The 3D nonlinear equilibrium and its associated magnetic topology are investigated on EAST for the first time for future understanding on the mechanism of how the Resonant Magnetic Perturbation (RMP) mitigates or suppresses the Edge-Localized Mode (ELM). Recently, a nonlinear transition from mitigation to suppression of the ELM by using RMP on EAST is observed $^{1}$. To understand the RMP...
For tokamaks to be attractive as the core of future fusion based power plants, it must operate in steady state or at least quasi-steady state without plasma current disruptions. As is evident from the predictions for ITER based on present day tokamak research, a major challenge would be to avoid disruptions in majority of plasma discharges with full plasma parameters achieving >99% good shots....
M. Nakamoto, H. Kajitani, T. Suwa, Y. Takahashi, M. Yamane, T. Baba, K. Sakamoto, K. Yoshizawa, Y. Uno, A. Ishikawa, M. Nakahira, N. Koizumi, M. Inoue 1, E. Fujiwara 1, T. Shichijyo 1, K. Kuno 2, T. Minato 2, T. Hemmi 3 and C. Luongo 3
National Institutes for Quantum and Radiological Science and Technology, 801-1 Mukouyama, Naka-shi, Ibaraki 311-0193, Japan
1 Mitsubishi Heavy Industries,...
Shattered pellet injection (SPI) systems that form cryogenic pellets of low and high-Z impurities in a pipe-gun [1] for injection to mitigate disruptions have been fabricated and installed for use in thermal mitigation and runaway electron dissipation experiments on JET and KSTAR. These systems are to support disruption mitigation research for ITER and are based on an ORNL 3-barrel design for...
The Chinese Helium Coolant Ceramic Breeder (HCCB) Test Blanket Module (TBM) and its ancillary systems (together called Test Blanket System or TBS) is one of important steps for the China magnetic confinement fusion development, which will contribute to validate the key tritium breeding blanket technologies under the burning plasma environment, including tritium extraction, heat removal,...
Core transport in present tokamaks is mostly ascribed to micro-turbulence driven by the non-linear saturation of ion-scale ITG-TEM [1] instabilities ($k_\theta\rho_i\le1$, where $k_\theta$ is the poloidal wave number and $\rho_i$ the ion Larmor radius). It has been shown that electron-scale ETGs [2] ($k_\theta\rho_e\le1$) can also impact the heat transport, also exchanging energy with ITG-TEM...
Recent experiments in JET-ILW have been successfully exploring a high-performance H-mode scenario with no gas dosing at low $q_{95}$ ($I_p=3$ MA, $B_t$=2.8 T, $q_{95}=$ 3.2) and low triangularity, with peak neutron rates reaching values of 3.6$\times 10^{16}$ s$^{-1}$. This was enabled by operation at very low gas fueling, which is challenging in JET with the metal wall due the need to control...
State-of-the-art deep-learning disruption prediction models based on the Fusion Recurrent Neural Network (FRNN) (1) have been further improved. Here we report the new capability of the software to output not only the “disruption score,” as an indicator of the probability of an imminent disruption, but also a “sensitivity score” in real-time to indicate the underlying reasons for the imminent...
A disruption predictor based on deep learning method is developed in HL-2A. Its structure is specially designed to deal with data from fusion devices, and shows to have a better performance on disruption prediction problem than ordinary models commonly used in computer science[1.]. Based on this deep learning algorithm, in-depth research are carried out in three aspects. Firstly, different...
In recent years the multi-scale interaction between large-scale tearing modes and micro-scale turbulence has been found to be of paramount importance for thoroughly understanding the tearing mode physics and the island-induced transport, which will ultimately lead to developing a more effective method of the tearing mode control and optimizing the plasma performance in fusion devices, such as...
Future DT operation in ITER and DEMO will face a significant number of challenges. From the physics point of view, the change from DD to DT plasmas is poorly understood. There are indications that the core confinement, the ELM behavior, the pedestal confinement and the Scrape of Layer behavior can significantly change from DD to DT. From the operational point of view, scenarios with high...
