Density fluctuation measurements at ASDEX Upgrade

01.01.2011 - 31.12.2013
Research funding project
ASDEX Upgrade is a medium sized divertor tokamak (R = 1.65 m, a = 0.5 m) at MPI Garching with an elongated cross-section, flexible shaping capability, versatile heating and current drive systems. Since 2008 all plasma facing components of ASDEX Upgrade are covered by tungsten. The goal of the ASDEX Upgrade program is to give physics input to critical elements of the ITER design and the preparation of ITER operation. The H-mode is the standard scenario for ITER and is therefore essential for the success of ITER. Key factors of the core like temperature, confinement, etc, depend highly on plasma edge properties. Therefore diagnostics to determine plasma edge parameters i.e. electron density and temperature with high temporal and spatial resolution are crucial to improve the understanding of the plasma edge physics. ASDEX Upgrade is well equipped for characterizing the edge and up to now the lithium beam diagnostic routinely delivers electron density edge profiles. Within the proposed project several experimental upgrades to the lithium beam diagnostic at ASDEX Upgrade are planned. The planned upgrades include (a) a new optical head to provide a toroidal view of the lithium beam, while the two existing optical heads view the beam from the top and the bottom, respectively in the poloidal plane. (b) a new data acquisition system to replace the old one to increase the sampling rate. (c) additional deflection plates to deflect the lithium beam vertically, which enables poloidal flow velocity measurements via quasi-twodimensional lithium beam emission spectroscopy. Once the upgrades are installed, we will attempt to measure (i) electron density fluctuations ne, (ii) poloidal flow velocity vpol and (iii) plasma edge current j(r). Both optics, the new and the old one, can be used to determine ne fluctuations using the new data acquisition system. For the vpol measurements the additional deflection plates allows us to measure the poloidal velocity via cross correlation. Additionally it should be tested for the first time if sodium (Na) instead of lithium (Li) improves the density fluctuation and poloidal velocity measurements due to the shorter lifetime of the Na I (3p-3s) transition. The position of the new optical head is optimal to allow edge current measurements. It is planned to measure the direction of the magnetic field via the ratio of the π- and σ-intensities from the Zeeman splitting. From the direction of the magnetic field it is possible to determine the edge current via Ampere’s law. The wavelength resolution of a Fabry-Perot interferometer should be sufficient to resolve the Zeeman components. The project is planned for a duration of two years starting in Jan 2011.

People

Project leader

Project personnel

Institute

Grant funds

  • Vereine, Stiftungen, Preise Type of funder Vereine, Stiftungen, Preise Specific program Friedrich Schiedel Stiftung für Energietechnik

Research focus

  • Climate Neutral, Renewable and Conventional Energy Supply Systems: 30%
  • Surfaces and Interfaces: 70%

Keywords

GermanEnglish
Plasmadiagnostikplasma diagnostics
KernfusionNuclear fusion
Elektronendichteelectron density

External partner

  • Max Planck Institut für Plasmaphysik Garching

Publications