Optical Contamination Research Articles

“Forbidden” stars in the eROSITA all-sky survey: X-ray emission from very late-type giants

We present the results of the first X-ray all-sky survey (eRASS1) performed by the eROSITA instrument aboard the Spectrum-Roentgen-Gamma (SRG) mission on X-ray emitting red giants and supergiants. Focusing on stars positioned at high galactic latitudes above 20°, we constructed a complete sample of such objects using the Gaia DR3 catalog and identified a sample 96 stars that appear as bona fide entries in the eRASS1 source catalog. By again restricting the sample to objects nearer than 1300 pc and eliminating all catalog entries that are due to optical contamination, we ended up with a sample of 16 genuine red giant or supergiant X-ray sources, most of which represent new X-ray detections. We present a low signal-to-noise X-ray spectrum of the nearby low-activity giant Arcturus obtained from a pointed observation with the XMM-Newton satellite and give a detailed account of our data analysis. We show that Arcturus-like X-ray emission cannot be the explanation for the X-ray emissions observed by eROSITA and provide a discussion of the possible nature of the detected X-ray sources.

Lessons Learned in Designing a Proposed Ultraviolet Sterilization System for Space

This paper presents a number of lessons learned while designing a proposed sterilization system for Mars Sample Return. This sterilization system is needed to inactivate any potentially hazardous Mars material on the exterior surface of the vessel containing sealed sample tubes filled with Mars rock cores, regolith and atmosphere. These returned samples would provide information on the geologic history of Mars, the evolution of its climate and the potential for ancient life. Mars Sample Return is categorized at Planetary Protection Category V Restricted Earth Return, so it is required to protect the Earth–Moon system from the biological impact of returning samples from Mars to Earth. This article reviews lessons learned in the development of a particular engineering implementation to support the protection of the Earth–Moon biosphere: the use of in situ ultraviolet LED illumination. The details of the biological efficacy of this approach or the policy-related impacts are outside of the scope of this manuscript. The lessons learned presented here include establishing design requirements for the system, the selection of a light source, optical design options, contamination control and approaches to thermal and power management.

Optical component reliability in high-energy laser systems: Challenges and insights

The laser-induced damage resistance of large optical components remains an important limitation for the maintenance costs, reliability, and further development of high energy/high-power (HEL/HPL) laser systems. With numerous manufacturers providing different laser-induced damage threshold (LIDT) values in the nanosecond regime, a simple ranking based on numbers alone may not provide a clear picture of the best choice. Variations in testing procedures, albeit following the ISO 21254 standard, further complicate the selection process. By employing a comprehensive 1-on-1 test procedure, it becomes possible to observe various parameters that influence LIDT values. An overview on how the laser beam size, the spectral characteristics of the tested optic and possible contamination of the surface are influencing the LIDT values will be presented.

Systemic validation of mono-herbal Siddha formulation Kanduparangi chooranam through ICP-OES, GC-MS and microbial contamination analysis

Introduction: Standardization of the Siddha drugs is the process that enhances the quality of the drug before entering into industrial purposes in pharmacological and pharmaceutical sciences. The reports from the instrumental analysis give adequate details to claim the therapeutic efficacy of the drugs without any hazardous effects which are already quoted in the Siddha classical textbooks. Materials and methods: The drug Kanduparangi chooranam was analyzed by the following methods, Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), total and specific microbial contamination test and Gas Chromatography-Mass Spectroscopy (GC-MS). Results and discussion: ICP-OES results of Kanduparangi chooranam showed that the toxic heavy metals like As, Cd, Hg and Pb were Below Detection Limit (BDL). The total viable aerobic bacterial count and total viable fungal count of Kanduparangi chooranam showed that 9.2x 102 and 12.3 x 102 respectively detected level contamination were under the limits value of safety as per WHO guidelines. Specific microbial contamination test of Kanduparangi chooranam showed that there was no growth of the following microorganisms, Salmonella species, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. GC-MS analysis revealed that there was no trace of chemical compounds of Organo-pesticide residues (Chlorine, Phophorus & Pyrithroids) and Aflatoxins B1, B2, G1 and G2. Conclusion: Kanduparangi chooranam which was prepared from purified roots of Pygmaeopremna herbacea in a proper way as per the Siddha classical method, is useful for treatment purposes devoid of toxic heavy metals, microbes, pesticides and aflatoxins.

