Iris Slot Waveguide Plasma Source for Symmetric Discharge

An iris structure is introduced as an intermediary component between the waveguide and plasma torch. The iris acts as a field-shaping element that modifies the electromagnetic field distribution, creating a more robust plasma excitation pattern that is less sensitive to waveguide length variations. This intermediary structure enables symmetric plasma formation even when the waveguide length deviates from the theoretical optimum.

The patent modifies the electromagnetic field parameters by introducing iris slots with specific dimensional ratios (height less than 70% of torch diameter). This parameter change transforms the field distribution from one that is highly sensitive to length variations into a more stable configuration that maintains plasma symmetry across a range of waveguide lengths.

The iris slot height is optimized to a specific parameter range (less than 70% of torch diameter) that balances two competing requirements: maintaining plasma symmetry and ensuring sufficient electromagnetic field coupling. This parameter optimization creates a compromise solution where the slots are narrow enough to shape the field for symmetric plasma but wide enough to maintain adequate energy transfer.

Instead of using full-height iris slots that would provide maximum coupling but poor symmetry, the patent employs partially-height slots that achieve sufficient coupling for stable plasma operation while prioritizing symmetry. The partial action approach accepts some reduction in coupling efficiency to gain the benefit of improved plasma uniformity.