On 10th December, the day had arrived: the operating team in the control room started up the magnetic field and initiated the computer-operated experiment control system. It fed around one milligram of helium gas into the evacuated plasma vessel, switched on the microwave heating for a short 1,3 megawatt pulse – and the first plasma could be observed by the installed cameras and measuring devices.
The helium discharges served primarily to clean the plasma vessel. The cleaner the vessel wall, the more the plasma temperature increased, finally attaining six million degrees.
In addition, plasma heating and data recording were tested, and the first measuring facilities for investigating the plasma were put into operation, such as X-ray spectrometers, interferometers, laser scattering and video diagnostics.
Then everything was ready for the next step – changing from helium to hydrogen plasmas, the proper subject of investigation.
The first hydrogen plasma, which was switched on on 3 February 2016 at a ceremony attended by numerous guests from the realms of science and politics, marked the start of scientific operation of Wendelstein 7-X. It reached a temperature of 80 million degrees and a lifetime of a quarter of a second.