This study was financially supported by the National Key Scientific Instrument and Equipment Development Projects (Grant No. 2014YQ120351), the Youth Innovation Promotion Association of CAS (Grant No. 2014136), and the China Innovative Talent Promotion Plans for Innovation Team in Priority Fields (Grant No. 2014RA4051).

1. Preparation of Standard Samples
NOTE: This step is not essential.
<ol>
	<li>Prepare raw material (Table 1). To make a 100 kg of sample #1, add 12.82 kg of Cr, 3.39 kg of Mo, 4.79 kg of Al, 1.00 kg of Ti, 0.60 kg of Cu, and approximately 77.4 kg of Ni to the crucible. During the melting process, some elements will be burned. The final ingredient is determined by the melting temperature, melting duration, and other working parameters. The ingredient test shows the quantity of each element inside the alloys.</li>
	<li>Perform vacuum induction melting at approximately 1,700 &#176;C for approximately 45 min for each standard sample. The furnace used to make standard samples can melt approximately 100 kg alloys each time for 2 sets of standard samples.</li>
	<li>Pour all molten liquid steel into a sticky mold to make standard samples, and naturally cool for at least 4 h. The size of the standard samples is determined by the furnace in the experiment. Use rod-shaped standard samples in the experiments with a rod diameter of 100 mm. The shape of the crucible in the furnace is a frustum cone with a cup-like container. The diameter of the rim is 150 mm, the bottom is 100 mm, and the depth is 200 mm. Chunked standard samples can also be employed.</li>
	<li>Use an electric saw to cut standard samples for the experiment. The length of the standard rod sample is determined by the furnace. Use a length of 150 mm for the experimental smelting system. Melt a piece of the samples for each experiment.</li>
	<li>Repeat these steps and make all standard samples. Ten samples are employed in this experiment.</li>
</ol>
2. Test Ingredient of Standard Alloy Samples
<ol>
	<li>Use a chemical analysis method to test the composition of all standard alloy samples. Test all elements in each sample. 
	NOTE: We strongly recommend sending these samples to an authority organization to perform the analysis. These samples are sent to the Central Iron &#38; Steel Research Institute of China for the ingredients test. The test results for these samples are listed in Table 2.</li>
</ol>
3. Smelt Samples
<ol>
	<li>Check the security of the smelting system, which includes the power supply, availability of each pump, vacuum hold ability of the experimental furnace, cooling water, and current.</li>
	<li>Place the standard samples into the smelting system. To ensure that a small amount of each sample is ablated by the laser, use small samples for the experiment. Due to the size of the crucible in the furnace, smelt approximately 10 kg samples each time.</li>
	<li>Open the vacuum pump until the pressure is lower than 0.1 Pa. Use 2 levels of pump to make the vacuum: mechanical pump and diffusion pump. The mechanical pump can reach approximately 1 Pa in 15 min, and the diffusion pump can reach 0.01 Pa after 40 min.</li>
	<li>Melt samples. Increase the furnace working current to approximately 130 A; this parameter is determined by the ingredients of the samples and the size of the furnace. A standard sample requires approximately 15 min to become molten. Due to oxidation or nitridation, the ingredients of liquid steel slowly change during the course of smelting.
	<ol>
		<li>To ensure precision of the experiment, determine the spectrum within 15 min after the standard samples are molten.</li>
	</ol>
	</li>
</ol>
4. Determine Laser Breakdown Spectra of Standard Samples
<ol>
	<li>Check availability of laser focusing and spectrum gathering system, laser generator, and spectrometer.</li>
	<li>Set the spectrometer and laser generator to work synchronously. Use a spectrometer output synchronization signal and laser passive working method in the system. The method of laser generator synchronization signal or method of synchronizer output synchronization signal can also be employed to control the laser generator and spectrometer.</li>
	<li>Open the laser generator and spectrometer; prepare to generate the pulse laser. The pulse width is 20 ns, the frequency is 5 Hz, and the energy of each pulse is 90 mJ.</li>
