Publications by Holger Reimerdes

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Fusion plasma regimes with a strongly radiating magnetic 𝑋 point are promising candidates to tackle the outstanding power exhaust challenge in reactor-scale devices. In this Letter, we report on a new type of 𝑋-point radiator, the XPTR (𝑋-point target radi ...

The most efficient and promising operational regime for the International Thermonuclear Experimental Reactor tokamak is the high-confinement mode. In this regime, however, periodic relaxations of the plasma edge can occur. These edge-localized modes pose a ...

SOLPS-ITER is a widely employed transport code for Scrape-Off Layer (SOL) modeling, commonly used to assist experimental interpretation in current tokamak experiments, and for the design of future devices. An aspect of particular importance for SOL transport is particle drifts. When drifts are included in SOLPS-ITER simulations, two types of numerical instabilities are frequently encountered. The first one is a core instability, that limits the maximum allowed time-step. For a typical simulation of an Ohmic

We present simultaneous profiles of the poloidal distribution of electron temperature and density (Te, ne), the poloidal emissivity distributions of a range of spectral lines together with the corresponding ion temperatures, Ti, in the TCV divertor plasma. ...

Experiments with high-power electron cyclotron heating (ECH) and current drive (ECCD) in the TCV tokamak are discussed. Power up to 2.7 MW from six gyrotrons is delivered to the tokamak at the second-harmonic frequency (82.7 GHz) in X-mode. The power is transmitted to the plasma by six independent launchers, each equipped with steerable mirrors that allow a wide variety of injection angles in both the poloidal and toroidal directions. Fully non-inductive operation of the tokamak has been achieved in steady

Negative triangularity (NT) is a promising ELM-free candidate for future fusion reactors. In this paper, the impact of increased divertor closure on density-ramp induced detachment in NT is assessed in the Tokamak `a Configuration Variable (TCV). Previous experiments in TCV have shown that at similar line-averaged density and divertor shape, NT shaping makes detachment access more difficult than in Positive Triangularity (PT) and results in a lower divertor neutral pressure. In this

Theory-based scaling laws of the near and far scrape-off layer (SOL) widths are analytically derived for L-mode diverted tokamak discharges by using a two-fluid model. The near SOL pressure and density decay lengths are obtained by leveraging a balance amo ...

The Super-X Divertor (SXD) is an alternative divertor configuration leveraging total flux expansion at the Outer Strike Point (OSP). While the extended 2-Point Model (2PM) predicts facilitated detachment access and control in the SXD configuration, these a ...

Power exhaust scenario and divertor design for a steady-state Japan (JA) DEMO and a pulse Europe (EU) DEMO1 have been investigated as one of the most important common issues in Broader Approach DEMO Design Activity. Radiative cooling is a common approach f ...

In the pursuit of realistically achievable design options for demonstrating fusion electricity generation and tritium self-sufficiency in a device to follow ITER, it is vital to explore as fully as possible the available design space and technology options ...

Parallel convection and E × B drifts act together to redistribute heat between the strike-points mechanisms is enhanced near the secondary X-point and is shown to dominate over heat in the low field side snowflake minus (LFS SF−). The cumulative heat conve ...

The ECW system on Tokamak a configuration variable (TCV) allows the study of a wide range of poloidal and toroidal launch angles. Both electron cyclotron heating (ECH) and electron cyclotron current drive (ECCD) experiments have been performed to demonstrate the modification of the electron temperature and current profiles. In particular a multi-channel hard X-ray camera (on loan from Cadarache) clearly shows the generation of a high energy electron tail, which increases with increasing toroidal launch angl

During detachment, a buffer of neutral atoms and molecules builds up between the target and the ionising plasma. Collisions between the plasma and the molecules play an important role in the detachment process. Studies of plasma-molecular kinetics indicate that the gas temperature increases during deepening detachment for a wide range of conditions on the MAST-U and TCV tokamaks. This is related to an increased D2 lifetime during detachment, leading to more plasma-molecule collisions that raise the molecula

Divertor detachment is investigated on the Tokamak a Configuration Variable (TCV) for conventional and alternative double-null (DN) magnetic geometries in L-mode, Ohmic density ramps and then compared to precisely matched single-null (SN) geometries. The p ...

