Laser-induced Fluorescence System Research Articles

Instant plastic waste detection on shores using laser-induced fluorescence and associated hyperspectral imaging

Plastic pollution is a rising environmental issue, with millions of tons of plastic debris collecting in the world's seas and on its shores. Hyperspectral imaging (HSI) has become increasingly widely used as a more precise approach that can identify targets in remote sensing aquatic missions. The interference from other beach materials, and the need for proper identification of litter types can make identifying dumped plastics on sand-surrounded beaches challenging. This study lays the groundwork for a physical laboratory setting for images captured by a hyperspectral (HS) imager. The suggested testing setup included the development of a fluorescence signature for the target theater of operations (low-density polyethylene (LD-PE) and wood surrounded by sand) for detecting polymers in a simulated beach environment using the laser-induced fluorescence (LIF) approach. Initially using broadband-spectrum light, strong sample diffuse reflectance contrast is observed in the imaging at wavelengths between 400 and 460 nm. Next, a dedicated LIF system for plastic litter discovery was developed using an ultraviolet (UV) laser source. Initial findings show that there is a distinct fluorescence signal for plastics at 450 nm and at 750 nm for wood. Our pilot studies support current efforts to determine the optimum spectral signature that these polymers will appear with clarity on shorelines using an inexpensive imagery combined with our UV LIF approach, which may have an impact on applications for the detection of beach pollution. The knowledge gained from this study can be used to construct reliable aerial conventional cameras for plastic waste environmental monitoring and management.

Instant identification of dental white spot using K-means algorithm via laser-induced fluorescence and associated hyperspectral imaging.

Dental caries (DC) is a chronic illness that affects 2 billion individuals worldwide, with 520 million of those suffering from it in their primary teeth. It is apparent that early DC detection and subsequent minimally invasive therapy are crucial clinical requirements. The first reversible clinical indication of demineralization is dental white spot (DWS) lesions. However, diagnosing DWS poses extreme challenges for practitioners. In this investigation, a customized laser-induced fluorescence system with a hyperspectral imaging (HI) camera and a non-ionization laser light supply was created for DWS localization and early DC detection. A UV laser diode source with a wavelength of 395nm was used for light stimulation for the 10 test samples of teeth. The emitted signature of the main tooth components, including dentin, DWS, enamel, and DC, was recorded. An attempt was made to increase the system's sensitivity to the fluorescent signal by applying a logarithmic scale to the spectral signature. Moreover, further discrimination may be achieved by signal strength. We identified that the fluorescent signal's peak intensity at 771nm works best for discriminating DWS from normal areas, or DC. For characterizing dentin, the re-emitted frequency at 500nm has the maximum intensity. Next, we presented our imaging grouping strategy that combines visual enhancement through a moving average, MA, filtering and segmenting an image using K-means clustering (K-mc) (K=8) for instant and precise DWS grouping for the constructed HI images at (500nm and 771nm). Despite the tiny structure and its DWS white appearance, our approach could successfully demarcate the DWS on the tested teeth. Dental examiners might benefit from our simple, non-invasive, non-ionizing optical diagnosis approach to help them make their first assessments and experience accurate and exact delineation of the DWS to obtain immediate and higher rates of early-stage DC detection.

Effect of hydrogen addition on combustion and thermal characteristics of impinging non-premixed jet flames for various heating value gases

This study experimentally investigates the effect of hydrogen addition on combustion and thermal characteristics of impinging non-premixed jet flames for low-heating values gases (LHVGs). We evaluate the flame morphology and stability using a concentric non-premixed combustor with an impingement plate. OH radicals are visualized using the OH* chemiluminescence and OH-planar laser-induced fluorescence (OH-PLIF) system. Emission characteristics are investigated by calculating CO and NOx emission indices. The results show that the flame stability region narrows as the heating value decreases but expands as hydrogen has been added. The low-OH radical intensity of LHVGs increases with the hydrogen addition. EICO and EINOx decrease with the reduction of heating values. EICO rapidly declines near the lifted flame limit due to the premixing of fuel and air downstream of the flame region. The effect of the hydrogen addition on EINOx is insignificant and shows very low emissions. The heat transfer rate into cooling water indicates a linear tendency with thermal power regardless of the fuel type. These findings show that LHVGs can be employed in existing-impinging flame systems so long as they remain within flame stability regions. Furthermore, hydrogen addition positively affects the expansion of flame stability, enhancing the utility of LHVGs.

