN转移的患者作为观察组(其中8例SLN转移阳性数≤2的患者为A组、38例SLN转移阳性数>2但未出现远处转移的患者为B组、22例远处转移患者为C组);计算各组患者的NLR、PLR,并分别以对照组和观察组NLR、PLR中位数为截断值,分析NLR、PLR与乳腺癌临床病理特征的相关性。结果观察组患者NLR、PLR均显著高于对照组(P<0.01)。观察组各亚组中,A、B两组及A、C两组NLR比较,差异均有统计学意义(P<0.05),但B、C两组NLR无显著差异(P>0.05);A、B两组和B、C两组PLR均无显著差异(P>0.05),但A、C两组PLR比较,差异有统计学意义(P<0.05)。对照组NLR、PLR与乳腺癌患者的年龄、肿瘤大小、组织学分级、ER、PR、HER-2、Ki-67均无明显相关性(P>0.05),但NLR与导管内癌栓显著相关(P=0.034);观察组NLR与乳腺癌患者的肿瘤大小(P=0.033)、Ki-67(P=0.016)、肿瘤分期(P=0.027)明显相关,而PLR仅与肿瘤分期显著相关(P=0.038)。结论乳腺癌SLN转移可引起患者的NLR、PLR发生变化,其中NLR可能作为SLN转移风险预测因子,且较高的NLR与较差的病理组织学特征和更具侵袭性的临床生物学行为密切相关。

Development of a compact torus injection system for the Keda Torus eXperiment

A compact torus injection system,KTX-CTI,has been developed for the planned injection experiments on the Keda Torus e Xperiment(KTX)reversed field pinch(RFP)device to investigate the physics and engineering issues associated with interaction between a compact torus(CT)and RFP.The key interests include fueling directly into the reactor center,confinement improvement,and the injection of momentum and helicity into the RFP discharges.The CT velocity and mass have been measured using a multichannel optical fiber interferometer,and for the first time the time evolution of the CT density profile during CT propagation is obtained.The effects of discharge parameters on the number of injected particles,CT velocity and CT density have been characterized:the maximum hydrogen CT plasma mass,m,CTis 50μg,corresponding to 30%of the mass in a typical KTX plasma;the CT velocity exceeds 120 km s-1.It is observed for the first time that multiple CTs can be produced and emitted during a very short period(<100μs)in one discharge,which is significant for the future study of repetitive CT injection,even with an ultra-high frequency.

The theoretical study on intermittency and propagation of geodesic acoustic mode in L-mode discharge near tokamak edge

Through a systematically developed theory,we demonstrate that the motion of Instanton identified in Zhang et al(2017 Phys.Plasmas 24122304)is highly correlated to the intermittent excitation and propagation of geodesic acoustic mode(GAM)that is observed in tokamaks.While many numerical simulations have observed the phenomena,it is the first theory that reveals the physical mechanism behind GAM intermittent excitation and propagation.The preceding work is based on the micro-turbulence associated with toroidal ion temperature gradient mode,and slab-based phenomenological model of zonal flow.When full toroidal effect is introduced into the system,two branches of zonal flow emerge:the torus-modified low frequency zonal flow(TLFZF),and GAM,necessitating a unified exploration of GAM and TLFZF.Indeed,we observe that the transition from the Caviton to Instanton is triggered by a rapid zero-crossing of radial group velocity of drift wave and is found to be strongly correlated with the GAM onset.Many features peculiar to intermittent GAMs,observed in real machines,are thus identified in the numerical experiment.The results will be displayed in figures and in a movie;first for single central rational surface,and then with coupled multiple central rational surfaces.The periodic bursting first shown disappears as being replaced by irregular one,more similar to the intermittent characteristics observed in GAM experiments.

