WWW.DISSERTATION.XLIBX.INFO
FREE ELECTRONIC LIBRARY - Dissertations, online materials
 
<< HOME
CONTACTS



Pages:   || 2 | 3 | 4 | 5 |   ...   | 18 |

«by YUAN LIU B.S. Information Engineering, Zhejiang University, 2006 M.S. Optics, University of Central Florida, 2010 A dissertation submitted in ...»

-- [ Page 1 ] --

DEVELOPMENT OF LASER SPECTROSCOPY FOR ELEMENTAL AND MOLECULAR

ANALYSIS

by

YUAN LIU

B.S. Information Engineering, Zhejiang University, 2006

M.S. Optics, University of Central Florida, 2010

A dissertation submitted in partial fulfillment of the requirements

for the degree of Doctor of Philosophy

in the College of Optics and Photonics at the University of Central Florida Orlando, Florida Spring Term 2013 Major Professor: Martin C. Richardson © 2013 Yuan Liu ii

ABSTRACT

Laser-Induced Breakdown Spectroscopy (LIBS) and Raman spectroscopy are still growing analytical and sensing spectroscopic techniques. They significantly reduce the time and labor cost in analysis with simplified instrumentation, and lead to minimal or no sample damage.

In this dissertation, fundamental studies to improve LIBS analytical performance were performed and its fusion with Raman into one single sensor was explored.

On the fundamental side, Thomson scattering was reported for the first time to simultaneously measure the electron density and temperature of laser plasmas from a solid aluminum target at atmospheric pressure. Comparison between electron and excitation temperatures brought insights into the verification of local thermodynamic equilibrium condition in laser plasmas.

To enhance LIBS emission, Microwave-Assisted LIBS (MA-LIBS) was developed and characterized. In MA-LIBS, a microwave field extends the emission lifetime of the plasma and stronger time integrated signal is obtained. Experimental results showed sensitivity improvement (more than 20-fold) and extension of the analytical range (down to a few tens of ppm) for the detection of copper traces in soil samples.

Finally, laser spectroscopy systems that can perform both LIBS and Raman analysis were developed. Such systems provide two types of complimentary information – elemental composition from LIBS and structural information from Raman. Two novel approaches were reported for the first time for LIBS-Raman sensor fusion: (i) an Ultra-Violet system which combines Resonant Raman signal enhancement and high ablation efficiency from UV radiation, and (ii) a Ti:Sapphire laser based NIR system which reduces the fluorescence interference in Raman and takes advantage of femtosecond ablation for LIBS.

iii To my family iv

ACKNOWLEDGMENTS

I would like to express my sincere gratitude and appreciation to my advisor Dr. Martin Richardson for the guidance and support during myPh.D. study. I would also like to thank my committee members Dr. Eric Van Stryland, Dr. Michael Bass, and Dr. Michael Sigman for their time and advice throughout my candidacy, proposal and defense.

Dr. Matthieu Baudelet and his great passion in spectroscopy played irreplaceable roles during my Ph.D. study. We went through all the projects described in this dissertation together.

Through numerous discussions, presentation rehearsals, and paper revisions with him, I gradually gained the skills and experiences needed to become a young scientist. Many thanks for all your time and inputs during the last five years.

Certainly Dr. Bruno Bousquet from the University of Bordeaux in France is a must-have name in this list. He is a great collaborator and mentor in LIBS and physics. His critical thinking and his way to plan and organize research projects impress me a lot. Without his support, a large portion of this dissertation could not be completed. It was my great pleasure to work with him during his visit.

I wish to thank Dr. Santiago Palanco, who brought me into the Laser Plasma Laboratory and introduced LIBS to me. I also want to thank Dr. Christopher Brown, and Dr. Matthew Weidman, from whom I learned the basic laboratory skills and fundamentals about LIBS.

