WENDELSTEIN 7-X

Figure 1:Max-Planck Institut in Greifswald (Germany)

The history of WENDELSTEIN 7-X
WENDELSTEIN 7-X Parameters
WENDELSTEIN 7-X Milestones
WENDELSTEIN 7-X Objectives

The History of WENDELSTEIN 7-X

Figure 2:WENDELSTEIN 7-X Sector

WENDELSTEIN 7-AS at IPP Garching was the first experiment of the new generation of "Advanced Stellarators", testing for the first time, the improved magnetic field configuration observed in these devices. In parallel, the Stellarator Theory Group at the Association EURATOM-IPP Garching (Germany) has been investigating for more than ten years the whole area of possible stellarator configurations and developed the fully optimised magnetic field for the follow-up device WENDELSTEIN 7-X. Its quality of plasma equilibrium and confinement will be on a par with that of a tokamak. The WENDELSTEIN 7-X stellarator, now being built at the Greifswald Branch of IPP, is thus able to demonstrate the power plant relevance of the "Advanced Stellarators". The European Union, the German Government and the state of Mecklenburg-Vorpommern provide the funding of WENDELSTEIN 7-X. The first contracts for the experiment components were placed with industry in 1996. The manufacture and testing of prototype components in support of the machine design is finished. In cooperation with IPF (University of Stuttgart) and a European company, Research Center Karlsruhe will develop and build the complete microwave heating system for WENDELSTEIN 7-X. The device is scheduled for operation in 2010. In contrast to tokamaks, stellarators confine the plasma without using the magnetic field internally generated from the plasma current, i.e. they use a field generated solely by external magnet coils. This makes stellarators highly suitable for steady-state operation.

Figure 3:WENDELSTEIN 7-X Inside

WENDELSTEIN 7-X Parameters

Plasma Major Radius	5.5 m
Plasma Minor Radius	0.35 m
Magnetic Field	3 T
Discharge time	< 30 minutes steady state with microwave heating
Plasma	hydrogen / deuterium
Plasma volume	30 m3
Plasma heating power	15 MW
Additional heating power (PAux)	5 MW NBI 1.5 MW ECRH
Plasma density	Up to 3 x 1020 particles/m3
Plasma temperature	Up to 100 million degrees

Figure 4:Fabrication of coils

WENDELSTEIN 7-X Milestones

1994	IPP Branch in Greifswald was founded.
1996	European experts' reports were finished, Phase 2: cost and manpower assessment: commitment of financing by the European Commission. First contracts for experiment components were placed with industry. Manufacture and testing of prototype components in support of the machine design is finished.
1998	First major order - for the 50 superconducting magnet coils - was awarded.
1999	WENDELSTEIN 7-X test magnet coil reaches superconducting condition in the TOSKA test facility at the Forschungszentrum Karlsruhe; tests completed.
2000	Tests of the Demo-Cryostat successfully completed.
2001	Production of the superconducting magnet coils launched.
2010	The device will be commissioned, the magnetic field will be mapped, and the scientific operation is foreseen to start.

Figure 5:Plasma (yellow) in the
magnetic coil (blue)

WENDELSTEIN 7-X Objectives

The WENDELSTEIN 7-X experiment comprises the stellarator device (magnet coils, cryostat, plasma vessel, and divertor), the plasma heating systems (using microwaves and fast neutral particles), the supply facilities (electric power and cooling), machine control, and diagnostics. Its objective is to prove the power plant relevance of advanced stellarators. Energy and particle confinement will be investigated in an optimized magnetic configuration and the stationary operation of a power plant relevant divertor system will be demonstrated. After an intensive R&D programme the project is in the phase of procurement of the main components - magnet system, the cryostat, power supplies, and various tools for the assembly.
The centrepiece of the experiment is the coil system composed of 50 non-planar, superconducting magnetic field coils. They will allow WENDELSTEIN 7-X to demonstrate the essential stellarator property, steady-state operation. The magnetic field cage produced will confine a plasma with temperatures up to 100 million degrees. WENDELSTEIN 7-X should thus be capable of yielding convincing proof of the power plant properties of stellarators, without actually producing an energy-yielding plasma. As the properties of an ignited plasma in tokamaks can be largely extended to stellarators, the experiment can dispense with the use of the radioactive fusion fuel, tritium, at great saving.