The intermittent excitation of geodesic acoustic mode by resonant Instanton of electron drift wave envelope in L-mode discharge near tokamak edge

There are two distinct phases in the evolution of drift wave envelope in the presence of zonal flow.A long-lived standing wave phase,which we call the Caviton,and a short-lived traveling wave phase(in radial direction) we call the Instanton.Several abrupt phenomena observed in tokamaks,such as intermittent excitation of geodesic acoustic mode(GAM) shown in this paper,could be attributed to the sudden and fast radial motion of Instanton.The composite drift wave-zonal flow system evolves at the two well-separate scales:the micro-scale and the meso-scale.The eigenmode equation of the model defines the zero-order(micro-scale) variation;it is solved by making use of the two-dimensional(2 D) weakly asymmetric ballooning theory(WABT),a theory suitable for modes localized to rational surface like drift waves,and then refined by shifted inverse power method,an iterative finite difference method.The next order is the equation of electron drift wave(EDW) envelope(containing group velocity of EDW) which is modulated by the zonal flow generated by Reynolds stress of EDW.This equation is coupled to the zonal flow equation,and numerically solved in spatiotemporal representation;the results are displayed in self-explanatory graphs.One observes a strong correlation between the Caviton-Instanton transition and the zero-crossing of radial group velocity of EDW.The calculation brings out the defining characteristics of the Instanton:it begins as a linear traveling wave right after the transition.Then,it evolves to a nonlinear stage with increasing frequency all the way to 20 kHz.The modulation to Reynolds stress in zonal flow equation brought in by the nonlinear Instanton will cause resonant excitation to GAM.The intermittency is shown due to the random phase mixing between multiple central rational surfaces in the reaction region.

The investigation of quasi coherent mode on EAST using Doppler reflectometry

An electrostatic Quasi coherent mode has been observed in density fluctuations and perpendicular velocity fluctuations with the frequency range of 3–80 k Hz on the Experimental Advanced Superconducting Tokamak using multi-channel Doppler reflectometry.It appears in the edge localized mode(ELM)-free period after L-H transition or in the inter-ELM period.The mode rotates almost together with the plasma with the poloidal wave number around 0.6cm-1 and its frequency chirps with plasma poloidal velocity.The mode can exist in a large radial coverage(ρ=0.75–0.98),and peaks near the top of pedestal,suggesting that it might be excited in the steep gradient pedestal region,and spread into the core area.

Preliminary compact torus injection experiments on the Keda Torus eXperiment reversed field pinch

A new compact torus injector(KTX-CTI)has been built for injection experiments on the Keda Torus eXperiment(KTX)reversed field pinch(RFP).The aim is to study the fundamental physics governing the compact torus(CT)central fueling processes.In experiments conducted under the sole influence of a 0.1 T toroidal magnetic field,the injected CT successfully penetrated the entire toroidal magnetic field,reaching the inner wall of the KTX vacuum vessel.Upon reaching the inner wall,the CT diffused both radially outward and toroidally within the vessel at a discernible diffusion speed.Moreover,the inherent helicity within the CT induced a modest KTX plasma current of 200 A,consistent with predictions based on helicity conservation.CT injection demonstrated the capability to initiate KTX discharges at low loop voltages,suggesting its potential as a pre-ionization and current startup technique.During RFP discharges featuring CT injection,the central plasma density was found to exceed the Greenwald density limit,with more peaked density profiles,indicating the predominant confinement of CT plasma within the core region of the KTX bulk plasma.

Mineral and Bone Disorder and Its Association with Cardiovascular Parameters in Chinese Patients with Chronic Kidney Disease

