This group works as a diagnostics tool for Tokamak plasmas from detecting x-emission from plasmas.
X-ray radiation emits from Tokamak plasma in the different energy ranges e.g soft x-ray emission (100ev-10kev),hard x-ray emission (100kev and above).
Soft X-ray imaging:
Soft x-ray is one of the important diagnostics of high temperature tokamak plasma. The major aim of this diagnostics in Aditya/SST1 is to measure the fluctuations in emission in order to study the mode structure of MHD oscillations and locate rational q-surfaces .
It can be used to measure the relative intensity of the emission in soft x-ray region of the spectrum. As radiated soft x-ray fluxes which are related with basic characteristics of plasma like density and temperature it is used in Adiya/SST1 to measure the chord averaged central temperature of plasma by the method of absorption foil ratio techniques with certain conditions. In the calculation we assume plasma distribution is mawellian and thermal plasma.
In Adiya we have two x-ray cameras one viewing plasma radially (0ο)and other one vertically at 90ο .through pin hole covered by 25μm Beryllium foil filter. Array of Silicon surface barrier detector is used with spatial resolution of 2cm and temporal resolution is 100 µ sec so that one can see m=0 (sawtooth) and m=1 oscillation. The diagnostics can be used for study sawtooth oscillation.
Soft x-ray radial camera in Aditya
Temperature profile with Ip
Vertical camera in Aditya
SST1 Soft x-ray system
Hard x-ray diagnostics
This diagnostics is used to monitor hard x-ray energy emitted from tokamak plasma limiter. NaI scintillated detector viewing the limiter placed at a distance of 2-3 meter away from Tokamak vessel. The energy of these Hard x-rays observed are of the order of few hundred keV to 5Mev .This diagnostics gives the information of energy and intensity of runaway electrons.
Fig . Hard X-Ray Diagnostics on SST1 Platform, view and detected hard x-Ray generated from limiter installed
Silicon drift detector spectrometer is used to measure the bremsstrahlung and continuum spectra of plasma using photon counting with multichannel analyzer. From this diagnostics measuring the slope of the spectra can derive, the electron temperature. High z-impurity contents can be estimated from the line spectra. One can study the non-thermal electrons (1kev-30kev) during ECR pre ionization and LHCD (lower hybrid current drive) operation.