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Design of compact spectrograph with shiftable spectral range based on transmission gratings
Malina, Jan ; Pořízka, Pavel (referee) ; Novotný, Jan (advisor)
The aim of this diploma thesis is to design a compact spectrometer with a transmission grating and a shiftable spectral range for the method of laser-induced breakdown spectroscopy (LIBS). The work in the theoretical part contains a basic description of spectroscopy and spectroscopic methods of LIBS, spectrometer and its individual parts. The practical part describes the spectrometer design procedure, introduces selected components and comments on the reason for their selection. Selected components are assembled into the final form of a spectrometer, which is further tested with the help of a simulation program to confirm its functionality. The result of the work is a comprehensive overview of the individual components of the spectrometer, aspects of its construction together with instructions and advice on its assembly, along with an example in the form of a designed set of commonly available catalog components.
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Impact of the atmosphere on laser ablation of matters
Černá, Svatava ; Hrdlička, Aleš (referee) ; Pořízka, Pavel (advisor)
This thesis deals with a general overview of laser-induced breakdown spectroscopy - ablation of material and plasma formation when a change of the surrounding environment occurs. The aim is to establish ideal conditions for improving detection, which is difficult for some elements when the measurement takes place in the ambient atmosphere. This is the reason why we change the ambient conditions, the gas (air, helium, argon) and its pressure. Buffer gases (helium, argon) influence the development of the material ablation and quality of generated plasma. That is why we inspect the changes in the signal according to particular atmospheres (signal change in buffer gases compared to the ambient atmosphere). The first part of the thesis presents the principle and physical nature of laser ablation with a brief search of experiments performed so far for similar purposes. Based on this search we determine conclusions about the influence of buffer gasses and pressure on the detection used gasses. In the second part of the work, the controlled experiment is presented, which consisted of the detection of spectral lines of fluorine and potassium, see chapter 5.6 and molecular transitions of calcium fluoride, see chapter 5.10. In a controlled experiment, we established two assumptions. The first assumption is the influence of the inert gas atmosphere, which should significantly improve the detection of fluorine and potassium compared to the air atmosphere. We confirmed this finding only for the argon atmosphere. In contrast, in the helium atmosphere, the detection of none of the elements improved. The second assumption is the effect of reducing the ambient pressure, which in combination with an inert gas should allow the detection of fluorine even at low concentrations in the sample. We consider the measured glass disk in chapter 5.7 to be such a sample. This assumption is not confirmed, as the increased intensity of the fluorine spectral line does not manifest itself in any way when the pressure in the vacuum chamber decreases. Finally, in chapter 7 from the results of individual parts of the experiment, the most suitable conditions for the future detection of the measured substances were proposed: fluorine, potassium and calcium fluoride molecules.
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Combination of laser spectroscopy methods for chemical analysis
Holub, Daniel ; Novotný, Karel (referee) ; Pořízka, Pavel (advisor)
The topic of this Master’s thesis is combination of laser spectroscopic methods. LIBS and Raman spectroscopy were chosen for the combination. This combination is applied to plastic identification and separation as a mean to automate sorting of plastic waste. Data handling was done via different methods of computer learning algorithms scripted in R language. Plastic sorting accuracy over 90 % was reached thanks to the combination of chosen methods. This work also addresses some issues implied by combination of two different methods.
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Development of universal software interface for detection units in optical spectroscopy
Belica, Martin ; Pořízka, Pavel (referee) ; Žalud, Luděk (advisor)
This master's thesis deals with the design and implementation of universal user interface for detection devices used in Laser-induced breakdown spectroscopy. The design and implementation are based on analysis of current state of instrumentation used in laser spectroscopy. The user interface should be able to work with high repetition frequency of measurement. Acquired spectra should be visualised to user and it is also necessary to save this data on hard drive. The resulting application must be universal. It means the application must support various types and vendors of detection devices.
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Design of an optomechanical module for laser-induced plasma imaging
Buday, Jakub ; Hrdlička, Aleš (referee) ; Pořízka, Pavel (advisor)
Laser-Induced Breakdown Spectroscopy (LIBS) is a method of analytical chemistry that provides a qualitative and quantitative analysis of a sample. The ablation process of a sample is fast and dynamic and the change of plasma in time and space is a question of a few microseconds. An examination that provides a good time and space resolution is necessary to understand better the physical processes. For this reason, the goal of this thesis is to design a basic optomechanic construction for this type of experiment. Furthermore, it is important to check the functionality of this design and to use it for a basic comparison between the spectroscopic and imaging data. Also, the time development of plasma will be observed under different experimental conditions. The goal of this thesis, in general, is to prove that the morphology of plasma is as it is described in available related literature.
