A source of photons includes a discharge chamber, a plurality of ion beam sources in the discharge chamber and a neutralizing mechanism. Each of the ion beam sources electrostatically accelerates a beam of ions of a working gas toward a plasma discharge region. The neutralizing mechanism at least partially neutralizes the ion beams before they enter the plasma discharge region. The neutralized beams enter the plasma discharge region and form a hot plasma that radiates photons. The photons may be in the soft X-ray or extreme ultraviolet wavelength range and, in one embodiment, have wavelengths in a range of about 10-15 nanometers. |