Experimental study of the characteristics of energetic electrons outside LCFS in EXL-50 spherical torus

Guo, Dong; Shi, Yuejiang; Liu, Wenjun; Yunyang, Song; Sun, T.; Liu, Bing; Li, Yingying; Tian, Xiaorang; Zhang, Guosong; Xie, Huasheng; Peng, Y. K. M.; Liu, Minsheng

doi:10.1088/1361-6587/ac5a08

Cited by 8 publications

(16 citation statements)

References 16 publications

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“…The simulation results were in good agreement with the available experimental data [33]. Some special experiments have been performed in EXL-50 to indicate the considerable population of energetic electrons outside the LCSF [35]. Moreover, a removable limiter will be installed in a future machine upgrade plan.…”

Section: Energetic Electrons and Current Drive Mechanismssupporting

confidence: 79%

Solenoid-free current drive via ECRH in EXL-50 spherical torus plasmas

Shi

Liu²,

Song³

et al. 2022

Nucl. Fusion

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As a new spherical tokamak (ST) designed to simplify engineering requirements of a possible future fusion power source, the EXL-50 experiment features a low aspect ratio (A) vacuum vessel (VV), encircling a central post assembly containing the toroidal field coil conductors without a central solenoid. Multiple electron cyclotron resonance heating (ECRH) resonances are located within the VV to improve current drive effectiveness. Copious energetic electrons are produced and measured with hard X-ray detectors, carry the bulk of the plasma current ranging from 50kA to 150kA, which is maintained for more than 1s duration. It is observed that over one Ampere current can be maintained per Watt of ECRH power issued from the 28-GHz gyrotrons. The plasma current reaches Ip>80kA for high density (>51018m-2) discharge with 150kW ECHR heating. An analysis was carried out combining reconstructed multi-fluid equilibrium, guiding-center orbits of energetic electrons, and resonant heating mechanisms. It is verified that in EXL-50 a broadly distributed current of energetic electrons creates smaller closed magnetic-flux surfaces of low aspect ratio that in turn confine the thermal plasma electrons and ions and participate in maintaining the equilibrium force-balance. effectiveness. Copious energetic electrons are observed via hard X-ray detectors, carry the bulk of the plasma current ranging from 50kA to 150kA, which is maintained for more than 1s duration. It is observed that over one Ampere current can be maintained per Watt of ECRH power issued from the 28-GHz gyrotrons. The plasma current with high line-density (approaching 〖10〗^19 m^(-2)) has been achieved for plasma currents as high as 76kA. An analysis was carried out combining reconstructed multi-fluid equilibrium, guiding-center orbits, and resonant heating mechanisms. It is verified that in EXL-50 a broadly distributed current of energetic electrons creates smaller closed magnetic-flux surfaces of low aspect ratio that in turn confine the thermal plasma electrons and ions and participate in maintaining the equilibrium force-balance.

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Section: Energetic Electrons and Current Drive Mechanismssupporting

confidence: 79%

Solenoid-free current drive via ECRH in EXL-50 spherical torus plasmas

Shi

Liu²,

Song³

et al. 2022

Nucl. Fusion

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“…In the absence of the CS coils, the plasma current in the EXL-50 device is driven and maintained solely by ECRH. In the EXL-50 experiments, the plasma current can reach as high as 80-100 kA at the lineintegrated density at m [22]. The EXL-50 device is equipped with five gyrotrons, which are used to generate high-power microwaves for ECRH.…”

Section: R Amentioning

confidence: 99%

Design of the electron cyclotron emission diagnostic on EXL-50 spherical torus

WANG 王,

XIE 谢,

TAO 陶

et al. 2024

Plasma Sci. Technol.

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The electron cyclotron emission diagnostic (ECE) system has been developed on ENN Spherical Torus (EXL-50). The ECE system aims to detect radiation from energetic electrons in the frequency range from 4 to 40 GHz. The system is composed of five subsystems with different frequency bands, i.e., C-band (4-8 GHz), X-band (8-12 GHz), Ku-band (12-18 GHz), K-band (18-26.5 GHz) and Kα-band (26.4-40 GHz), and it using heterodyne detection. K-band and Kα-band subsystems are located horizontally in the EXL-50 equatorial plane while C-band, X-band and Ku-band subsystems are vertically located under EXL-50 vacuum vessel. The quasi-optical system has been developed to direct the microwaves from plasma to the antennas for horizontal detection subsystems. The antennas for vertical detection are attached directly to the port beneath the torus at R=700mm, i.e., the magnetic axis of the torus. The system integration, bench test and the initial experimental results will be given in detail.

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“…The 0D codes for tokamak plasma start-up primarily include DYON [19], SCENPLINT [22,23], and BKD0 [24,25]. Kim built a new tokamak start-up model based on Lloyd's 0D theoretical model [18], which is suitable for both pure Ohmic start-up and EC wave assisted start-up under finite electric fields.…”

Section: Theoretical Model For Ec Wave (Assisted) Startup Simulationmentioning

confidence: 99%

“…Therefore, the 0D model can be utilized to predict the start-up process of STs and stellarator devices. According to the work of Lloyd et al [18], Kim [19], and others who have established 0D models for tokamak start-up, this work combines the characteristics of STs and stellarators, establishes a new model, autonomously develops program code, and conducts comparative validation. Start-up simulation researches are carried out based on the parameters of the target devices.…”

Section: Introductionmentioning

confidence: 99%

Numerical study of plasmas start-up by electron cyclotron waves in NCST spherical tokamak and CN-H1 stellarator

LIU 刘,

ZHENG 郑,

GONG 龚

et al. 2024

Plasma Sci. Technol.

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According to the physics of tokamak start-up, this paper constructs a zero-dimensional (0D) model applicable to electron cyclotron (EC) wave assisted start-up in NCST spherical torus (spherical tokamak) and CN-H1 stellarators. Using the constructed zero-dimensional model, the results obtained in this paper under the same conditions are compared and validated against references results for pure hydrogen plasma start-up in tokamak. The results are in good agreement, especially regarding electron temperature, ion temperature and plasma current. In the presence of finite Ohmic electric field in the spherical tokamak, a study on the EC wave assisted start-up of the NCST plasma at frequency of 28 GHz is conducted. The impact of the vertical magnetic field B v on EC wave assisted start-up, the relationship between EC wave injection power P inj, Ohmic electric field E, and initial hydrogen atom density nH0 is explored separately. It is found that under conditions of Ohmic electric field lower than ITER (~ 0.3 V m-1), EC wave can expand the operational space to achieve better plasma parameters. Simulating the process of 28 GHz EC wave start-up in the CN-H1 stellarator plasma, the plasma current in the zero-dimensional model is replaced with the current in the poloidal coil of the stellarator. Plasma start-up can be successfully achieved at injection powers in the hundreds of kilowatts range, resulting in electron densities on the order of 1017 to 1018 m-3.

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Experimental study of the characteristics of energetic electrons outside LCFS in EXL-50 spherical torus

Cited by 8 publications

References 16 publications

Solenoid-free current drive via ECRH in EXL-50 spherical torus plasmas

Solenoid-free current drive via ECRH in EXL-50 spherical torus plasmas

Design of the electron cyclotron emission diagnostic on EXL-50 spherical torus

Numerical study of plasmas start-up by electron cyclotron waves in NCST spherical tokamak and CN-H1 stellarator

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