64 research outputs found
Towards a new image processing system at Wendelstein 7-X: From spatial calibration to characterization of thermal events
Wendelstein 7-X (W7-X) is the most advanced fusion experiment in the stellarator line and is aimed at proving that the stellarator concept is suitable for a fusion reactor. One of the most important issues for fusion reactors is the monitoring of plasma facing components when exposed to very high heat loads, through the use of visible and infrared (IR) cameras. In this paper, a new image processing system for the analysis of the strike lines on the inboard limiters from the first W7-X experimental campaign is presented. This system builds a model of the IR cameras through the use of spatial calibration techniques, helping to characterize the strike lines by using the information given by real spatial coordinates of each pixel. The characterization of the strike lines is made in terms of position, size, and shape, after projecting the camera image in a 2D grid which tries to preserve the curvilinear surface distances between points. The description of the strike-line shape is made by means of the Fourier Descriptors
Forward modeling of collective Thomson scattering for Wendelstein 7-X plasmas: Electrostatic approximation
In this paper, we present a method for numerical computation of collective Thomson scattering (CTS). We developed a forward model, eCTS, in the electrostatic approximation and benchmarked it against a full electromagnetic model. Differences between the electrostatic and the electromagnetic models are discussed. The sensitivity of the results to the ion temperature and the plasma composition is demonstrated. We integrated the model into the Bayesian data analysis framework Minerva and used it for the analysis of noisy synthetic data sets produced by a full electromagnetic model. It is shown that eCTS can be used for the inference of the bulk ion temperature. The model has been used to infer the bulk ion temperature from the first CTS measurements on Wendelstein 7-X
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HIGH-TEMPERATURE IRRADIATION OF UO-BeO BODIES
As a part of the ML-1 reactor fuel evaluation program, UO/sub 2/-- BeO bodies containing two UO/sub 2/ compositions, 70 and 80 wt% UO/sub 2/, were irradiated to a burnup equivalent to 8750 hours of ML-1 reactor operation (8.5% U/ sup 235/). It was estimated that maximum cladding surface temperatures of 1710 nif- F were attained during irradiation. Reference design burnup for the ML-1 is 9.7% U/sup 235/, in 10,000 hours of operation at maximum clad surface temperatures of 1750 nif- F. Postirradiation examination of the test specimens revealed that the cladding of one of the 80 wt% UO/sub 2/-- BeO specimens had ruptured after severe swelling. All other specimens showed little external effect from the irradiation. Fission gas release from the fuel varied between 0.59 and 2.7% except for the failed specimen which released about 69%. Considerable change was observed in the microstructure of the irradiated specimens although subsequent x-ray diffraction examination did not indicate serious damage to the crystal structure of either the BeO or UO/sub 2/. The data obtained from this experiment are in substantial agreement with that determined in irradiation experiments performed at other facilities. The performance of 70 wt% UO/sub 2/--BeO was considered to be suitable for use in the ML-1 reactor. (auth
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