Background：Mineral and bone disorder （MBD）,especially hyperphosphatemia,is an independently risk factor for adverse prognosis in patients with chronic kidney disease （CKD）.However,CKD-MBD among Chinese population was poorly studied.This study aimed to investigate the status of MBD and its association with cardiovascular parameters in Chinese patients with predialysis CKD.Methods：Chinese Cohort Study of Chronic Kidney Disease （C-STRIDE） is a prospective multicenter cohort study involving predialysis CKD patients in China.Markers of MBD,including serum phosphorus,calcium,and intact parathyroid hormone,were measured in baseline samples at the patients＆#39; entry.The association between serum phosphorus and abdominal aortic calcification （AAC）,left ventricular hypertrophy （LVH） were examined by logistic regression models.Results：Altogether 3194 predialysis patients with mean estimated glomerular filtration of 51.8 ± 33.1 ml·min^- 1· 1.73 m^- 2 were included.The proportion of patients with hyperphosphatemia were 2.6%,2.9%,6.8%,and 27.1% in CKD Stages 3a,3b,4,and 5,respectively.Moreover,71.6% of the patients with hyperphosphatemia did not receive any phosphate-binder （PB）.Lateral abdominal X-rays were obtained in 2280 patients,9.8% of the patients were diagnosed as having AAC.Altogether 2219 patients had data of echocardiography,and 13.2% of them were diagnosed with LVH.Multivariate logistic regression analysis showed that serum phosphorus was independently associated with the presence of AAC and LVH.Conclusions：In Chinese patients with CKD,the percentage of hyperphosphatemia is comparable to that of other countries while the usage of PBs is suboptimal.The prevalence of vascular calcification in Chinese patients is relatively lower compared with the Caucasian population.

A community-based comprehensive intervention to reduce syphilis infection—among low-fee female sex workers in China:a matched-pair,community-based randomized study

Background:Low-fee female sex workers(FSWs)are at high risk of acquiring and spreading human immunodeficiency virus(HIV)/sexually transmitted diseases(STDs)in China.There is an urgent need to develop comprehensive intervention measures targeted towards low-fee FSWs to reduce HIV/STD infections.Thus,this study aimed to reduce HIV/STD infections among low-fee FSW through a matched-pair,comiDunity-based randomized intervention trial carried out in 12 cities in three provinces in China.Methods:Four cities from Guangxi Zhuang Autonomous Region,four from Yunnan Province,and four from Hunan Province were paired and participants received either the intervention package(including condom promotion,HIV and syphilis testing,reimbursement for syphilis treatment costs,and free anti-retroviral therapy or the current standard of care.Venue-based,convenience sampling was used to recruit FSWs.A face-to-face interview and HIV and syphilis blood testing was conducted at baseline and follow-up intervals of 24 months.Generalized linear mixed models(GLMM)were used to evaluate the effect of the intervention package on reducing HIV/STD infection in the FSWs.Results:A total of 1024 eligible FSWs were enrolled in the baseline survey and 843 in the follow-up.GLMM results showed that syphilis infeaion was reduced by 49%in the intervention group compared to the current standard of care group(P=0.0378,OR=0.51;95%CI:0.27-0.96).FSWs aged 35 years or older were 2.38 times more likely to get syphilis infection compared to those younger than 35 years old(P<0.0001,OR=2.38,95%CI:1.55-3.65).The risk of syphilis infection among more educated FSWs was 0.43 times less than those with lower levels of education(P<0.05,OR=0.43,95%CI:0.63-0.93).Conclusions:This study demonstrates that comprehensive interventions can lead to significant declines in syphilis infection amongst low-tier FSWs.Integrating both behavioral and biomedical intervention measures should be considered when developing programs for low-fee FSWs.Trial registration:CHiCTR-TRC-12002655.

Edge localized modes suppression via edge E × B velocity shear induced by RF sheath of ion cyclotron resonance heating in EAST

The control of large edge localized modes(ELMs) is a critical issue for the successful operation of future burning plasma devices,such as the international thermonuclear experimental reactor(ITER) and China fusion engineering test reactor(CFETR). In this paper, we present a new active and effective means of ELM suppression using ion cyclotron resonant heating(ICRH) on the experimental advanced superconducting tokamak(EAST). We obtained the key role of the external E × B velocity shear near the pedestal top and the scrape-off-layer(SOL) induced by the RF sheath potential of ICRH in ELM suppression. The experimental results showed a positive correlation between the RF sheath and the E × B shear rate in SOL. BOUT++ simulations indicate that increased E × B velocity shear rates in the pedestal and SOL regions promote ELM suppression;thereby, supporting the experimental observations on EAST. These findings suggest a new simple approach to access the ELM suppressed regimes in plasma with low torque input as ITER baseline discharges.