Redesign of a HV Blumlein Pulser for Pulse Upgrade in The Microsecond Range

At INPE we have developed a HV 100 kV/200 A (nominal) Blumlein pulser with pulse duration of 1 μs in order to achieve higher ion energies in plasma implantation process. High voltage nitrogen glow discharges were obtained with simultaneous ion implantation using the Blumlein pulser as a single source. By using this pulser the obtained results for implanted silicon samples have indicated that N₂⁺ ion penetration depths increase with higher applied voltages and treatment times. Unfortunately, depth values are much less than the predicted by the SRIM (Stopping & Range of Ions in Matter) simulation mainly due to the short pulse duration. The basic reason is that the pulse peak duration obtained (800 ns) is of the order of the acceleration & implantation times for the ions coming from plasma sheath formed around the treated sample. Increasing pulse duration of the Blumlein system to encourage its use in aluminum and polymer treatments is a possibility that we are exploring. For this, we are redesigning our pulser to obtain longer pulse duration of the order of 5 μs. The drawbacks of this new design are the reduced nominal voltage characteristic of 60 kV and the necessity of charging the cables up to 30 kV, although in practice (as the generator structure is in air) corona discharges have limited the output voltage up to 50/60 kV for repetition rates of ~100 Hz used in our treatments.