	<li>Use spectrum deposit software to trigger the laser output and gather the spectrum. Set the integration time of the spectrometer to 10 ms, and each laser pulse generates a frame of the spectrum. If the integration time is too short, the spectrum signal intensity will be too weak. If the integration time is too long, more background signals will be gathered.</li>
	<li>Adjust the laser focusing position, and effectively ablate the sample. Optimize the focusing position until the strongest spectrum signal is obtained. This process is used to adjust the focusing point. The spectrometer numerical divided signal intensity ranges from 0 to 65,535. In most cases, the intensity of a signal should exceed 15% of the saturation signal, which indicates that the highest peak intensity should exceed 10,000. If the signal intensity is too small, the quantitative analysis will have low precision.</li>
	<li>Optimize the delay time. Choose the delay after bremsstrahlung, and the strength of the signal need with the optimized delay time should be sufficient.</li>
	<li>Use the spectrometer to gather a spectrum for the analysis. Gather 20 frames of the spectrum, and obtain the average for LIBS analysis.</li>
	<li>Shut off the working current of the furnace and cool the samples. Solidification of the samples requires approximately 15 min.</li>
	<li>Inject nitrogen into the experimental furnace to break the vacuum.</li>
	<li>Open the lid of the experimental furnace and remove the solidification samples.</li>
	<li>Repeat step 3.3 to 4.10 until all samples are measured.</li>
</ol>
5. Construct Calibration Curve of Quantitative Analysis
<ol>
	<li>Spectrum pretreatment
	<ol>
		<li>Background correction. Delete the background effect caused by braking radiation. The method of baseline correction is employed in the experiment.</li>
		<li>Spectrum-peak searching. Use a two-order derivative method to identify peaks of each element; local minimum points are weighted.</li>
		<li>Spectrum fitting. Apply a Lorentz spectra overlay to the selected peaks to prevent self-corrosion or overlap. The spectral peak intensity, stretch status, and center wavelength is obtained by a fitting algorithm.</li>
	</ol>
	</li>
	<li>Import the chemical ingredient analysis results of all standard samples.</li>
	<li>Construct the calibration curve.
	<ol>
		<li>Choose an inner relative standard wavelength. The main element spectral lines are always selected.</li>
		<li>Choose a calibration wavelength. Select from the NIST spectrum database15.</li>
		<li>Fit the curve. Use linear fitting or quadratic fitting.</li>
	</ol>
	</li>
	<li>Achieve analysis precision. Calculate the fitting factor and relative standard error after fitting. A program is used to automatically select the best relative standard wavelength and calibration wavelength from the wavelength base of NIST15.</li>
</ol>
6. Elemental Composition Analysis of Molten Alloy
NOTE: The experimental setup has been divided to two parts, namely, the detector head and the control cabinet, as shown in Figure 1. The same laser and spectrometer parameters, moulting, and spectrum gathering process employed in the previous process are utilized to ensure accurate quantitative analysis results.
<ol>
	<li>Put the unknown sample into the smelting system.</li>
	<li>Vacuum the experimental system.</li>
	<li>Increase the smelting current until the sample is molten. The melting temperature is approximately 1,700 &#176;C, and the melting time is approximately 45 min.</li>
	<li>Open the laser generator and realize the pulse laser output. Use the following laser parameters: pulse width is 20 ns, frequency is 5 Hz, and energy of each pulse is 90 mJ.</li>
	<li>Open the spectrometer and the spectrum deposit software to determine the spectrum. Employ the same spectrometer with a spectral range from 190 to 600 nm and resolution of 0.06 nm at a wavelength of 200 nm. The integration time of the spectrometer is 10 ms. The spectrometer is used to trigger the laser and determine the spectrum.</li>
	<li>Adjust laser focusing position. Optimize focusing position until the strongest spectrum signal is attained; the value of the highest peak should exceed 10,000.</li>
	<li>Determine laser breakdown spectrum. Each laser pulse generates a frame of the spectrum; 20 frames of the spectrum are obtained and averaged for the analysis.</li>
	<li>Spectrum pretreatment. Perform background correction, such as deleting the background effect caused by braking radiation, as mentioned in 5.1.3, to perform spectrum fitting.</li>
	<li>Elemental concentration calculation. Perform analysis elemental concentration by the internal standard method from the calibration curve.</li>
</ol>

