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Control of FADIS and ECE Line-of-Sight measurements at ASDEX-Upgrade

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Control of FADIS and ECE Line-of-Sight measurements at ASDEX-Upgrade

Rechten: Alle rechten voorbehouden

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Nuclear fusion is seen as one of the future technologies for roducing electrical power. In a hot and con ned plasma deuterium and tritium will melt together and form a helium nucleus and a neutron. This process produces a total of 17.6 MeV energy. In the plasma instabilities occur. Suppression of these local weaknesses in magnetic
con nement is needed. This can be done with Electron Cyclotron esonance Heating, m-wave injection in the center of these islands.

For heating the plasma with ECRH, a Fast Directional switch, FADIS, is inserted for either fast power switching or as frequency band lter in a line-of-sight ECE-setup. The line-of-sight ECE setup is next step in detecting and suppressing weaknesses in magnetic
con nement in the plasma.

Control of FADIS, with dynamic mirror, is needed for both fast power switching and frequency band ltering. The control routine written by TNO Delft requires the parameters of the mirrors and cavity length to be known accurately. In this report one of the main goals is developing a graphical user interface, GUI, with a fit functionality to find these parameters.

The fit routine for finding the cavity length (L0) and the mirror coe cients(rq, r0, r1) are found with the use of Matlab. First the best L0 is found with the matlab fminbnd function. This function searches for a minimum in a Error function by changing the L0 between two boundaries. This Error function uses the least squares method. After finding a value for L0 a similar method is used for nding the other parameters. Because these constants have in uence on each other, they are tted at once with the Matlab function fminsearch.

The developed FADIS GUI with t routine showed promising results with old measurements at the Wendelstein 7-X tokamak in Greifswald. Testing the fit routine on the new measurements at ASDEX-Upgrade tokamak in Garching was not possible due to the short time(80ms) of the calibration shots.

For measuring the location of NTMs Electron Cyclotron Emission is used. The plasma emits m-waves and with a radiometer these waves can be detected. The line-of-sight ECE setup uses the same transmission line as used for ECRH. This makes it easier to construct a control for suppression of the NTMs. But before the ECE signal can be
measured, the high-power from the gyrotron must be ltered out. This is done with FADIS, a Mach-Zehnder lter, two notch lters and a pin-switch.

At the end of April 2012 measurements were performed at the ASDEX-Upgrade tokamak in Garching, Germany. The rst results with the line-of-sight ECE setup showed similar signals as the conventional ECE setup. It was possible to detect NTMs. It can be concluded that the line-of-sight ECE setup is a working technique for measuring the
plasma heat and detecting magnetic islands in the plasma. However further improvement in signal/noise ratio is needed before a complete magnetic island control system can become operational.

Toon meer
OrganisatieDe Haagse Hogeschool
OpleidingTISD Technische Natuurkunde
AfdelingAcademie voor Technologie, Innovatie & Society Delft
PartnersFom Differ
Jaar2012
TypeBachelor
TaalEngels

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