Past and present members in the Laser Plasma Laboratory kindly offered me consistent and generous help. I would like to thank Tony and Nick for their help on all sorts of electronic problems, thank John for the assistance in setting up the laser channel used in the Thomson

–  –  –

system and Zygo interferometer, thank Ji-Yeon and Pankaj for showing me how to operate the Cary spectrometer, and thank Khan, Nathan, Benn and many others (sorry we are a large group and can’t put all the names who helped me) for lending me optical and mechanical components and also the conversations and happy time with them.

Last but not least, I would like to thank many friends I met at CREOL and UCF. These people added diversity and color during this important period of my life.

–  –  –

ABSTRACT

ACKNOWLEDGMENTS

TABLE OF CONTENTS

LIST OF FIGURES

LIST OF TABLES

LIST OF ABBREVIATIONS

CHAPTER 1 INTRODUCTION

1.1 Motivation

1.2 Pros and Cons of Current methods

1.3 LIBS and Raman: key anchors in analysis

1.4 Overview of the thesis

CHAPTER 2 LASER-INDUCED BREAKDOWN SPECTROSCOPY

2.1 LIBS Introduction

2.2 Fundamentals of LIBS Plasma

2.2.1Plasma formation

2.2.2 Equilibrium state of laser-induced plasma





–  –  –

2.3 Diagnostics for LIBS Plasmas

2.3.1 Excitation Temperature

2.3.2 Electron Density

2.3.3 Thomson Scattering for Te and ne Diagnostics

2.4 LIBS Instrumentation

2.4.1 Lasers

2.4.2 Spectrometers

2.4.3 Detectors

2.4.4 Improvement of LIBS

CHAPTER 3 LASER PLASMA DIAGNOSTICS BY THOMSON SCATTERING..... 36

3.1 Introduction

3.2 Experimental

3.2.1Experimental setup

3.2.2 Synchronization

3.3 Air plasma

3.3.1 Collective Thomson scattering spectra

–  –  –

3.3.3 Time resolved Te and ne measurements for air plasma

3.4 Aluminum plasma

3.4.1 Plasma imaging and probe position

3.4.2 Plasma heating

3.4.3 Thomson scattering spectrum

3.4.4 Time resolved Te and ne measurements

3.4.5 McWhirter criterion and Local Thermodynamic Equilibrium

3.5 Conclusion

–  –  –

SPECTROSCOPY

4.1 Motivation

4.2 Experimental

4.2.1 Microwave system

4.2.2 Ablation system

4.2.3 Detection system

4.3 MA-LIBS Plasma Characterization

4.3.1 Plasma Emission

ix 4.3.2 Plasma temperature estimation

4.3.3 Electron density

4.4 Performance of MA-LIBS

4.4.1 Signal enhancement

4.4.2 Improvement of sensitivity

4.4.3 Selective enhancement of lines

4.4.4 Enhancement of molecular emission

4.4.5 Enhancement dependence on laser irradiance

4.4.6 Influence of atmosphere condition

4.5 Conclusion

CHAPTER 5 FUNDAMENTALS OF RAMAN SPECTROSCOPY

5.1 Raman Scattering and Molecule Vibration

5.1.1 Spontaneous Raman scattering

5.1.2 Raman active modes

5.1.3 Raman intensity

5.2 Raman spectroscopy

5.2.1 Spontaneous Raman Spectroscopy

–  –  –

5.2.3 Comparison with IR spectroscopy

5.2.4 Fluorescence in Raman spectroscopy

CHAPTER 6 MOLECULAR INFORMATION FROM LIBS SPECTRA AND LIBS-RAMAN

SENSOR FUSION

6.1 Motivation

6.2 Correlation between LIBS signal and moisture content

6.2.1 Introduction

6.2.2 Experimental

6.2.3Results and discussions

6.2.4 Conclusion

6.3 LIBS-Raman Sensor Fusion

6.3.1 Introduction

6.3.2 532 nm LIBS-Raman System

6.3.3 266 nm LIBS-Raman System

6.3.4 785 nm LIBS-Raman System

6.3.5 Summary of LIBS-Raman sensor fusion

CHAPTER 7 CONCLUSIONS AND FUTURE WORK

xi

7.1 Conclusion

7.2 Future work

REFERENCE

–  –  –

Figure 2.1: AES procedure and comparison with LIBS.

