The German funding arrangement for the project was negotiated in 1994, establishing the Greifswald Branch Institute of the IPP in the north-eastern corner of the recently integrated
East Germany. Its new building was completed in 2000. Construction of the stellarator was originally expected to reach completion in 2006. Assembly began in April 2005. Problems with the coils took about 3 years to fix. A three-laboratory American consortium (Princeton, Oak Ridge, and Los Alamos) became a partner in the project, paying €6.8 million of the eventual total cost of €1.06 billion. In 2012, Princeton University and the Max Planck Society announced a new joint research center in plasma physics, to include research on W7-X. The end of the construction phase, which required more than 1 million assembly hours, was officially marked by an inauguration ceremony on 20 May 2014. After a period of vessel leak-checking, beginning in the summer of 2014, the cryostat was
evacuated, and magnet testing was completed in July 2015. The aim for operation phase 1 (OP 1.1), beginning 10 December 2015, was to conduct integrated testing of the most important systems as quickly as possible and to gain first experience with the physics of the machine. On that first day, the reactor successfully produced helium plasma (with temperatures of about 1 MK) for about 0.1s. For this initial test with about 1 mg of
helium gas injected into the evacuated plasma vessel, microwave heating was applied for a short 1.3 MW pulse. More than 300 discharges with helium were done in December and January with gradually increasing temperatures finally reaching six million degrees Celsius, to clean the vacuum vessel walls and test the plasma diagnostic systems. Then, on 3 February 2016, production of the first hydrogen plasma initiated the science program. The highest temperature plasmas were produced by four-megawatt microwave heater pulses lasting one second; plasma electron temperatures reached 100 MK, while ion temperatures reached 10 MK. More than 2,000 pulses were conducted before shutdown. Five poloidal graphite limiters served as the main plasma-facing components during this first campaign (instead of the divertor modules). Experimental observations confirmed 3D modeling predictions that showed heat and particle flux deposition patterns on the limiters in clear correlation with the lengths of the open magnetic field lines in the plasma boundary. Such tests were planned to continue for about a month, followed by a scheduled shut-down to open the vacuum vessel and line it with protective carbon tiles and install a "divertor" for removing impurities and heat from the plasma. The science program continued while gradually increasing discharge power and duration. The special magnetic field topology was confirmed in 2016. Operational phase 1 (OP 1.1) concluded 10 March 2016 and an upgrade phase began. Operational phase 1 continued (OP 1.2) in 2017 to test the (uncooled) divertor. In June 2018 a record ion temperature of about 40 million degrees, a density of 0.8 × 1020 particles/m3, and a confinement time of 0.2 second yielded a record fusion product of 6 × 1026 degree-seconds per cubic metre. During the last experiments of 2018, the density reached 2 × 1020 particles/m3 at a temperature of 20 million degrees. With good plasma values, long-lasting plasmas with long discharge times of 100 seconds were obtained. Energy content exceeded 1 megajoule. In 2021 an analysis of X-ray imaging crystal spectrometer data collected in the 2018 experiment substantially reduced troubling
neoclassical transport heat loss. Collisions between heated particles cause some to escape the magnetic field. This was due to magnetic field cage optimization that was essential in achieving the record results. In 2025 a fuel injector that combined continuous refueling with pulsed heating was tested. Over 43 seconds, 90 hydrogen pellets fired into the plasma at up to 800 metres (2,600 feet) per second heated it to a peak temperature of 30 million C. Energy turnover increased to 1.8 gigajoules over a six-minute run, exceeding the 1.3 gigajoules produced in February 2023. It exceeded the record achieved by the
Experimental Advanced Superconducting Tokamak (EAST) in China in 2025.
Timeline ==Financing ==