<ol>
	<li>Radziemski, L., Cremers, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+brief+history+of+laser-induced+breakdown+spectroscopy:+From+the+concept+of+atoms+to+LIBS+2012.">A brief history of laser-induced breakdown spectroscopy: From the concept of atoms to LIBS 2012.</a> Spectrochimica Acta Part B: Atomic Spectroscopy. 87, 3-10 (2013).</li><li>El Haddad, J., Canioni, L., Bousquet, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Good+practices+in+LIBS+analysis:+Review+and+advices.">Good practices in LIBS analysis: Review and advices.</a> Spectrochimica Acta Part B: Atomic Spectroscopy. 101, 171-182 (2014).</li><li>Mueller, M., Gornushkin, I. B., Florek, S., Mory, D., Panne, U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Approach+to+Detection+in+Laser-Induced+Breakdown+Spectroscopy.">Approach to Detection in Laser-Induced Breakdown Spectroscopy.</a> Analytical Chemistry. 79 (12), 4419-4426 (2007).</li><li>Noll, R., Fricke-Begemann, C., Brunk, M., Connemann, S., Meinhardt, C., Schsrun, M., Sturm, V., Makowe, J., Gehlen, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Laser-induced+breakdown+spectroscopy+expands+into+industrial+applications.">Laser-induced breakdown spectroscopy expands into industrial applications.</a> Spectrochimica Acta Part B: Atomic Spectroscopy. 93, 41-51 (2014).</li><li>Leon, R., David, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+brief+history+of+laser-induced+breakdown+spectroscopy:+From+the+concept+of+atoms+to+LIBS+2012.">A brief history of laser-induced breakdown spectroscopy: From the concept of atoms to LIBS 2012.</a> Spectrochimica Acta Part B: Atomic Spectroscopy. 87, 3-10 (2013).</li><li>El Haddad, J., Canioni, L., Bousquet, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Good+practices+in+LIBS+analysis:+Review+and+advices.">Good practices in LIBS analysis: Review and advices.</a> Spectrochimica Acta Part B: Atomic Spectroscopy. 101, 171-182 (2014).</li><li>Gonzaga, B. F., Pasquini, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+compact+and+low+cost+laser+induced+breakdown+spectroscopic+system:+Application+for+simultaneous+determination+of+chromium+and+nickel+in+steel+using+multivariate+calibration.">A compact and low cost laser induced breakdown spectroscopic system: Application for simultaneous determination of chromium and nickel in steel using multivariate calibration.</a> Spectrochimica Acta Part B: Atomic Spectroscopy. 69, 20-24 (2012).</li><li>Peter, L., Sturm, V., Noll, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Liquid+steel+analysis+with+laser-induced+breakdown+spectrometry+in+the+vacuum+ultraviolet.">Liquid steel analysis with laser-induced breakdown spectrometry in the vacuum ultraviolet.</a> Applied Optics. 42 (30), 6199-6204 (2003).</li><li>Hubmer, G., Kitzberger, R., M&#246;rwald, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Application+of+LIBS+to+the+in-line+process+control+of+liquid+high-alloy+steel+under+pressure.">Application of LIBS to the in-line process control of liquid high-alloy steel under pressure.</a> Analytical and Bioanalytical Chemistry. 385 (2), 219-224 (2006).</li><li>Sun, L. X., Yu, H. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Automatic+estimation+of+varying+continuum+background+emission+in+laser-induced+breakdown+spectroscopy.">Automatic estimation of varying continuum background emission in laser-induced breakdown spectroscopy.</a> Spectrochimica Acta Part B: Atomic Spectroscopy. 64, 278-287 (2009).</li><li>Lin, X. M., Chang, P. H., Chen, G. H., Lin, J. J., Liu, R. X., Yang, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+melting+iron-based+alloy+temperature+on+carbon+content+observed+in+laser-induced+breakdown+spectroscopy.">Effect of melting iron-based alloy temperature on carbon content observed in laser-induced breakdown spectroscopy.</a> Plasma Science &amp; Technology. 17 (11), 933-937 (2015).</li><li>Rai, A. K., Yueh, F. Y., Singh, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Laser-induced+breakdown+spectroscopy+of+molten+aluminum+alloy.">Laser-induced breakdown spectroscopy of molten aluminum alloy.</a> Applied Optics. 42 (12), 2078-2084 (2003).</li><li>Hanson, C., Phongikaroon, S., Scott, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Temperature+effect+on+laser-induced+breakdown+spectroscopy+spectra+of+molten+and+solid+salts.">Temperature effect on laser-induced breakdown spectroscopy spectra of molten and solid salts.</a> Spectrochimica Acta Part B: Atomic Spectroscopy. 97, 79-85 (2014).</li><li>Darwiche, S., Benrabbah, R., Benmansour, M., Morvan, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Impurity+detection+in+solid+and+molten+silicon+by+laser+induced+breakdown+spectroscopy.">Impurity detection in solid and molten silicon by laser induced breakdown spectroscopy.</a> Spectrochimica Acta Part B: Atomic Spectroscopy. 74, 115-118 (2012).</li><li>Linstrom, P. J., Mallard, W. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=NIST+Chemistry+WebBook,+NIST+Standard+Reference+Database+Number+69.">NIST Chemistry WebBook, NIST Standard Reference Database Number 69.</a> National Institute of Standards and Technology. , 20899 (2018).</li></ol>