Dimensionless experiments test the invariance of plasma physics to changes in the dimensional plasma parameters, when the canonical dimensionless parameters, such as rho_star, nu_star, β, q, ... are conserved [1], [2]. In particular, isotope identity experiments exploit the change in isotope ion mass A = mi/mp to obtain plasmas with identical dimensionless profiles in the same tokamak. In...
The Final Design Review (FDR) of the ITER Plasma Control System (PCS) for First Plasma will be held in July 2020 following the conceptual and preliminary designs [1,2] to prepare for First Plasma operation scheduled for the end of 2025. ITER operation follows the Staged Approach of the ITER Research Plan (IRP) [3]. The main goals of the First Plasma campaign include achieving a plasma current...
$\qquad$ Characterizing and understanding the power threshold conditions for ITER to achieve H-modes ($P_{LH}$) is a major goal of a series of L-H transition experiments undertaken at JET since the installation of the ITER-like-wall (JET-ILW), with Beryllium wall tiles and Tungsten divertor [1,2,3,4]. In this contribution we report on results from L-H transitions studies in H, D and new almost...
Introduction
Electron cyclotron systems of fusion installations are based on powerful millimetre wave sources – gyrotrons, which are capable to produce now megawatt microwave power in very long pulses. Gyrotrons for plasma fusion installations usually operate at frequencies 40-170 GHz. Requested output power of the tubes is about 1 MW and pulse duration is between seconds and thousands...
This paper presents a progress of the achievement of performance tests of ITER-gyrotrons developed in QST and design of dual-frequency (170 GHz and 104 GHz) gyrotron to enhance various operation scenarios in ITER such as characteristics studies of H-mode/ELM at low magnetic field. Major achievements of the ITER gyrotron developments are as follows: (i) Manufacturing of 6 out of 8 sets of ITER...
The mitigation of thermomechanical and runaway loads during disruptions and Vertical Displacement Events (VDEs) in ITER is essential for the project to execute the ITER Research Plan culminating (1) in the demonstration of the fusion power production goals (Q = 10 inductive operation for 300-500 s and Q = 5 for 1000 s and in steady-state up to 3000 s). To mitigate these loads ITER is equipped...
In a recently conducted test for assessing compatibility of accelerator grid of Neutral beam [1] for their performance at 150 C, failure has been evidenced across an electrodeposited (ED) bond layer, which forms a vacuum boundary with cooling medium. This happens to be the first instance where an electrodeposited bond has been subjected to Hot Helium Leak test under operational conditions of...
Nonlinear two-fluid MHD simulations reveal the role of resonant field penetration in ELM suppression and density pump-out in low-collisionality ITER-Similar-Shape (ISS) plasmas in the DIII-D tokamak$^1$. The operational window for ELM suppression in DIII-D ISS plasmas coincides with calculations for magnetic island formation at the pedestal top ($n_e<3\times10^{19}m^{-3}, B_r/B_t >10^{-4},...
Since the initial JET operations with the metal wall (JET-ILW), the experimental results have shown a pedestal pressure in baseline plasmas that tends to be 10-20% lower than in the corresponding earlier carbon wall operations (JET-C) [1]. While this degradation seems mainly correlated with the high fueling rates typical of JET-ILW [2,3] and/or the lack of carbon impurity [4,5], an exhaustive...
Good confinement of the fusion-born alpha particles is essential to ensure adequate burning plasma performance in next-step fusion devices. Among the processes determining this confinement, instabilities triggered by energetic particles (EPs) may play a major role, and are currently being studied in various tokamaks using auxiliary power sources to sustain EP populations. Instabilities...
A series of experiments have been executed at JET to assess the efficacy of the newly installed Shattered Pellet Injection (SPI) system in mitigating the effects of disruptions. In this contribution, the results from these JET SPI experiments are presented and their implications for the ITER disruption mitigation scheme discussed.
An effective Disruption Mitigation System (DMS) that minimizes...
The present contribution is devoted to the neutral beam injectors (NBIs) for ITER heating and current-drive. First, updated information is provided about the development status of the entire NBI prototype (MITICA); starting in 2021, the first experiments will be dedicated to high-voltage holding tests in vacuum. Then the contribution describes the full-scale prototype of the NBI ion source...
