10.6084/m9.figshare.1012442.v1 James R Harries James R Harries Mitsuru Nagasono Mitsuru Nagasono Hiroshi Iwayama Hiroshi Iwayama Eiji Shigemasa Eiji Shigemasa Filter bandwidths using the (2,0)<sub><em>n</em></sub> absorption profiles as functions of helium column density IOP Publishing 2013 column density fwhm fel scss cm helium column density wavelength SASE pulses helium gas cell bandwidth profile Atomic Physics Molecular Physics 2013-08-13 00:00:00 Figure https://iop.figshare.com/articles/figure/_Filter_bandwidths_using_the_2_0_sub_em_n_em_sub_absorption_profiles_as_functions_of_helium_column_d/1012442 <p><strong>Figure 6.</strong> Filter bandwidths using the (2,0)<sub><em>n</em></sub> absorption profiles as functions of helium column density. For <em>n</em> = 2 (red) the two half-widths (dashed lines) are shown along with the full-width at half-maximum. Only the FWHMs are shown for <em>n</em> = 3 (blue), <em>n</em> = 4 (green), and <em>n</em> = 5 (purple). The dashed vertical lines show the maximum column density used in this work (68 <b>×</b> 10<sup>17</sup> cm<sup>−2</sup>) and the column density which would correspond to 2 m of gas at atmospheric pressure (5 <b>×</b> 10<sup>21</sup> cm<sup>−2</sup>). The solid black circles show the bandwidths obtained in the spectra plotted in figures <a href="http://iopscience.iop.org/0953-4075/46/16/164021/article#jpb465316f3" target="_blank">3</a> and <a href="http://iopscience.iop.org/0953-4075/46/16/164021/article#jpb465316f4" target="_blank">4</a>.</p> <p><strong>Abstract</strong></p> <p>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.</p>