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Design of optomechanical module for chemical mapping using Laser-Induced Breakdown Spectroscopy
Švábíková, Anna ; Samek, Ota (referee) ; Pořízka, Pavel (advisor)
Tato diplomová práce se zabývá návrhem optomechanického modulu pro chemické mapování metodou spektroskopie laserem buzeného plazmatu (LIBS). Cílem je vyvinout modul, který bude umožňovat analýzu spektrálních čar zinku v ultrafialové (UV) oblasti. V práci jsou popsány teoretické základy metody LIBS a následně je provedena rešerše zaměřená na problematiku dálkové LIBS analýzy. V diplomové práci jsou prezentovány možné optické návrhy fokusační a sběrné optiky, z nichž jsou vybrané následně otestovány. Výsledkem práce je konstrukční návrh modulu.
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Processing of tomographic data by principal component analysis method for archaeological applications
Prokop, David ; Žídek, Jan (referee) ; Pořízka, Pavel (advisor)
Rentgenová počítačová tomografie je metoda sloužící ke 3D zobrazování vnitřní struktury objektů. Mikrostruktura objektů ukrývá důležité informace, které mohou být použity k jejich charakterizaci. Tato práce podává spojení mezi datasety získanými pomocí rentgenové počítačové mikrotomografie a oblastí statistického zpracování dat. Výstupem metody, pak bude klasifikace vzorků na základě informací o jejich mikrostruktuře. Z výsledků klasifikace vzorků, pak můžeme vyvodit různé hypotézy týkající se původu vzorků. Tato práce by mimo jiné mohla sloužit jako takový nový vhled do problematiky kombinace dat různého původu, pomocí metod statistické analýzy.
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Interconnection of Restricted Boltzmann machine method with statistical physics and its implementation in the processing of spectroscopic data
Vrábel, Jakub ; Hrdlička, Aleš (referee) ; Pořízka, Pavel (advisor)
Práca sa zaoberá spojeniami medzi štatistickou fyzikou a strojovým učením s dôrazom na základné princípy a ich dôsledky. Ďalej sa venuje obecným vlastnostiam spektroskopických dát a ich zohľadnení pri pokročilom spracovaní dát. Začiatok práce je venovaný odvodeniu partičnej sumy štatistického systému a štúdiu Isingovho modelu pomocou "mean field" prístupu. Následne, popri základnom úvode do strojového učenia, je ukázaná ekvivalencia medzi Isingovým modelom a Hopfieldovou sieťou - modelom strojového učenia. Na konci teoretickej časti je z Hopfieldovej siete odvodený model Restricted Boltzmann Machine (RBM). Vhodnosť použitia RBM na spracovanie spektroskopických dát je diskutovaná a preukázaná na znížení dimenzie týchto dát. Výsledky sú porovnané s bežne používanou Metódou Hlavných Komponent (PCA), spolu so zhodnotením prístupu a možnosťami ďalšieho zlepšovania.
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Visualization of spectroscopic data using Principal Component Analysis
Šrenk, David ; Žák, Libor (referee) ; Pořízka, Pavel (advisor)
This diploma thesis deals with using laser-induced breakdown plasma spectroscopy for determining the elemental structure of unknown samples. It was necessary to design an appropriate method to qualify material by laser-induced emission spectrum. Pretreatment of data and using a variety of chemometrics methods had to be done in order to qualify the structure of elements. We achieved a required solution by projecting the data to a new PCA space, creating clusters and computing the Euclidean distance between each cluster. The experiment in the practical part was set to detect an interface of two elements. We created a data file simulating the ablation on the interface. This data set was gradually processed applying a mathematical-chemical-physical view. Several data procedures have been compiled: approximation by Lorenz, Gauss and Voigt function and also a pretreatment method such as the detection of outliers, standardization by several procedures and subsequent use of principal components analysis. A summarization of processes for input data is fully described in the thesis.
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Approaches to signal correction and standardization in laser spectroscopy
Schiffer, Štěpán ; Hrdlička, Aleš (referee) ; Pořízka, Pavel (advisor)
The subject of this diploma thesis is the study of a sample position influence on results of an experiment in laser spectroscopy. The aim is to design an appropriate way for standardization of signal obtained at different conditions with the respect to its applicability for stand-off analysis. In the theoretical part of the diploma thesis there are the basics of LIBS method described together with the issues of stand-off experiment and both, basic and advanced approches for the processing and correction of obtained spectra. Also the experiment is designed here, which is used for the analysis of the sample inclination and distance influence on the detected signal. The choice of appropriate ways for the signal correction follows and their applicability and efficiency is then experimentally tested.
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