Backscattering Cross Section Research Articles

Drizzle microphysical property and vertical air motions retrieval using Doppler lidar and radar measurements

The microphysical changes in cloud formation and development are closely related to the vertical air motions. It is difficult to simultaneously detect microphysical parameters of drizzle and vertical air motions. This study proposes a method for the drizzle microphysical property and vertical air motions retrieval using Doppler lidar and radar measurements. The wavelength of lidar is 1.55 µm, and it undergoes Mie scattering or geometric scattering in drizzle. The wavelength of radar is 8.6 mm, and it undergoes Rayleigh scattering or Mie scattering in drizzle. The difference in scattering mechanisms of two wavelengths enables them to retrieve the microphysical parameters of vertical air motions and raindrops. This wavelength-dependent backscattering cross section causes differently shaped reflectivity-weighted Doppler velocity spectra leading to wavelength-dependent mean Doppler velocity, and spectra width. In this algorithm, the echo power intensity, mean Doppler velocity and spectra width of lidar and radar are used for the retrieval of microphysical parameters and vertical air motions. The feasibility of the proposed method is simulated and analyzed, which is suitable for stratiform clouds rainfall with low turbulence. Finally, an observation case is provided and analyzed.

Optical properties of chain-like atmospheric aerosol particles

Using the generalized multiparticle Mie-solution method, this study examines the optical properties of chain-like particles under different atmospheric conditions and various arrangements. The structural composition of aerosols exhibits a more pronounced impact on their extinction and absorption cross sections when the incident wavelength is below 600 nm, whereas significant changes are observed in backscattering cross sections for incident wavelengths above 600 nm. As the orientation angle between the incident wave and particle chain increases, the extinction cross sections and absorption cross sections exhibit varying degrees of decline. Furthermore, marine atmospheric aerosol chains demonstrate similar extinction cross sections to those of polluted atmospheric aerosols, and their absorption cross sections closely resemble those of clean atmospheric aerosols. In addition, for a particle chain of fixed length, the greater the disparity in particle sizes within the chain, the larger the difference between the backscattering cross section and that of the chains with equal particle sizes. This research provides theoretical support for assessing the climate effects of aerosols and inverting aerosol properties by LiDAR data.

Optical Characterization of Marine Aerosols Using a Morphologically Realistic Model With Varying Water Content: Implications for Lidar Applications and Passive Polarimetric Remote Sensing

AbstractRetrieving the physical properties and water content of marine aerosols requires understanding the links between the particles' optical and microphysical properties. By using a morphologically realistic model with varying salt mass fractions fm, describing the transition from irregularly shaped, dry salt crystals to brine‐coated geometries, optical properties relevant to polarimetric remote sensing are computed at wavelengths of 532 and 1,064 nm. The extinction cross section and its color ratio depend on particle size, but are insensitive to changes in fm; thus, measured extinction coefficients at two wavelengths contain information on both particle number and size. The lidar ratio's dependence on both size and wavelength has implications for inverting the lidar equation. The results suggest that active observations of the backscattering cross section's color ratio and the depolarization ratio, as well as, passive observations of the degree of linear polarization offer avenues to obtain the water content of marine aerosols.

Measurements of particle extinction coefficients at 1064 nm with lidar: temperature dependence of rotational Raman channels.

Aerosol intensive optical properties, including lidar ratio and particle depolarization ratio, are of vital importance for aerosol typing. However, aerosol intensive optical properties at near-infrared wavelength are less exploited by atmospheric lidar measurements, because of the comparably small backscatter cross section of Raman-scattering and a low efficiency of signal detection compared to what is commonly available at 355 nm and 532 nm. To obtain accurate optical properties of aerosols at near-infrared wavelength, we considered three factors: Raman-spectra selection, detector selection, and interference-filter optimization. Rotational Raman scattering has been chosen for Raman signal detection, because of the higher cross-section compared to vibrational Raman scattering. The optimization of the properties of the interference filter are based on a comprehensive consideration of both signal-to-noise ratio and temperature dependence of the simulated lidar signals. The interference filter that has eventually been chosen uses the central wavelength at 1056 nm and a filter bandwidth (full-width-at-half-maximum) of 6 nm. We built a 3-channel 1064-nm rotational Raman lidar. In this paper two methods are proposed to test the temperature dependence of the signal-detection unit and to evaluate the quality of the Raman signals. We performed two measurements to test the quality of the detection channel: cirrus clouds in the free troposphere and aerosols in the planetary boundary layer. Our analysis of the measured Raman signals shows a negligible temperature dependence of the Raman signals in our system. For cirrus measurements, the Raman signal profile did not show crosstalk even for the case of strong elastic backscatter from clouds, which was about 100 times larger than Rayleigh scattering in the case considered here. The cirrus-mean extinction-to-backscatter ratio (lidar ratio) was 27.8 ± 10.0 sr (1064 nm) at a height of 10.5-11.5 km above ground. For the aerosols in the planetary boundary layer, we found the mean lidar ratio of 38.9 ± 7.0 sr at a height of 1.0-3.0 km above ground.

