Max Planck Institute for Plasma Physics

Overview

The Max Planck Institute for Plasma Physics (Max-Planck-Institut für Plasmaphysik, IPP) is a German research center focused on the physics and technology required to develop nuclear fusion as a viable energy source. As part of the Max Planck Society and an associate of the Helmholtz Association, IPP is one of the largest fusion research centers in Europe. The institute's strategy is distinguished by its dual-pronged approach, simultaneously advancing the two most promising magnetic confinement concepts: the tokamak and the stellarator. This is embodied in its two flagship experiments: the ASDEX Upgrade tokamak in Garching and the Wendelstein 7-X (W7-X) stellarator in Greifswald.

IPP's work is central to the European fusion roadmap, managed under the EUROfusion consortium. The ASDEX Upgrade experiment serves as a critical testbed for developing operational scenarios and components for the international ITER project. Concurrently, the W7-X experiment explores the stellarator as a potentially more stable, steady-state alternative for a future Demonstration Power Plant (DEMO). The institute's research spans theoretical plasma physics, materials science, plasma-wall interaction, heating and diagnostic systems, and reactor design, positioning it as a comprehensive hub for fusion science and engineering.

Physics and Research Approach

IPP's research program is structured around its two major experimental devices, each investigating a different magnetic confinement topology.

Tokamak Research: ASDEX Upgrade

The Axially Symmetric Divertor Experiment (ASDEX) Upgrade is a medium-sized tokamak designed to address physics and engineering questions critical for ITER and DEMO. Its research focuses on achieving stable, high-performance plasmas in a reactor-relevant configuration. A key feature of ASDEX Upgrade is its all-tungsten plasma-facing wall, the same material chosen for the ITER divertor. This allows for detailed studies of plasma-wall interactions with a high-Z material, including tungsten erosion, transport, and redeposition, which are vital for the lifetime of components in a future reactor. According to studies on the device, tungsten concentrations in the core plasma can be kept at acceptably low levels under specific conditions [1].

Operational scenarios for ITER, such as the high-confinement mode (H-mode), are a primary focus. Research on ASDEX Upgrade investigates methods to control or mitigate edge localized modes (ELMs)—violent plasma instabilities that can damage vessel walls—through techniques like resonant magnetic perturbations (RMPs) and pellet pacing. The device also explores high-density plasma regimes that are compatible with a detached divertor, a state where the plasma heat flux to the target plates is significantly reduced through radiation, a necessary condition for DEMO.

Stellarator Research: Wendelstein 7-X

The Wendelstein 7-X is the world's largest and most advanced stellarator. Unlike tokamaks, which rely on a large, inductively driven plasma current for confinement, stellarators generate their confining magnetic field entirely through external coils. This complex, three-dimensional coil system is computationally optimized to minimize neoclassical transport and MHD instabilities, making stellarators inherently immune to disruptive events and well-suited for steady-state operation. W7-X is based on the Helically-Advanced Stellarator (Helias) concept.

The primary scientific goal of W7-X is to demonstrate that this optimized stellarator configuration can confine a high-temperature, high-density plasma with performance comparable to that of a tokamak of similar size, while maintaining steady-state conditions. Initial experimental campaigns have successfully confirmed the predicted reduction in neoclassical energy losses [2]. The long-term program for W7-X involves progressively increasing pulse length and heating power, culminating in 30-minute high-performance plasma discharges. This requires actively cooled plasma-facing components, which were installed during a major upgrade completed in 2022.

Historical Development

IPP was founded in 1960 in Garching, near Munich, as a limited liability company (GmbH) with the Max Planck Society and physicist Werner Heisenberg as its main shareholders. Its initial mission was to explore the potential of controlled nuclear fusion. Early work involved various linear and toroidal pinch devices.

In the 1970s, IPP shifted its focus to the tokamak concept, building the Pulsator device. This was followed by the landmark ASDEX machine, which began operation in 1980. In 1982, researchers on ASDEX, led by Friedrich Wagner, discovered the H-mode, a spontaneous transition to a state of dramatically improved energy confinement [3]. This discovery was a pivotal moment in fusion research, as the H-mode became the standard operating regime for all subsequent high-performance tokamaks, including JET and ITER.

Recognizing the critical challenge of power exhaust, IPP designed and built ASDEX Upgrade, which started operation in 1991. It was specifically designed with a poloidal divertor configuration similar to that planned for ITER, allowing for reactor-relevant studies of plasma-wall interaction and heat exhaust.

Following German reunification, the Greifswald branch of IPP was established in 1994, inheriting the stellarator research program from the former East German Academy of Sciences. This led to the decision to construct Wendelstein 7-X, building on the experience from the preceding Wendelstein 7-AS experiment. Construction of W7-X began in 2005, and it achieved first plasma on December 10, 2015 [4].

Current Status (as of 2026)

As of 2026, IPP continues to operate its two flagship devices at the forefront of global fusion research.

ASDEX Upgrade is a central pillar of the EUROfusion program, conducting experiments directly in support of the ITER research plan. Its operational schedule is tightly coordinated with JET and other European tokamaks to address high-priority physics issues. Current campaigns focus on refining ELM control techniques, developing integrated scenarios for Q=10 operation in ITER, and understanding the physics of plasma detachment with a metallic wall. The device is undergoing continuous upgrades to its heating, diagnostic, and control systems to maintain its role as a leading research platform.