Measurement and Prediction of Droplet Entrainment in Inclined Liquid–Liquid Flow by PLIF Method

Inclined liquid-liquid two-phase flows widely exist in petroleum, chemical, and other important industrial processes. The study of droplet entrainment in inclined flow is of great significance for investigating the heat/mass transfer between phases and optimizing the industrial production processes. In this study, a planar laser-induced fluorescence (PLIF) system is designed to visualize the inclined liquid-liquid flows. The silicone oil (organic phase) and water/glycerol mixture (aqueous phase) are used as the experimental media. The length and amplitude of the interfacial waves are derived from the flow visualizations. The relationship between the critical wavelengths and Froude number is explored to indicate the transition from stratified flow (ST) to stratified flow with mixing at the interface (ST&MI). The wave aspect ratio is derived to characterize the instability and breakage of the interfacial wave. Meanwhile, the entrainment ratios of dispersed droplets in the continuous phases are detected, and the effects of the flow rate and the interfacial shear on the droplet entrainment are studied. Finally, a physical model is developed to predict the droplet entrainment ratios based on the force balance analysis of the interfacial wave. In general, the developed model is effective in predicting the droplet entrainment ratio with mean absolute errors of 0.015 and 0.023 for the organic and aqueous droplets, respectively.

Non-invasive caries detection and delineation via novel laser-induced fluorescence with hyperspectral imaging

Carious is a global chronic disease; 2 billion people and 520 million children suffer from permanent and primary teeth caries respectively. Early caries detection via precise, non-invasive, non-ionizing radiation is highly appreciated. Carious deteriorate the chemical structure of sound tooth tissues, with variation in its optical properties. In this study, customized laser-induced fluorescence system consists of non-ionizing laser light source and hyperspectral camera was developed for early caries detection. Tested tooth sample was illuminated with laser source of 385 nm and 5 mW power. The emitted spectrum signature for main tooth elements including enamel, dentin, stain, and caries were captured. Logarithmic scale of spectrum signature was applied in an attempt to enhance system sensitivity to fluorescent signal. Fluorescence signature at 500 nm secured the maximum fluorescence intensity difference for different tooth elements. Consequently 2D hyperspectral image at 500 nm was constructed. Enhanced 2D image was accomplished via nonlinear filter to enhance contrast. Segmentation via K mean clustering was adopted for precise caries delineation. This narrative, facile, non-invasive, non-ionizing technique experienced precise and accurate delineation of different caries stages (normal, moderate, and severe).

Effect of Blowby on the Leakage of the Three-Piece Oil Control Ring and Subsequent Oil Transport in Upper Ring-Pack Regions in Internal Combustion Engines

The lubricating oil consumption (LOC) in internal combustion engines contributes to emission and deteriorates the performance of the aftertreatment. In this work, an optical engine with a 2D Laser-induced fluorescence (2D-LIF) system was used to study operating conditions critical to real driving oil emissions. Additionally, numerical models were used to analyze the ring dynamics, oil flow and gas flow. It was found that the intake pressure that results in zero blowby is the separation line between two drastically different oil flow patterns in the ring pack. With intake pressure lower than the separation line, the oil accumulation of the three-piece oil control ring groove (TPOCR) begins to increase, followed by the drastic increase of the oil accumulation in the third land, second land, and finally visible oil leaking through the top ring gap, given enough time. The time required for the oil to leak through different rings was investigated using both measurements and modeling. The effects of drain holes and rail gaps, as well as their relative rotation on oil accumulation and leakage from the TPOCR groove, were analyzed. These findings contribute to improving ring pack designs and engine calibration in spark ignition (SI), gas, and hydrogen engines equipped with TPOCR to minimize the negative impacts of LOC.

Quasi-3D visualization and local parameter measurement of horizontal and nearly horizontal liquid–liquid two-phase flows by using PLIF method

