Development of the diagnostics for ITER tokamak, which is presently under construction by several international partners at Cadarache in France, is a major challenge because of severe environment, strict engineering requirements, and the need for high reliability in the measurements. The diagnostic systems in the upper, equatorial and lower port cells on ITER are designed to be integrated within the interspace and port cell support structures. These structures are interfacing with remote handling rail system for the cask operations, thus facilitating the removal and installation of the diagnostics in the port and hence minimizing time for working close to the tokamak. In this paper, the challenges associated with the integration of the diagnostics in the port interspace and port cell, as well as their solutions will be addressed and presented. The interspace and the port cell support structures, as well as their interfaces with the biological shield, will be discussed.

Most of ITER's diagnostics will be provided with viewing lines (optical, microwave, spectroscopic) for the monitoring of key characteristics of the plasma or for the achievement of physical measurements inside the vacuum vessel. For many of them the nature of the physical signal transmitted through the viewing lines requires the implementation of window assemblies incorporating either Glass/Ceramic or Beryllium window. The main requirements of the Diagnostic Window Assemblies are the transmission of the signals without attenuation or disturbances, the containment of vacuum, the confinement of in-vessel radioactive materials. Although they are generally not in direct viewing of the plasma, they are exposed to severe environmental conditions in normal and accidental conditions.The concept chosen for ITER Diagnostic Window Assemblies is based on a system of two windows with a monitored interspace, largely inspired from previous large machine solutions. Such a system is able to satisfy the transmission and vacuum requirements. Although this capability has previously proven a high reliability level, ITER conditions, which are more stringent, impose the requirement for improvement of existing designs and even the development of novel solutions, in particular to assure the radioactive material confinement function, which must be met in all circumstances including all off-normal conditions. Moreover the qualification of these concepts shall meet the nuclear safety requirements, although non metallic and beryllium components are not covered by existing codes and standards.This paper presents designs of window assemblies for different diagnostics. It gives an update of the current R&D programme implemented to solve several technical issues specific to ITER. Finally it presents the approach to the demonstration that safety requirements will be met by these components, involving the development of ITER Practice for replaceable non-metallic windows. (C) 2013 Elsevier B.V. All rights reserved.

Extensive diagnostics systems will be installed on the ITER machine to provide the measurements necessary to control, evaluate and optimize plasma performance in ITER and to further the understanding of plasma physics. These include measurements of temperature, density, impurity concentration, and particle and energy confinement times. ITER diagnostic systems extend from the center of the Tokamak to the various diagnostic areas, where they are controlled and acquired data is processed. This mainly includes the areas such as ports, port cells, gallery, diagnostics enclosures and cubicle areas. The diagnostics port plugs encloses the front end of the diagnostic systems and the diagnostics building houses the diagnostics equipment, instrumentation and control cubicles. There are several systems providing services to diagnostics. These mainly include ITER buildings, electrical power services, cooling water services, Heating Ventilation and Air Conditioning (HVAC), vacuum services, liquid and gas distribution services, cable engineering, de-tritiation systems, control cubicles, etc. Requirements of these service systems have to be defined, even though many of the diagnostics are at an early stage of development. It is a real challenge to define and to design diagnostics systems considering the constraints imposed by these service systems. This paper summarizes the provision of these services to the individual diagnostics and diagnostics areas as well as the total requirements to a significant level of definition. It demonstrates the impact of this as a design restraint and requirement on both the diagnostics and the service systems as they are further specified, designed and procured. (C) 2013 Elsevier B.V. All rights reserved.

The Electron Cyclotron Emission (ECE) diagnostic provides essential information for plasma operation and for establishing performance characteristics in ITER. Recently, the design of the ITER ECE diagnostic has been taken through the conceptual design review and now entering the detailed design phase (1, 2). The baseline ECE system on ITER permits measurements of both the X- and O-mode radiation in the frequency range from 70 GHz up to 1 THz along two lines-of-sight, perpendicular and oblique at about 10 degrees, in the equatorial port. The system as planned meets the ITER measurement requirements. Nevertheless, there are several other mm-wave diagnostics in ITER, such as HFS, LFS and plasma position reflectometry, as well as Collective Thomson scattering system, whose transmission lines allow, in principle, additional measurements of parts of the ECE spectrum with upgrades of their back-ends, improvements in filtering and/or additional receivers. A discussion of whether and how supposedly to enable such ECE measurements is given here.

This paper explains the present status of the ITER electron cyclotron emission (ECE) diagnostic and gives an outlook on the upcoming technical and design activity. The open questions of calibration and stability of ECE systems, as well as proposals for the calibration, the design of the front end, and the transmission line are reviewed. The possible role of ECE in the neoclassical tearing mode detection and stabilization by electron cyclotron heating is also discussed. Because integration of the ITER ECE diagnostic within the tokamak requires proper definition of interfaces with many different components located both in-vessel and ex-vessel, a special attention is paid to address the associated issues.