The authors have nothing to disclose.

For elemental analysis, popular methods are X-ray fluorescence (XRF), spark discharge optical emission spectrometry (SD-OES), atomic absorption spectroscopy (AAS), and inductive couple plasma (ICP). These methods are mainly suited for a laboratory and industrial online application for molten alloys, which is determined by the characters of these technologies, is difficult. XRF uses X-rays to shock samples, and SD-OES makes sparks on the samples. The working distance of these two methods are always in the range of several...

Due to its unique features, such as remote sensing, fast analysis, and no need for sample preparation, laser-induced breakdown spectroscopy (LIBS) offers unique capabilities for on-line concentration determination1,2,3. Although the use of the LIBS technique in different fields has been investigated4,5,6, a considerable attempt to develop its capabilities in industrial applications is ongoing.
Analysis of molten material contents during the course of industrial processes can effectively improve the product quality, which is a promising development direction of LIBS. Experimental findings have been reported about the application of LIBS in the industrial field, such as findings about argon oxygen liquid steel7,8,9,10,11, molten aluminium alloy12, molten salt13, and molten silicon14. The majority of these materials exist in the environment of air or an assistant gas. However, vacuum induction melting (VIM) is another good application field of LIBS to realize processing control. A VIM furnace can realize smelting at temperatures higher than 1,700 &#176;C for alloy refining; it is the most popular method for refining high-purity metal and alloys such as iron-base or nickel-base alloys, high purity alloys, and clean magnetic alloys. During the course of melting, the pressure in a furnace is always in the region of 1-10 Pa, and the composition of air in the furnace mainly includes the air absorbed on the sample or the inner wall of the furnace and some vaporous oxide or nitride metal. These working situations induce quite different LIBS measurement situations for smelting in air. Here, we report an experimental investigation of the analysis of molten alloy during the course of VIM by LIBS.
An optical window is added to a furnace for laser ablation and radiant light detection. A silica glass with a diameter of 80 mm serves as the window. An emitting laser and gathering of radiant light employ the same window; it is a co-axial optical structure that focuses on the same point. The working focal length is approximately 1.8 m, and the focusing length of the experimental setup can be adjusted from 1.5 to 2.5 m.
Based on the practicality of industrial online analysis, precision, repeatability and stability is more important than the low limit of detection (LOD) during molten alloy ingredient analysis. The technical route of a four-channel linear CCD spectrometer is chosen, the spectral range of the spectrometer ranges from 190 to 600 nm, the resolution is 0.06 nm, and the wavelength is 200 nm. A laser diode pumped Q-switched laser (constructed in house) is used to ablate molten alloy, with an output energy of 100 mJ, a frequency of 5 Hz, an FWHM pulse width of 20 ns, and a working wavelength of 1064 nm. The remaining part will present the VIM LIBS-analysing process and live measurement, followed by an introduction of the data processing results.

<table><tbody><tr><td>Laser source</td><td>Gklaser Co.,Ltd.</td><td></td><td></td></tr><tr><td>Molten alloy to be measured</td><td></td><td></td><td></td></tr><tr><td>Smelting furnace</td><td>Tianyu Co.,Ltd.</td><td></td><td></td></tr><tr><td>Spectrometer</td><td>Avantes</td><td></td><td></td></tr><tr><td>standard samples</td><td></td><td></td><td>Well known of its composition</td></tr></tbody></table>

quantitative analysis of vacuum induction melting by laser-induced breakdown spectroscopy

Vacuum induction melting is a popular method for refining high purity metal and alloys. Traditionally, standard process control in metallurgy involves several steps, include drawing samples, cooling, cutting, transport to the laboratory, and analysis. The whole analysis process requires more than 30 minutes, which hinders on-line process control. Laser-induced breakdown spectroscopy is an excellent on-line analysis method that can satisfy the requirements of vacuum induction melting because it is fast and noncontact and does not require sample preparation. The experimental facility uses a lamp-pumped Q-switched laser to ablate melted liquid steel with an output energy of 80 mJ, a frequency of 5 Hz, a FWHM pulse width of 20 ns, and a working wavelength of 1,064 nm. A multi-channel linear charge coupled device (CCD) spectrometer is used to measure the emission spectrum in real time, with a spectral range from 190 to 600 nm and a resolution of 0.06 nm at a wavelength of 200 nm. The protocol includes several steps: standard alloy sample preparation and an ingredient test, smelting of standard samples and determination of the laser breakdown spectrum, and construction of the elements concentration quantitative analysis curve of each element. To realize the concentration analysis of unknown samples, the spectrum of a sample also needs to be measured and disposed with the same process. The composition of all main elements in the melted alloy can be quantitatively analyzed with an internal standard method. The calibration curve shows that the limit of detection of most metal elements ranges from 20-250 ppm. The concentration of elements, such as Ti, Mo, Nb, V, and Cu, can be lower than 100 ppm, and the concentrations of Cr, Al, Co, Fe, Mn, C, and Si range from 100-200 ppm. The R2 of some calibration curves can exceed 0.94.

Ten nickel-based alloy samples (#1-#10) are used to construct internal-standard calibration curves. The compositions of all samples are listed in Table 1. The elemental concentrations of these samples are orthogonally designed to avoid signal interference. The concentration of each element in all samples is measured with chemical analysis methods.
Nickel is the internal standard element. The calibration curves o...

Watch this Scientific Journal Video about Quantitative Analysis of Vacuum Induction Melting by Laser-induced Breakdown Spectroscopy at JoVE.com

Quantitative Analysis of Vacuum Induction Melting by Laser-induced Breakdown Spectroscopy

During vacuum induction melting, laser-induced breakdown spectroscopy is used to perform real-time quantitative analysis of the main-ingredient elements of a molten alloy.

