Plasma Stored Energy Analysis during Neutral Beam Injection in the Globus-M2 Tokamak Using the PET Equilibrium Code and Diamagnetic Measurements

The thermal energy stored in plasma W_p , normalized internal plasma inductance l_i and current beta β_I are calculated via the free-boundary equilibrium PET code. The equilibrium reconstruction algorithm is iterative method of minimizing two parameters, the distance between the reconstructed plasma boundary and that simulated by the PET code, as well as the difference between the plasma diamagnetic flux from PET and the experimental one. The discharges from the Globus-M2 tokamak with a toroidal magnetic field up to 0.9 T and a plasma current of 0.3–0.4 MA in a mode with auxiliary heating by two atomic injectors are analyzed. The possibility of using approximate formulas for estimating W_p and l_i is considered. The measured diamagnetic flux is used to determine β_dia and then to calculate W_dia . The normalized internal plasma inductance l_i is additionally determined from the measured vertical magnetic field under the assumption that β_p = β_dia .