IMPROVEMENTS IN AND RELATING TO COATING PROCESSES

An apparatus (1b) and method of depleting a plasma of electrons in a plasma coating apparatus is disclosed. The invention involves generating a plasma comprising ions (9), particulate material (5) and electrons (6) adjacent a target (4); forming a plasma trap (52) to constrain the plasma near to the target (4), and depleting the plasma of electrons by: providing an additional magnetic field (8b) that is superimposed over the magnetic field of the plasma trap (3, 52), which extends beyond a boundary layer (52) of the plasma trap, and which draws electrons (6) from, or near to, the boundary layer (52) of the plasma trap away from the target (4). The invention proposes applying a baseline voltage (50) to the target (4); and by applying periodic voltage pulses (13b) to the target (4). The additional magnetic field (8b) depletes the plasma of electrons, such that when a voltage pulse (13b) is applied to the target (4), ions (9) can be ejected from the plasma with reduced electron shielding. This has been shown to improve ion bombardment and reduce adverse electron bombardment effects.