Significant stabilizing effect of kinetic thermal ions is found for the LHD plasmas. The kinetic MHD simulations for the LHD plasmas at high magnetic Reynolds number show that the high beta plasmas can be maintained since the saturation level of the pressure driven MHD instabilities is significantly reduced by the kinetic thermal ions. This results from the fact that the response of the...
The ITER Disruption Mitigation System (DMS) should ensure that heat loads,
ElectroMagnetic (EM) loads, and Runaway Electron (RE) impacts remain tolerable during
ITER disruptions. The design of the Baseline ITER DMS, which shall be available from the
beginning of ITER operation, relies on Shattered Pellet Injection (SPI). Up to 24 pellets may
be injected from 3 equatorial ports, plus 3...
Disruption in the TOKAMAK device is generally known as one of the most harmful events. The subsequent event of the thermal quench and the current quench cause collateral heat-damage and structural damages. These two potential sources of danger are relatively well known because it is easy to conceive that the confined thermal energy and the magnetic field energy associated with the plasma...
The JT-60 Super Advanced (JT-60SA) tokamak construction have been achieved respecting the requirements of very tight tolerance for the assembly and by handling very heavy components in a very close space environment. The construction of this large superconducting tokamak represents a big step forward in the world nuclear fusion history, opening the road for ITER and DEMO. Precise assembly is...
In magnetically confined fusion devices, nonlinear wave-wave interaction has been noticed to play important roles in the production of new modes. On NSTX, nonlinear interactions among low-frequency energetic particle modes (EPMs) and high-frequency toroidal Alfvén modes (TAEs) have been reported $[1]$. On JET, a 3/2 neoclassical tearing mode (NTM) is stabilized through the nonlinear coupling...
As the planned JET DT campaign [1] draws nearer, the necessity of high quality data, especially kinetic data, is more apparent than ever. This is especially the case of ion temperature data, which have required substantial work to overcome the diagnostic difficulties encountered in the early years of the JET ITER Like Wall (ILW) project, due to reduced light impurity levels and the presence...
Experiments in L-mode plasmas on HL-2A tokamak show that the electron and impurity transport is related to the normalized electron temperature gradient with opposite trends. In discharges with inner-deposited ECRH, the increase of the normalized electron temperature gradient in the confinement zone (0.25≤ρ≤0.5, ρ is the normalized minor radius) tends to pump out electrons and accumulate...
In this paper, the JT-60SA cryogenic system and the results of the commissioning and annual operations are summarized. During the commissioning of the cryogenic system, performances for each component and the automatically controlled operation sequence have been confirmed. Notably, mitigation of cryogenic heat load fluctuations in large superconducting tokamak machines is essential. The...
In this paper, we present the recent experimental results of cross phase influence on turbulent momentum and particle transport in the edge of HL-2A tokamak. The mathematical expressions for cross phases are derived in Fourier domain. The fluctuations and turbulent flux are measured by Langmuir probes. For Reynolds stress, prominent phase scattering in the strong shear layer is found, which...
Core density profile peaking and particle transport have been recently extensively studied on several tokamaks [1,2,3]. In JET, the earlier research of the significance of the NBI fueling on density peaking [4] was recently confirmed when thanks to the development of the gas puff modulation technique it was found that in ITG dominated plasmas, NBI is responsible for typically half of the...
Assembly of 1 MV power supply (PS) components to produce 1 MeV negative ion beams have been completed for the ITER neutral beam test facility (NBTF). To realize 1 MV insulation after the assembly of long and complicated components, (i) dust and particle during the assembly were controlled, (ii) the transmission line (TL) with a total length of 100 m composed of 22 series connected vessels was...
The Lithium Tokamak eXperiment-$\beta$ (LTX-$\beta$), the upgrade to LTX, is designed to utilize low recycling walls and the resultant gradient-free temperature profiles [D. P. Boyle et al., Phys. Rev. Lett. 119, 015001 (2017)] to robustly stabilize ion and electron temperature gradient-driven modes. Low recycling and the resultant low collisionality in the scrape-off layer (SOL) plasma [R....
Introduction
In ITER the density of deuterium and tritium will be controlled by injection of cryogenic pellets, with D and T isotopes separately to allow active isotope ratio control. Due to technical limitations and high pedestal temperatures the pellets will be ablated at the plasma periphery, about at the pedestal top. For deeper penetration one have to invoke curvature drift and...
