29th Symposium on Fusion Technology (SOFT 2016)

P4.050 Laser-induced Fluorescence for ITER Divertor Plasma

8 Sep 2016, 14:20

1h 40m

Foyer 2A (2nd floor), 3A (3rd floor) (Prague Congress Centre)

Board: 50

Poster D. Diagnostics, Data Acquisition and Remote Participation P4 Poster session

Speaker

Alexey Gorbunov (NRC Kurchatov Institute)

Description

Laser-induced fluorescence (LIF) diagnostic system on ITER will be used for local measurements of helium density (nHe) and ion temperature (Ti) in the divertor region. The diagnostics is combined with divertor Thomson scattering (DTS) via common laser injection and signal collection optics. Physical aspects of the LIF method for measuring the plasma parameters and the layout of the system elements are in the focus of this work. The LIF method is based on laser pumping of the allowed transition between the excited states of the atom / ion and subsequent registration of the fluorescent radiation of the same or other transition. Dye lasers, optical parametric oscilators (OPO), Ti:Sapphire lasers tunable in the visible and near UV ranges can be used as the pulsed excitation sourses. A Nd:YAG laser with an OPO is preferred for the density measurements (nHe) due to simplicity of its design, broad spectral line and wide operating range (380-1100 nm). Dye lasers allow both extra narrow (3-5 pm) and wide (up to 300 pm) spectrum generation. They can be used in the applications requiring continuous tuning of the laser wavelength (measurements of Ti). A new approach for Ti measurement at one time-point using two synchronized tunable dye lasers will be presented. Multichannel filter polychromators similar to those of DTS will be used to observe the signals on the interesting fluorescent lines. The active LIF signals and background radiation are estimated using the developed collisional-radiative models. The estimations demonstrate the ability to measure nHe with temporal resolution 20 ms and the errors ∆nHe < 20% in both He and DT-regimes. Ion temperature can be obtained from the Doppler broadening. The accuracy of different approaches for the Ti measurements will be estimated.