Horizontal and nearly horizontal liquid–liquid two-phase flows are widely encountered in petroleum, chemical, and other important industrial production fields. The three-dimensional (3D) flow visualization and the local parameter measurement are of great significance for understanding the flow dynamics and revealing the flow-pattern transition mechanism. In this paper, experiments of horizontal and nearly horizontal (+5°) liquid–liquid flow are carried out in an acrylic pipe with an inner diameter of 20 mm. Silicone oil (organic phase) and water/glycerol mixture (aqueous phase) are used as the test fluid. A novel planar laser-induced fluorescence (PLIF) system is designed to detect the flow structures. The incident direction of the laser sheet is along the radial section of the pipe, and the PLIF camera is positioned at 60° to the plane of the laser sheet, referred to as PLIF-60. In the experiment, the two-dimensional (2D) flow images at the pipe radial section are captured by the PLIF-60 system. Considering the effect of the angle between the laser sheet and the PLIF camera, the flow images are corrected to remove the horizontal and vertical distortions. The liquid–liquid stratified interface and the entrained droplets are identified in the corrected flow images. A droplet tracking method is proposed to derive the droplet diameter and its quantity distribution. Quasi-3D flow structures are reconstructed upon the accurate detection of the stratified interface and the entrained droplets. The evolution characteristics of the interface structures and the spatial distributions of droplets are studied. In addition, aqueous phase holdup and droplet entrainment ratios at pipe axial and radial sections are extracted based on the quasi-3D flow visualizations. The effects of the flow conditions and the pipe inclinations on the profiles of the aqueous phase holdup and the droplet entrainment ratio are uncovered.

Intercomparison of OH radical measurement in a complex atmosphere in Chengdu, China.

Atmospheric oxidation is a driving force of complex air pollution, and accurate hydroxyl radical (OH) measurement is helpful in investigating the radical-cored photooxidation mechanism in the troposphere. A self-developed laser-induced fluorescence instrument by the Anhui Institute of Optics Fine Mechanics, Chinese Academy of Sciences (AIOFM-LIF), was able to measure OH concentration with high sensitivity and good time resolution, and a detection limit of 1.7 × 105 cm-3 (1σ, 30 s). A long-period, multi-level intercomparison of hydroxyl radical (OH) measurements between AIOFM-LIF and PKU-LIF (the Peking University laser-induced fluorescence system) was conducted in Chengdu, China. The measurement between two instruments was in excellent agreement in the 5-min time resolution. Linear regression analysis reported a linear slope of 0.96 with a 0.68 × 106 cm-3 offset, and the correlation coefficient R2 was 0.85. The overall linearity with only a slight offset indicated a negligible influence on OH measurement. No noticeable artifacts from ozonolysis were observed under the condition of high ozone and ozonolysis-related compound concentrations. In addition to the subtraction of background signal through wavelength modulation, the dynamic correction on ozone photolysis interference ensured high intercomparison quality in both relatively constant and rapidly varying periods. Based on the reliability of OHAIOFM and OHPKU, comparisons under different oxidation-related species (NOx, VOCs, O3, PM2.5) levels and typical scenarios (rich-BVOC and high-reactivity) were carried out to evaluate the performance under complex atmospheres. A slightly higher drift was observed in a certain scenario, but the general data variability due to environmental changes did not affect the measurement accuracy. The intercomparison demonstrated that both systems are able to achieve reliable OH data under typical conditions of complex atmospheric pollution in China. Additional improvements are necessary for future intercomparisons in order to enhance the confidence in OH detection accuracy.

A portable UAV-based laser-induced fluorescence lidar system for oil pollution and aquatic environment monitoring

A portable laser-induced fluorescence (LIF) lidar detection system for the unmanned aerial vehicle (UAV) was developed. The system consists of a transmitting and receiving module, a data processing module and a wireless transmission module. The total weight of the LIF lidar system is 5 kg. The system emits 405 nm laser to irradiate the water body, which can realize the monitoring of oil spills and chlorophyll content in the seawater by receiving the fluorescence signal with a spectral range of 400–750 nm. The fluorescence detection data of the LIF system on the UAV are synchronized to the ground terminal through a wireless transmission module, and the acquired fluorescence data are processed by a ground computer in real-time. The performance of the system was tested at a flight altitude of 30 m, and the spectral data of the seawater and oil slicks seawater were studied. The obtained results demonstrate the ability of the LIF lidar system to realize seawater fluorescence remote sensing measurement. The system is convenient and inexpensive for routinely sea monitoring and oil spill monitoring on a regional scale.