Vacuum induction melting is a popular method for refining high purity metal and alloys. Traditionally, standard process control in metallurgy involves ...

quantitative-analysis-vacuum-induction-melting-laser-induced

Research

JoVE Journal

Engineering

7.2K Views.  Chinese Academy of Sciences. We hebben industriële online monitoring van de gesmolten legeringen component gerealiseerd door laser-geïnduceerde afbraak spectroscopie. Door deze technologie kunnen hoofd- en spoorelementen van de gesmolten legeringen in realtime worden geanalyseerd. Een vacuüm inductie smeltoven kan smelten voor legering raffinage, en dit is de meest populaire methode voor het raffineren van legeringen.Analyse van de gesmolten materiaalcomponenten tijdens industriële processen kan de productiekw...

Video: Quantitative Analysis of Vacuum Induction Melting by Laser-induced Breakdown Spectroscopy

Characterization of Surface Modifications by White Light Interferometry: Applications in Ion Sputtering, Laser Ablation, and Tribology Experiments

In materials science and engineering it is often necessary to obtain quantitative measurements of surface topography with micrometer lateral resolution. From the measured surface, 3D topographic maps can be subsequently analyzed using a variety of software packages to extract the information that is needed.
In this article we describe how white light interferometry, and optical profilometry (OP) in general, combined with generic surface analysis software, can be used for materials science and engineering tasks. In this article, a number of applications of white light interferometry for investigation of surface modifications in mass spectrometry, and wear phenomena in tribology and lubrication are demonstrated. We characterize the products of the interaction of semiconductors and metals with energetic ions (sputtering), and laser irradiation (ablation), as well as ex situ measurements of wear of tribological test specimens.
Specifically, we will discuss:
<ol class="lroman">
	<li>Aspects of traditional ion sputtering-based mass spectrometry such as sputtering rates/yields measurements on Si and Cu and subsequent time-to-depth conversion.</li>
	<li>Results of quantitative characterization of the interaction of femtosecond laser irradiation with a semiconductor surface. These results are important for applications such as ablation mass spectrometry, where the quantities of evaporated material can be studied and controlled via pulse duration and energy per pulse. Thus, by determining the crater geometry one can define depth and lateral resolution versus experimental setup conditions.</li>
	<li>Measurements of surface roughness parameters in two dimensions, and quantitative measurements of the surface wear that occur as a result of friction and wear tests.</li>
</ol>
Some inherent drawbacks, possible artifacts, and uncertainty assessments of the white light interferometry approach will be discussed and explained.

White light microscope interferometry is an optical, noncontact and quick method for measuring the topography of surfaces. It is shown how the method can be applied toward mechanical wear analysis, where wear scars on tribological test samples are analyzed; and in materials science to determine ion beam sputtering or laser ablation volumes and depths.

In materials science and engineering it is often necessary to obtain quantitative measurements of surface topography with micrometer lateral resolution. ...

Dependence of Laser-induced Breakdown Spectroscopy Results on Pulse Energies and Timing Parameters Using Soil Simulants

The dependence of some LIBS detection capabilities on lower pulse energies (&lt;100 mJ) and timing parameters were examined using synthetic silicate samples. These samples were used as simulants for soil and contained minor and trace elements commonly found in soil at a wide range of concentrations. For this study, over 100 calibration curves were prepared using different pulse energies and timing parameters; detection limits and sensitivities were determined from the calibration curves. Plasma temperatures were also measured using Boltzmann plots for the various energies and the timing parameters tested. The electron density of the plasma was calculated using the full-width half maximum (FWHM) of the hydrogen line at 656.5 nm over the energies tested. Overall, the results indicate that the use of lower pulse energies and non-gated detection do not seriously compromise the analytical results. These results are very relevant to the design of field- and person-portable LIBS instruments.

LIBS detection capabilities on soil simulants were tested using a range of pulse energies and timing parameters. Calibration curves were used to determine detection limits and sensitivities for different parameters. Generally, the results showed that there was not a significant reduction in detection capabilities using lower pulse energies and non-gated detection.

The  dependence of some LIBS detection capabilities on lower pulse energies (&lt;100  mJ) and timing parameters were examined using synthetic silicate ...