X-Point Radiator (XPR) regimes have been obtained in WEST tokamak experiments with nitrogen seeding during the experimental campaigns of 2023 and 2024. These experiments showed the formation of a stable toroidal radiating ring near the X-point, similar to ...

Increased focus has been recently given to the ion temperature Ti near the separatrix and in the scrape-off layer (SOL) due to its impact on plasma confinement, wall sputtering, heat fluxes, and edge turbulence. In current tokamaks, high pedestal collisionality often clamps pedestal top ion and electron temperatures together. However, thermal decoupling occurs in the SOL due to the different ion and electron masses, leading to T-i/T-e>1 at the separatrix and in the SOL. Despite consistently observing elevat

Neoclassical tearing modes are one of the most serious concerns for operation on a next-step tokamak device. The modes occur on present tokamaks at normalized pressure (beta (N)) values comparable to those envisaged For baseline scenarios in future devices, such as ITER-FEAT. Further, empirical scalings based on data from many of the present machines point to much lower thresholds on a larger device. However, physics-based models indicate an important role for the seed island mechanisms, which may in fact g

In 2021 JET exploited its unique capabilities to operate with T and D-T fuel with an ITER-like Be/W wall (JET-ILW). This second major JET D-T campaign (DTE2), after DTE1 in 1997, represented the culmination of a series of JET enhancements-new fusion diagno ...

Future fusion reactors require a safe, steady-state divertor operation. With deep divertor detachment, which is typically induced by impurity seeding, the radiation concentrates in a small region at the X-point or on closed flux surfaces above the X-point. ...

Alternative divertor configurations (ADCs) experiments are carried out in the TCV tokamak and analysed with the support of interpretative SOLPS-ITER simulations. Four different geometrical features are isolated in the outer divertor, and their impact on detachment access and control is tested: • Poloidal connection length • Poloidal flux expansion • Total flux expansion • The presence of a secondary X-point Each of these is expected to facilitate detachment access and control, through different mechanisms,

Holger Reimerdes

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𝑋-Point Target Radiator Regime in Tokamak Divertor Plasmas

Effect of energetic ions on edge-localized modes in tokamak plasmas

Verification of techniques for accelerated and stable SOLPS-ITER simulations including plasma drifts

Interpretation of divertor ion temperature measurements from an attached towards a detached regime

High-power ECH and fully non-inductive operation with ECCD in the TCV tokamak

Impact of divertor closure on power exhaust in Negative Triangularity in TCV

Theory-based scaling laws of near and far scrape-off layer widths in single-null L-mode discharges

Parallel flows as a key component to interpret Super-X divertor experiments

Plasma exhaust and divertor studies in Japan and Europe broader approach, DEMO design activity

Exploring a broad spectrum of design options for DEMO

Parallel convection and E × B drifts in the TCV snowflake divertor and their effects on target heat-fluxes

Sustained fully non-inductive scenarios using pressure and current profile control with ECCD

A Novel Understanding of the Role of Plasma-molecular Kinetics on Divertor Power Exhaust

Detachment in conventional and advanced double-null plasmas in TCV

Experiments and SOLEDGE3X modeling of dissipative divertor and X-point Radiator regimes in WEST

Separatrix Ion to Electron Temperature Ratio in the Tcv and Asdex Upgrade Tokamaks

Neoclassical tearing modes

Overview of T and D-T results in JET with ITER-like wall

The X-Point radiating regime at ASDEX Upgrade and TCV

Assessment of Alternative Divertor Configurations in TCV via experiments and interpretative SOLPS-ITER modelling