The Influence of AP Addition on the Combustion Characteristics of TKX‐50 with Concentrated Ignition

AbstractIn order to study the influence of ammonium perchlorate (AP) addition on the combustion reaction process of dihydroxylammonium 5,5’‐bistetrazole‐1,1’‐ diolate (TKX‐50), a concentrated ignition system was used to evaluate the ignition and combustion characteristics of the samples. The self‐luminescence characteristics and the OH concentration distribution in the flame of TKX‐50 and TKX‐50/AP composites were captured by a high‐speed camera and a planar laser induced fluorescence system (PLIF), respectively. The combustion products were then analyzed by a scanning electron microscope (SEM) and a X‐ray energy dispersive spectrometer (EDS). The results show that the reaction of TKX‐50 undergoes three stages with concentrated ignition, and a bright yellow color appears in the flame due to the formation of NH2α during the combustion process. When the materials of AP is added, there are pre‐ignition occurred for twice. The ignition delay time increases, and the reaction in the pyrolysis phase is more intense. Besides, the burning rate is faster and the flame brightness is significantly weakened due to the decrease of NH2α. During the combustion process, the high‐concentration OH signal of the two samples distribute on the two wings of the flames, and the peak signals are similar under the 10 Hz laser excitation. For the samples before and after the combustion reaction, the morphology is quite different, and the specific residue composition needs be further analyzed.

Quantitative study on the interference of OH radicalmeasurement in the air pollution complex

<p indent="0mm">OH radical is the most important gas-phase oxidant in the troposphere, which oxidizes the primary pollutants to secondary pollutants and causes the regional secondary pollution. Hence, it is crucial to acquire comprehensive knowledge of the radical chemistry to mitigate the secondary air pollution. However, the well-established photochemistry is insufficient to describe the chemical processes in the complex air mixture. For instance, the model severely underpredicts OH radical concentration in forest areas. <italic>In situ</italic> measurement of OH radical is an efficient way to quantify the atmospheric oxidation capacity and improve our understanding of atmospheric chemical mechanisms. While due to its high reactivity and low concentration, measurement of OH radical is one of the most challenging tasks in the atmospheric research. Laser-induced fluorescence (LIF) is the most widely used technique to measure OH due to its high sensitivity and selectivity. However, studies have shown that under high volatile organic compounds (VOCs) conditions, LIF technique based on traditional spectral modulation methods may suffer from interference, whose origin has not yet been known. In this study, based on the Peking University Laser-Induced Fluorescence system (PKU-LIF), a chemical modulation method was developed, to separate interference by quantifying the chemical background signals, through chemical removing of the ambient OH prior to be sampled into the detection cell, thereby enabling accurate measurement of OH radical. During the winter campaign in Beijing in 2016, simultaneous OH radical measurement based on both the chemical modulation method and the spectral modulation method was achieved for the first time, and two sets of OH radical concentrations were obtained. It was found that, the two sets of OH radical concentrations agreed within the combined uncertainties of 31% (correlation slope: 0.88±0.01), indicating that there was no significant interference in the measurement of OH based on the traditional spectral modulation method during this winter campaign. It is worth nothing that whether the LIF measurement of OH radicals will suffer from interference and the degree of interference highly depend on the specific instrument configurations and the environmental conditions. Therefore, when applying LIF technique to measure the concentration of OH radical under complex environments in the future, the chemical modulation method is required to achieve accurate OH measurement.

Ultra-sensitive detection of O-GlcNAc transferase based on micro-structured optical fiber biosensor with enhanced fluorescence collection

The development of optical fiber-based biosensors is greatly promoted by the increasing demand for simple, rapid and miniaturized analytical devices for accurate and sensitive detection of biomolecules in the clinical diagnosis, biomedicine and pharmaceutical fields. O-GlcNAc transferase (OGT) is considered to be a novel promising therapeutic target for disease diagnosis since it is closely related to O-linked-β-N-acetylglucosamine glycosylation (O-GlcNAcylation). At present, the detection and study of OGT has been hampered by its ultralow cellular abundance and low stability of enzyme activity. Here we present a micro-structured optical fiber (MSOF)-based biosensor for ultra-sensitive analysis of OGT. We utilize MSOF as carrier to immobilize fluorescence-labeled peptide based on streptavidin-biotin affinity and non-radioactive UDP-GlcNAc as sugar donor to perform O-GlcNAc glycosylation modification. Moreover, we improve the laser-induced fluorescence (LIF) system by combining concave mirror and microscope objective as fluorescence collector to further enhance the detection sensitivity. With the advantages of large surface area of MSOF and high fluorescence collection efficiency, the MSOF-biosensor shows an ultralow limit-of-detection of 3.40 × 10−2 pM for OGT assays. The feasibility of its clinical application has also been demonstrated by the analysis of blood samples from breast cancer patients, providing a promising analysis platform for sensitive diagnosis of OGT.