Chemistry

Simulation of the Planetary Interior Differentiation Processes in the Laboratory

A planetary interior is under high-pressure and high-temperature conditions and it has a layered structure. There are two important processes that led to that layered structure, (1) percolation of liquid metal in a solid silicate matrix by planet differentiation, and (2) inner core crystallization by subsequent planet cooling. We conduct high-pressure and high-temperature experiments to simulate both processes in the laboratory. Formation of percolative planetary core depends on the efficiency of melt percolation, which is controlled by the dihedral (wetting) angle. The percolation simulation includes heating the sample at high pressure to a target temperature at which iron-sulfur alloy is molten while the silicate remains solid, and then determining the true dihedral angle to evaluate the style of liquid migration in a crystalline matrix by 3D visualization. The 3D volume rendering is achieved by slicing the recovered sample with a focused ion beam (FIB) and taking SEM image of each slice with a FIB/SEM crossbeam instrument. The second set of experiments is designed to understand the inner core crystallization and element distribution between the liquid outer core and solid inner core by determining the melting temperature and element partitioning at high pressure. The melting experiments are conducted in the multi-anvil apparatus up to 27 GPa and extended to higher pressure in the diamond-anvil cell with laser-heating. We have developed techniques to recover small heated samples by precision FIB milling and obtain high-resolution images of the laser-heated spot that show melting texture at high pressure. By analyzing the chemical compositions of the coexisting liquid and solid phases, we precisely determine the liquidus curve, providing necessary data to understand the inner core crystallization process.

The high-pressure and high-temperature experiments described here mimic planet interior differentiation processes. The processes are visualized and better understood by high-resolution 3D imaging and quantitative chemical analysis.

A planetary interior is under high-pressure and high-temperature conditions and it has a layered structure. There are two important processes that led to ...

Measurement and Analysis of Atomic Hydrogen and Diatomic Molecular AlO, C2, CN, and TiO Spectra Following Laser-induced Optical Breakdown

In this work, we present time-resolved measurements of atomic and diatomic spectra following laser-induced optical breakdown. A typical LIBS arrangement is used. Here we operate a Nd:YAG laser at a frequency of 10 Hz at the fundamental wavelength of 1,064 nm. The 14 nsec pulses with anenergy of 190 mJ/pulse are focused to a 50 &#181;m spot size to generate a plasma from optical breakdown or laser ablation in air. The microplasma is imaged onto the entrance slit of a 0.6 m spectrometer, and spectra are recorded using an 1,800 grooves/mm grating an intensified linear diode array and optical multichannel analyzer (OMA) or an ICCD. Of interest are Stark-broadened atomic lines of the hydrogen Balmer series to infer electron density. We also elaborate on temperature measurements from diatomic emission spectra of aluminum monoxide (AlO), carbon (C2), cyanogen (CN), and titanium monoxide (TiO).
The experimental procedures include wavelength and sensitivity calibrations. Analysis of the recorded molecular spectra is accomplished by the fitting of data with tabulated line strengths. Furthermore, Monte-Carlo type simulations are performed to estimate the error margins. Time-resolved measurements are essential for the transient plasma commonly encountered in LIBS.

Measurement and Analysis of Atomic Hydrogen and Diatomic Molecular AlO, C2, CN, and TiO Spectra Following Laser-induced Optical Breakdown

Time-resolved atomic and diatomic molecular species are measured using LIBS. The spectra are collected at various time delays following the generation of optical breakdown plasma with Nd:YAG laser radiation&#160;and are analyzed to infer electron density and temperature.

In this work, we present time-resolved measurements of atomic and diatomic spectra following laser-induced optical breakdown. A typical LIBS arrangement ...

Laser-induced Breakdown Spectroscopy: A New Approach for Nanoparticle's Mapping and Quantification in Organ Tissue

Emission spectroscopy of laser-induced plasma was applied to elemental analysis of biological samples. Laser-induced breakdown spectroscopy (LIBS) performed on thin sections of rodent tissues: kidneys and tumor, allows the detection of inorganic elements such as (i) Na, Ca, Cu, Mg, P, and Fe, naturally present in the body and (ii) Si and Gd, detected after the injection of gadolinium-based nanoparticles. The animals were euthanized 1&#160;to 24 hr&#160;after intravenous injection of particles. A two-dimensional scan of the sample, performed using a motorized micrometric 3D-stage, allowed the infrared laser beam exploring the surface with a lateral resolution less than 100 &#956;m. Quantitative chemical images of Gd element inside the organ were obtained with sub-mM sensitivity. LIBS offers a simple and robust method to study the distribution of inorganic materials without any specific labeling. Moreover, the compatibility of the setup with standard optical microscopy emphasizes its potential to provide multiple images of the same biological tissue with different types of response:&#160;elemental, molecular, or cellular.

Laser-induced breakdown spectroscopy performed on thin organ and tumor tissue successfully detected natural elements and artificially injected gadolinium (Gd), issued from Gd-based nanoparticles. Images of chemical elements reached a resolution of 100 &#956;m and quantitative sub-mM sensitivity. The compatibility of the setup with standard optical microscopy emphasizes its potential to provide multiple images of a same biological tissue.

Emission spectroscopy of laser-induced plasma was applied to elemental analysis of biological samples. Laser-induced breakdown spectroscopy (LIBS) ...

