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High-Vacuum CF Flange Viewports for Ø1" Windows
Ø1" Flat Window
Annealed Copper Gaskets,
Flange Mounting Hardware Pack
Thorlabs' high-vacuum-compatible Ø2.75" (DN40) CF Flange Viewports for Ø1" Optics are offered with one of three uncoated window substrates: sapphire (150 nm - 4.5 µm), CaF2 (180 nm - 8.0 µm), or UVFS (185 nm - 2.1 µm). Please see the Graphs tab for transmission data. Additionally these viewports are compatible with our selection of stock Ø1" windows with thicknesses between 4.9 - 5.15 mm. These flanges are not compatible with wedged windows.
Designed for use at high-vacuum (HV) pressures, Thorlabs' CF viewports utilize Viton O-Ring seals to create an air-tight metal/glass seal, allowing for pressures down to 10-8 Torr. The vacuum windows are interchangeable, enabling the user to swap out vacuum windows mounted in our HV CF flanges. Additionally, CF flanges (viewports without vacuum windows) are also available that are also compatible with our Ø1" windows. Before swapping and attempting to install additional windows, please review the procedure outlined in the Window Installation tab above.
The graphs below show the transmission of light through uncoated sapphire, calcium fluoride (CaF2), and UV fused silica substrates. Raw data in the Excel format is available by clicking on the links below the graphs.
Our high-vacuum (HV) viewports offer superb flexibility by allowing the user to install or swap out windows as they desire, or as experimental conditions demand. Installation of the windows is relatively quick and simple. This guide explains how to install and change windows in our Ø1.5" HV viewports. The installation procedures for the Ø1" HV viewports are identical to those for the Ø1.5" HV viewports with the only difference being that the front face plate of the Ø1" viewport contains 4 screws instead of 6.
Inspect the o-ring and seat for pits, scratches, or contamination. Remove any loose debris from the seat using compressed air.
Install the o-ring in the seat, and place the window on top of the o-ring (left image). Place the face plate on top of the window (right image).
Place the screws in the face plate holes and use the 2 mm hex key to turn each screw ~1.5 turns so that they are flush with the face plate but not tight.
Use a torque driver set to 30 in-oz to screw in all six setscrews. Refer to the sequence shown in the pattern above for the correct order in which the screws should be torqued. Please note that over-torquing the screws will risk damaging the window. While the viewports for Ø1" windows only have 4 screws, use the same sequence for tightening the screws.
Thorlabs' Ø2.75” CF flange does not include a window but is compatible with any Thorlabs Ø1" window that is 4.9 to 5.15 mm thick. When combined with the appropriate window, this flange allows for optical access into high-vacuum (HV) systems down to 10-8 Torr. This fixed (non-rotating) flange has six 1/4" (M6) through holes for bolting onto any standard Ø2.75" CF flange. Please note that mounting hardware is not included.
The CF-style flange utilizes a knife-edge mechanism to create an airtight seal between mating pieces. To create the seal, a copper gasket (available below) is most often employed. As the bolts of the mating pair are tightened, the knife edge “bites” into the copper gasket, deforming it. The extruded metal fills all the machining marks and surface defects, which yields a leak-tight seal.
Thorlabs' Ø2.75” CF flange viewports allow for optical access into high-vacuum (HV) systems down to 10-8 Torr. These are fixed (non-rotating) flanges with Ø1" windows that provide a Ø0.7125" clear aperture. These viewports have six 1/4" (M6) through holes for bolting onto any standard Ø2.75" CF flange. Please note that mounting hardware is not included. Our HV CF viewports can be purchased with one of three uncoated windows: sapphire, CaF2, or UVFS. Additionally, the provided window may be replaced with any of our Ø1" windows that are 4.9 - 5.15 mm thick.
Thorlabs offers mounting hardware and single-use copper gaskets for mating Ø2.75" CF flanges. These flanges utilize a knife-edge mechanism to create an airtight seal between mating pieces. To create the seal, a copper gasket is most often employed. As the bolts of the mating pair are tightened, the knife edge bites into the copper gasket, deforming it. The extruded metal fills all the machining marks and surface defects, which yields a leak-tight seal.
1/4-hard and annealed copper gaskets are sold in sets of 10. We recommend the 1/4-hard copper gaskets for most applications; for more delicate devices, such as viewports, we recommend using the softer annealed copper gaskets to lower the chance of deformation in the optic due to stress in the flange. The set of stainless steel mounting hardware includes six silver-plated bolts, six nuts, and twelve washers. The silver plating on the bolts acts as a lubricant to prevent galling between the stainless steel surfaces of the bolt and the nut.