Effect of hydrogen addition on flame stability and structure for low heating value coaxial nonpremixed flames

ABSTRACT An investigation of effect of hydrogen addition on flame stability and structure i.e. combustion characteristics of low heating value gases (LHVGs) that consist of methane, propane, nitrogen is carried out experimentally and numerically. For the experiment, a coaxial non-premixed jet-type combustor and Planar Laser Induced Fluorescence (PLIF) system are used to evaluate the flame stability limit and flame shapes and visualize OH radical distribution, respectively. For the numerical analysis of hydrogen added LHVGs, the calculation using the FLUENT software with decreased GRI 3.0 mechanism is performed to study the 2D flame temperature distribution and radial flame structure. As a result, the flame length of LHVGs reduces as hydrogen is added. CH* and OH* radicals visualized by chemiluminescence system are distributed closer to the nozzle as hydrogen is added to LHVGs. OH-PLIF images show that OH intensity of LHVG 6000 is higher with hydrogen addition. The flame stability of LHVGs is improved with hydrogen addition. As for the numerical result, the reduction of flame length and width of LHVG 6000 are predicted with adding the hydrogen.

High stability 500 Hz MOPA system for planar laser-induced fluorescence

A high pulse energy laser diode-pumped Nd:YAG master oscillator power amplifier (MOPA) laser is demonstrated. The maximum energy of 68 mJ, 9.6 ns, 1064 nm laser at a pulse repetition frequency of 500 Hz is achieved by utilizing the amplifier composed of three LD side-pumped Nd:YAG modules. Moreover, the maximum laser energy of 35.6 mJ is obtained at 532 nm by employing a KTP crystal as a frequency doubler. When ambient temperature ranges from 5 °C to 45 °C, the master oscillator has a pulse energy jitter of <5%. During the shake-environment test, the maximum-pulse-energy jitter of the MOPA laser is less than 2%. The developed MOPA laser has been used in a laser-induced fluorescence system and the variation of the flow field is obtained at a repetition rate of 500 Hz.

Impact Region of Nonbuoyant Orthogonal Discharge

The results of experimental studies into the behavior of nonbuoyant discharges impacting a solid boundary are presented. The discharges were released perpendicular to the boundary at nondimensional heights (H/d) ranging from to 36 to 173, where H/d is the ratio of the jet discharge height above the boundary to the jet diameter. Although the primary focus was on concentration field measurements using a laser-induced fluorescence system, additional velocity field data are presented from a recent study that used a similar discharge configuration and a particle tracking velocimetry system. Integral models provided a relatively simplistic framework for quantifying and interpreting the flow behavior in the vicinity of the boundary. The new data sets enabled defining the scale of the impact region based on the ability of integral techniques to model the flow entering and leaving this region. These data sets also offered insights into the flow behavior in the impact region and provided the basis for determining the influence of the impact region on the flow behavior.

Analysis of fluorescence simulation and experiments for sea surface oil film based on LIF.

In order to effectively analyze the fluorescence distribution of sea surface oil film detected by laser-induced fluorescence (LIF), a novel, to the best of our knowledge, simulation model of the oil film fluorescence was established based on the Monte Carlo method. Using this simulation model, the fluorescence distribution of oil film with different thickness in emission direction and spatial distribution were analyzed. Based on the fluorescence mechanism model of oil film detected by LIF, a criterion for the LIF system calibration, i.e., the fluorescence intensity ratio between oil film and clean seawater (FIR) using the fluorescence collected from clean seawater as a reference was proposed. The validity of the fluorescence simulation model was verified by using the FIR results of theory and simulation. The fluorescence spectra of oil films with different thickness and FIR parameters of corresponding thickness were obtained by experiments. By analyzing the fluorescence spectra of different oil products and oil film thickness, the fluorescence influencing factors of oil film detected by LIF were obtained. The results show that the fluorescence coverage area increases gradually with the increase of oil film thickness. When the incident light is in the same direction as the fluorescence receiving direction, the obtained fluorescence intensity is larger. Moreover, the FIR used as the calibration criterion of the LIF monitoring system can effectively characterize the thickness of oil film on the sea surface for LIF to detect sea surface oil film in real applications.