The SST-1 machine is the first medium size superconducting tokamak operational at Institute for Plasma Research India. It comprises of set of toroidal (TF) as well as poloidal field (PF) superconducting coils system. In order to cool and maintain these magnets under superconducting state, a dedicated specially designed helium cryogenic system of cold capacity 1350 W at 4.5 K along with its...
This report focuses on the development of the thermal insulation devices including thermal shield (TS) and cryostat for the superconducting tokamak JT-60SA.
- Design, manufacturing and acceptance test were successfully completed
by 2019 and installation will be done by March 2020.
- The technique and knowledge to realize high accuracy manufacturing
and short time installation of...
The 2018 ITER Research Plan states that “Operation of ITER will have to strongly focus on avoiding disruptions with a high success rate and on mitigating those in which avoidance techniques fail” (1). The development of a disruption mitigation system for ITER will not suffice. We discuss a nonlinear effect that can allow the RF current drive stabilization of larger islands than would otherwise...
The disruption mitigation technology remains the key issue of safe and reliable device operation in future large tokamaks including ITER [1,2]. Several approaches have been proposed and experimentally tested in contemporary devices, which demonstrate opportunities of massive gas, pellets, dust and liquid gets injection in preventing the avalanche as the most dangerous mechanism of the runaway...
Disruption mitigation remains a unresolved critical issue for ITER. Over 90% of the massive stored energies in ITER must be radiated for a mitigated disruption [1]. The most promising present strategy is to inject a large amount of material into the plasma using a shattered pellet injector (SPI). This study presents an exploration of SPI parameters on mitigation performance and the mitigation...
The control of edge localized mode is crucial for protecting the plasma facing components in the magnetic fusion reactor. In the investigation of ELM control, it has been commonly observed that the pedestal turbulence enhances during edge localized mode (ELM) mitigation with supersonic molecular beam injection (SMBI) [1], lower hybrid current drive (LHCD) [2] and impurity seeding [3][4]. The...
Due to concerns of erosion and damage to divertors caused by Type-I edge-localized modes (ELMs) in ITER tokamak$[1]$, resonant magnetic perturbation (RMP) has been proposed as an efficient technique for ELM control and has been extensively studied in the past few decades. Complete suppressed of type-I ELMs by RMPs was first demonstrated in DIII-D $[2]$. Since then, suppression or mitigation of...
Pedestal formed in the plasma edge of high confinement mode (H-mode) strongly affects edge localized modes (ELMs) burst. Thus, understanding the physics of the pedestal instabilities is key to reducing the uncertainties associated with the realization of burning plasma conditions and the appropriate control of ELMs. Fusion power depends strongly on the pedestal pressure. RF waves, such as...
Runaway electrons (REs) are a crucial issue for future large tokamaks, especially during disruptions, due to the local impact of RE beam and large thermal loads they can place on the plasma facing components [1]. Therefore, a very active field of research has been opened up in the past decades on RE dynamics during disruptions [2]. Utilizing the newly developed key systems in the HL-2A tokamak...
N. Zhang$^1$, Z. C. Yang$^1$, Y. Liu$^1$, Y. Q. Liu$^2$, T. F. Sun$^1$,X. Q. Ji$^1$, P. Piovesan$^3$, V. Igochine$^4$, D. L. Yu$^1$, S. Wang$^1$, G. Q. Dong$^1$, R. Ke$^1$ , J. M. Gao$^1$, W. Deng$^1$, N. Wu$^1$, Q. W. Yang$^1$, M. Xu$^1$ and X. R. Duan$^1$, The HL-2A Team, The ASDEX Upgrade Team and The EUROfusion MST1 Team
$^1$ Southwestern Institute of Physics, P. O. Box 432, Chengdu...
Pellet injection is used in tokamaks and stellarators for fueling, ELM pacing and disruption mitigation. Injection of shattered pellets is a critical part of the envisaged ITER disruption mitigation system. Rapid deposition of a large amount of material is expected to result in a quick cooling of the entire plasma. However, it has recently been demonstrated that a considerable transfer of...