Electrodynamic approach for calculating the absorption spectra of plasmons in a rectangle with a two-dimensional electron gas excited by an incident electromagnetic wave

The purpose of this research is to develop an electrodynamic method for calculating the plasmon spectrum in a three-dimensional structure with a two-dimensional electron gas excited by an incident electromagnetic wave. Methods. The developed method is based on solving integral equations formed with respect to induced currents in the conducting parts of a three-dimensional structure. Results. The convergence of the method and the calculation time were studied. The conditions for the convergence of calculations of higher plasmon resonances in a rectangular structure with a two-dimensional electron gas are determined. The normal incidence of an arbitrarily polarized electromagnetic wave on a rectangle with a two-dimensional gas is studied. The spectra of the absorption, extinction, forward and back scattering cross sections of the incident wave are calculated. Conclusion. It is found that in a rectangular structure containing a two-dimensional electron gas, the spectrum of plasmon resonances is modified in comparison with established by two-dimensional models of problem formulation, in which the structure is assumed to be infinite and homogeneous in one of the directions. It has been established that the incident wave most effectively excites fundamental plasmon modes. Plasmonic modes exhibit strong charge accumulation at the edges of the rectangle, which significantly affects the resonant excitation frequencies of plasmonic modes.

A high sensitivity microbeam RBS setup for heavy elements implantation profiles analysis

This work presents a new setup that integrates heavy ion RBS with microbeam technology combined with high detection solid angle for the measurement of the depth profile and areal distribution of heavy elements in silicon using a Si microbeam. Focussed 2.4 MeV Si2+ ions were scanned over the frontal or lateral surface of silicon wafers to measure both the areal concentrations and depth profiles of all elements heavier than silicon. Tests were done on samples with Pt concentration range of 4 × 10 12–2 × 10 14 at/cm 3 that was diffused via the Pt-Silicide surface layer process from one lateral surface into the 400 µm thick Si wafers. It is important to note that employing a Si ion beam instead of the conventional He ion beam serves the purpose of not only increasing the backscattering cross section, as in well-established heavy element RBS, but also reducing pileup by eliminating scattering from the Si substrate, which is essential for sensitive analysis. This allows a significant increase in microbeam currents without increasing the count rate in large area detectors. A set of two large area PIN diodes (10x10 mm) were used in an optimized configuration resulting in 1,04 sr detection solid angle. Additionally, an appropriate microbeam collimator was used to shield the PIN diodes from events caused by forward scattering and scattering of the Si ion beam halo from different components in the reaction chamber. Lateral scans of the silicon wafer were performed by focussed Si ions, with ∼10 µm spot size and of the nA range beam currents. The RBS intensity maps containing the Pt depth profile were obtained with a sensitivity of 6.7 × 109 at/cm2.

Calculation of Resonance Fluorescence Scattering Cross Sections of Metal Particles in the Middle and Upper Atmosphere and Comparison of Their Detectability

Resonance fluorescence scattering is the physical mechanism with which lidar detects atmospheric metal layers. The resonance fluorescence scattering cross section is an important parameter for lidar data processing. In this work, the resonance fluorescence backscattering cross sections of most detectable metal atoms and ions in the atmosphere were calculated. The calculated maximum backscattering cross section of Na at the D2 line is 7.38 × 10−17 m2/sr; K at the D1 line is 7.37 × 10−17 m2/sr; Fe at the 372 nm line is 7.53 × 10−18 m2/sr; Fe at the 374 nm line is 6.98 × 10−18 m2/sr; Fe at the 386 nm line is 3.75 × 10−18 m2/sr; Ni at the 337 nm line is 4.05 × 10−18 m2/sr; and Ni at the 341 nm line is 2.05 × 10−17 m2/sr; Ca is 3.06 × 10−16 m2/sr; Ca+ is 1.12 × 10−16 m2/sr. The influence of the laser linewidth on the effective scattering cross section was discussed. If the laser linewidth is lower than 2 GHz to detect Na, the laser center frequency locked at the D2a line is a better option than the D2 line in order to obtain greater signals. If an unlocked lidar is used to detect Na, the frequency at D2a should be used as the laser center frequency when the effective scattering cross section of Na was calculated, because the absorption cross section of Na atom has two local maxima. This work proposes a quantifiable comparative method for assessing the observation difficulty of different metal particles by comparing their relative uncertainties in lidar observation. It is assumed that under the same observation conditions, the detectability of different metal atoms and ions is compared. Using Na as a basis for comparison, the relative uncertainty of Ni at 337 nm is the highest, about a factor of 21 larger than that of Na, indicating that it is the most difficult to be detected. The purpose of this work is to present a quantifiable comparison method for the detection difficulty of the metal particles by lidar in the middle and upper atmosphere, which has great significance for the design of the lidar system.

