Here are some common optical cavities. The optical output is usually extracted through one mirror that is only partially reflective "a leaky mirror" or a hole in the mirror covered with a window. My tube uses a flat output coupler (front mirror), r=infinity, refl = 90% and a spherical rear mirror, r=20m, refl = 100%.
OpticsLaser Research Optics is a good source for front and back mirrors
Output Coupler Part # OC-1012-Z-80 ZnSe $ 150.00
Total Reflector, Silicon Part # TRCC-1012-S-(specify radii 2,3, 5, 10 etc)-HES $ 75.00 from stock
888-239-5545 Phone toll free
E-mail Bruce Sunderland at Laser Research Optics
Gas Mixture and Vacuum Pump
A current limited supply is needed. Several kilovolts will be needed to start the discharge, and several hundred volts may be needed to maintin it. A neon sign transformer or supply works well. You can directly use AC current if you dont mind the beam being amplitude modulated at 120 Hz. You can build a ballast bank to limit an ordinary HV transformer, see Altair Tesla Page and many other internet Tesla sites for ideas and examples.
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