Illustration of the standard approach for photo-detector absolute spectral characterisation.
(a) Illustration of a set of Bremsstrahlung-dominated spectra (S0-SK) generated with a SXR tube. (b) Illustration of a stair-shaped approach of the energy response. (c) Illustration of a 1st order polynomial decomposition of the spectral response. The examples shown here are not experimental results, only illustrative drawings.
Geometry of the SXR diagnostic on Tore Supra. The vertical camera comprises 6 additional LOS through an additional pinhole that will be ignored in this paper.
Operating principles of the SXR tube and experimental setup common to any detector (Si p-i-n or SBD).
Electronic acquisition chains of the Si p-i-n (left) and the Si SBD (right). The RECEPTIX chip has fixed gain of 4, the existence of which was not known until recently.
Correspondence between bits and actual energy scale for the Si p-i-n acquisition chain output, determined using pre-identified fluorescence lines.
Experimentally evaluated thickness of the commercial Al foils used as low-energy filters to protect the Si p-i-n detector.
Experimental non-linearity of the system [source + Si p-i-n + MCA] with respect to the source current intensity. A common parabolic fit is used for different spectra. The uncertainty (2*delta) contains 95% of the points with random noise.
(a) Some of the experimental spectra measured by the Si p-i-n for the 8 kV source voltage, with various current intensity (μA) and number of Al foils (Al). The effect of the non-linearity of the MCA response versus the current intensity (f(I)) and of the various external filters and Si p-i-n spectral response was de-convoluted so as to get the original spectra radiated from the source. (b) Resulting de-convoluted-experimental source spectra (7–14 kV). Bremsstrahlung radiation is dominant, except from Ag L-lines (anode) around 3 keV.
Planar (a) and 3D (b) views of the various positions (coloured squares) at which measurements of spectra were made with the Si p-i-n. The aim was to characterize the spatial distribution of the source emission.
Experimental topology of the spatial distribution of the source emission in angular coordinates (degrees).
Schematic of the source geometric representation used for spatial distribution extrapolation. Ellipse dimensions (a), (b), position (L), and inclination (θ) were hand-tuned so as to fit best the experimentally determined spatial topology.
Comparison between the experimentally determined spatial distribution of the source and the modeled extrapolation using geometrical parameters. Phi1 and Phi2 are defined as atan(Y/d) and atan(Z/d), respectively, where d is the distance between the source and the detector and Y and Z are distances in a plane perpendicular to the source's geometric axis.
(a) [SBD + AMPIX] voltage measurements from session 2. A stop-watch was used to monitor the time-evolution of the dark current. (b) Three measurement series were conducted during this session, with 0, 2, and 4 Al foils, respectively.
Schematic of the SBD model used showing the main geometrical features and parameters.
The 8 (3 × 2 + 1 × 2) possible spectral responses of the SBD found experimentally with a least-square approach. Also included are the ideal response of a 300 μm SBD and another solution found in literature.
Experimentally determined spectral response envelope (grey area) and two satisfactory fits with the model described in Subsection V B , plotted in log-log (a) and linear-linear (b) scales.
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