In magnetically controlled fusion devices, improving plasma performance is crucial for enhancing the confinement efficiency. An improved regime, high confinement mode (H-mode), has been chosen as the standard operating scenario for the international thermonuclear experimental reactor (ITER). Recently, the energy confinement improvement by externally seeded low or medium Z impurities has been...
The mechanism of excitation of beta-induced Alfv\'{e}n eigenmodes (BAEs) with magnetic island larger than a threshold without energetic ions is studied. It is found that the nonlinear coupling between Geodesic acoustic mode and magnetic island can drive the pair of BAEs. To excite the BAEs, the phase of BAEs to island should be $\pi/2$ and the magnetic island is larger than a threshold. The...
INTRODUCTION
Understanding the interaction of Alfvén Eigenmodes (AEs) and energetic particles, namely fusion alphas, is of utmost importance to the operation and performance of future tokamaks, such as ITER and SPARC. In the JET tokamak, a toroidal array of eight in-vessel antennas was installed [1] to actively excite stable AEs with frequencies ranging 25 – 250 kHz, typical of BAEs, RSAEs,...
The nonlinear interactions between energetic particle (EP) and Alfvén waves are very important for astrophysics and high temperature plasma physics, especially for magnetically confined fusion plasma, because they will affect the redistribution and transport of EPs significantly. When the EPs have sufficiently strong pressure gradient, they can excite a non-normal mode, named energetic...
Alpha particles are the key players of a burning plasma as they provide the self-heating required for the sustainment of the fusion burn. At the same time, however, there is only little experimental knowledge on their properties, mostly because of the limited availability of deuterium-tritium (DT) plasmas. Among the challenges that the scientific program of the Joint European Torus (JET) is...
Experimental investigations of frequency slowly-sweeping Alfvenic modes have been carried out on the HL-2A Tokamak. There are two different kinds of instabilities in the neutral beam heated plasma, i.e., the typical reversed shear Alfven eigenmodes (RSAEs) and the high modes with frequency slowly sweeping from 500kHz to 100kHz. On one hand, the RSAEs are driven unstable by the passing fast...
Gamma-ray spectrometry of the plasma [1] is one of the tools giving information on the heating efficiency. The source of gamma-ray is nuclear reactions between energetic confined ions and plasma impurities, i.e. Be and bulk plasma ions. Gamma-ray diagnostics allow monitoring the energy distributions of the fusion products, ions accelerated during ICRF heating and plasma fuel ions and provide...
To verify the CarMa0NL modelling for COMPASS-U, the numerical results are cross-validated with general analytical predictions [Pustovitov V. D., Nuclear Fusion 55 113032 (2015)]: the computed vertical force on the tokamak wall is found to be almost zero during fast transients, as it should be. This test proves the credibility of the model and computational method. The role of poloidal eddy...
Optimized stellarators promise comparable energy confinement to existing tokamaks. Recent results from the Wendelstein 7-X device are consistent with this possibility. At the same time, stellarators offer considerable advantages, such as disruption-free operation without a Greenwald density limit. On the other hand, transport in optimized stellarators will be dominated by turbulence, unlike...
JET has addressed one of the key issues for the baseline scenario in ITER by demonstrating for the first time a high-performance H-mode with high confinement using a neon (Ne)-seeded radiative divertor. Although the ITER Tritium plant is being designed to deal with both nitrogen (N) and Ne, the use of N leads to the formation of tritium-containing ammonia [1]. Its accumulation in the ITER...
Achieving high-$\beta_N$ for current and future tokamaks is a challenging and important issue, where \beta_N is the normalized toroidal beta. High-$\beta_N$ is beneficial for the ignition and fusion reaction, as well as the ratio of bootstrap current is proportional to $\beta_N$. Recently, on HL-2A a high-performance region, combining edge and internal transport barriers (double transport...
The report presents the results of the design development of the equatorial diagnostic port #11 of the final project level and the upper diagnostic ports ## 02,07,08 of the preliminary design level. Ports are being developed at the Budker Institute of Nuclear Physics of the Siberian Branch of the Russian Academy of Sciences (BINP SB RAS or shot BINP) in close cooperation with the ITER central...