Figure 2.2:Plasma creation steps

Figure 2.3: Ionization with (a) multiphoton ionization, and (b) cascade ionization.

In the figure, e- represents electrons; hν represents photons; IB is inverse Bremsstrahlung absorption........... 11 Figure 2.4: Illustration of the regimes where Saha equation and Boltzmann distribution are applied.

Parameters in this figure can be found in the Saha equation and Boltzmann distribution.

Figure 2.5: The evolution of plasma emission over time.

(Courtesy of Matthew Weidman)...... 16 Figure 2.6: A LIBS spectrum from an yttrium aluminum garnet (YAG) crystal.

Figure 2.7: Calibration curve for LIBS measurements of Cu in soil using the 324.

75 nm line... 19 Figure 2.8: Boltzmann plots of Cr I in plasma from a Cr:LiCAF crystal. Estimated plasma temperature is about 7980 K.

Figure 2.9: Direction diagram for Thomson scattering.

Figure 2.10: Simulated normalized Thomson scattering spectra with Te = 8000 K and ne ranges from 1017 to 1013 cm-3.

The α values are 3.08, 2.18, 0.97, 0.69, 0.31, 0.22, 0.10, 0.07 and 0.03 respectively.

Figure 2.11: Fitting a real TS spectrum.

An air plasma was created and probed by a 532 nm laser.

The Te is estimated to be 66811 ± 360 K, and ne is 3.936 ± 0.016 × 1017 cm-3.

Figure 2.12: A typical LIBS system.

(DG: delay generator)

Figure 2.13: Schematic diagram of a Czerny-Turner spectrometer (a), and light diffraction from a reflection grating (b).

–  –  –

Figure 2.16: Common configurations of DP-LIBS.

(a) Collinear configuration, (b) orthogonal configuration with a reheating pulse, (c) orthogonal configuration with a pre-ablation pulse..... 34 Figure 2.17: MA-LIBS experimental setup [87]

Figure 3.1: Schematics of the experimental setup.

In the figure, WP = wave plate, PBS = polarization beam splitter, L1-6 = Lens 1-6.

Figure 3.2: Timing sequence for synchronization.

(a) Flash lamp and Q-switch; (b) Synchronization of the two lasers, the shutter, and the camera.

Figure 3.3: Synchronization for Thomson scattering experiment.

FL: flash lamp, QS: Q-switch, Tgr: External trigger input.

Figure 3.4: Typical collective Thomson scattering signal: ICCD image of the spectrum (left) and spectrum after binning (right).

Figure 3.5: Fitting (red) of the spectrum (blue) in Figure 3.

4. Te was found to be 58500 K and ne was 4.39×1017 cm-3.

Figure 3.6: Thomson scattering spectrum image taken at 2 µs after plasma creation.

................. 47 Figure 3.7: The difference between two normalized Rayleigh scattering spectra from air (red) and the difference between the normalized TS spectrum from an air plasma 4 µs after the plasma creation and the normalized Rayleigh scattering spectrum (blue).

Figure 3.8: Gaussian fit of the Thomson scattering spectrum from air plasma at 4 µs after plasma creation.

Figure 3.9: Te and ne of air plasma as a function of the delay time.

Figure 3.10: Probe laser and plasma images at different delay time.

–  –  –

2.2, and 3 μs after the plasma formation.

Figure 3.12: a) Raw Thomson scattering spectrum and b) Fitting of the blue-shifted satellite peak of the spectrum for the Al plasma 800 ns after plasma creation at 1 atm pressure.

Figure 3.13: Time evolution of the Te and ne of the Al plasma at 1 atm pressure.

Figure 3.14: The maximum transition energy that satisfies the McWhirter criterion as a function of delay time between the plasma ignition and detection.

The black squares are the calculated ΔE values from the measured Te and ne pairs at their specific delay time, when the McWhirter criterion is just satisfied. The red line is a linear fit of the energy as a function of the delay time.