Emission Spectroscopic Boundary Layer Investigation during Ablative Material Testing in Plasmatron

Ablative Thermal Protection Systems (TPS) allowed the first humans to safely return to Earth from the moon and are still considered as the only solution for future high-speed reentry missions. But despite the advancements made since Apollo, heat flux prediction remains an imperfect science and engineers resort to safety factors to determine the TPS thickness. This goes at the expense of embarked payload, hampering, for example, sample return missions. 
Ground testing in plasma wind-tunnels is currently the only affordable possibility for both material qualification and validation of material response codes. The subsonic 1.2MW Inductively Coupled Plasmatron facility at the von Karman Institute for Fluid Dynamics is able to reproduce a wide range of reentry environments. This protocol describes a procedure for the study of the gas/surface interaction on ablative materials in high enthalpy flows and presents sample results of a non-pyrolyzing, ablating carbon fiber precursor. With this publication, the authors envisage the definition of a standard procedure, facilitating comparison with other laboratories and contributing to ongoing efforts to improve heat shield reliability and reduce design uncertainties.
The described core techniques are non-intrusive methods to track the material recession with a high-speed camera along with the chemistry in the reactive boundary layer, probed by emission spectroscopy. Although optical emission spectroscopy is limited to line-of-sight measurements and is further constrained to electronically excited atoms and molecules, its simplicity and broad applicability still make it the technique of choice for analysis of the reactive boundary layer. Recession of the ablating sample further requires that the distance of the measurement location with respect to the surface is known at all times during the experiment. Calibration of the optical system of the applied three spectrometers allowed quantitative comparison. At the fiber scale, results from a post-test microscopy analysis are presented.

Development of new ablative materials and their numerical modeling requires extensive experimental investigation. This protocol describes procedures for material response characterization in plasma flows with the core techniques being non-intrusive methods to track the material recession along with the chemistry in the reactive boundary layer by emission spectroscopy.

Ablative Thermal Protection Systems (TPS) allowed the first humans to safely return to Earth from the moon and are still considered as the only solution ...

Laser-heating and Radiance Spectrometry for the Study of Nuclear Materials in Conditions Simulating a Nuclear Power Plant Accident

Major and severe accidents have occurred three times in nuclear power plants (NPPs), at Three Mile Island (USA, 1979), Chernobyl (former USSR, 1986) and Fukushima (Japan, 2011). Research on the causes, dynamics, and consequences of these mishaps has been performed in a few laboratories worldwide in the last three decades. Common goals of such research activities are: the prevention of these kinds of accidents, both in existing and potential new nuclear power plants; the minimization of their eventual consequences; and ultimately, a full understanding of the real risks connected with NPPs. At the European Commission Joint Research Centre&#39;s Institute for Transuranium Elements, a laser-heating and fast radiance spectro-pyrometry facility is used for the laboratory simulation, on a small scale, of NPP core meltdown, the most common type of severe accident (SA) that can occur in a nuclear reactor as a consequence of a failure of the cooling system. This simulation tool permits fast and effective high-temperature measurements on real nuclear materials, such as plutonium and minor actinide-containing fission fuel samples. In this respect, and in its capability to produce large amount of data concerning materials under extreme conditions, the current experimental approach is certainly unique. For current and future concepts of NPP, example results are presented on the melting behavior of some different types of nuclear fuels: uranium-plutonium oxides, carbides, and nitrides. Results on the high-temperature interaction of oxide fuels with containment materials are also briefly shown.

We present experiments in which real nuclear fuel, cladding, and containment materials are laser heated to temperatures beyond 3,000 K while their behavior is studied by radiance spectroscopy and thermal analysis. These experiments simulate, on a laboratory scale, the formation of a lava-phase following a nuclear reactor core meltdown.

Major and severe accidents have occurred three times in nuclear power plants (NPPs), at Three Mile Island (USA, 1979), Chernobyl (former USSR, 1986) and ...

A Practical Guide on Coupling a Scanning Mobility Sizer and Inductively Coupled Plasma Mass Spectrometer (SMPS-ICPMS)

A large variety of analytical methods are available to characterize particles in aerosols and suspensions. The choice of the appropriate technique depends on the properties to be determined. In many fields information about particle size and chemical composition are of great importance. While in aerosol techniques particle size distributions of gas-borne particles are determined online, their elemental composition is commonly analyzed offline after an appropriate sampling and preparation procedure. To obtain both types of information online and simultaneously, a hyphenated setup was recently developed, including a Scanning Mobility Particle Sizer (SMPS) and an Inductively Coupled Plasma Mass Spectrometer (ICPMS). This allows first to classify the particles with respect to their mobility diameter, and then to determine their number concentration and elemental composition in parallel. A Rotating Disk Diluter (RDD) is used as the introduction system, giving more flexibility regarding the use of different aerosol sources. In this work, a practical guide is provided describing the different steps for establishing this instrumentation, and how to use this analysis tool. The versatility of this hyphenated technique is demonstrated in example measurements on three different aerosols generated out of a) a salt solution, b) a suspension, and c) emitted by a thermal process.

