• Asim Kumar Chattopadhyay

      Articles written in Pramana – Journal of Physics

    • Second-harmonic ion cyclotron resonance heating scenarios of Aditya tokamak plasma

      Asim Kumar Chattopadhyay S V Kulkarni R Srinivasan Aditya Team

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      Plasma heating with the fast magnetosonic waves in the ion cyclotron range of frequencies (ICRF) is one of the auxiliary heating schemes of Aditya tokamak. Numerical simulation of second-harmonic resonance heating scenarios in low-temperature, low-density Aditya plasma has been carried out for fast magnetosonic wave absorption in ICRF range, using full-wave ion cyclotron heating code TORIC combined with Fokker–Planck quasilinear solver SSFPQL and the results are explained. In such low-temperature, low-density plasma, ion absorption for second-harmonic resonance heating is less but significant amount of direct electron heating is observed.

    • Minority heating scenarios in $^{4}\rm{He(H)}$ and $^{3}\rm{He(H)}$ SST-1 plasmas


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      Anumerical analysis of ion cyclotron resonance heating scenarios in two species of low ion temperatureplasma has been done to elucidate the physics and possibility to achieve H-mode in tokamak plasma. The analysis is done in the steady-state superconducting tokamak, SST-1, using phase-I plasma parameters which is basically L-mode plasma parameters having low ion temperature and magnetic field with the help of the ion cyclotron heating code TORIC combined with ‘steady state Fokker–Planck quasilinear’ (SSFPQL) solver. As a minority species hydrogen has been used in $^{3}\rm{He}$ and $^{4}\rm{He}$ plasmas to make two species $^{3}\rm{He(H)}$ and $^{4}\rm{He(H)}$ plasmas to study the ion cyclotron wave absorption scenarios. The minority heating is predominant in $^{3}\rm{He(H)}$ and $^{4}\rm{He(H)}$ plasmas as minority resonance layers are not shielded by ion–ion resonance and cut-off layers in both cases, and it is better in $^{4}\rm{He(H)}$ plasma due to the smooth penetration of wave through plasma–vacuum surface. In minority concentration up to 15%, it has been observed that minority ion heating is the principal heating mechanism compared to electron heating and heating due to mode conversion phenomena. Numerical analysis with the help of SSFPQL solver shows that the tail of the distribution function of the minority ion is more energetic than that of the majority ion and therefore, more anisotropic. Due to good coupling of the wave and predominance of the minority heating regime, producing energetic ions in the tail region of the distribution function, the $^{4}\rm{He(H)}$ and $^{3}\rm{He(H)}$ plasmas could be studied in-depth to achieve $\rm{H}$-mode in two species of low-temperature plasma.

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