Scientists at the Max Planck Institute in Germany have fired up the revolutionary Wendelstein 7-X stellarator, the world’s largest nuclear fusion device of its type, to a temperature of 80 million degrees Celsius and have successfully produced and sustained its first flash of hydrogen plasma.
Operation of Wendelstein 7-X started on December 10, 2015 and it has generated more than 300 discharges with the rare gas, helium. The primary purpose of these helium discharges is to clean the plasma vessel walls, which in turn would help plasmas to attain temperature of up to six million degrees. During this period, plasma heating and data recording were also tested and the measuring facilities for investigating the plasma were put into operation with complex instrumentation such as X-ray spectrometers, interferometers, laser scattering and video diagnostics. Having done this, their trial runs with helium plasma became a success. This was the first time Wendelstein 7-X was shown to produce and sustain plasma gas.
“This makes everything ready for the next step”, Professor Dr. Thomas Klinger, Project Head for Wendelstein 7-X said in a press release. “We are changing from helium to hydrogen plasmas, our proper subject of investigation.”
As a matter of fact, generating hydrogen plasma is far more difficult than producing and sustaining helium plasma. So even if today’s experiment produced and sustained hydrogen plasma even for a little time in terms of milliseconds, we are one step closer to achieving the clean and limitless energy of nuclear fusion.
Well, the first hydrogen plasma which was switched on by the German Chancellor Angela Merkel, who herself has a doctorate in physics, marks the start of scientific operation of this Wendelstein 7-X nuclear fusion device. A 2-megawatt pulse of microwave heating transformed a tiny quantity of hydrogen gas into an 80 million degrees Celsius low-density hydrogen plasma.
Of course to initiate a fusion process, this much of temperature is needed, or else, hydrogen atoms wouldn’t be energetically excited and there wouldn’t be formation of any plasma cloud.
There is also a separation of the electrons from the nuclei of the hydrogen atoms. Wendelstein 7-X’s superconducting magnetic cage keeps the charged particles levitate without making contact with the walls of the plasma chamber, because in order to make sure the plasma sustained, charged particles must not be in contact with the cold walls of the reactor. So, once the reactor reaches its required temperature, which is 80 million degrees Celsius in this case, the quantum mechanical phenomenon known as quantum tunnelling comes into play; that is – the hydrogen particles tunnel through a barrier and begin to collide and fuse, which in turn releases energy and forms heavier elements.
“With a temperature of 80 million degrees and a lifetime of a quarter of a second, the device’s first hydrogen plasma has completely lived up to our expectations,” said Dr. Hans-Stephan Bosch, whose division is responsible for operation of Wendelstein 7-X.
Researchers will carry on their experiment with hydrogen plasma till the mid of March. The plasma vessel will then be opened for installation of carbon tiles to protect the vessel walls and “divertor” to eliminate impurities inside the reactor vessels. Moreover, they are planning successive extensions until, in about four year and with it, they hope discharges lasting 30 minutes can be produced with full heating power of 20 megawatts.
“These facilities will enable us to attain higher heating powers, higher temperatures, and longer discharges lasting up to ten seconds,” explained Thomas Klinger.
Wendelstein 7-X, the world’s largest stellarator-type fusion device, is not actually designed to produce any usable energy. The purpose of this fusion reactor is to simply recreate the process that powers our Sun. Furthermore, researchers want to put the quality of the plasma confinement equally as that of a tokamak for the very first time.