ITER plasma boundary and first-wall diagnostics are summarized in terms of their physical implementation and physics motivation. The challenge of extracting diagnostic signals while maintaining nuclear shielding is discussed, as well as the problems associated with high levels of erosion and redeposition.

A study is conducted on the conceptual design of the structure and cooling channels of the upper port plug of International Thermonuclear Experimental Reactor (ITER). Modification of the earlier port plug design is made and a simple fabrication method is proposed. It is shown that the newly designed port plug can accommodate the installation of both diagnostic and electron cyclotron heating (ECH) devices. Design assessment is carried out through structural and thermo-hydraulic analyses. Results of the analyses show that the port plug structure is stable against one of the most severe plasma events and the total pressure drop of the coolant is within the allowable level.

In this chapter, we consider generic issues affecting the implementation of diagnostics in a burning plasma experiment (BPX). These are, directly or indirectly, caused by the radiation environment. In the first instance, handling nuclear radiation issues becomes a dominant factor in the choice of machine and diagnostic layout, construction, and maintenance. We discuss these integration issues first as they set the background against which more specific issues must be addressed. These include nuclear radiation effects on specific types of components and assemblies such as cables, fibers, and mirrors, and also thermal and mechanical degradation issues that must be considered in all component designs. One important consequence of the maintenance challenges brought about by the radiation environment is that degradation of front-line optical components by particle bombardment, normally handled by component replacement, also becomes far more challenging and in situ mitigation techniques must be sought. For the same reason, recalibration techniques become more difficult. At the same time, BPX operation time is precious and extracting the optimum performance from the device may require the use of more sophisticated diagnostic techniques. Therefore, the requirements on reliability and data availability are more stringent and must be applied more widely than is common on present devices. An important goal of BPX operation is to enable the design of future power plants. We consider briefly the development needs for diagnostics for these and conclude with an assessment of the present state of readiness of the diagnostic community for the detailed design and construction of a full diagnostic set for a BPX.

Monte-Carlo calculations of the fluxes of forward and scattered neutrons at points of arrangement of the detectors for the analyzed design of the ITER multichannel vertical neutron collimator have been performed with the MCNP model. A concept of a vertical neutron collimator positioned in the diverter port is proposed, and the efficiency of its application for determining the spatial distribution of the ITER tokamak reactor’s neutron source is demonstrated with allowance for the calculation results and the possibilities of integrating the collimator into the ITER structure.

The maximum temperature expected in ITER is in the region of 40keV and the minimum average density of approximately 3×1019m−3 is also expected. The proven capability, convenience, and port occupancy of the LIDAR Thomson scattering approach, demonstrated on JET, makes it an excellent candidate for ITER. Nonetheless, there are formidable design challenges in realizing such a diagnostic system. The expected high temperature presents its own problem of a very large relativistic blueshift of the scattered spectrum (e.g., λ∕λ0∼0.35 for Te=40keV), impacting on the laser choice and spectrometer/detector system. The combination of coupling high power lasers to the plasma and broadband wavelength detection has been examined in terms of minimizing the operational risk to the overall system, while optimizing the diagnostic performance. Part of the exercise has also included identifying the present critical components, and reducing their impact, e.g., on diagnostic reliability and performance, and attempt to make the design compatible with possible long term developments and operational requirement. Issues such as redundancy of key operational components, e.g., lasers are explored.

The operating conditions of a neutron diagnostic system responsible for measuring the neutron yield in the ITER tokamak reactor are analyzed. Based on results of physical calculations and analysis of suitable methods for measuring the neutron yield, an original concept of a system for measuring neutron fluxed in the divertor zone of the ITER is proposed. The design for the neutron flux monitor located in the divertor zone of the tokamak is selected in view of the requirements specified for the neutron diagnostic system of the ITER and its operating conditions. Four fission chambers with different sensitivities and radiator materials are used as sensitive elements of the monitor. This system is capable of measuring neutron fluxes over the entire dynamic range of the neutron yield in the ITER with an error of ≤10% and a time resolution of 1 ms that are necessary for studying the physical mechanism of thermonuclear plasma ignition and burning. Several possible variants for housing the detector unit inside the divertor assembly and integrating it in the existing project are proposed. The problems of carrying out efficiency calibration of the divertor neutron monitor with the aim of determining the absolute value of the neutron yield in the ITER tokamak reactor are discussed.

Reflectometry with wavelengths in the centimetre to millimetre-wave range will be used in ITER to measure the density profile in the main plasma and divertor regions and to measure the plasma position and shape in order to provide a reference for the magnetic diagnostics in long pulses. In addition, it is expected to provide key information for the measurement of density fluctuations. A set of reflectometers to meet the relevant ITER measurement requirements has been included in its present outline as part of the ITER design since 2001 and is being adapted to the present ITER baseline and to accommodate progress with reflectometry techniques and measurement capabilities. It comprises low and high field side (HFS and LFS, respectively) ordinary (O-) mode systems for the measurement of the density profile in the gradient regions, a LFS extraordinary (X-) mode system for the detailed study of the edge profile, an HFS X-mode system operating in the left hand cutoff to measure the core profile, a dedicated O-mode system for plasma-wall gap measurement and a multi-band, multiple line of sight O-mode system to measure divertor density profiles. This paper describes the evolution of the design, in particular some recent improvements in the engineering implementation and improvements aimed at enhancing the measurement capability. It concludes with a brief assessment of the likely measurement performance against the ITER measurement requirements for the parameters of interest and the overall confidence that the technique will be implanted on ITER.

