Qualitative-portable to quantitative-laboratory LIBS

Laser Induced Breakdown Spectroscopy (LIBS) offers possibility for fast detection of sample composition without its preparation. For this reason it is attractive anywhere where the fast detection and no sample preparation are needed. As in many other branches the technical and scientific progress improves and spreads the possibilities of LIBS based devices and laboratory apparatuses. The time-resolved spectroscopy is allowed by spectrograph equipped with fast camera, broadband spectra can be acquired in single exposition by broadband spectrometers. Smaller and lighter laser sources together with compact spectrometers can be implemented to portable device and can be used out of laboratory. Computers offer quick data processing. The device named ChemCam installed on the NASA's next Mars rover, curiosity, is good example of high technology application in LIBS. However, there are still challenges and we hope that this work will be fruitful for anyone who is interested in the LIBS. The project of presented thesis was performed as a joint supervision project between the Department of Experimental Physics at Comenius University in Bratislava and 'Laboratoire Interdisciplinaire Carnot de Bourgogne' at Universite de Bourgogne in Dijon. The aim of the project was to join experience from both laboratories, experience in laser constructions from Dijon and experience with spectroscopy from Bratislava. The both are essential for LIBS. In Bratislava the work was coordinated by prof. Pavel Veis and it was focused on LIBS under the laboratory conditions. The time-resolved broadband spectrometry was used in the research. In order to achieve required spectra, the spectral response of the optical system was determined which was later used for the corrections. The research of self-absorption phenomena started in the last period with aim to use this effect, usually considered as negative, for the composition determination. In Dijon the work was supervised by Dr. Olivier Musset and directed toward development of LIBS device which could be used out of laboratory. The small laser which was previously developed in the laboratory was implemented in the device. The development was successfully finished and testing process began in the last period of the thesis. The geological samples have been used for the testing process which was performed in deep cooperation with geologists. The first chapter comprises a brief introduction to LIBS. It is divided into some parts about laser induced plasma, laser induced breakdown and evolution of the plasma after breakdown. The section dealing with local thermodynamic equilibrium is also included. The section describes importance of LTE and the possibilities to determine this state. The second chapter is dedicated to the developed portable LIBS device. In the introduction, different type of LIBS devices are presented with their possibilities. Then the portable device developed in Dijon is described part by part with brief characteristic of developed software. The device possibilities and limits are sketched in the last section of the chapter with respect to results obtained in the testing process. The third chapter deals with capabilities of LIBS apparatus which was set up in the laboratory. The process of spectral response measurement and its results are presented and consequently used in next sections in process of plasma parameters determination. The composition of used samples are determined by using of calibration free method with aim to choose proper location in the plasma for which results are the most representative. The last chapter includes introduction to the subject of self-absorption phenomena. The simple model and basic theory are presented with suggestion how to use the phenomena in positive way. The simple experiment and its results are presented at the end of the chapter together with discussion about the possibilities and perspectives of the suggested method. (author)