This photo shows the output end of the laser. The windows which form the gas seals are not at Brewster, but simply angled to eliminate reflection back down the axis of the laser tube. 

This photo shows the laser tube in an ionised state, but not yet producing laser light (Copper Vapour not upto pressure).

This photo showing the laser tube in full output. As you can see the windows on the end of the tube reflecting the light out of the axis of the laser tube. Also in view,  are glass discs with round holes - these discs are used to define the actual laser bore, and allow any condensation of Copper Bromide to occur away from the laser path. 

This photo shows the complex electronics involved in the control of the the laser power supply. The PCB on the left is the heater controller. The heater connections and the associated themocoupler connections are at the top of the photo (group of three connectors). The PCB on the right is the thyratron driver / controller.

Another view of the heater control PCB.