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Output data |
Main | Bolometers | Bolometer | Collecting data & | Measurement &
page |  | position | Resolution | Experiments

| Output data is several volts signal showing evolution of radiation falling during the shot on each detector. After multiplication of signal with coefficients they correspond to radiated power from tokamak. For visualisation and analysis of data the IDL routine was evolved. The contour plot shows evolution of radiation in space and time and gives estimation of maximal radiation and movement of plasma inside tokamak chamber. Data from one selected time gives chord integrated radiation profile. An obtained dependency of the radiated power on a distance of the chord from the plasma centre is usually peaked during the typical CASTOR discharge. Fitting the data with Gaussian curve, it is possible to estimate the radiation losses centre (roughly corresponding to the plasma column position), radiation FWHM (full width at half of maximum) and the maximum of radiated intensity. |

In some cases, namely at the beginning of the discharge, the plasma profile is not peaked, but hollow. Then the data don’t fit to the Gaussian distribution, consequently more complicated approximations should be used, for example the fit consisting of the two Gaussian curves. In this case, the introduction of the above mentioned parameters is problematic and is used only for a comparison. From Gaussian fitting in selected time interval, the evolution of plasma maximal radiation position, FWHM, and radiated power can be computed. Asymmetrical Abel inversion can be used for a reconstruction the radiation profile from single array data at each time step, i.e. 1 µs, assuming a radial symmetry in one direction. For tomography, what combines data from both arrays, the Cormacks method is used. Radiation from the edge plasma region is influenced by turbulent events. Their typical size is about 1 cm and the lifetime about 10-40 µs. Subtracting the mean value from bolometric signal, changes of radiation causes by turbulences can be visualised. Autocorrelation analysis gives periodicity and frequency of fluctuating part of signal. The cross-correlation analysis shows also the direction of movement of the structures. Because of chord integration of the data, the final determination of the structures position is complicated. |

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