TY - JOUR
T1 - Application of matched-filter concepts to unbiased selection of data in pump-probe experiments with free electron lasers
AU - Callegari, Carlo
AU - Takanashi, Tsukasa
AU - Fukuzawa, Hironobu
AU - Motomura, Koji
AU - Iablonskyi, Denys
AU - Kumagai, Yoshiaki
AU - Mondal, Subhendu
AU - Tachibana, Tetsuya
AU - Nagaya, Kiyonobu
AU - Nishiyama, Toshiyuki
AU - Matsunami, Kenji
AU - Johnsson, Per
AU - Piseri, Paolo
AU - Sansone, Giuseppe
AU - Dubrouil, Antoine
AU - Reduzzi, Maurizio
AU - Carpeggiani, Paolo
AU - Vozzi, Caterina
AU - Devetta, Michele
AU - Faccialà, Davide
AU - Calegari, Francesca
AU - Castrovilli, Mattea Carmen
AU - Coreno, Marcello
AU - Alagia, Michele
AU - Schütte, Bernd
AU - Berrah, Nora
AU - Plekan, Oksana
AU - Finetti, Paola
AU - Ferrari, Eugenio
AU - Prince, Kevin Charles
AU - Ueda, Kiyoshi
N1 - Funding Information:
This work was supported by the X-ray Free Electron Laser Priority Strategy Program of the Ministry of Education, Culture, Sports, Science, and Technology of Japan (MEXT); by JSPS and CNR under the Japan-Italy Research Cooperative Program; by the Grant-in-Aid for the Global COE Program 'the Next Generation of Physics, Spun from Universality and Emergence' from the MEXT; by the Grants-in-Aid (No. 20310055 and No. 21244062) from the Japan Society for the Promotion of Science (JSPS); by the JSPS KAKENHI Grant Number JP 16J02270; by the Swedish Research Council and the Swedish Foundation for Strategic Research; by the ERC Starting Research Grant UDYNI No. 307964; by the European Union Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 641789 "MEDEA" (Molecular Electron Dynamics investigated by IntensE Fields and Attosecond Pulses); by the DOE-SC-BES under Award No. DE-SC0012376; and by the Italian Ministry of Education, Universities and Research (MIUR) (PRIN 2012-NOXSS)
Publisher Copyright:
© 2017 by the authors.
PY - 2017
Y1 - 2017
N2 - 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.
AB - 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.
KW - Correlation
KW - Data processing
KW - Free electron laser
KW - Matched filter
KW - Pump-probe
KW - Statisticalweight
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U2 - 10.3390/app7060621
DO - 10.3390/app7060621
M3 - Article
AN - SCOPUS:85020870294
VL - 7
JO - Applied Sciences (Switzerland)
JF - Applied Sciences (Switzerland)
SN - 2076-3417
IS - 6
M1 - 621
ER -