Detail showing the transmission near (2,0)₃ for a column density of ~68 × 10¹⁷ cm⁻²

Figure 3. Detail showing the transmission near (2,0)₃ for a column density of ~68 × 10¹⁷ cm⁻². The inset shows the two single-shot spectra with the highest transmitted intensities at the wavelengths of zero cross-section (red, blue), along with the calculated average transmission (black).

Abstract

Using the third harmonic of the FEL radiation from the SPring-8 compact SASE (self-amplified stimulated emission) source SCSS we have studied the effects on SASE pulses with central wavelengths near 20 nm due to passage through a helium gas cell. The positions of zero ionization cross-section close to wavelengths corresponding to double-excitations allow operation as an efficient wavelength filter, with effectively 100% transmitted peak intensity until the Doppler-broadening limit is reached. We discuss how the time profile of the SASE pulses is affected, and discuss potential applications.