Figure 3.15: Aluminum spectrum 600 ns after plasma creation for the Boltzmann plot.

............. 60 Figure 3.16: Excitation temperatures measured based on lines from atoms (black squares) and singly ionized ions (red circles).

Figure 4.1: Schematic illustration of the microwave cavity (Courtesy of Guangming Tao).

....... 66 Figure 4.2: Experimental setup for MA-LIBS.

Figure 4.3: Comparison between LIBS (black) and MA-LIBS (red) spectrum of Pb samples.

... 69 Figure 4.4: Comparison between the plasma emission at 405.8 nm with (red dot) and without (black square) the microwave. Plasma emission was normalized to characterize the emission per 50 ns.

Figure 4.5: Spectra of Pb plasma with (red) and without (black) microwave 18 ms after the laser pulse with gate width 2 ms.

Comparing with Figure 4.3, the high intensity in this spectrum is mainly due to much higher gain from the ICCD camera (from 1 to 100).

–  –  –

microwave.

Figure 4.7: Electron density estimate of MA-LIBS plasma using non-collective Thomson scattering method, and a comparison with normal LIBS plasma.

Figure 4.8: Spectra for (a) Mg; (b) Al; (c) Ba; (d) Na; (e) K and (f) Ca.

(1: MA-LIBS, 2: LIBS)

Figure 4.9: Spectra of Montana soil NIST standard reference material using (a) traditional LIBS and (b) MA-LIBS.

Figure 4.10: Spectra of the soil sample S1 containing 1232 mg kg-1 of Cu with MA-LIBS (left) and LIBS (right).

Figure 4.11: Calibration curves of Cu for MA-LIBS (black squares) and the traditional LIBS (red circles).



Pages:   || 2 | 3 | 4 | 5 |   ...   | 18 |


Similar works:

«Modeling SHANK2 Related Neuropsychiatric Disorders in Mice by Andrea Lynn Pappas Department of Neurobiology Duke University Date: _Approved: _ Yong-hui Jiang, Supervisor _ Rebecca Yang, Chair _ Ben Philpot _ Scott Soderling Dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Neurobiology in the Graduate School of Duke University 2015 i v ABSTRACT Modeling SHANK2 Related Neuropsychiatric Disorders in Mice by Andrea Lynn...»

«Making Art, Creating Infrastructure: deviantART and the Production of the Web by Daniel Perkel A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Information Management and Systems and the Designated Emphasis in New Media in the Graduate Division of the University of California, Berkeley Committee in charge: Professor Nancy Van House, Chair Professor Paul Duguid Professor Jenna Burrell Professor Laura Sterponi Fall 2011 Making Art,...»

«Making Room: The Geography of Rooming House Regulation in Toronto. by Lisa Marie Freeman A thesis submitted in conformity with the requirements for the degree of Doctor of Philosophy Department of Geography University of Toronto © Copyright by Lisa Marie Freeman 2013 Making Room: The Geography of Rooming House Regulation in Toronto Lisa Marie Freeman Doctor of Philosophy Department of Geography University of Toronto 2013 Abstract This dissertation addresses the contemporary moment of the...»

«MOTIVATED VISUAL PERCEPTION: HOW WE SEE WHAT WE WANT TO SEE A Dissertation Presented to the Faculty of the Graduate School of Cornell University In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy by Emily E. Balcetis August 2006 © 2006 Emily E. Balcetis MOTIVATED VISUAL PERCEPTION: HOW WE SEE WHAT WE WANT TO SEE Emily E. Balcetis, Ph. D. Cornell University 2006 In 2001, a U.S. nuclear submarine surfaced underneath a Japanese fishing vessel, causing it to sink—9...»

«“Heidegger and Marcuse: On Reification and Concrete Philosophy,” The Bloomsbury Companion to Heidegger,” F. Raffoul and E. Nelson, eds., Bloomsbury Press, 2013, pp. 171-176 Andrew Feenberg Introduction Herbert Marcuse (1898–1979) completed his doctorate in 1922 but decided not to pursue the habilitation which would have qualified him for an academic career. Instead, he returned to Berlin where he established an antiquarian bookstore with a partner. When he read Being and Time shortly...»