Recent experiments at the JET tokamak with ITER-Like-Wall studied intrinsic rotation in a large tokamak, addressing questions related to the effects of collisionality and hydrogen isotope type on the amplitude of the measured toroidal rotation and rotation reversals of Ohmic plasmas. The isotope effect on the intrinsic rotation was investigated by comparing the rotation of the main ion in...
The JT-60SA tokamak is a large-scale fusion installation located in Naka (Japan) to be operated as a satellite for the ITER tokamak and also to explore DEMO plasma regimes [1]. JT 60SA first plasma will be run end 2020 and will represent the energization of the worldwide largest superconducting cryomagnetic system in operation for fusion. The magnet system is composed of 18 Toroidal Field (TF)...
Abstract
The nuclear fusion reactor ITER (International Thermonuclear Experimental Reactor) foresees a Pressure Suppression System (PSS) in order to manage a Loss of Coolant Accident (LOCA) or other over pressurization accidents in the Vacuum Vessel (VV) which has a pressure limit fixed at 150 kPa (abs).
This system (VVPSS) has a key safety function because a large internal...
Abstract In the frame of the EUROfusion breeding blanket research activities, two reference blanket concepts are developed, the helium cooled pebble bed and the water cooled lead lithium (WCLL) blankets, which represent the most attractive designs for a DEMO reactor $\left[ 1\right] $. Test Blanket Modules (TBMs) derived from these concepts will be tested in ITER.
The design of breeding...
Abstract. The study is devoted to theoretical analysis of the models for calculating the disruption forces in tokamaks. It is motivated by the necessity of reliable predictions for ITER. The task includes the evaluation of the existing models, resolution of the conflicts between them, elimination of contradictions by proper improvements, elaboration of recommendations for dedicated...
The intensive experimental and theoretical study of the Edge Localized Modes (ELMs) and methods of their control is of great importance for ITER [1]. The application of small external Resonant Magnetic Perturbations (RMPs) has been demonstrated to be efficient in ELMs suppression/mitigation in present day tokamaks [2]. RMPs are foreseen as one of the methods of ELMs control in ITER [3]. ...
A transition from an interchange mode with high mode numbers $(m,n)$ for $m$ (poloidal) and $n$ (toroidal) to a non-resonant $(m,n)=(1,1)$ mode is found in the nonlinear magnetohydrodynamic (MHD) simulation for a Large Helical Device (LHD) plasma with net toroidal current. This transition occurs when the rotational transform is closed to unity in the core region. Because partial collapses...
A novel understanding of the collective processes that can emerge in fusion burning plasmas is shown to generate new perspectives for meaningful experiments that can be undertaken in the near term. In particular ``Di-ballooning’’ modes, that propagate only in the toroidal direction and are standing in both the poloidal and the radial direction, are identified.
The poloidal profiles of these...
The NSTX-U Recovery Project is completing the transition from the design phase to the fabrication and installation phase in the early part of 2020. The design that has been established is based on the findings of the 2017 Extent of Condition review, and includes significant technical improvements to the machine core and auxiliary systems, in order to provide a high-reliability use facility....
A helical coil designed to passively generate non-axisymmetric fields during a plasma disruption has been shown (via electromagnetic circuit and linear MHD modeling) to be effective at deconfining runaway electrons (REs) before the RE beam current grows to dangerous levels. Magnetic equilibria from DIII-D RE experiments were used to calculate the toroidal electric field generated during the...
The extreme energy content in ITER makes the disruptions a matter of grave concern. The current strategy of disruption mitigation in ITER relies on the injection of cryogenic pellets into the disruptive plasma [1]. Pellet ablation is an essential factor in disruption mitigation, which calls for dedicated theoretical support in modeling this process in the plasma and establishing related...
Plasma rotation in thermonuclear fusion plasma plays an important role for particle and energy confinement and it can stabilize magnetohydrodynamic instabilities if some rotation level is achieved. In early studies, the relation between plasma confinement and radial electric field E_r was studied via measurements of the electric potential distribution and also via spectroscopic measurements of...
Plasma detachment is the desired operational regime for ITER baseline scenario and in next-step fusion reactors, as it allows to reduce the heat fluxes impacting onto the divertor plasma-facing components (PFCs) below their material limits. It is typically characterized by a reduction of plasma pressure between the upstream separatrix and the divertor targets, which is caused by dissipation of...