Wendelstein 7-X is in its main experimental phase, focused on exploiting its new actively cooled divertor and wall components. Following the successful restart in 2023, the machine has demonstrated stable operation with significantly increased heating power and energy throughput, achieving plasma energies over 1 gigajoule [5]. The current research campaigns (OP2) are aimed at systematically extending pulse duration towards the ultimate goal of 30 minutes. This involves careful commissioning of the water-cooling circuits and developing robust plasma control strategies for long-pulse operation. The results from W7-X are crucial for assessing the viability of the stellarator line for a future power plant.

Notable Implementations

IPP's primary implementations are its own large-scale experiments, but its influence extends to collaborations and technology transfer.

• ASDEX Upgrade (Garching): As a user facility within the EUROfusion framework, it hosts hundreds of scientists from across Europe each year. Its design choices, particularly the all-tungsten wall and ITER-like divertor, make it an indispensable tool for the mainstream tokamak path.
• Wendelstein 7-X (Greifswald): A global collaboration involving numerous US, Japanese, and European institutions. The US contribution, for example, included key magnetic coil components and diagnostic systems. W7-X represents the state of the art in stellarator design and construction.
• ITER Collaboration: IPP is a major contributor to the ITER project. Beyond the physics research from ASDEX Upgrade, IPP develops and supplies key technologies, including diagnostics like reflectometry and heating systems such as the ion cyclotron resonance heating (ICRH) antennas.
• DEMO Design: IPP is heavily involved in the conceptual design of DEMO, the planned demonstration fusion power plant. This includes contributing to the physics basis, developing models for the plasma core and edge, and designing key components like the tritium breeding blanket.

Open Challenges

Despite significant progress, IPP faces several scientific and engineering challenges that are representative of the broader fusion community's hurdles.

1. Tungsten Wall Integration in Tokamaks: While ASDEX Upgrade has shown that tungsten walls are feasible, managing tungsten accumulation in the plasma core, especially during transient events, remains a challenge. Preventing unacceptable radiation losses from heavy impurities is critical for a burning plasma like ITER's.

2. Steady-State Stellarator Operation: For W7-X, the primary challenge is achieving simultaneous high-performance and true steady-state operation. This requires demonstrating effective control of plasma density and impurities over 30-minute timescales, which has never been done before in a device of this scale. Managing the immense, continuous heat loads on the divertor is the principal engineering obstacle [6].

3. Divertor Power Exhaust: For both tokamaks and stellarators, handling the extreme heat flux to the divertor is arguably the single greatest challenge for a commercial power plant. While ASDEX Upgrade and W7-X are exploring advanced divertor concepts (e.g., detached and island divertors), a fully robust and validated solution that can withstand the neutron environment of a reactor is not yet established. The required heat flux mitigation factor for DEMO is significantly higher than what has been achieved to date.

4. Tritium Breeding and Handling: While not an experimental focus of its current machines, IPP's DEMO design activities must address the challenge of creating a closed tritium fuel cycle. Developing a breeding blanket that can achieve a tritium breeding ratio (TBR) greater than 1 and withstand the harsh reactor environment is a formidable materials science and engineering problem.

Outlook

Over the next 5-15 years, IPP is positioned to make critical contributions toward the realization of fusion energy. The institute's trajectory is closely aligned with the European fusion roadmap.

For the tokamak line, ASDEX Upgrade will continue to serve as a primary support device for ITER, which is expected to begin its first plasma operations within this period. IPP's experiments will focus on preparing for ITER's deuterium-tritium (D-T) phase, testing control strategies and validating physics models that will be essential for maximizing ITER's scientific return. The data from ASDEX Upgrade will be instrumental in finalizing the design of the European DEMO.

For the stellarator line, the next decade represents a make-or-break period. Wendelstein 7-X is expected to systematically push towards its design goal of 30-minute, high-power discharges. Success in these campaigns would provide the first definitive proof that an optimized stellarator can sustain a reactor-grade plasma in steady state, significantly boosting its credibility as a concept for a power plant. A positive outcome from W7-X could lead to the initiation of a dedicated stellarator-based DEMO design effort in Europe.

IPP will also intensify its work on reactor technology and materials science, bridging the gap between plasma physics and fusion engineering. The institute's theoretical and computational physics groups will continue to leverage exascale computing to develop predictive models essential for designing and licensing future fusion devices. Through its dual-pathway strategy, IPP will remain a central and influential institution in the global quest for fusion energy.

References

1. Tungsten transport in the all-W ASDEX Upgrade — Nuclear Fusion (2011)
2. Experimental confirmation of the stellarator optimization in Wendelstein 7-X — Nature Communications (2019)
3. A Regime of Improved Confinement and High Beta in Neutral-Beam-Heated Divertor Discharges of the ASDEX Tokamak — Physical Review Letters (1982)
4. First plasma in the Wendelstein 7-X stellarator — Max Planck Institute for Plasma Physics (2015)
5. Wendelstein 7-X stellarator reaches milestone: one gigajoule energy turnover — Max Planck Institute for Plasma Physics (2023)
6. Overview of the Wendelstein 7-X project — Nuclear Fusion (2015)
7. IPP Annual Report 2022/2023 — Max Planck Institute for Plasma Physics (2024)
8. The European strategy for fusion energy R&D — Fusion Engineering and Design (2021)