The Wendelstein 7-X concept proves its efficiency – Florida News Times

One of the most important optimization goals underlying the Wendellstein 7-X fusion device at the Max Planck Institute of Plasma Physics (IPP) in Greifswald has been identified.Journal IPP Scientist Analysis Nature Show: With an optimized magnetic field cage, plasma energy loss is reduced in the desired way. Wendelstein 7-X aims to overcome the shortcomings of early stellarators and to prove that stellar type devices are suitable for power plants.

The optimized Wendelstein 7-X Stellarator, which went into operation five years ago, aims to demonstrate that a stellar fusion plant is suitable for a power plant.Magnetic field surrounding Hot plasma It was then planned with great theoretical and computational effort to keep it away from the vessel wall and avoid the disadvantages of early stellarators. One of the most important goals is energy Plasma loss caused by magnetic field ripple. This causes the plasma particles to drift outward and be lost despite being constrained by the lines of magnetic force.

Unlike competing tokamak devices, where this so-called “neoclassical” energy and particle loss is not a major issue, this is a serious weakness of traditional stellarators. This makes the power plant designed on this basis very large and therefore very expensive, as the loss increases significantly as the plasma temperature rises.

On the other hand, in tokamak, the loss due to magnetic field ripple is negligible due to the symmetrical shape. Here, energy loss is mainly determined by the movement of small vortices in the plasma, turbulence. Turbulence is also added as a stellarator loss channel. Therefore, reducing neoclassical loss in order to catch up with the good confinement properties of tokamak is an important task for stellarator optimization. Therefore, the Wendelstein 7-X magnetic field is designed to minimize these losses.

In a detailed analysis of the Wendelstein 7-X experimental results, scientists led by Dr. Craig Beidler of the IPP’s Stellar Theory Division investigated whether this optimization had the desired effect. With the heating equipment available so far, the Wendelstein 7-X was already able to generate hot plasma and set a stellarer world record for “fusion products” at high temperatures. This product of temperature, plasma density, and energy confinement time indicates how close you are to the value of the burning plasma.

Such recordable plasmas are currently being analyzed in detail. With high plasma temperature and low turbulence loss, the neoclassical loss of energy balance can be fully detected here. These account for 30% of the heating power, which is a significant part of the energy balance.

The effect of the Wendelstein 7-X neoclassical optimization has been demonstrated by a thought experiment. It was assumed that the same plasma values ​​and profiles that produced record results with the Wendelstein 7-X were achieved in plants with unoptimized magnetic fields. .. Then the expected neoclassical loss was calculated there. Clear results were obtained. These losses are greater than the physically impossible input heating power. “This shows that the plasma profile observed at Wendelstein 7-X can only be considered in magnetic fields with low neoclassical loss. Conversely, this proves Wendelstein’s optimization. increase. magnetic field It successfully reduced the loss of neoclassicalism. “

However, plasma discharges have only been short so far. Water-cooled wall coverings are currently installed to test the performance of the Wendelstein concept in continuous operation. Researchers equipped in this way will gradually work to a plasma that is 30 minutes long. Next, you can see if the Wendelstein 7-X can meet its optimization goals with continuous operation, which is the main advantage of Stellarator.

Background

The purpose of fusion research is to develop climate- and environment-friendly power plants. Like the Sun, it is the generation of energy from the fusion of atomic nuclei. Fusion fires only ignite at temperatures above 100 million degrees Celsius, so fuel (low density hydrogen plasma) must not come into contact with the walls of cold vessels. It is held by a magnetic field and floats almost non-contact in a vacuum chamber.

The Wendelstein 7-X magnetic cage is created by a ring of 50 superconducting magnetic coils. Those special shapes are the result of advanced optimization calculations. With their help plasma Confinement Stellarator Reaching the level of competing tokamak facilities.