The commissioning of the power supplies for superconducting coils in JT-60SA has been done with dummy load (Inductance: 7.64 mH, Resistance: 6.995 m$\Omega$) since June 2019. The most important results are that (i) Integrated operation of the different PS components was completed successfully, (ii) High voltage generation of the rated voltage of 5 kV by Switching Network Unit (SNU) was...
The paper summarizes the studies carried out on a novel arrangement of the core X Ray Crystal Spectroscopy (XRCS) system for ITER, particularly with respect to physics analysis and system integration in a different equatorial port in ITER. The XRCS Core diagnostic is the only one available for ITER at PFPO-1 (Pre-Fusion Power Operation-1) phase, and offers key parameters like core ion...
In this presentation, we report recent advances in the development of the CFQS quasi-axisymmetric stellarator as a joint project of National Institute for Fusion Science, Japan and Southwest Jiaotong University, China. The quasi-axisymmetric stellarator (QAS) offers good plasma confinement properties with low aspect ratio, giving a prospect to become a compact fusion reactor. MHD equilibrium...
Ion Cyclotron Resonance Frequency (ICRF) heating plays an important role in many present day experiments and it is one of the auxiliary heating methods that will be used in ITER. In this contribution, we will review the recent key ICRF results from the JET and ASDEX Upgrade (AUG) tokamaks in preparation of ITER.
In the recent JET campaigns, the focus has been in the preparation of...
Shattered pellet injection (SPI) has been selected as the baseline disruption mitigation (DM) system for ITER. SPI utilizes cryogenic cooling to desublimate low pressure (<100 mbar) gases onto a cold zone within a pipe gun barrel, forming a cylindrical pellet. Pellets are dislodged from the barrel and accelerated using either a gas driven mechanical punch or high-pressure light-gas delivered...
This paper presents numerical modelling to assess the fast shutdown scenario by shattered pellet injection (SPI) in a baseline strategy of the ITER Disruption Mitigation System (DMS). A new versatile 1.5D disruption simulator INDEX is applied for this purpose and a SPI ablation/assimilation model has been implemented. Pre-thermal quench (pre-TQ) H$_2$/D$_2$ SPI is proposed as a promising...
![Impurity Density and Total Pressure Profiiles and 3D Visualization][1]
The efficacy of ITER's DMS must be evaluated within the next several years and, since in-situ evaluation is impossible, verified and validated simulations are critical. High fidelity 3D initial value simulations of Shattered Pellet Injection and Dispersive Shell Pellet (SPI and DSP) simulations show favorable...
Plasma Exhaust and Plasma Wall Interaction are subjects of intense studies in fusion energy research for the understanding of the amount of heat loads and the lifetime of Plasma Facing Components. In order to ensure reliable predictive edge modeling in this context, it is mandatory to determine the transport properties of the Scrape Off Layer (SOL), a region largely influenced by the presence...
MHD stability at edge pedestal in QH-mode plasmas in DIII-D and JT-60U was analyzed by considering plasma rotation and ion diamagnetic drift effects. It was found for the first time the coupled rotation and ion diamagnetic drift effects can stabilize a kink/peeling mode in both experiments in case the rotation direction is counter to the plasma current direction although it has been recognized...
ITER Council has decided to reduce the number of port from three to two for testing TBM due to the introduction of a Disruption Mitigation System during November 2018. Since then, India is proposing Helium Cooled Solid Breeder (HCSB) concept to be tested in one half of the two ports available for the same in ITER. Indian HCSB concept is having Reduced Activation Ferritic Martensitic Steel...
Perhaps the most attractive fusion reactor concept is the stellarator since it has minimal recycling power, minimal auxiliary systems and no time dependent electro-magnet systems. However, progress has been delayed by two formidable challenges: obtaining sufficient![Solution to the normal distribution of permanent magnets required to provide the shaping fields for an NCSX like equilibrium...
In Wendelstein 7-X, the vacuum rotational transform, $\bar\iota$, has a rather small shear and does not cross any major rational surfaces. Nevertheless, during plasma operation it can be modified by electron cyclotron current drive (ECCD) in such a way that the resulting iota profile passes through low-order rational values, potentially triggering magnetohydrodynamic (MHD) events.
