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Data Acquisition System and Data Processing for the New Thomson Scattering System on the COMPASS Tokamak
Aftanas, Milan ; Bílková, Petra ; Böhm, Petr ; Weinzettl, Vladimír ; Stöckel, Jan ; Hron, Martin ; Pánek, Radomír ; Scannell, R. ; Walsh, M.
The Thomson scattering (TS) will be one of crucial plasma diagnostics of the COMPASS tokamak. This newly build-up multi-point system consists of two Nd:YAG lasers (1.6J at 1064nm, 30Hz each) and cascade filter polychromators with avalanche photodiodes. It will enable measurements of both the electron temperature Te (20eV − 5000eV ) and density ne (1019 − 1020m−3) profiles with spatial resolution up to 3mm in the vertical direction in 56 spatial points. The uniquely designed complex data acquisition system based on fast analog digital convertors (1GS/s) reflects the need to retrieve/digitize the signal originated from scattering process of the laser pulse lasting less than 10ns. This paper presents a detailed review of the architecture of the control and the data acquisition (DAQ) system and its features. LabViewr will be used as a main layer for the TS data acquisition. Routines specifically written for controlling the DAQ of TS on COMPASS are presented.
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Atomic Beam Probe Diagnostic for COMPASS Tokamak
Háček, Pavel ; Weinzettl, Vladimír ; Stöckel, Jan ; Anda, G. ; Veres, G. ; Zoletnik, S. ; Berta, M.
The COMPASS tokamak has been re-installed in IPP Prague after its transport from Culham in UK. New diagnostic tools are under development to address the scientific program focused on H-mode and pedestal physics. Atomic Beam Probe (ABP) is an innovatory diagnostic for measurement of poloidal magnetic field and plasma current fluctuations in the plasma edge. It is planned to be an extension of the beam emission spectroscopy system by collecting the lithium ions stemming from beam ionization. In the first approximation, ionization is proportional to the local plasma density. The poloidal magnetic field moves the ions toroidally. Therefore, the two-dimensional poloidal-toroidal measurement of the ion current in the exit port reveals information on both the density and magnetic field profiles, thereby also on the edge current profile. This article reviews the concept of the ABP diagnostic and the status of its installation on the COMPASS tokamak.
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Impurity Dynamics in Turbulent Plasma in Tokamak Scrape-off Layer
Seidl, J. ; Krlín, Ladislav
We simulate behavior of plasma impurities in turbulent potential in tokamak scrape-off layer. Assuming low density of impurities we use test particle approach to investigate movement of individual particles in time evolving potential of isolated structure generated by interchange instability. Behavior of the plasma is modeled using reduced fluid model. We compare behavior of test particles under guiding center drift approximation with full-orbit 2D Hamiltonian equations of motion. While we find flow of particles governed purely by ExB drift to be incompressible, including also polarization drift results in compressibility of the flow. Particles traced along their full orbits exhibit the compressibility as well, however, larger in space and different in its amplitude. We therefore conclude that neglecting finite Larmor radius and assuming dynamics based on drift approximation may introduce significant error into simulations of impurity behavior in tokamak SOL.
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