Review of radio frequency conditioning discharges with magnetic fields in superconducting fusion reactors

Cal, E. de la; Gauthier, E.

doi:10.1088/0741-3335/47/2/001

Cited by 43 publications

(5 citation statements)

References 46 publications

(81 reference statements)

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“…He and D 2 discharge cleaning could remove additional H by ion-induced desorption and isotopic exchange to further reduce particle recycling in EAST. ICRF cleaning exhibited stronger effects on the removal of hydrogen than did GDC-likely due to larger symmetric flux of energetic ions and neutrals to bombard the entire first wall and produce high hydrogen desorption rates [34]. In addition, at room temperature, discharge cleaning is limited to depths corresponding to the ion implantation range, typically a few nanometers [4].…”

Section: Comparison Of Controlled Particle Recycling and The H/(h+d) ...mentioning

confidence: 99%

Comparison of various wall conditionings on the reduction of H content and particle recycling in EAST

Zuo

Zhen

et al. 2011

Plasma Phys. Control. Fusion

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Reductions in H content and particle recycling are important for the improvement of ion cyclotron range of frequency (ICRF) minority heating efficiency and the enhancement of plasma performance of the EAST superconducting tokamak. During recent years several techniques of surface conditioning such as baking, glow discharge cleaning/ICRF discharge cleaning, surface coatings, such as boronization, siliconization and lithium coating, have all been attempted in order to reduce the H/(H+D) ratio and particle recycling in EAST. Even though boronization and siliconization were both reasonably effective methods to improve plasma performance, lithium coatings were observed to reduce the H content and particle recycling to levels low enough to allow the attainment of enhanced plasma parameters and operating modes on EAST. For example, by accomplishing lithium coating using either vacuum evaporation or the real-time injection of fine lithium powder, the H/(H+D) ratio could be routinely decreased to about 5%, which significantly improved ICRF minority heating efficiency during the autumn campaign of 2010. Due to the reduced H/(H+D) ratio and lower particle recycling, and a reduced H-mode power threshold, improved plasma confinement and the first EAST H-mode plasma were obtained. Furthermore, with increasing accumulation of deposited lithium, several new milestones of EAST performance, such as a 6.4 s-long H-mode, a 100 s-long plasma duration and a 1 MA plasma current, were achieved in the 2010 autumn campaign.

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Section: Comparison Of Controlled Particle Recycling and The H/(h+d) ...mentioning

confidence: 99%

Comparison of various wall conditionings on the reduction of H content and particle recycling in EAST

Zuo

Zhen

et al. 2011

Plasma Phys. Control. Fusion

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“…The removing efficiency of ICR plasmas on impurity and hydrogen isotope particles is higher than ECR due to a more homogeneous distribution of poloidal plasmas. Nevertheless, ICR plasmas are poloidally asymmetric, such as the n e at a factor 2-3 lower in the high-field side than in the low-field side [1,2]. The very high frequency (VHF∼140 MHz, higher than normally used in ICR) discharge was used for wall conditioning with hydrogen (H) atoms in the B 0 of 750 G and the gas pressure of 2.7×10 −2 Pa at the Uragan-2M torsatron.…”

Section: Introductionmentioning

confidence: 99%

“…Impurities and fuel particles are released due to strong plasma-wall interaction (PWI) in magnetically controlled fusion devices (such as stellarators and tokamaks), which affects the performance of the fusion plasma. With the view of controlling the surface state of the plasma-facing components (PFCs), and thus, the fluxes of fuel and impurities between the PFCs and the plasma, a wide variety of techniques are applied, which are called 'wall conditioning' [1,2]. The present and future superconducting tokamaks such as ITER and DEMO, need efficient and alternative wall conditioning methods for the routine operation in the steady-state high axial magnetic field (B 0 ), which prevents the use of conventional glow discharge conditioning (GDC) [3].…”

Section: Introductionmentioning

confidence: 99%

Development of a helicon-wave excited plasma facility with high magnetic field for plasma–wall interactions studies

Zhang

Huang

Chen

et al. 2018

Plasma Sci. Technol.

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The high magnetic field helicon experiment system is a helicon wave plasma (HWP) source device in a high axial magnetic field (B 0 ) developed for plasma-wall interactions studies for fusion reactors. This HWP was realized at low pressure (5×10 −3 −10 Pa) and a RF (radio frequency, 13.56 MHz) power (maximum power of 2 kW) using an internal right helical antenna (5 cm in diameter by 18 cm long) with a maximum B 0 of 6300 G. Ar HWP with electron density ∼10 18 -10 20 m −3 and electron temperature ∼4-7 eV was produced at high B 0 of 5100 G, with an RF power of 1500 W. Maximum Ar + ion flux of 7.8×10 23 m −2 s −1 with a bright blue core plasma was obtained at a high B 0 of 2700 G and an RF power of 1500 W without bias. Plasma energy and mass spectrometer studies indicate that Ar + ion-beams of 40.1 eV are formed, which are supersonic (∼3.1c s ). The effect of Ar HWP discharge cleaning on the wall conditioning are investigated by using the mass spectrometry. And the consequent plasma parameters will result in favorable wall conditioning with a removal rate of 1.1×10 24 N 2 /m 2 h.

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“…To obtain highly confined and high-parameter plasma, an excellent first wall is necessary for fusion devices like tokamak and stellarator [1]. The impurities and previously entrapped fuel particles on the first wall will impair plasma density control and even lead to plasma disruption [2]. Advanced wall conditioning techniques are constantly being developed [3,4], which need long-term experimental validation before they are applied to fusion devices.…”

Section: Introductionmentioning

confidence: 99%

Helimak control system

Yang

Wen

et al. 2023

J. Inst.

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The excellent wall condition is essential for fusion devices to generate reproducible high-parameter plasma. Wall conditioning techniques should be validated before applying on large fusion devices to reduce potential risk. Helimak, a toroidal steady state magnetic confinement device, was reassembled and upgraded to a technical validation platform for wall conditioning. A new control system has been developed to achieve the upgrade of Helimak. The control system is based on a distributed control architecture, which provides not only efficient development but also flexible control mechanisms. For each auxiliary subsystem, a corresponding local control module is developed to drive and control a variety of equipment. The control network ensures real-time transmitting of the parameters and data. A dedicated trigger network and timing control module can improve synchronization and real-time performance. Data acquisition system based on mature commercial busses provides sufficient data acquisition capabilities for diagnostic tools. The data management system uses MDSplus to provide convenient data access. An independent interlock and safety system is designed for comprehensive and reliable personal protection. After engineering commissioning, the Helimak has realized wall conditioning by electron cyclotron resonance heating (ECRH) plasma at different resonance positions. The flexibility of control systems allows the installation of more wall conditioning tools in the future that will provide the ability to validate combined wall conditioning techniques. Helimak will become a low-cost, reliable technology verification platform, which will help to achieve advanced scenarios in tokamak and stellarator.

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Review of radio frequency conditioning discharges with magnetic fields in superconducting fusion reactors

Cited by 43 publications

References 46 publications

Comparison of various wall conditionings on the reduction of H content and particle recycling in EAST

Comparison of various wall conditionings on the reduction of H content and particle recycling in EAST

Development of a helicon-wave excited plasma facility with high magnetic field for plasma–wall interactions studies

Helimak control system

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