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Abstract The paper presents experimental results obtained during the first operational phase (called OP1.1) of the Wendelstein 7-X stellarator (W7-X). One of W7-X diagnostics that delivers information about plasma impurities and was commissioned during the OP1.1, is the Pulse Height Analysis (PHA) system which provides soft X-ray spectra of highly ionized impurity species over a very broad energy range with energy resolution not worse than 200 eV and with temporal resolution of 100 ms. The line-of-sight integrated spectra, collected by a Silicon Drift Detector in the energy range between 0.9 and 10 keV, have been analyzed for various experimental conditions and are discussed with respect to results from other diagnostics. In this work, injected impurities (argon and neon) as well as intrinsic impurities (sulphur and chlorine) have been identified. Spectral lines corresponding to heavier impurities have not been observed. [ABSTRACT FROM AUTHOR]

In metallic tokamaks, the interplay between particle transport and MagnetoHydroDynamic (MHD) activity might lead to impurities accumulation and finally to disruption. Studying such phenomena is thus essential if stationary discharges are to be achieved. Measuring the soft X-ray (SXR) radiation ([0.1 keV; 20 keV]) of magnetic fusion plasmas is a standard way of accessing valuable information on particle transport and MHD. Generally, like at Tore Supra (TS), the analysis is performed with a 2D tomographic system composed of several cameras equipped with silicon barrier diodes (SBD). On WEST the installation of an upper divertor masks many of the actual TS vertical diodes so that no proper tomography is possible. This paper presents the design of a new SXR diagnostic for the WEST project developed in collaboration with IPPLM (Poland) and the Warsaw University of Technology, based on a triple gas electron multiplier (GEM) detector. Preliminary simulations performed to size and position the detector and its electronics inside the vertical thimble are also presented, in particular estimation of magnetic field and temperature variation affecting GEM spatial resolution and signal quality. As a conclusion, perspectives about tomographic capabilities of the new system for studying impurity transport are given. [ABSTRACT FROM AUTHOR]

Abstract: The engineering and design of the soft X-ray Multi Camera Tomography System (XMCTS) in Wendelstein 7-X stellarator (W7-X) must fulfill several additional requirements compared to short pulse machines. The XMCTS has to withstand irradiation and electron cyclotron microwave loads in addition to being ultra high vacuum compatible, having low magnetic permeability and using low neutron activation materials (e.g. Co≤2000ppm). A further difficulty is the limited space inside the plasma vessel, which requires special engineering solutions. After detailed design development, supported by finite element analyses, prototypes have been manufactured and tested. At the end all test results have successfully proven that the components fulfill the requirements and that reliable and stable measurements will be possible with the XMCTS diagnostics during W7-X operation. The paper describes the design and the technological development, in particular on the electric multipin feedthrough (UHV barrier between in vessel detectors and the preamplifiers), the active cooling of the electronic components (reducing dark current/noise increase), the pneumatic shutter (protection of the detectors from sputtering and during baking) and the fiber optics illumination system (calibration of the detectors). [Copyright &y& Elsevier]

• Activation and radwaste analysis was completed for ITER soft X-ray camera. • Combine specific activity and clearance index to determine the radwaste classification. • The linear relationship between the neutron flux and specific activity is obtained by expanding the neutron flux, so that the activation of SXR can be rapidly predicted. • The SXR model is simplified and integrated into ITER CLITE model. The Soft X-Ray camera (SXR) is designed to measure the polar profile of plasma X-ray emissivity with high spatial and temporal resolution. The camera is located on the Equatorial 12 Port Plug of ITER Tokamak. During the nuclear operation phase, a large number of high-energy neutrons are generated. These neutrons will activate the camera components and make them radioactive. In order to evaluate the activation of SXR's structural and shielding materials, an activation and radwaste analysis has been performed, and the results are summarized in this paper. A simplified model of all necessary parts of SXR is integrated into the ITER C-lite model for neutron transport. The activation of the components is calculated using the FISPACT-2007 code. The safety scenario SA2 for ITER activation calculations is recommended as irradiation history. The contact dose rate provides recommendations for the maintenance of SXR. The security risk of decay heat to SXR is analyzed. Specific activity and clearance index provide the basis for the classification of radwaste. The linear relationship between the neutron flux and activation parameters is obtained by expanding the neutron flux, so that the activation of SXR can be rapidly predicted according to the flux measured in the actual operation of ITER. [ABSTRACT FROM AUTHOR]

A visual summary of an article's main findings are: 1) The EUV and SX signals with three specific peaks are detected by AXUV photodiode. From the analysis of time resolved of the AXUV signal, it is inferred that the first and main signal peak can dominantly be related to the free-free transition mechanism of radiation which is comparable to the theoretical results. 2) Also the latter physical signals-peaks with appropriate time-delay can be related to the free-band and bond-bond transitions respectively. 3) The energy of EUV and SX pulse emission is observed to be approximately linear, proportional to the laser pulse energy. 4) The time integrated results show that, the very low average energy conversion efficiency is mainly due to the ambient gas pressure and the angle of detection directions relative to the normal surface of the target. This paper addresses the experimental results and analysis of the time-resolved and time-integrated of AXUV (absolute extreme ultraviolet) photodiode diagnostics. These results are obtained by the measurement of EUV and soft X-ray (SX) power radiation of plasma-produced under the interaction of laser pulse (intensity ∼5 × 1011 W/cm2, pulse durations in the range of 10−30 ns and wavelength 1064 nm) with one steel-316 target. The EUV and SX signals with the three specific peaks are detected by AXUV photodiode. From the analysis of time resolved of the AXUV signal, it is inferred that the first signal peak can dominantly be related to the free-free transition mechanism of radiation and also the latter related to the free-band and bond-bond transitions respectively. The energy of EUV and SX pulse emission is observed to be approximately linear, proportional to the laser pulse energy. The time integrated results show that, the average energy conversion efficiency is determined to be about 3.7 %. [ABSTRACT FROM AUTHOR]