MEASUREMENT OF THE CROSS SECTIONS FOR THE YIELD OF CHARACTERISTIC X-RAY RADIATION FROM 1-MeV PROTONS

This article presents the results obtained by measuring the characteristic x-ray production cross sections arising from the interaction of accelerated protons with the target atoms (PIXE). The PIXE production data were measured at the excitation of the K-, L-, and M-shells of target atoms in the mass range from Mg to Bi by 1 MeV protons. We use the approach based on the calculation of the PIXE production cross sections through the Rutherford backscattering cross section, which can be calculated from the Rutherford formula with high accuracy. This approach makes it possible to reduce the errors in measuring of the PIXE production cross sections and, thus, to improve the accuracy of the data obtained. Further, it is planned to expand the research area including protons of other energies and heavy charged particles in the energy range of 0.5–1.7 MeV/nucleon.

Echo grid integration: A novel method for preprocessing multibeam water column data to quantify underwater gas bubble emissions

AbstractWater column imaging multibeam echo sounder systems (MBESs) are a promising technology for quantitative estimates of the gas bubble volume flow within large gas seepage areas. Considerable progress has been made in recent years toward applicable calibration methods for MBESs as well as developing inversion models to convert acoustically measured backscattering cross sections to gas bubble volume flow. However, MBESs are still not commonly used for quantitative gas flow assessments. A reason for this is the absence of published processing methods that demonstrate how MBES data can be processed to quantitatively represent bubble streams. Here, we present a novel method (echo grid integration) that allows for assessing the aggregated backscattering cross section of targets within horizontal water layers. This derived value enables quantifying bubble stream gas flow rates using existing acoustic inversion methods. The presented method is based on averaging geo‐referenced volume backscattering coefficients onto a high‐resolution 3D voxel‐grid. The results are multiplied with the voxel volume to represent measurements of the total backscattering cross‐section within each voxel cell. Individual gridded values cannot be trusted because the beam pattern effects cause the values of individual targets to “smear” over multiple grid‐cells. The true aggregated backscattering cross‐section is thus estimated as the integral over the grid‐cells affected by this smearing. Numerical simulation of MBES data acquisition over known targets assesses the method's validity and quantify it's uncertainty for different, realistic scenarios. The found low measurement bias (< 1%), and dispersion (< 5%) are promising for application in gas flow quantification methods.

A benchmark study of large-angle neutron scattering cross section of tungsten using two shadow bars technique at 14 MeV

In fusion reactor design, neutron leaks intensively from blanket material through a gap. In this streaming phenomenon, backscattering cross section is known to be very crucial. In the present study, the author's team carried out a new experiment for benchmarking the large angle scattering cross section of tungsten using a DT neutron source of OKTAVIAN facility, Osaka University, Japan. Tungsten-containing material is under consideration as the radiation shield in a fusion reactor. The experimental geometry consists of a DT neutron source, two shadow bars, niobium foil, and a tungsten target. Four irradiations were performed at a neutron energy of 14 MeV using DT neutrons to extract only the contribution of large angle scattering cross section. By using two shadow bars, room return contribution was effectively suppressed. Consequently, only backscattering neutrons were measured by using a niobium foil. In the present benchmark study, obtained experimental data were compared with numerical calculations by MCNP6 using various nuclear data libraries, including JENDL-4.0, JENDL-5, JEFF-3.3, and ENDF/B-VIII.

