Status of ITER neutron diagnostic development

Abstract

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.

Overview of neutron and confined escaping alpha diagnostics planned for ITER

“…As shown in figure 1, the number of events produced in a 10 mg 238 U chamber behind the blanket might not be sufficient even during a high performance DT shot. A better location, such as inside the divertor cassette where 2 × 10 12 (E n > 13.8 MeV), 10 13 (1 MeV < E n < 13.8 MeV), and 2 × 10 12 (thermal) n cm −2 s −1 ) neutron flux is expected, was proposed recently by Krasilnikov et al [13].…”

“…An in-vacuum type micro-fission chamber has been designed specifically for use in the ITER and various test experiments, including radiation tests, have been performed [14]. A high performance 238 U fission chamber with 1.5 g of 238 U was also developed [13]. A 1.5 g 238 U chamber combined with current or Campbelling mode electronics may provide a megahertz response during a DT shot of fusion output higher than 10 MW if installed inside the divertor cassette.…”

“…Additional viewing chords (#7-#10) were proposed recently by Krasilnikov et al [13]. As the outer region can only be seen by detectors much closer to the plasma, the pivot points should be near the plasma edge and the detectors should be installed inside the port plug.…”

“…To obtain the two-dimensional tomography of the neutron/alpha birth profile, and to distinguish the non-uniformity on the MFS, the divertor vertical neutron camera (DVNC) was proposed by Krasilnikov, Walker et al [13,15]. The concept of DVNC is shown in figure 3.…”

“…Gamma-ray spectroscopy placed on the first wall using the 10 B(α, pγ ) 13 C reaction was proposed by Kiptily et al The geometry for detection has not yet been examined.…”