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Abstract: For the ITER core charge exchange recombination spectroscopy (CXRS) upper port plug #3 (UPP) diagnostics, a fast shutter is necessary for the first optical mirrors. The shutter concept for the reference CXRS layout has been well developed and studied focusing on the structure dynamic behavior. This paper presents two shutter concepts for the new baseline layout. Concept-1 is similar to the reference concept, including the helium actuator attached to the diagnostic shielding module (DSM) in the primary vacuum. Concept-2 considers the actuator outside the primary vacuum. It is attached to the back side of the UPP and connected to the shutting mechanism with a push–pull rod. Assembly and disassembly, actuator location, and actuation type are key issues for concept assessment. For a feasibility study, two different leak cases for the shutter concepts have also been analyzed. Concept-1 requires a specialized actuator design compatible with the in-vessel conditions. The actuator size is limited by the lack of available space in the DSM. This option needs complex procedures to access the actuator for maintenance. Concept-2 allows the use of standard pneumatic/hydraulic actuators and other industrial components. Space allocation is needed inside the UPP to accommodate the push–pull rod system. Concept-2 allows independent maintenance procedures for the actuator(s) and the shutting mechanism. It was generally concluded that both options are suitable for the new baseline layout, and are to be studied in detail. [Copyright &y& Elsevier]

Abstract: The core Charge Exchange Recombination Spectroscopy (core CXRS) diagnostic system for ITER is projected with 7 consecutive in-vacuum mirrors. Based on overall system stability, maintenance and lifetime considerations, ITEr grade Stainless Steel 316L(N) was chosen as first candidate for the substrate of the mirrors two to seven. A robust design with remote handling friendly bolted interface has been devised. It features uniformly distributed internal temperature control with minimal welds. The design, simulation results and plans for a prototype are discussed. Mirrors 4–7 are planned with a multilayer dielectric coating at preferably >98% reflectivity. The ability to manufacture such a coating on SS316L(N)-substrate which works reliably under ITER conditions is investigated. A 64 λ/4 layer coating of TiO2 and SiO2 was chosen for initial investigations. Adhesion tests were carried out and testing under ITER-conditions is under preparation. The paper covers the coating, sample manufacturing and status of the testing. [Copyright &y& Elsevier]

Abstract: The upper port #3 in ITER will be used by the core Charge Exchange Recombination Spectroscopy (core CXRS) to channel out light from the inside of the vacuum vessel. Recent research about the lifetime of the first two mirrors and changes in the upper port plug geometry initiated further investigations into possible alternative system design concepts. Two new variants of the optical system were chosen for further investigation. The different sub-systems of core CXRS such as optical system, retractable tube and shutter are introduced together with their impact on the system design and their interactions. Space constraints originating from the envelope of the UPP and requirements emerging from the ITER environment such as remote handling and other maintenance considerations are also included in the investigation. Alternative system concepts taking the constraints into account are presented and discussed. Implications for further design work on the subsystems are derived from the results. [Copyright &y& Elsevier]

Abstract: For the optical system of the core CXRS port plug several designs were developed in the last years. A survey is given of the three most relevant designs. The first design is based on an off-axis ellipsoid mirror as main imaging component. This design has been the basis of opto-mechanical design as described in previous publications . This design is presented and assessed with regard to the optical properties, the sensitivity to first mirror degradation, the possibility to include a tube to allow replacement of the first mirror (as a possible mitigation of the first mirror degradation) and the manufacturability. Two alternatives are presented that alleviate the issues connected to the optical design. These alternatives may improve both lifetime and manufacturability of the core CXRS port plug. [Copyright &y& Elsevier]

Abstract: New optical configurations for the ITER core CXRS system offer the possibility of longer ducts between the first mirror and the plasma. This has led to a renewed optimization of the availability, using a simple model of the degradation of the first mirror that starts with the conditions of (a) the required measurement performance and (b) the geometry of the port plug. It is found that for a fully passive system the design should strive for the longest duct length possible. Given known data, this will result in a diagnostic lifetime still substantially shorter than ITER lifetime. When an option of cleaning the first mirror is introduced (assuming this is a feasible option) the optimum is less straightforward, because the lifetime of the second mirror then also becomes important. The optimum then depends on the ratio between the cleaning interval and the ITER lifetime. Options are presented for various sets of assumptions. Finally practical limitations of supporting subsystems (cleaning system, shutter, calibration system) may influence the final design. Examples of such limitations with their impact are presented. [Copyright &y& Elsevier]