Concept Design and Integration Aspects of ITER Radial Neutron Camera L. Bertalot1, A. Encheva1, Y. Kashchuk1,2, S. Jakhar1, J.M. Drevon1, T. Giacomin1, M.-F. Direz1, K.M. Patel1, A. Prakash1, S. Simrock1, V. Udintsev1, C.I. Walker1, M. Walsh1, A. Rakhmanov2, F. Lucca3, A.Marin3, M. Roccella3 A. Suarez1, R. Reichle1 and ITER Team 1
ITER Organisation, Route de Vinon sur Verdon, 13115 Saint Paul Lez Durance, France Institution “PROJECT CENTER ITER”, 1, Akademika Kurchatova pl., Moscow 3 L.T.Calcoli SaS, Piazza Prinetti 26/B, 23807 – Merate (LC), Italy 2
The Radial Neutron Camera (RNC) is a multichannel neutron collimator intended to characterize fusion plasma neutron sources. The ITER RNC diagnostic will measure the time-resolved neutron emission profile, providing the evaluation of the fusion power density and α-source emissivity profile, ion temperature profile and others parameters. Knowledge of the spatial and energy distribution of the fast ions is also important for optimizing fusion burn control, Alfvén eigenmode control, and the auxiliary fusion plasma heating systems like Neutral Beam and ICRF. The RNC consists of two fan-shaped arrays of collimators that view the plasma through a vertical slot in the blanket shield module of Equatorial Port plug#1. The sight lines intersect at a common aperture defined by the port plug and penetrate the vacuum vessel through stainless steel windows, cryostat, and biological shield. Each flight tube culminates in a set of neutron detectors chosen to provide the required range of sensitivity, as well as time and energy resolution. Compact neutron spectrometers (CVD diamond detectors and organic scintillators) with fast response will be applied for neutron flux characterization. The spatial plasma coverage in the vertical direction is limited because of the port height. Additional sight lines with collimators and detectors mounted in the port plug are included to give measurements in the outer edge regions of the plasma. Together with the RNC, five other diagnostics systems are installed in the same port plug. Among all customers in this port, the RNC is the most bulky diagnostic. In order to rationalize the integration of diagnostics in the equatorial port plugs and standardize the interfaces with other diagnostics components, a new approach of installing the components in vertical drawers, has been proposed. The design and integration of all RNC components is an important engineering activity. This paper outlines the engineering challenges of the ITER Radial Neutron Camera, in particular: tight space due to the many customers in Equatorial Port #1, need for a vertical cut-out for all sight lines covering the total height of the port plug, cooling of the in-port as well of the external detectors, integration of the heavy collimator part with the Port Interspace and the Port Cell areas, and the RNC maintenance scheme with associated remote handling operations, electrical connections, and vacuum containment constraints. Besides all those integration challenges, the electromagnetic, thermal and seismic loads are the main design driver for the system. Keywords: ITER, diagnostics, neutron diagnostics, interfaces, integration
1. Introduction This paper reports the conceptual design results of Radial Neutron Camera (RNC) for ITER [1]. The first concept of RNC was proposed in ref. [2]. Further work was carried out in references [3], [4] & [5]. ITER project has now entered into a practical phase of diagnostic integration into machine when one need to take into account the requirements of engineering services, infrastructure and interfaces with other ITER subsystems such as vacuum, cooling, remote handling etc. Particularly in this paper, special attention was given to the neutron induced activation by streamed neutrons through RNC slots which have impact on the shut-down dose rate in the Port Interspace. This is a major challenge for designers: on the one hand it is necessary to reduce the induced activation levels from 1 mSv/h down to an acceptable level below 100 Sv/h and on the other hand, there is a limitation on the weight load on the Interspace and Port Cell Support Structures. In general, the RNC design optimization is a scope of preliminary design phase, nevertheless in the present paper we are considering approaches to RNC design, which shall help to meet system requirements and be in compliance with other machine systems. Synergy of RNC data with other neutron diagnostics can reduce the measurement error in fusion power with high time resolution. This is especially important in the ITER scenario where fusion power measurement plays the role of machine protection and RNC is a backup diagnostic _______________________________________________________________________________ author’s email:
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for it. By using compact neutron spectrometers such as CVD diamond detectors and organic scintillators, measurement of the spatial distribution of the ion temperature in the center of the plasma core and determination of fuel ratio is also possible. System requirements for RNC include wide plasma coverage a/r < 0.85, time resolution 1 ms for neutron emission profile, and 100 ms for ion temperature profile.
2. System Description ITER RNC is composed of two fan-shaped collimating structures: In-Port and Ex-Port. RNC lines-of-sight (LOS) are uniformly distributed: 20 channels of Ex-Port system look at the plasma core and 8 channels of In-Port system look at the plasma edge and providing plasma coverage up to a/r~0.85. The in-port RNC system (Figure 1) is located inside port plug and it has 2 removable cassettes with 4 collimators in each cassette to observe plasma edge (0.6
