3. a) Consider low-pressure hydrogen plasma contained in a grounded torus vacuum vessel by a toroidal magnetic field. A cross-section of the vessel is shown in Fig. Q3. At the centre of the plasma, the electron density (ne) is 5 1020 m. The magnetic field strength B is 1 Tesla. i) ii) iii) iv) v) vi) A ii) H plasma Fig. Q3 O O B X B-field direction X X Vessel wall What is the positive ion density (ni) at the centre of the plasma? What principle have you used reach your answer? Complete the balanced reaction equations for the following interaction between electrons and H molecules in the plasma that lead to the: Dissociation of H, e+ H ? Direct ionisation of H2, e+ H ? Dissociative ionisation of H e+ H ? Name region X at the boundary of the plasma and say what important plasma parameter characterises the width d of region X. In your answer book draw a sketch of the electric potential profile that exists along the line A-B shown in fig. Q3. In your answer book draw a sketch of the profiles of electron ne and ion density n; that exists along the line A-B shown in fig.Q3 Calculate the electron gyro-frequency oo in the plasmas b) Physical sputtering is a very important plasma-surface interaction process. Briefly describe what sputtering is. A metal surface of area 0.01 m is bombarded by argon ion flux of