Deformation of Gas Lenses by Gravity

Gravity forces cause distortions in tubular gas lenses. A theory is derived here which yields excellent quantitative agreement with measured distortions for various tube lengths, diameters, and gases. It is shown that in a gas lens of optimum design the displacement of the optical center has a maximum at the end of the lens. The amount of displacement increases with the fourth power of the tube diameter and with the square of the gas pressure.