A diamond window component for an optical tool suitable for harsh environments

An optical tool comprises a chemically inert tubular body 2 defining an internal channel and an opening; a diamond window 6 is bonded to a mounting ring 4 mounted within the channel. The mounting ring 4 comprises a material having a low coefficient of linear thermal expansion of 14.0 x 10-6 K-1 or less at 20°C and a high thermal conductivity of 60 Wm-1K-1 or more at 20°C such as molybdenum. The tubular body 2 comprises an internally tapered end portion 8 and the mounting ring 4 is press-fit into the tapered end portion 8. The optical probe is suitable for use in hostile environments. The diamond window 6 may be joined to the mounting ring 4 using a gold/tantalum braze 10. The tubular body 2 may comprise a plurality of portions 11 projecting from the end wall 13 to protect the window from damage. The mounting ring 4 may have an internal taper 16 so that an optical fibre can be threaded along the body 2. The optical tool may be configured to perform attenuated total reflectance (ATR) spectroscopy.