High sensitivity imaging Thomson scattering for low temperature plasma

A highly sensitive imaging Thomson scattering system was developed for low temperature ͑0.1-10 eV͒ plasma applications at the Pilot-PSI linear plasma generator. The essential parts of the diagnostic are a neodymium doped yttrium aluminum garnet laser operating at the second harmonic ͑532 nm͒, a laser beam line with a unique stray light suppression system and a detection branch consisting of a Littrow spectrometer equipped with an efficient detector based on a "Generation III" image intensifier combined with an intensified charged coupled device camera. The system is capable of measuring electron density and temperature profiles of a plasma column of 30 mm in diameter with a spatial resolution of 0.6 mm and an observational error of 3% in the electron density ͑n e ͒ and 6% in the electron temperature ͑T e ͒ at n e =4ϫ 10 19 m −3 . This is achievable at an accumulated laser input energy of 11 J ͑from 30 laser pulses at 10 Hz repetition frequency͒. The stray light contribution is below 9 ϫ 10 17 m −3 in electron density equivalents by the application of a unique stray light suppression system. The amount of laser energy that is required for a n e and T e measurement is 7 ϫ 10 20 / n e J, which means that single shot measurements are possible for n e Ͼ 2 ϫ 10 21 m −3

Status of ITER neutron diagnostic development

Due to the high neutron yield and the large plasma size many ITER plasma parameters such as fusion power, power density, ion temperature, fast ion energy and their spatial distributions in the plasma core can be measured well by various neutron diagnostics. Neutron diagnostic systems under consideration and development for ITER include radial and vertical neutron cameras (RNC and VNC), internal and external neutron flux monitors (NFMs), neutron activation systems and neutron spectrometers. The two-dimensional neutron source strength and spectral measurements can be provided by the combined RNC and VNC. The NFMs need to meet the ITER requirement of time-resolved measurements of the neutron source strength and can provide the signals necessary for real-time control of the ITER fusion power. Compact and high throughput neutron spectrometers are under development. A concept for the absolute calibration of neutron diagnostic systems is proposed. The development, testing in existing experiments and the engineering integration of all neutron diagnostic systems into ITER are in progress and the main results are presented. © 2005 IAEA, Vienna