29th Symposium on Fusion Technology (SOFT 2016)

P4.058 Hardware solutions for ITER divertor thomson scattering

8 Sep 2016, 14:20

1h 40m

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

Board: 58

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

Speaker

Eugene Mukhin (Ioffe Institute)

Description

ITER Divertor Thomson scattering (DTS) was discussed in a number of presentations and papers. The development of diagnostic equipment for ITER DTS is under way and coming to its conclusion. Choice and justification of lasers and polychromator design as well as first mirror protection are the focus of the presentation. Q-switched Nd:YAG laser for DTS in ITER (1.064mm, 2J, 50Hz, 3ns) is implemented. To minimize the energy loss caused by divergence, the near field image must be transmitted to the first laser mirror requiring the uniform energy distribution acrossthe laser footprint. Expecting that laser diode pumping instead of flash-lamp will improve the near-field energy distribution as well as considerably increase its service life, the diode-pumped version of the laser is under development. Compact and powerful DTS acquisition system (5 MS/s, 12 bit) is prepared to embed the digitizer into DTS spectrometers. The chief reasons for this are: fiber input with TS signal and fiber output with digitized signals protect from electromagnetic interferences; does not require additional cooling for low power electronics, providing more reliable operation and compact design than in previous polychromators; an order higher sample rate (5 MS/s instead of 500 MS/s) allows using oscilloscopic mode for nanosecond laser pulse measuring; considerably lower ADC cost saves the diagnostic budget. Good progress was achieved in the development of optics protection. Specifically shaped diagnostic channel was suggested to prevent beryllium deposition caused by hydrodynamic fluxes. This approach was verified on simulators of dynamic loads on ITER divertor - Magnum, Pilot and QSPA. RF plasma cleaning of metal deposits was thoroughly investigated. Common approach, which can be routinely used in ITER by all optical diagnostics is under development. The DTS on Globus-M at Ioffe Institute commissioning will provide demonstration and testing of the equipment performance and technical solutions developed for ITER DTS.