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Title: Application of Matched-Filter Concepts to Unbiased Selection of Data in Pump-Probe Experiments with Free Electron Lasers
Authors: Callegari, Carlo
Takanashi, Tsukasa
Fukuzawa, Hironobu
Motomura, Koji
Iablonskyi, Denys
Kumagai, Yoshiaki
Mondal, Subhendu
Tachibana, Tetsuya
Nagaya, Kiyonobu  kyouindb  KAKEN_id
Nishiyama, Toshiyuki
Matsunami, Kenji
Johnsson, Per
Piseri, Paolo
Sansone, Giuseppe
Dubrouil, Antoine
Reduzzi, Maurizio
Carpeggiani, Paolo
Vozzi, Caterina
Devetta, Michele
Faccialà, Davide
Calegari, Francesca
Castrovilli, Mattea
Coreno, Marcello
Alagia, Michele
Schütte, Bernd
Berrah, Nora
Plekan, Oksana
Finetti, Paola
Ferrari, Eugenio
Prince, Kevin
Ueda, Kiyoshi
Author's alias: 永谷, 清信
西山, 俊幸
Keywords: correlation
matched filter
free electron laser
data processing
statistical weight
Issue Date: 16-Jun-2017
Publisher: MDPI AG
Journal title: Applied Sciences
Volume: 7
Issue: 6
Thesis number: 621
Abstract: Pump-probe experiments are commonly used at Free Electron Lasers (FEL) to elucidate the femtosecond dynamics of atoms, molecules, clusters, liquids and solids. Maximizing the signal-to-noise ratio of the measurements is often a primary need of the experiment, and the aggregation of repeated, rapid, scans of the pump-probe delay is preferable to a single long-lasting scan. The limited availability of beamtime makes it impractical to repeat measurements indiscriminately, and the large, rapid flow of single-shot data that need to be processed and aggregated into a dataset, makes it difficult to assess the quality of a measurement in real time. In post-analysis it is then necessary to devise unbiased criteria to select or reject datasets, and to assign the weight with which they enter the analysis. One such case was the measurement of the lifetime of Intermolecular Coulombic Decay in the weakly-bound neon dimer. We report on the method we used to accomplish this goal for the pump-probe delay scans that constitute the core of the measurement; namely we report on the use of simple auto- and cross-correlation techniques based on the general concept of “matched filter”. We are able to unambiguously assess the signal-to-noise ratio (SNR) of each scan, which then becomes the weight with which a scan enters the average of multiple scans. We also observe a clear gap in the values of SNR, and we discard all the scans below a SNR of 0.45. We are able to generate an average delay scan profile, suitable for further analysis: in our previous work we used it for comparison with theory. Here we argue that the method is sufficiently simple and devoid of human action to be applicable not only in post-analysis, but also for the real-time assessment of the quality of a dataset.
Rights: © 2017 by the authors. Licensee MDPI, Basel, Switzerland. This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
DOI(Published Version): 10.3390/app7060621
Appears in Collections:Journal Articles

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