Design of a two-photon laser-induced fluorescence system on Experimental Advanced Superconducting Tokamak (EAST)

The neutral gas surrounding the fusion plasma in a tokamak has a significant effect upon its quality; however, it is difficult to measure the properties of neutral particles in a tokamak, such as particle density, isotopy, or temperature. Herein, we transform a recently designed horizontal Thomson scattering (TS) diagnostic system into a two-photon laser-induced fluorescence (TALIF) system that measures the edge neutral density of the plasma in Experimental Advanced Superconducting Tokamak (EAST). The TALIF system can measure the neutral density from 0.95 to 1.1 in normalized poloidal flux coordinates and includes 10 measurement points in the radial direction with spatial resolution of 5 mm and a temporal resolution of 1 ms at a cadence of 10/30 Hz. These two systems, TALIF and TS diagnostic, can share the same port, beam path, collection optics, and optical fibers. The horizontal TS diagnostic system can be further developed into a TV Thomson scattering (TVTS) diagnostic system via a CCD detector. The TALIF system and the TVTS diagnostic system can even share a detector. This TALIF system can play a significant role in allowing neutral particle measurement in current and future fusion tokamaks.

Experimental study of combustion inhibition by trimethyl phosphate in turbulent premixed methane/air flames using OH-PLIF

The influence of turbulent fluctuation on combustion inhibition by trimethyl phosphate (TMP) is investigated in turbulent premixed methane/air flames. The instantaneous flame structures are detected by OH Planar Laser-Induced Fluorescence (OH-PLIF) system, and some statistical parameters, including the global consumption speed, mean fuel consumption rate and mean heat release rate, are attempted to quantify the inhibition effectiveness of TMP in the turbulent premixed flames. Results show that the turbulent combustion regime of the methane/air flame may be changed from the thin reaction zone (TRZ) to the distributed reaction zone (DRZ) regime, due to the high loading of inhibitor. The addition of agent can obviously decrease the turbulent consumption speed. Meanwhile, the relative inhibition efficiency of TMP in the turbulent flame is much lower than that in the laminar configuration. From the point view of reaction, one possible reason is that the difference of the turbulent transportation between the active radicals (H and OH) and the phosphorus-containing species (PO2, HOPO, HOPO2, etc.) may lead to decreasing the capacity of radical scavenging. By increasing the jet velocity, the mean fuel consumption rate and mean heat release rate decrease for the neat flames, but increase for the inhibited ones. The main reason is that the velocity increment is smaller than the increment of flame volume for the neat cases, but is larger than that for the doped configurations. Because of no consistent tendency, these two statistic variables may not the preferred parameters for the evaluation of turbulent flame inhibition.

The investigation of OH radicals produced in a DC glow discharge by laser-induced fluorescence spectrometry

In this paper the OH radicals produced by a needle–plate negative DC discharge in water vapor, N2 + H2O mixture gas and He + H2O mixture gas are investigated by a laser-induced fluorescence (LIF) system. With a ballast resistor in the circuit, the discharge current is limited and the discharges remain in glow. The OH rotation temperature is obtained from fluorescence rotational branch fitting, and is about 350 K in pure water vapor. The effects of the discharge current and gas pressure on the production and quenching processes of OH radicals are investigated. The results show that in water vapor and He + H2O mixture gas the fluorescence intensity of OH stays nearly constant with increasing discharge current, and in N2 + H2O mixture gas the fluorescence intensity of OH increases with increasing discharge current. In water vapor and N2 + H2O mixture gas the fluorescence intensity of OH decreases with increasing gas pressure in the studied pressure range, and in He + H2O mixture gas the fluorescence intensity of OH shows a maximum value within the studied gas pressure range. The physicochemical reactions between electrons, radicals, ground and metastable molecules are discussed. The results in this work contribute to the optimization of plasma reactivity and the establishment of a molecule reaction dynamics model.

Compact, portable, laser induced fluorescence diagnostic for laboratory plasma sources.

As diagnostic groups are increasingly called upon to participate in experimental campaigns at remote facilities, there is a need to develop portable versions of plasma diagnostic systems. One such diagnostic is laser induced fluorescence (LIF). Here, we describe a portable LIF apparatus that eliminates the need for an optical table, beam splitters, and an optical chopper. All of the light exiting the laser system is coupled through optical fibers to the experiment and housekeeping diagnostics. The collected light is coupled through an optical fiber as well. A key feature is modulation of the tapered amplifier current instead of physical modulation of the laser output. Using this portable LIF system, measurements of ion temperature, ion flow, and relative metastable ion density are reported for two different remote experiments.