High Pressure Viewport
Client – Semiconductor R&D
- 0.6” view fused silica viewport on 2.2” UHV Flange (metal seal, “helicoflex”)
- Viewport must transmit laser, and be rated to operate at 1500 psi & 200 C (Temperature rating limited by AR Coating)
- Pressure test to failure at minimum 6000 psi to confirm 4X safety-factor
- The system required multiple viewports for transmitting pulses of a high powered laser into a pressurized system, but prior to operation the system required ultra-high vacuum evacuation and bake-out cycle for cleanliness.
- The internal environment included numerous gases, pressure from UHV to 1500 psi, and temperatures to 200 C. Standard viewports used in laser applications were not suited for the gas environment, or the extreme internal pressure. The flange system was also unique, so the viewport design must be mounted in the “helicoflex” style flange with a metal gasket.
- MPF designed a weldable Fused Silica window sub-assembly, which was resistant to corrosion in the specific gases being used. The material grade of Fused Silica and AR Coating applied to the window allowed for optimum transmission of the laser.
- The high internal pressure load combined with UHV/Bake-out procedures required a specialized flange mount. The sapphire sub-assembly was welded into the custom flange mount and mechanically supported for safety under high-pressure operation.
- The custom window sub-assembly and final assembly required special fixtures for brazing, welding and pressure tests. Pressure test requirements specified testing to 4X expected load (or 6000 psi). Actual tests confirmed failure between 7000-8000 psi, which exceeded the requirements.