Modeling experimental low energy ion scattering multi-angle maps with molecular dynamics FAN

Multi-angle maps obtained with low energy ion scattering (LEIS) are not only a convenient way to visualize the atomic-level surface structure of single crystals, but also provide a comprehensive data set that is useful for quantitative fitting with models. However, modeling these maps is often difficult due to the complexity of the scattering process, as well as the number of simulations needed to accurately reproduce a single experimental map. For example, traditional molecular dynamics (MD) and binary collision approximation (BCA) simulations typically require on the order of one billion simulated ion trajectories to obtain sufficient statistics. This problem is exacerbated when modeling impact-collision ion scattering spectroscopy (ICISS) maps, as backscattering cross sections are much smaller than forward-scattering cross sections. A workaround to this problem was given by Neihus and Spitzl in the form of FAN (Niehus and Spitzl, 1991), a simulation that approximates the angular dependence of the backscattering signal by only simulating ion trajectories that reach and emanate from lattice atoms, using a BCA code. This greatly reduces the number of trajectories that must be calculated, though it can oversimplify some of the more complex collision sequences. In this work, we develop a fully three-dimensional FAN code that uses MD to simulate trajectories rather than the BCA. Our approach exploits the improved speed of FAN, while retaining the more accurate ion trajectory calculations of MD. We apply the MD-FAN simulation to model LEIS measurements on two surfaces. First, we benchmark our MD-FAN simulation in a comparison to a BCA simulation for 3 keV He+ incident on W(111) that has been previously reported in Wong et al. (2020). The MD-FAN map had stronger agreement with the experimental ICISS measurements than did the BCA map, despite containing nearly 100-fold fewer ion trajectories. Second, to obtain experimental data sets for a more complex surface, we perform experimental ICISS measurements using a 3 keV He+ beam on a magnetite single crystal, Fe3O4(001) to generate a multi-angle map. The simulated MD-FAN map for the Fe3O4(001) surface once again agreed well with the experimental map, allowing for quantitative comparisons. The MD-FAN simulation also provided insight into the scattering processes, revealing that some of the observed pattern arises from 3 keV He+ that have backscattered into the detector from Fe atoms more than 2 nm below the surface.

Numerical investigation on the accuracy of size information of fractal soot aerosols retrieved by lidar: Optical property, morphology effect, and parameterization scheme

Lidar is effective in retrieving size distribution of atmospheric particles such as soot aerosols in real-time based on Mie scattering theory. However, the fundamental spherical shape assumption of Mie theory is obviously discrepant with the actual situations of atmospheric soot particles which are fractal and mixed with coating materials. In this study, the effects of fractal shapes and morphological parameters such as fractal dimension (Df), volume fraction (Vf), and particle radius (r) of soot aerosols on the size information retrieved by lidar based on Mie theory were investigated from the numerical aspect, closed-cell and coated-aggregate models were employed to represent soot aerosols thinly and heavily coated by non-absorbing materials, respectively. Optical properties of fractal soot particles were calculated at first, then backscattering and extinction properties were employed to retrieve backscattering equivalent radius (rbk) and extinction equivalent radius (rext) based on Mie theory, just like the lidar retrieval. Results revealed that optical properties of spherical and fractal models differ significantly with the variation of volume equivalent radius (rvol). Radius retrieval errors based on extinction cross-section are much smaller than that based on backscattering cross-section. The retrieval accuracy of coated-aggregate is higher than bare fractal aggregate and closed-cell models. Retrieved size distribution parameters mean radius are generally underestimated while standard deviation are overestimated for both models. Furthermore, parameterization schemes connecting rext and rvol of soot were constructed, retrieval errors are effectively reduced from about 25% to 10%, which is meaningful for the improvement of size retrieval accuracy of soot using lidar observations.

Optical properties of marine aerosol: modelling the transition from dry, irregularly shaped crystals to brine-coated, dissolving salt particles