A Practical Guide on Coupling a Scanning Mobility Sizer and Inductively Coupled Plasma Mass Spectrometer SMPS-ICPMS

In this work a practical guide is provided, describing the different steps to establish the coupling of SMPS and ICPMS systems, and how to use them. Three descriptive examples are presented.

A large variety of analytical methods are available to characterize particles in aerosols and suspensions. The choice of the appropriate technique depends ...

In Situ Measurement of Vacuum Window Birefringence using 25Mg+ Fluorescence

Accurate control of the polarization states of laser light is important in precision measurement experiments. In experiments involving the use of a vacuum environment, the stress-induced birefringence effect of the vacuum windows will affect the polarization states of laser light inside the vacuum system, and it is very difficult to measure and optimize the polarization states of the laser light in situ. The purpose of this protocol is to demonstrate how to optimize the polarization states of the laser light based on the fluorescence of ions in the vacuum system, and how to calculate the birefringence of vacuum windows based on azimuthal angles of external wave plates with Mueller matrix. The fluorescence of 25Mg+ ions induced by laser light that is resonant with the transition of |32P3/2,F = 4, mF&#160;= 4<img align="center" alt="Equation 100" src="/files/ftp_upload/61175/61175img1.jpg" style="color: rgb(68, 0, 68); font-size: 18px; font-weight: 700;" />&#160;&#8594;&#160;|32S1/2,F = 3, mF&#160;= 3<img align="center" alt="Equation 100" src="/files/ftp_upload/61175/61175img1.jpg" style="color: rgb(68, 0, 68); font-size: 18px; font-weight: 700;" />&#160;is sensitive to the polarization state of the laser light, and maximum fluorescence will be observed with pure circularly polarized light. A combination of half-wave plate (HWP) and quarter-wave plate (QWP) can achieve arbitrary phase retardation and is used for compensating the birefringence of the vacuum window. In this experiment, the polarization state of the laser light is optimized based on the fluorescence of 25Mg+ ion with a pair of HWP and QWP outside the vacuum chamber. By adjusting the azimuthal angles of the HWP and QWP to obtain maximum ion fluorescence, one can obtain a pure circularly polarized light inside the vacuum chamber. With the information on the azimuthal angles of the external HWP and QWP, the birefringence of the vacuum window can be determined.

In Situ Measurement of Vacuum Window Birefringence using 25Mg+ Fluorescence

Presented here is a method to measure the birefringence of vacuum windows by maximizing the fluorescence counts emitted by Doppler cooled 25Mg+ ions in an ion trap. The birefringence of vacuum windows will change the polarization states of the laser, which can be compensated by changing the azimuthal angles of external wave plates.

Accurate control of the polarization states of laser light is important in precision measurement experiments. In experiments involving the use of a vacuum ...

Imaging Metals in Brain Tissue by Laser Ablation - Inductively Coupled Plasma - Mass Spectrometry (LA-ICP-MS)

Metals are found ubiquitously throughout an organism, with their biological role dictated by both their chemical reactivity and abundance within a specific anatomical region. Within the brain, metals have a highly compartmentalized distribution, depending on the primary function they play within the central nervous system. Imaging the spatial distribution of metals has provided unique insight into the biochemical architecture of the brain, allowing direct correlation between neuroanatomical regions and their known function with regard to metal-dependent processes. In addition, several age-related neurological disorders feature disrupted metal homeostasis, which is often confined to small regions of the brain that are otherwise difficult to analyze. Here, we describe a comprehensive method for quantitatively imaging metals in the mouse brain, using laser ablation - inductively coupled plasma - mass spectrometry (LA-ICP-MS) and specially designed image processing software. Focusing on iron, copper and zinc, which are three of the most abundant and disease-relevant metals within the brain, we describe the essential steps in sample preparation, analysis, quantitative measurements and image processing to produce maps of metal distribution within the low micrometer resolution range. This technique, applicable to any cut tissue section, is capable of demonstrating the highly variable distribution of metals within an organ or system, and can be used to identify changes in metal homeostasis and absolute levels within fine anatomical structures.

Imaging Metals in Brain Tissue by Laser Ablation - Inductively Coupled Plasma - Mass Spectrometry LA-ICP-MS

Quantitatively mapping metals in tissue by laser ablation - inductively coupled plasma - mass spectrometry (LA-ICP-MS) is a sensitive analytical technique that can provide new insight into how metals participate in normal function and disease processes. Here, we describe a protocol for quantitatively imaging metals in thin sections of mouse neurological tissue.

Quantitative Analysis of Vacuum Induction Melting by Laser-induced Breakdown Spectroscopy

Samenvatting

Meer video's verkennen

Hoofdstukken in deze video