The ITER research plan has been recently re-elaborated to lay out a robust path to achieve the Project’s fusion production goals and technical objectives. This includes changes to device and ancillaries configuration to minimize previously identified risks such as: changing plasma facing material of the first wall from beryllium (Be) to tungsten (W), modifying the heating and current drive...
Long pulse operation in a W environment : feedback from WEST
P. Manas1, P. Maget1, R. Dumont, J. Dominski2, T. Fonghetti1, J. Morales1, A. Ekedahl1, N. Fedorczak1, J. Gaspar3, E. Tsitrone1, and the WEST Team*
1 CEA, IRFM, F-13108 Saint-Paul-lez-Durance, France
2 Princeton Plasma Physics Laboratory, 100 Stellarator rd, Princeton 08540 New Jersey,USA
3 Aix-Marseille Université, CNRS, IUSTI,...
The mission of the KSTAR device is to sustain high-performance plasma for 300 seconds[1]. In the 2023 experimental campaign, KSTAR maintained H-mode plasma for 102 seconds. The operating conditions of this discharge were $I_P$=400 kA, $B_T$=1.95 T, $P_{NBI}$=3.9 MW, and $P_{EC}$=1.1 MW. The plasma characteristics of this plasma were $V_{loop}$~70 mV, $β_P$~2.5, $β_N$~2.1, $T_{e,core}$>6.0 keV,...
Stellarators offer a relatively straightforward route to steady state fusion power operation. Future reactors, such as DEMO, are expected to operate quasi-continuously with divertor heat fluxes as low as 5 MW/m$^2$ [1]. This requires that most of the power leaving the plasma has to be radiated away by the plasma impurities in the so-called detached regime, in which the divertor target plates...
This study shows the experimental results on the density limit and ultra-high neutral pressure in the sub-divertor volume at LHD for high density steady state operation, and good particle exhaust.
A new density scaling for tokamaks was reported in [1] based on edge turbulent transport. It shows a strong dependence on heating power and is similar to the Sudo density limit in the helical...
Recent high poloidal beta ($\beta_P$) scenario experiments on EAST and DIII-D have made coordinated breakthroughs for high confinement quality at high density near the Greenwald limit. Experiments on DIII-D have achieved $f_{Gr}$ ($=$line-averaged density$/$Greenwald density) above 1 simultaneously with $H_{98y2}$ around 1.5, as required in compact steady-state fusion pilot plant designs but...
In the last experimental campaign of the JET tokamak in December 2023, long discharge operation (>30s) in deuterium plasmas was developed to assess the sustainment of the plasma performance over many resistive time scales and to address plasma-wall interaction physics in a full metallic environment with the ITER-like wall (ILW), with a W divertor and a Be first wall [1]. Two types of long...
QUEST is a medium-sized spherical tokamak which has parameters of R~0.64m, a~0.4m, BT<0.25T. The plasma facing walls (PFWs) are made of metals such as tungsten, atmospheric sprayed tungsten (APS-W), stainless steel type 316 (SS 316L) and 316L (SS316). A RF heating source is available for long pulse operation (LPO). A hot wall has been installed to regulate PFWs temperature. Taking advantage of...
Plasma-wall interaction (PWI) plays a crucial role in plasma control in fusion devices. Apart from impurity generation and power exhaust issues, fuel recycling at plasma-facing components (PFCs) introduces additional challenges by affecting plasma density control and fueling efficiency. Hydrogen transport, retention and release from PFCs is influenced by the incoming ion and neutral particle...
In order to operate for long pulses, magnetic confinement fusion (MCF) devices are typically equipped with actively-cooled plasma-facing components (PFCs). These have been installed in several existing long-pulse MCF machines, but are expected to be more widely used in the next generation of high-powered, long-pulse devices (e.g. ITER, DEMO & commercial power plants). The circulation of...
Reaching the milestone of > 1GJ of heating energy was an important demonstration of the physical and technical capabilities of the W7-X stellarator. This milestone was achieved using exclusively ECRH power, which was also a challenge for the ECRH system itself and the handling of ECRH-specific loads on the components in the vessel. This is especially true for high density operation and not...
After the successful integration of passive active multijunction (PAM) launcher in ADITYA-U tokamak, the lower hybrid current drive (LHCD) experiments with PAM launcher is conducted in ADITYA-U tokamak. The PAM launcher, designed to launch up to 250kW of rf power at 3.7 GHz, for one second, was successfully installed on radial port#5 of the tokamak. It was validated for UHV compatibility (10-9...
Lower hybrid current drive (LHCD) has proven to be one of the most efficient methods to sustain long pulse plasma operation in tokamak. In order to sustain good LHW (lower hybrid wave) -plasma coupling required for long pulse plasma, it is the first time that the coupling feedback control is designed and realized in EAST through PID (Proportion Integration Differentiation) method by choosing...
Abstract:
The objective of WEST experiments is to master long-pulse operation (1000 s) while exposing the actively cooled ITER-grade tungsten divertor to power fluxes up to 10 MW/m2. The reliability and performance of the Lower Hybrid Current Drive (LHCD) system are critical for the success of long pulse operation on WEST as it allows to drive significant non-inductive current in the...
The experiments on plasma initiation performed in EAST with the electron cyclotron wave (ECW) pre-ionization and assisted start-up have demonstrated that ITER can produce plasma initiation in a low toroidal electric field (<0.3V/m). The parameter domain of breakdown is significantly extended towards higher prefill gas pressure. The effect of ECW injection timing, power, toroidal injection...
In the European roadmap to fusion energy, EU-DEMO will be the first machine with a net electricity generation and demonstrating the integration of all reactor-relevant functions, e.g. self-sustaining tritium production. Currently, the EU-DEMO design is based on the tokamak configuration, with a pulsed plasma and a discharge duration not shorter than two hours. In general, the EU approach...
