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Self-absorption in laser-induced plasmas in simulated Martian atmospheric conditions

Hansen, Peder Bagge and Schröder, Susanne and Vogt, David and Kubitza, Simon and Rammelkamp, Kristin and Hübers, Heinz-Wilhelm (2019) Self-absorption in laser-induced plasmas in simulated Martian atmospheric conditions. 10th Euro-Mediterranean Symposium onLaser-Induced Breakdown Spectroscopy, 8-13 september 2019, Brno, Czech Republic.

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ChemCam on board the Mars rover Curiosity is the first LIBS instrument on Mars. In 2020,two more LIBS instruments will follow [1,2]. Thus, understanding the capabilities andchallenges of LIBS in Mars’ atmosphere is of high interest. A general challenge of LIBS is self-absorption (SA). The effect of SA depends on the atmospheric conditions. In Earth’satmosphere SA affects the intensities of the emission lines strongly and breaks the linearityof calibration curves which limits their accuracy [3]. While SA is expected to be lower inMartian conditions, no extensive studies on this have been reported. In this study weinvestigate SA in LIBS spectra acquired in simulated Martian atmospheric conditions. LIBSspectra of salts are obtained with two different setups: A high-resolution LIBS setup with ahigh spectral range and a plasma imaging setup allowing for spatially resolvedmeasurements of the full plasma at a selected small spectral range. In measurements madewith the plasma imaging setup, the effect of SA on the Ca(II) doublet at 393 nm and 396 nmcan be observed. Fig. 1A shows the intensity ratio of the two emission lines for line-of-sightmeasurements through the plasma plume at different distances from the plasma axis. Withnegligible SA the ratio would be 2.1. We find a strong influence of SA, especially for largeeffective path lengths through the plasma center. For the calculation of the SA effect inspectra of the high-resolution LIBS setup, the plasma is modelled as a two-layer plasma inlocal thermal equilibrium. Temperature, electron density, and effective path length of eachlayer are varied and the resulting simulated spectra are compared to the measurements tofind the best fit, see Fig. 1B. From the values of the best fit we find that many strong emissionlines are significantly affected by SA, even though the effect is not obvious from the lineprofiles because of the instrumental broadening.

Item URL in elib:https://elib.dlr.de/136161/
Document Type:Conference or Workshop Item (Poster)
Title:Self-absorption in laser-induced plasmas in simulated Martian atmospheric conditions
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Hansen, Peder BaggePederBagge.Hansen (at) dlr.deUNSPECIFIED
Schröder, SusanneSusanne.Schroeder (at) dlr.deUNSPECIFIED
Vogt, DavidDavid.Vogt (at) dlr.dehttps://orcid.org/0000-0003-1109-6960
Kubitza, SimonSimon.Kubitza (at) dlr.deUNSPECIFIED
Rammelkamp, KristinKristin.Rammelkamp (at) dlr.deUNSPECIFIED
Hübers, Heinz-WilhelmHeinz-Wilhelm.Huebers (at) dlr.deUNSPECIFIED
Date:9 September 2019
Refereed publication:Yes
Open Access:Yes
Gold Open Access:No
In ISI Web of Science:No
Keywords:LIBS, laser-induced breakdown spectroscopy, SA, self-absorption, Mars
Event Title:10th Euro-Mediterranean Symposium onLaser-Induced Breakdown Spectroscopy
Event Location:Brno, Czech Republic
Event Type:international Conference
Event Dates:8-13 september 2019
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Space Technology
DLR - Research area:Raumfahrt
DLR - Program:R SY - Technik für Raumfahrtsysteme
DLR - Research theme (Project):R - Vorhaben OptoRob
Location: Berlin-Adlershof
Institutes and Institutions:Institute of Optical Sensor Systems > Terahertz and Laser Spectroscopy
Deposited By: Hansen, Peder Bagge
Deposited On:21 Sep 2020 12:38
Last Modified:05 Oct 2020 10:22

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