Indeed,...
The termination of high performance plasmas in tokamak devices with high Z metal plasma facing components presents challenges related to the influx of heavy impurities which, if not kept under control, cause an increase of the radiative losses, radiative cooling and high probability of disruption.
A number of key players in these dynamics have been identified by intensive research performed...
![(top left) growt rate of the ideally unstable $2/3$ mode. (top right) radial displacement of this mode. (bottom) Stochastization of the core region due to the perturbed field associated with this mode.][1]
We present a new model of the sawtooth oscillation that can explain direct measurements which show $q_0$ well below 1 during the entire cycle, and observations that indicate the $q=1$...
Jing Wu1*, Jiming Chen1, Liman Bao2, Pinghuai Wang1, Kun Wang3, Stefan Gicquel2, Xiaobo Zhu1, Qian Li1, Hui Gao1, Weishan Kang1, Rene Raffray2
1Southwestern Institute of Physics, Chengdu 610041, China
2ITER Organization, 13115 St Paul Lez Durance, France
3China Int’l Nuclear Fusion Energy Program Execution Center, Beijing 100862, China
*E-mail: wj@swip.ac.cn, Tel:...
Jiming Chen1*, Pinghuai Wang1,Kun Wang2, Liman Bao3, Xiaobo Zhu1, Jing Wu1, Stefan Gicquel3, Qian Li1, Hui Gao1, Jialin Li1, Rene Raffray3, Ming Xu1, Xuru Duan1
1Southwestern Institute of Physics, Chengdu 610041, China
2China Int’l Nuclear Fusion Energy Program Execution Center, Beijing 100862, China
3ITER Organization, 13115 St Paul Lez Durance, France
*E-mail: chenjm@swip.ac.cn, Tel:...
It is an extreme challenge to reduce the transient peak of the heat load on the plasma facing components (PFC) in tokamak plasma$[$1$]$. One effective way is to increase the wetted area on the divertor target by splitting the strike point. Most of the experimental results show that the change of magnetic topology induced by RMP and LHCD is responsible for the strike point splitting$[$2-4$]$....
This contribution presents a numerical assessment of the impact of density fluctuations on the electron cyclotron (EC) wave in view of neoclassical tearing mode control in European DEMO. We show that, using the current design for the EC system launching the EC wave from equatorial outboard plane, the quality of the EC current profile is severely affected by the density fluctuations located at...
Parametric decay instability (PDI) is a kind of nonlinear wave-wave interaction, which significantly influence the wave accessibility and heating in plasmas. In fusion plasmas, the parametric process is typically displaying as quasi-mode decay, such as nonlinear landau damping or ion cyclotron harmonic decay. [1] For these quasi-mode decays, the previous kinetic theory [2] for PDI, where...
At the present time, the preparing for physical start-up of tokamak T-15MD is completed in the National Research Center “Kurchatov Institute”. Tokamak T-15MD has the following parameters: R=1.48 m, a=0.67 m, B=2.0 T, Ipl= 2.0 MA [1]. The electromagnetic system is capable of maintaining without overheating (more 60ºC) the plasma current of 1MA for 40s, 700 kA for 120 s, 500 kA for 250 s and 300...
We report recent advances in reducing the coil complexity for optimized stellarators. Three efforts have been dedicated. First, the FOCUS code which uses fully 3-D representations for coils and employs analytically calculated derivatives has been applied in designing coils for new stellarators. FOCUS allows searching for more design space and thus is able to find more possible solutions....
In JET plasma with a carbon wall (JET-C), and most other existing tokamaks, exceeding a critical density results in a H-L back transition, even when well above the H-mode power threshold. In contrast, at high density, JET plasma with a Be/W ITER-like wall (JET-ILW) always enter a ‘dithering’ phase before the H-L back transition, which enables a ($\approx20\%$) higher H-mode density limit (HDL)...
- Introduction : Disruptions are one of the major concerns in ITER and other future tokamaks [1]. A particularly troublesome type of disruption is a vertical displacement event (VDE) where control of the vertical position of the plasma column is lost. In addition to heat, particle flux, and energetic electrons impacting the first wall, significant electromagnetic loads will arise.. For...
