JET next campaigns foresee various scans in the fuel mixture, full T operation anda 50-50 D-T campaign called DTE2 before the end of the decade. The mainscientific objectives include the assessment of the isotopic effects on various plasma aspects: mainly on confinement, on the threshold to access the H modeand on ELM behaviour. Another very important subject of investigation will be thephysics of the alpha particles. From a technical point of view, the total yieldavailable for the entire D-T phase is expected to be 1.7?10^21 n, about a factor of6 higher than the previous main D-T campaign on JET, DTE1. Therefore theradiation field will be quite relevant for next step devices, since the neutron flux atthe first wall (~10^13 n/s·cm^2), for example, will be comparable to the one inITER behind the blanket. From the point of view of diagnostics developments, for many years JET diagnostics have been upgraded in order to provide adequate support for thescientific exploitation of JET programme. The main efforts have concentrated onimproving three main aspects of JET measuring capability: 1) the quality of themeasurements of the electrons and ions 2) the diagnostic for the fusion products3) interpretation codes 4) diagnostic technologies for ITER.In terms of general diagnostic capability, compared to the previous DTE1, JET diagnostics have a much better spatial and temporal resolution of the electrons (about one order of magnitude improvement for each parameter). The accuracy and consistency of the various independent measurements of the same parameter have also increased significantly; the three independent measurements of theelectron temperature, for example, agree now well within 10%. On the other hand,various improvements of the active charge exchange are being pursued toovercome the significant difficulties encountered in measuring the temperature and rotation velocity of the ions. Moreover, solutions have been found to operate some cameras, both visible and IR, even during the full D-T phase to provide imaging of the plasma and the first wall. A new set of reflectometers is expected toprovide valuable information about the changes in the turbulence with thedifferent fuel mixtures. With regard to the fusion products, JET now can deploy a consistent set of techniques to measure the neutron yield and neutron spectra and to diagnose thefast particles. A full calibration of the neutron diagnostics with a 14 MeV source hasbeen successfully completed, complementing the previous calibration for the 2.45MeV neutrons. Vertical and horizontal lines of sight are foreseen for neutronspectrometry, in order to separate the RF component from the other contributions. Various gamma ray spectrometers are being developed to cover all the various operational scenarios and to discriminate the trapped and passing components ofthe alphas. The redistribution of the alphas will be measured with the gamma raycameras, recently upgraded with full digital electronics; new detectors (LaBr3) have been tested to bring the time resolution of the system in the ten of ms range.The lost alphas will also be diagnosed with improved spatial and temporal resolution, using Faraday cups and a scintillator probe, while an upgraded system to detect the TAE modes, and their interactions with the fast ions, has been proved for the first time to work also in divertor configurations. For most major diagnostics, and in particular for practically all the enhancements,a very significant effort has been exerted to improve JET interpretative capabilityvia the development of specific synthetic diagnostics. From the measurements ofthe fusion product to the instabilities and tomographies, a series of advancedcodes can be now deployed to better link the diagnostic outputs with the physics of the plasma configurations. Interesting developments are also taking place in thefields of data mining, for the efficient retrieval of the information, and in the exploitation of many measurements for real time control. From a technological perspective, the full T and D-T campaigns will provide aunique opportunity to test ITER relevant technologies. From radiation hard detectors, for example Hall probes, to neutron absorbers and to shielding concepts, the potential of various solutions in real radiation fields will be assessed. The effects of neutrons and gamma on ancillary technologies and systems, such as fibre optics and electronics circuits, are also expected to be sufficiently high to derive useful information about the competitive advantage of various potential solutions.
New JET Diagnostic Capability to Support theScenario Development and the Physics Programme at Different Fuel Mixtures.
Murari A;
2019
Abstract
JET next campaigns foresee various scans in the fuel mixture, full T operation anda 50-50 D-T campaign called DTE2 before the end of the decade. The mainscientific objectives include the assessment of the isotopic effects on various plasma aspects: mainly on confinement, on the threshold to access the H modeand on ELM behaviour. Another very important subject of investigation will be thephysics of the alpha particles. From a technical point of view, the total yieldavailable for the entire D-T phase is expected to be 1.7?10^21 n, about a factor of6 higher than the previous main D-T campaign on JET, DTE1. Therefore theradiation field will be quite relevant for next step devices, since the neutron flux atthe first wall (~10^13 n/s·cm^2), for example, will be comparable to the one inITER behind the blanket. From the point of view of diagnostics developments, for many years JET diagnostics have been upgraded in order to provide adequate support for thescientific exploitation of JET programme. The main efforts have concentrated onimproving three main aspects of JET measuring capability: 1) the quality of themeasurements of the electrons and ions 2) the diagnostic for the fusion products3) interpretation codes 4) diagnostic technologies for ITER.In terms of general diagnostic capability, compared to the previous DTE1, JET diagnostics have a much better spatial and temporal resolution of the electrons (about one order of magnitude improvement for each parameter). The accuracy and consistency of the various independent measurements of the same parameter have also increased significantly; the three independent measurements of theelectron temperature, for example, agree now well within 10%. On the other hand,various improvements of the active charge exchange are being pursued toovercome the significant difficulties encountered in measuring the temperature and rotation velocity of the ions. Moreover, solutions have been found to operate some cameras, both visible and IR, even during the full D-T phase to provide imaging of the plasma and the first wall. A new set of reflectometers is expected toprovide valuable information about the changes in the turbulence with thedifferent fuel mixtures. With regard to the fusion products, JET now can deploy a consistent set of techniques to measure the neutron yield and neutron spectra and to diagnose thefast particles. A full calibration of the neutron diagnostics with a 14 MeV source hasbeen successfully completed, complementing the previous calibration for the 2.45MeV neutrons. Vertical and horizontal lines of sight are foreseen for neutronspectrometry, in order to separate the RF component from the other contributions. Various gamma ray spectrometers are being developed to cover all the various operational scenarios and to discriminate the trapped and passing components ofthe alphas. The redistribution of the alphas will be measured with the gamma raycameras, recently upgraded with full digital electronics; new detectors (LaBr3) have been tested to bring the time resolution of the system in the ten of ms range.The lost alphas will also be diagnosed with improved spatial and temporal resolution, using Faraday cups and a scintillator probe, while an upgraded system to detect the TAE modes, and their interactions with the fast ions, has been proved for the first time to work also in divertor configurations. For most major diagnostics, and in particular for practically all the enhancements,a very significant effort has been exerted to improve JET interpretative capabilityvia the development of specific synthetic diagnostics. From the measurements ofthe fusion product to the instabilities and tomographies, a series of advancedcodes can be now deployed to better link the diagnostic outputs with the physics of the plasma configurations. Interesting developments are also taking place in thefields of data mining, for the efficient retrieval of the information, and in the exploitation of many measurements for real time control. From a technological perspective, the full T and D-T campaigns will provide aunique opportunity to test ITER relevant technologies. From radiation hard detectors, for example Hall probes, to neutron absorbers and to shielding concepts, the potential of various solutions in real radiation fields will be assessed. The effects of neutrons and gamma on ancillary technologies and systems, such as fibre optics and electronics circuits, are also expected to be sufficiently high to derive useful information about the competitive advantage of various potential solutions.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
