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Eddy current induced electromagnetic (EM) loads during plasma events are the design driver for ITER port plug (PP) structure, diagnostic first wall (DFW), shield module (DSM) and diagnostic system supported by the PP structure. Generic models using commercial software OPERA, MAXWELL and ANSYS are developed and benchmarks are performed for global EM analysis to obtain port-specific design driving EM loads. The 20 degree vessel sector models of the upper and equatorial PP structure take the same ITER TF, CS and PF coil and plasma current (15 MA baseline plasma scenario) as input, then solve for eddy current induced on all passive structural components for various DINA disruption cases. The worst load case can be exponential decay or linear decay of plasma current depending on the dimension and location of diagnostic components inside the PPs. Static and transient magnetic fields from generic models are mapped onto an excel datasheet to establish component design load specification. Three levels of modeling effort are suggested. The global model analysis is used to validate the impact of component design to the PP global system response as well as to study its component dynamic effect as a result of the disruption loads on the PP structure. The local sub-model analysis can be used to extract more accurate EM loads on diagnostics and the excel datasheet of static and transient field maps are used as the initial design load specification for in-port components.

There will be 50 diagnostic systems installed on ITER. All have been implemented with great success on experimental fusion reactors around the world. Despite this deep experience, implementation of diagnostic systems on ITER remains very challenging. Structural, nuclear and optical engineering challenges arise from loads that are at least an order of magnitude higher and last for much longer than any previous experiment. Complicating this challenge is an acceleration of the design process because the systems delivered to ITER must be ready for full power D-T operations from day-One. Talented engineering teams around the world are tackling these challenges in many innovative ways. In this paper ITER diagnostic systems from the US will be used to show a selection of examples of how the “D-T Ready” engineering challenges are being answered.

According to ITER integration procurement arrangements, the installment of diagnostics in a port should not increase the shutdown dose rate (SDDR) in the port interspace area by no more than ~50 microSv/hr above the baseline, assuming another 50 microSv/hr is attributed to contribution from the port structure and other ITER in-vessel components, such that the upper SDDR limit of 100 microSv/hr is not exceeded 106 s after shutdown. It was found that placing the initial design of the Motional Stark Effect, MSE, and the Charge Exchange Recombination Spectroscopy, CXRS, in the equatorial port #3 (EPP3) resulted in an increase in the SDDR that far exceeded the limit. When we follow the optimization process discussed in this paper, substantial reduction in the port interspace SDDR was achieved. The results of the present work show that even when we combine the optimized CXRS and MSE diagnostics with a third GDC diagnostic, the excess of the SDDR over the baseline value did not exceed the allowed upper limit. The present work is based on utilizing the 3-D CAD-based Attila code for assessing the SDDR.

ITER diagnostic port plugs perform many functions including structural support of diagnostic systems under high electromagnetic loads while allowing for diagnostic access to the plasma. During plasma disruptions, a large amount of induced current flows locally at electrical contacts between diagnostic first walls (DFWs) and the diagnostic shield modules (DSMs). Even a small gap voltage (10-30V) between DFWs, DSMs and supporting rails may trigger local arcing and cause arc damage to the conducting structure. This is particularly true when we consider the ionized gas environment and halo current effect. We perform global electromagnetic analysis with contact details for DFWs and DSMs to quantify the gap voltage and local current transfer effect during plasma disruptions. Electrical contacts between the DFWs and DSMs may also have significant impact on disruption load and thus affect design of the DFW attachment scheme. Large current transfer (>100 kA) between DFWs and DSMs through the attachment keys and tabs during disruption implies local heating and potential welding. This paper reviews the contact current and electrical potential difference between the DFWs, DSMs and the port plug structure. We also assess the impact on the system design itself due to electrical contact among various components.

ITER will incorporate In Vessel Coils (IVCs) as a method of stabilizing “Edge Localized Modes” (ELM) and providing “Vertical Stabilization” (VS). To meet the ELM and VS Coil requirements strong coupling with the plasma is required so that it is necessary for the coils to be installed in the vessel just behind the blanket shield modules. Due to this close proximity to the plasma the radiation and temperature environment is severe and conventional electrical insulation materials and processes cannot be used. The development of mineral insulated conductor technology has been required in the IVC design to deal with this high radiation and high temperature environment. While mineral insulated conductor technology is not new, building a large magnet with high current carrying capability and a conductor diameter larger than the mineral insulated conductor currently manufactured requires R&D and the extension of existing technologies. A 59mm Stainless Steel Jacketed Mineral Insulated Conductor (SSMIC) using MgO is being developed for this application. The IVC ELM and VS coils design includes both the development of the fabrication techniques for the SSMIC and the design and analysis of the ELM and VS Coil assemblies.

A collaboration is underway between Princeton Plasma Physics Lab and UCLA to develop skill in the use of ATTILA, to benchmark ATTILA against MCNP and to develop Solid Works CAD models for neutronics analysis of the diagnostic ports. MCNP along with the cross section library FENDL 2.1 is the accepted standard tool for neutronics analysis of ITER against which results from ATTILA are being compared. The MCNP community has established a set of benchmark results for a standardized 40 degree CAD model of ITER. These benchmark results create a framework for the acceptance of new applications like A TTILA by the ITER central neutronics, quality assurance and nuclear safety groups. Analysis of the benchmark model with ATTILA also leads to the setting of discrete ordinates solution parameters and model mesh refinement that will help to accelerate the analysis of future diagnostic port design iterations. Flux and heating results in the Divertor, Blanket Shield Modules and Equatorial Port Shielding from the ATTILA benchmarking show good correlation with MCNP results. TF heating results were in error by up to 50% due to poor mesh refinement and boundary condition issues in that area. Detailed models of the Upper and Equatorial ports, port plugs and diagnostics are under development. The detailed port study models will be 40 degree ITER models to preserve the shape of the neutron source loading. These models will include the inner and outer vacuum vessel, inner-wall shielding, blanket shield modules, divertor and cryostat. Models of the OH, TF and PF coils will not be included to save on element count.

A multi-channel Thomson scattering system viewing the edge and core of the KSTAR plasma will be installed at the midplane port Bay-N. An engineering design study was undertaken at PPPL in collaboration with the Korea Basic Science Institute (KB Si to determine the optimal optics and cassette design. Design criteria included environmental, mechanical and optical factors. All of the optical design options have common design features; the Thomson scattering laser, an in-vacuum shutter, a quartz heat shield and primary vacuum window, a set of optical elements and a fiber optic bundle. Neutron radiation damage was a major factor in the choice of competing lens-based and mirror-based optical designs. Both the mirror based design and the lens design are constrained by physical limits of the Bay-N cassette and interference with the Bay-N micro-wave launcher. The cassette will contain the optics and a rail system for maintenance of the optics