Extracting ion emission lines from femtosecond-laser plasma X-ray spectra heavily contaminated by spikes

フェムト秒レーザープラズマによる高ノイズX線スペクトルからのイオンの放出線の抽出

Gasilov, S. V.*; Faenov, A. Y.; Pikuz, T. A.*; Villoresi, P.*; Poletto, L.*; Stagira, S.*; Calegari, F.*; Vozzi, C.*; Nisoli, M.*

Gasilov, S. V.*; Faenov, A. Y.; Pikuz, T. A.*; Villoresi, P.*; Poletto, L.*; Stagira, S.*; Calegari, F.*; Vozzi, C.*; Nisoli, M.*

Charged-coupled device (CCD) detectors are widely used nowadays for the registration of X-ray spectra of multicharged ions, generated in a plasma during interaction of ultrashort, ultraintenselaser pulses with solid targets. In this work we propose "mean to median" algorithm for the removal of noise from the X-ray spectra of femtosecondlaser plasma. Series of spectra is necessary for the identification of corrupted data points by the developed method. The algorithm was tested with model spectra and was used for extracting information about spectral lines of Ne like ions of Fe XVII and He like Al ions which allowed to calculate plasma parameters. It is demonstrated that M2M method is able to clean spectra with more then 0.1 of corrupted pixels. The method is also valid if variations in spectral lines induced by fluctuations in laser beam intensity are present.