Abstract <p>The complex of neutral particle analyzers is included in the priority group of diagnostic systems of the ITER tokamak that is under construction. A critical element that ensures operation of the neutral particle analyzers is a stripping target, which is a thin carbon foil with a thickness of 10–20 nm and a diameter of 20&#xa0;mm, in which the neutral particle flux entering the instrument is ionized. The particle detection efficiency and the accuracy in determining the ratio of fuel ion concentrations in a plasma depend on parameters of the stripping target. A visual control system has been developed for fast determination of the mechanical integrity of stripping targets without vacuum disturbance, and results of its testing are presented. This system is based on a radiation-resistant D40M inspection camera (produced by AO Diakont) and is able to detect individual point defects in foil cells with dimensions of 0.35 × 0.35 mm<sup>2</sup>. The work is focused on the radiation resistance of the system elements most sensitive to the intense neutron background of the ITER facility, i.e., to the D40M camera and LEDs of a module used for background illumination of the stripping foil. These elements have been irradiated by a fast-neutron beam with energy as high as 14 MeV. It is shown that the video camera modified according to the test results, as well as gallium nitride-based commercially available LEDs irradiated to 1&#xa0;MeV (Si) equivalent neutron fluence of 3 × 10<sup>14</sup> and 10<sup>15</sup> cm<sup>−2</sup>, respectively, retains its performance when used as part of the visual control system. As a result, the system is capable of functioning throughout the operational lifetime of the ITER tokamak.</p>

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Visual Control System for Stripping Foils of Neutral Particle Analyzers at the ITER Tokamak: Development and Testing

  • V. I. Afanasyev,
  • S. S. Kozlovsky,
  • A. D. Melnik,
  • M. I. Mironov,
  • A. N. Mokeev,
  • A. S. Navolotsky,
  • V. G. Nesenevich,
  • M. P. Petrov,
  • S. Ya. Petrov,
  • F. V. Chernyshev

摘要

Abstract

The complex of neutral particle analyzers is included in the priority group of diagnostic systems of the ITER tokamak that is under construction. A critical element that ensures operation of the neutral particle analyzers is a stripping target, which is a thin carbon foil with a thickness of 10–20 nm and a diameter of 20 mm, in which the neutral particle flux entering the instrument is ionized. The particle detection efficiency and the accuracy in determining the ratio of fuel ion concentrations in a plasma depend on parameters of the stripping target. A visual control system has been developed for fast determination of the mechanical integrity of stripping targets without vacuum disturbance, and results of its testing are presented. This system is based on a radiation-resistant D40M inspection camera (produced by AO Diakont) and is able to detect individual point defects in foil cells with dimensions of 0.35 × 0.35 mm2. The work is focused on the radiation resistance of the system elements most sensitive to the intense neutron background of the ITER facility, i.e., to the D40M camera and LEDs of a module used for background illumination of the stripping foil. These elements have been irradiated by a fast-neutron beam with energy as high as 14 MeV. It is shown that the video camera modified according to the test results, as well as gallium nitride-based commercially available LEDs irradiated to 1 MeV (Si) equivalent neutron fluence of 3 × 1014 and 1015 cm−2, respectively, retains its performance when used as part of the visual control system. As a result, the system is capable of functioning throughout the operational lifetime of the ITER tokamak.