GLADIS with anniversary pulse and expanded capabilities
Double success for the heat flux test stand in Garching: On 8 January, the GLADIS team celebrated its 300,000th pulse. And since the beginning of 2026, the Max Planck Institute for Plasma Physics (IPP) facility has been undergoing expansion for high-performance operation with a grant of 3.2 million euros.
There was no champagne flowing on Thursday, 8 January 2026. Instead, the GLADIS control room was filled with the concentrated routine of work. However, on this seemingly normal working day, the entire core team of the heat flux test stand had gathered to witness the facility's 300,000th test pulse. Division Manager Prof. Rudolf Neu was also present when GLADIS Project Manager Dr. Johann Riesch triggered the anniversary measurement at 2:18 p.m.
„Since GLADIS started on 12 January 2005, we have counted every pulse, whether it was on a component, a preliminary test or even just a technical operation,“ says Dr. Riesch. The 300,000th pulse was a preparation for investigations for the US fusion company Commonwealth Fusion Systems (CFS), which is currently building the tokamak demonstrator machine SPARC near Boston. This is intended to generate more fusion energy than is required for heating. As part of a collaboration with the company, the IPP is testing the heat resistance of tiles that are to be installed in the SPARC vacuum vessel.
Preliminary work for the digital twin of SPARC
At the anniversary pulse, GLADIS did not yet test yet an original components for SPARC but rather a test plate with an identical material mixture – a tungsten heavy metal alloy with the elements nickel and iron. The plate was irradiated for ten seconds with a power of five megawatts per square metre. In the process, it heated up to 1180 degrees Celsius. The original component was then examined two weeks later.
These experiments use optical spectroscopy to determine how severe particle erosion could be on the wall tiles during a fusion experiment. Commonwealth Fusion Systems' goal is to create a digital twin of SPARC that can be used to predict tile erosion under high heat loads. „The tests in GLADIS are used to calibrate the digital twin,“ explains Dr Riesch.
Such experiments are the strength of the Garching LArge DIvertor Sample test facility – GLADIS for short. The facility tests materials and components that will later be installed inside fusion reactors in direct contact with hot plasma – where heat loady occur that cannot be realistically simulated in any other way. Unlike more widely used electron beam test stands, GLADIS uses two neutral beam injectors, each with a power output of over one megawatt. Inside the injectors, ions, typically hydrogen ions, are first generated and then accelerated with high voltage. On their way to the component, most of the ions are neutralised and then strike the component as a high-energy neutral particle beam. Upon impact, the kinetic energy is released very homogeneously and with extremely low penetration depth (approximately 100 nanometres) into the surface – conditions similar to real plasma loads. By this power densities of up to 40 megawatts per square metre per injector are achieved. The heat load is similar to that in a rocket engine for space flight. Due to these unique characteristics, GLADIS was awarded the rating „indispensable“ for European fusion research by independent experts as part of the „EUROfusion Facilities Review 2023“.
Realistic material tests for continuous operation in power plants
GLADIS is currently being expanded with additional capabilities that will allow it to better simulate the operating conditions expected in a future fusion power plant. To this end, the facility will be upgraded for high-performance operation within three years. “Currently, we can work with pulses of up to 45 seconds. At high heat fluxes, it is even less,” says project manager Riesch. “In future, at least 30 minutes should be possible.” The upgrade is being funded by the Federal Ministry of Research, Technology and Space (BMFTR) with a total of 3.2 million euros within the project GLADIS HD (Heavy Duty).
GLADIS can thus provide significant support for the transition from fusion research to application. In current basic experiments, wall components are typically designed for plasma discharge times of a few seconds. In power plants, they must withstand high loads over long periods of time. In future, these high-performance components can be tested under realistic conditions in GLADIS. “We will then also measure effects that are not accessible with our current capabilities, such as thermal creep, i.e. the deformation of a material under continuous heat load,” explains Dr Riesch. GLADIS will play a key role in the planned replacement of the current carbon wall in the IPP Stellarator Wendelstein 7-X. The heat flux test stand will qualify the power plant-relevant tungsten components used for continuous operation.
New power supply, improved cooling and more accurate diagnostic systems
GLADIS will also play an important role in the preparation of future neutral beam heating systems for fusion power plants. With more than 300,000 pulses to date, the test stand is the world's longest-operating neutral beam source and can provide important insights for the continuous operation of such systems in power plants. Here, too, the significant increase in pulse time is helpful. Dr. Riesch's team will work closely with the IPP's ITED (ITER Technology and Diagnostics) division, which is developing neutral particle heating technology for the international ITER research facility.
All GLADIS components will be enhanced for the upgrade. This will enable continuous operation as well as much shorter pulse-pause ratios.
The core elements are:
- A new high-voltage power supply: A large share of the budget is allocated to a continuous high-voltage power supply (70 kilovolts). This is the most complex part of the GLADIS conversion. The system will fill the volume of a medium-sized seminar room.
- Improved cooling: As the total heat load increases due to longer pulses, all subsystems and the vacuum vessel must be optimised and equipped with new components.
- A control and diagnostic system capable of continuous operation: Longer operating times increase the requirements for monitoring and data acquisition. To this end, systems are being installed that monitor components in real time and process large amounts of data efficiently.
The three-year expansion will be carried out in three stages. After one year, pulses with a power of 20 megawatts per square metre and a duration of one minute are planned. After three years, 30-minute pulses should finally be possible.
“We are carrying out the entire expansion while continuing normal operations. That is one of the biggest challenges,” explains Dr Riesch. Thus, even during the demanding expansion phase, GLADIS will continue to be available to the world's best fusion facilities for testing.