An aerosol-optics model for water-coated marine aerosols is introduced that accounts for irregularities in the geometry of dry salt particles, and that mimics the processes of water-adsorption, dissolution of salt, and rearrangement of the liquid mantle following dissolution. The model can be tuned to adjust how rapidly the dry salt particles become spherical as water is being added to them. Size-shape distributions of the model are generated and employed to compute the ensemble-averaged extinction and backscattering cross sections, the lidar ratio, and the linear backscatter depolarisation ratio (LDR). A power law distribution that is frequently used in chemical transport models yields lidar ratios and LDR values that are consistent with field and satellite observations. But the results are found to be quite sensitive to the assumed size distribution. A generic lognormal size distribution tends to produce higher extinction cross sections, backscattering cross sections, and somewhat higher lidar ratios than the power-law distribution, while the depolarisation ratios are of comparable magnitude. We further gauged the model’s performance by comparing it with homogeneous superellipsoids. For a salt mass fraction of 0.97, the cross sections and the lidar ratio of cubic superellipsoids (i.e., those with unit aspect ratios) agree best with the reference model over all effective radii at a superellipsoid roundness parameter of 0.6. The LDR is more challenging to reproduce. For a salt mass fraction of 0.97, cubic homogeneous superellipsoids mostly give lower LDR values than the reference model. However, by increasing one aspect ratio, the superellipsoids can be tuned to yield higher LDR values. For a salt mass fraction of 0.91, the reference model yields LDR values below 0.1. Homogeneous superellipsoids that match the cross sections and lidar ratio of the reference model tend to give LDR values exceeding the reference results, at least for super-micron particles.

Backscattering Analysis Utilizing Relaxed Hierarchical Equivalent Source Algorithm (RHESA) for Scatterers in Vegetation Medium

The backscattering cross section of cylindrical and elliptical disk-shaped scatterers was investigated in this study, utilising a new numerical solution method called the relaxed hierarchical equivalent source algorithm (RHESA). The results were compared with the backscattering cross section of similar cases, using analytical method validation from literature. The objective of this research was to look into the possibility of replacing analytical methods with the RHESA in volume scattering calculations, and integrating it into modelling the backscattering of layers of dense media for microwave remote sensing in vegetation; as RHESA provides the freedom to model any shape of scatterer, as opposed to the limited shapes available of scatterers in analytical method models. The results demonstrated a good match, indicating that the RHESA may be a good fit for modelling more complicated media, such as vegetation, in future studies.

Depolarization Ratio for Randomly Oriented Ice Crystals of Cirrus Clouds

The depolarization ratio and backscattering cross sections have been calculated for shapes and size of ice crystals that are typical in cirrus clouds. The calculations are performed in the physical-optics approximation. It is shown that the depolarization ratio approaches some constant when the size of the crystals becomes much larger than the incident wavelength. For the transparent ice crystals, when absorption is absent, the magnitude of this constant strongly depends on crystal shapes. This fact allows inferring the crystal shape from magnitudes of the depolarization ratio in lidar signals. For the lidar wavelengths, where absorption of light is considerable, the depolarization ratio of lidar signals can be used for inferring crystal sizes. Such results are important for the development of algorithms interpreting the signals obtained by both ground-based and space-borne lidars.

Composition, Roughness, and Topography from Radar Backscatter at Selk Crater, the Dragonfly Landing Site

The Selk crater region is the future landing site of NASA’s Dragonfly mission to Titan. The region was imaged by the Cassini RADAR at incidence angles from 5° to 72° and at various polarization angles. Using this data set, we mapped six terrain units and assembled a backscatter curve for each, providing normalized backscatter cross section (σ 0) as a function of incidence angle. By fitting these backscatter curves with a sum of a quasi-specular and diffuse terms and evaluating three alternative formulations of the first and two for the second, we extracted the best-fit surface effective dielectric constant, rms slope, and scattering albedo. Although the parameters’ absolute values are model dependent, relative values between terrains indicate real variations in surface properties. The results are consistent with the impact exposing and fracturing a low-loss tangent material such as the water-ice bedrock, which is likely also present in the hummocky terrains and to a lesser degree in the plains and interdune regions. The dunes and dark terrains are composed of smooth, uniform material with low dielectric constant (1.5–2.3 median values for all models) compatible with organic sand. A diffuse single-scattering model enabled independent derivation of the dielectric constant from high-incidence observations, leading to low values (<2) over all terrains, indicating a depolarizing (sub)surface. Finally, radarclinometry revealed lateral variations in rim height, which remains below 300 m along the SARTopo profile but reaches up to 600 m at other locations, hinting at a rim less eroded than previously thought.

