ASDEX Upgrade

ASDEX Upgrade is, compared to other international tokamaks, a midsize tokamak experiment. Its operation started in 1990 and it successes ASDEX, which was in operation from 1980 until 1990. Its name is derived from Axial Symetric Divertor EXperiment. Like ASDEX, ASDEX Upgrade has a poloidal divertor, which was optimized to meet the requirements of a future fusion reactor. In order to get an overview of the experiment, the global parameters are listed here.

technical data:
Total height of the experiment	9 m
Total radius over all	5 m
Weight of the experiment	800 t
Material of the first wall	tungsten coating on carbon
Number of toroidal field coils	16
Number of poloidal field coils	12
Maximum magnetic field	3.1 T
Plasma current	0.4 MA - 1.6 MA
Pulse duration	< 10 s
Time between pulses	15 - 20 min
Amount of data / pulse	in 1999 0.5 GB, now 4GB raw data + analysed data
Plasma heating:	up to 27 MW
Ohmical heating	1 MW
Neutral beam injection heating	20 MW (with 2H = D)
Injection energy	60 keV and 100 keV
Ion-Cyclotron heating	6 MW (30 MHz - 40 MHz)
Electron-Cyclotron heating	2 x 2 MW (140 GHz)

Typical plasmas properties

The plasma is controlled through a system of 12 vertical field coils und kept in its elliptical shape with an X-point above the bottom divertor. The purely toroidal field is usally kept constant during the entire discharge. Nevertheless it can also be varied during the discharge to some degree, if the physical requirements need such a field variation. Additionally there are two vertical field coils close to the plasma for a fast control of the plasma.

 

Cross section of ASDEX Upgrade with the new divertor II. The vertical field coils which can be clearly seen are located outside of the toroidal field coils far away from the plasma and control the plasma shape and position.

The described set of coils is controled in real-time by a control computer. This computer calculates through a large number of measurement coils the actual values from the plasma position and plasma shape and corrects the currents in the field coils in order to achieve the desired values. In the following table typical values for a plasma are shown.

 

typical plasma parameters:
Major plasma radius R0	1.65 m
Minor horizontal plasma radius a	0.5 m
Minor vertical plasma radius b	0.8 m
Ellipticity b/a	1.8
Triangularity (top/bottom)	0.1 / 0.3, since 1999: 0.4 / 0.4
Plasma types	deuterium, hydrogen, helium
Plasma volume	14 m3
Plasma mass	3 mg
Electrondensity	1 x 1020 m-3
Plasma temperature	60 to 100 million degree