The ITER neutron diagnostic system needs to cover both the DD- and DT-phases of ITER experiments. To ensure the required accuracy for diagnosing both phases, it is preferable to calibrate the diagnostic system to both DD and DT neutrons. In this paper, the feasibility of two kinds of calibration measurements has been verified through MCNP simulations for the ITER ex-vessel neutron yield monitor. It is indicated that both calibration procedures using DD and DT neutron generators can be implemented with the required accuracies within a realistic measurement time. In the advanced DD-phase of the ITER experiment with high density D plasma producing high energy tritons, where a number of DT neutrons are produced, the independent calibration to DD or DT neutrons could lead to unacceptable measurement uncertainty. An effective method to reduce the measurement uncertainty for the two-component neutron source is discussed.

The beam neutralization system for measurement of the spatial and velocity distributions of alpha particles of ITER plasmas was studied. As forward angle detection against the beam injection direction is required for effective neutralization, arrangement of the measurement system using possible ports in ITER configuration is proposed. The count rate of neutralized alpha particles produced by the double charge exchange interaction with energetic He0 beam particles injected is estimated. The ratios of signal to neutron-induced noise are evaluated. When a He0 beam produced by autodetachment from a 1–1.5MeV He− beam of 10mA is injected, the signal to noise ratio becomes greater than 1 at ρ<0.4, even without beam modulation. Usage of a lock-in technique at the frequency of radio-frequency quadrapole accelerator will make measurement at the outer region possible.

The development of diagnostic systems for next step Burning Plasma experiments (BPX) such as ITER requires RD (ii) review of the requirements for measurements of the neutron/α source profile and assessment of possible methods of measurement; (iii) determination of the life-time of plasma facing mirrors used in optical systems; (iv) assessment of radiation effects on coils used for measuring the plasma equilibrium and development of new methods to measure steady state magnetic fields accurately in a nuclear environment; and (v) Development of measurement requirements and assessment of techniques for measurement of dust and erosion. This paper presents the recent progress in these areas.

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 well measured 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, 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 neutron flux monitors 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.

A concept for the multichannel neutron collimator of the ITER is presented. The design of the collimator is based on the use of a 12-collimator radial neutron camera that was developed earlier and two complementary compact neutron cameras. It is proposed that the compact neutron cameras be placed inside the shielding blocks located in the equatorial (nine collimators) and diverter diagnostic (seven collimators) ITER ports. The plasma would thereby be fully covered in the vertical direction, and the total number of collimator channels would be 21 (12 channels in the radial camera and nine channels in the compact camera). The collimator length and diameters, as well as the optimal materials for the shielding blocks and the inner walls of the collimators, were determined using the MCNP code. It is shown by simulation that, for an adequate collimation of neutron fluxes to be achieved, the collimators should be 1.0–1.5 m long, have an i.d. of 4–5 cm, and be enclosed in a water–iron shielding. It is proposed that threshold fission chambers based on 238U and natural- and CVD-diamond detectors be used as the sensors. The computations are presented to demonstrate that this composition and arrangement of the channels in the radial and compact cameras makes it possible to measure the two-dimensional spatial distribution of the neutron source and the total thermonuclear power to an accuracy of ∼10%.

Long pulse (> several hundred seconds) operation of a tokamak leads to an enhanced requirement for plasma measurements in two respects. Measurements of many plasma parameters (plasma shape and position, density, temperature etc) are required for times typically 10 - 100 times as long as on existing machines. Secondly, in order to achieve the long pulse operation it is likely that measurements of additional parameters - eg NTMs, RWMs, ITBs - will be required. Many of the measurements will have to be made at a sufficiently high level of stability and reliability for use in control loops. In order to make measurements during long pulses, diagnostic systems and components will have to have a high level of stability of operation and performance. Where possible, diagnostic techniques should be chosen which are rugged against these difficulties. Measures such as active alignment systems, in-situ calibration, special components (eg long pulse integrators) will be required. For a DT machine such as ITER, there will, in addition, be effects arising because of the environment which will have to be taken into account in the diagnostic designs: for example, Radiation Induced EMF (RIEMF) and thermal EMFs in magnetic sensors, erosion and deposition damage to diagnostic first mirrors, and enhanced absorption and photoluminescence in windows and optical fibres. The diagnostic designs also have to satisfy stringent requirements on tritium confinement, vacuum integrity, remote handling etc. In this paper the long pulse issues are summarised and examples of systems where special measures have been adopted are given. Areas where further developments are needed are identified.