High-efficiency concave-grating monochromator with wavelength-independent focusing characteristics

A cylindrical grating with tangential focusing provided by exponentially spaced grooves can be used by itself or in conjunction with an elliptical mirror to construct a monochromator that has better resolution over its entire tuning range than a toroidal-grating monochromator has at its optimum wavelength. In contrast to conventional Wads-worth or Rowland circle designs, a cylindrical-grating monochromator is always in focus, always on blaze with respect to the principal ray, has wavelength-independent resolution and focusing properties, and can be tuned over an order of magnitude with a simple linear motion.