A critical challenge for a compact fusion pilot plant is to resolve the path to a high fusion performance core with a dissipative divertor approach, finding solutions that are mutually compatible to marry them together. This must also be integrated with surrounding plasma interacting technologies and materials. An upgrade to DIII-D is proposed to close gaps on reactor physics regimes in...
Environmentally acceptable nuclear energy is an important component of global energy today. However, the difficulties associated with the production of nuclear fuel, reprocessing and disposal of radioactive waste from fission reactors limit its development. The integration of technologies can ensure long-term and sustainable development of the world energy system. One of the most promising...
Predictions of fusion’s radiation fields and associated nuclear quantities are fundamentally needed to serve a range of performance, safety and regulatory criteria - at all stages of the plant lifecycle, ranging from conceptual design to decommissioning. Radiation fields comprise the spatial, energy and temporal distribution of neutron and photon fluxes throughout the fusion device in various...
Since 2016, the WEST tokamak has brilliantly demonstrated its capability to perform long plasma discharges in a fully metallic environment.
WEST, qualified as a long pulse machine, presents the specific features of a permanent magnetic field produced by 18 Superconducting Toroidal Field coils cooled at 1.8K thanks to its liquid helium cryogenic system, the entire plasma facing components...
The WEST (Tungsten Environment in Steady-state Tokamak) project in France is crucial for reaching sustainable fusion energy by simulating reactor-like conditions. WEST provides a unique facility to integrated and test technologies for Long Pulse Operations.
Previous operation on Tore Supra, and numerous studies showed that all components receiving convective heat flux from particles and...
Nuclear fusion is expected to be available as energy technology source of energy from mid-50s of present century. One key aspect for the success of such technology will be the reliability growth implemented in the design since the early phases. In fact, nuclear fusion plants are expected to exploit many fusion specific components with relatively low technology readiness level, or in some cases...
Abstract—The pursuit of fusion energy as a sustainable and clean power source has spurred the development of advanced fusion devices, exemplified by the China Fusion Engineering Experimental Reactor (CFETR) and the Burning plasma Experimental Superconducting Tokamak (BEST). These devices aim for long-pulse steady-state operation, presenting significant challenges for their DC transmission...
Neutral Beam Injection (NBI) requires high particle energies if one of its aims is to contribute to current drive in large fusion tokamaks. For example, 1 MeV D is foreseen for the ITER NBI. At such energies, the NBI must be based on a source of negative hydrogen ions (N-NBI) due to their higher neutralization efficiency of up to 60% in a gas neutralizer. Negative hydrogen ions are produced on...
While Neutral Beam Injection (NBI) with beam energies in excess of about 100 keV/amu (e.g. on ITER, JT-60SA, DTT) requires sources for negative ions (“N-NBI”), positive-ion-based (“P-NBI”) systems have attracted renewed interest for smaller long-pulse fusion devices such as volumetric neutron sources (VNS). In these devices, like for instance the tokamak-based VNS currently studied by...
Tokamak-based fusion neutron sources (FNS) can effectively address the fuel problems of nuclear energy and future fusion power plants operation [1]. FNS primary mission is testing technological systems being exposed to intense neutron flux and evaluation of relevant effects in materials and structural components designed for future nuclear reactors, fusion-fission and pure thermonuclear...
It has been observed that lost fast ions in NBI plasma will hit the first wall of the device to affect the long pulse steady-state operation. The fast-ion loss mechanisms include prompt loss, ripple loss and resonant loss due to MHD instabilities[1]. Also, MHD instabilities are closely related to fast-ion beta βf [2-3]. In our research, we focused on the simulation and experimental...
The control of the core-plasma kinetic state determining the overall fusion power, usually referred to as burn control, arises as one of the most fundamental problems in nuclear fusion. Feedback control of the burn condition will be necessary to avoid undesirable transient performance, to respond to changes in plasma confinement, impurity content, or operation conditions, which could...
Control developments, including porting a Proximity Controller [1] to aid in continuous disruption prevention and upgrading the existing Real-Time Feed-Forward algorithm [2] for robust and reliable shape control during long-pulse sustainment and ramp-down, have been implemented to support long-pulse scenarios on KSTAR with its new tungsten divertor. The proximity controller calculates the...
The WEST superconducting tokamak features a full tungsten environment and is equipped with an actively cooled ITER-grade divertor providing valuable input for future operation at ITER. Versatile multi-energy soft and hard X-ray pinhole cameras have been developed, calibrated, deployed and operated for long-pulse plasmas at WEST. These cutting-edge instruments, serving as novel enabling...
Metallic impurities induced by divertor heat load and ELM filaments are the main challenges in achieving long-pulse high-performance H-mode operations. Long-pulse (>50s) no-ELM H-mode discharges with feedback-controlled divertor detachment by nitrogen seeding from outer horizontal target plate of the lower divertor have been achieved under boronized metal wall in the EAST tokamak. Figure 1...
The DIII-D research program will close key gaps in knowledge for the design and operation of long-pulse tokamak fusion pilot plants (FPPs) by deploying increased electron cyclotron heating and current drive power to reach and study more relevant plasma regimes. The U.S. is focused on low capital cost compact FPPs on the path to commercialization. Steady-state or long-pulse inductive tokamaks...
WEST is a machine designed for attaining Long Pulse Operation [1] with Lower-hybrid Heating and Current Drive (LHCD), superconducting coils, actively-cooled components and a W wall. In 2024, a more than six-minutes-long L-mode plasma was sustained with 1.15 GJ of injected energy. In parallel, developments were undertaken on the modeling side. The High Fidelity Pulse Simulator (HFPS) [2], an...
