GLAST (tokamak)

GLAST (GLAss Spherical Tokamak), is a small spherical magnetic confinement tokamak fusion reactor installed at the National Tokamak Fusion Program (NTFP) by the Pakistan Atomic Energy Commission (PAEC) in 2008. It is a Magnetic confinement fusion spherical tokamak with an insulating vacuum vessel. The device is primarily used to conduct scientific studies and experiments to identify the mechanism responsible for current generation during start-up phase of the tokamak discharge. The tokamak was developed by the PAEC indigenously, and offers research on control plasmas. Initial plasma in GLAST-II is achieved successfully. Plasma diagnostics including triple Langmuir probe and Optical Emission Spectroscopy systems are developed to measure basic plasma parameters such as electron temperature, electron number density, floating potential and impurity content in the discharge. Triple Langmuir probe is capable to record instantaneous plasma characteristics.^[5-8] Plasma current is then enhanced up to 5 kA by applying a small vertical magnetic field that provides additional plasma heating and shaping ^[9].The evolution of ECH-assisted pre-ionization and subsequent current formation phases in one shot are well envisioned by probe measurements. Probe data seem to correlate with microwave absorption and subsequent light emission. Intense fluctuations in the current formation phase advocate for efficient equilibrium and feedback control systems. Moreover, emergence of some strong impurity nitrogen lines in the emission spectrum, even after few shots propose crucial need for improvement in the base vacuum level. A noticeable change in the profile's shape of floating potential, electron temperature, ion saturation current (Isat) and light emission is observed with changing hydrogen fill pressure and vertical field^[8,9].