Revisiting the Hail Radar Reflectivity–Kinetic Energy Flux Relation by Combining T-Matrix and Discrete Dipole Approximation Calculations to Size Distribution Observations

Abstract The retrieval of hail kinetic energy with weather radars or its simulation in numerical models is challenging because of the shape complexity and variable density of hailstones. We combine 3D scans of individual hailstones with measurements of the particle size distributions (PSD) and T-matrix calculations to understand how hail reflectivity Z changes when approximating hailstones as spheroids, as compared to the realistic shapes obtained by 3D scanning technology. Additionally, recent terminal velocity relations are used to compare Z to the hail kinetic energy flux . We parameterize the hail backscattering cross sections at L, S, C, and X bands as a function of size between 0.5 and 5.0 cm, matching the range of the observed PSDs. The scattering calculations use the T-matrix method for size parameters below 1.0 and the discrete dipole approximation (DDA) method otherwise. The DDA calculations are done for 48 digital models of realistic hailstones of sizes between 1 and 5 cm. The DDA cross sections are calculated for multiple orientations and averaged assuming a fully random orientation distribution to provide a single value per hailstone. The T-matrix reflectivity assuming solid ice spheres presents negligible differences to DDA results for size parameters below 1.0. Therefore, T matrix was used to fill in the gaps left by the DDA calculations. The results are mapped to the same size bins of the observed PSDs, allowing the calculation of the radar reflectivity. This is then correlated to , allowing a potential improvement of past retrieval methods of from Z in multiple wavelengths.

Correction of Path-Integrated Attenuation Estimates Considering the Soil Moisture Effect for the GPM Dual-Frequency Precipitation Radar

Abstract Spaceborne precipitation radars, including the Tropical Rainfall Measuring Mission’s Precipitation Radar (PR) and the Global Precipitation Measurement Mission’s Dual-Frequency Precipitation Radar (DPR), measure not only precipitation echoes but surface echoes as well, the latter of which are used to estimate the path-integrated attenuation (PIA) in the surface reference technique (SRT). In our previous study based on analyzing PR measurements, we found that attenuation-free surface backscattering cross sections (denoted by ) over land increased in the presence of precipitation. This behavior, called the soil moisture effect, causes an underestimate of the PIA by the SRT as the method does not explicitly consider this effect. In this study, measurements made by Ku-band Precipitation Radar (KuPR) and Ka-band Precipitation Radar (KaPR), which comprise the DPR, were analyzed to examine whether KuPR and KaPR exhibit similar dependencies on the soil moisture as does the PR. For both KuPR and KaPR, an increase in was observed for a large portion of the land area, except for forests and deserts. Results from the Hitschfeld–Bordan (HB) method suggest that increases with the surface precipitation rate for light precipitation events. Meanwhile, for heavy precipitation, owing to the degradation of the HB method, it is difficult to estimate quantitatively. Thus, a correction method for PIA that considers the soil moisture effect was developed and implemented into the DPR standard algorithm. With this correction, the surface precipitation rate estimates increased by approximately 18% for KuPR and 15% for the normal scan of KaPR over land.

Black carbon aerosol number and mass concentration measurements by picosecond short-range elastic backscatter lidar

Black carbon aerosol emissions are recognized as contributors to global warming and air pollution. There remains, however, a lack of techniques to remotely measure black carbon aerosol particles with high range and time resolution. This article presents a direct and contact-free remote technique to estimate the black carbon aerosol number and mass concentration at a few meters from the emission source. This is done using the Colibri instrument based on a novel technique, referred to here as Picosecond Short-Range Elastic Backscatter Lidar (PSR-EBL). To address the complexity of retrieving lidar products at short measurement ranges, we apply a forward inversion method featuring radiometric lidar calibration. Our method is based on an extension of a well-established light-scattering model, the Rayleigh–Debye–Gans for Fractal-Aggregates (RDG-FA) theory, which computes an analytical expression of lidar parameters. These parameters are the backscattering cross-sections and the lidar ratio for black carbon fractal aggregates. Using a small-scale Jet A-1 kerosene pool fire, we demonstrate the ability of the technique to quantify the aerosol number and mass concentration with centimetre range-resolution and millisecond time-resolution.

Enhancement of backscattering cross section from an equivalent human cylinder under oblique incidence

An analysis about the enhancement of backscattering radar cross section from an equivalent human body cylinder using a specific type of coating is presented. The types of coatings considered for the human body are taken to inductive meta surface (MS), inductive MS followed by a dielectric layer and an epsilon negative (ENG) metamaterial. An eigenfunction expansion method has been used to derive analytical expressions for the scattered electric and magnetic fields. It is investigated that inductive MS and inductive MS followed by a dielectric layer type of coatings cannot be used to enhance the backscattering radar cross section from the human body. It is found that an ENG metamaterial coating having specific permittivity and coating thickness can be used to significantly enhance the back-scattering radar cross section from the human body under oblique incidence. Therefore, an ENG metamaterial coating is selected for the proposed model and finally, the modelling of the proposed design is suggested.