«The Color of Change? Race and Charter Schools in an Age of Neoliberal Education Reform By Ebony M. Duncan Dissertation Submitted to the Faculty of the Graduate School of Vanderbilt University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY in Sociology August, 2014 Nashville, Tennessee Approved: Katharine M. Donato, Ph.D. Tony N. Brown, Ph.D. Richard N. Pitt, Ph.D. Stella M. Flores, Ed.D. ACKNOWLEDGEMENTS This work would not have been possible without the...»

«Molecular Modeling of Polymer Free Volume Distribution A Dissertation Presented to The Academic Faculty by Derrick B. Callander In Partial Fulfillment Of the Requirements for the Degree Doctor of Philosophy in Chemical and Biomolecular Engineering Georgia Institute of Technology December 2005 Copyright © Derrick B. Callander 2005 Molecular Modeling of Polymer Free Volume Distribution Approved by: Dr. Peter J. Ludovice, Advisor Dr. William J. Koros School of Chemical and Biomolecular School of...»

«VIDEO-BASED ANALYSIS OF MATHEMATICS CLASSROOM PRACTICE: EXAMPLES FROM FINLAND AND ICELAND by Lasse Tuomas Savola Dissertation committee: Professor Bruce Vogeli, Sponsor Professor Herbert Ginsburg Professor Robert McClintock Professor O. Roger Anderson Professor Patrick Gallagher Submitted in partial fulfillment of the requirements for the Degree of Doctor of Philosophy under the Executive Committee of The Graduate School of Arts and Sciences Columbia University 2008 © 2008 LASSE TUOMAS SAVOLA...»

«A Numerical Study of Micro Synthetic Jet and Its Applications in Thermal Management A Thesis Presented to The Academic Faculty by Shuo Li In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy The G. W. Woodruff School of Mechanical Engineering Georgia Institute of Technology December 2005 A Numerical Study of Micro Synthetic Jet and Its Applications in Thermal Management Approved by: Professor Marc K. Smith, Advisor Professor Sue Ann Bidstrup Allen Mechanical...»

«Instructions for use Numerical Simulation of Gas Flow with Electrochemical Reaction in a Polymer Electrolyte Fuel Cell by K. M. Salah Uddin A dissertation presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy (PhD) in the Division of Mechanical and Space Engineering Hokkaido University, Japan September 2013 ABSTRACT The aim of this dissertation was to investigate the performance of Polymer Electrolyte Fuel Cell (PEFC). The investigation involved...»

«THEORETICAL STUDIES OF THE STRUCTURE-PROPERTY RELATIONSHIPS OF HOLEAND ELECTRON-TRANSPORT MATERIALS FOR ORGANIC PHOTOVOLTAIC APPLICATIONS A Dissertation Presented to The Academic Faculty by Laxman Pandey In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the School of Chemistry and Biochemistry Georgia Institute of Technology August 2013 Copyright © 2013 by Laxman Pandey THEORETICAL STUDIES OF THE STRUCTURE-PROPERTY RELATIONSHIPS OF HOLEAND ELECTRON-TRANSPORT...»

«FABRICATION, CHARACTERIZATION, AND APPLICATION OF MULTIFUNCTIONAL MICROCANTILEVER HEATERS A Dissertation Presented to The Academic Faculty by Jungchul Lee In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in the George W. Woodruff School of Mechanical Engineering Georgia Institute of Technology May 2007 FABRICATION, CHARACTERIZATION, AND APPLICATION OF MULTIFUNCTIONAL MICROCANTILEVER HEATERS Approved by: Dr. William P. King, Advisor Dr. Mark G. Allen George W....»





 
<<  HOME   |    CONTACTS
2016 www.dissertation.xlibx.info - Dissertations, online materials

Materials of this site are available for review, all rights belong to their respective owners.
If you do not agree with the fact that your material is placed on this site, please, email us, we will within 1-2 business days delete him.