Effective Optical Scattering Range Determination Based on Ray Tracing

Surface imperfections or contamination on an optical smooth surface is usually inevitable and causes scattering. The directional information of the scattered ray can be related to the spatial frequency through the grating equation. On the other hand, the layout of the optical system determines whether a scattered ray will finally reach the detector according to the positions and directions of the scattered rays. Therefore, the scattering propagation in an optical system is usually band-limited and the effective optical range differs for different systems. In this paper, a method based on ray tracing is described that can statistically determine the optical scattering and the band of roughness. The results can be an essential reference for optical surface polishing and contamination control.

Phenofit: An R package for extracting vegetation phenology from time series remote sensing

Abstract Satellite‐derived vegetation indices (VIs) provide a way to analyse vegetation phenology over decades globally. However, these data are often contaminated by different kinds of optical noise (e.g. cloud, cloud shadow, snow, aerosol), making accurate phenology extraction challenging. We present an open‐source state‐of‐the‐art R package called to extract vegetation phenological information from satellite‐derived VIs. adopts state‐of‐the‐art phenology extraction methods, such as a weight updating function for reducing optical noise contamination, a growing season division function for separating the VI time series into different vegetation cycles, and rough and fine fitting functions for reconstructing VI time series. They work together to make phenology extraction from frequently contaminated VIs easier and more accurate. Compared against other widely used phenology extraction tools, for example, and , provides flexible input and output options, a practical growing season division function, rich curve fitting and phenology extraction functions, and robust performance under different kinds of optical noise. In addition to working with VIs from mesoscale satellites (e.g. MODIS and AVHRR), can also reconstruct vegetation time series and extract phenology using other sources, such as VIs from high‐resolution optical satellites (e.g. Sentinel‐2 and Landsat) and radar satellites (e.g. Sentinel‐1), vegetation greenness indices from digital cameras and gross primary production estimations from eddy‐covariance sites. As such, can contribute to the study of ecological process dynamics and assist in effective modelling of global change impacts on vegetation, as caused by climate variability and human intervention. Code and data of case studies are available at https://zenodo.org/record/6425745 (Kong, 2022a).

MIL-101(Cr) MOF as an Effective Siloxane Sensor.

Volatile methylsiloxanes (VMSs) are common silicone degradation byproducts that cause serious concern for the contamination of sensitive electronics and optics, among others. With the goal of fast, online detection of VMS, we herein highlight the mesoporous MIL-101(Cr) MOF as a promising mass sensing layer for integration with a quartz crystal microbalance (QCM), using an in-house modified gravimetric adsorption system capable of achieving extremely low concentrations of siloxane D4 (down to 0.04 ppm), targeting applications for monitoring in indoor spaces and spacecraft. Our developed MIL-101(Cr)@QCM sensor achieves near-perfect reversibility with no hysteresis alongside excellent repeatability over cycling and fast response/recovery times under 1 min. We attribute this capability to optimum host/guest interactions as uncovered through molecular simulations.

Investigation of Radioactivity Levels and Lead in Soil and Shore Sediment from Port Said, Egypt

Soil is one of the foremost vital foundations of life for humans, animals, and plants, so the soil contamination by radionuclides is a dangerous threat of human health. This study investigated the ²²⁶Ra, ²²⁸Ra, ⁴⁰K, ¹³⁷Cs and pb to assess their risks in soil cover of Port Said governorate. So, 41 samples (29 soil samples and 12 shore sediment samples) were collected to cover the districts area, beaches and industrial areas in Port Said governorate. Activity concentrations of ²²⁶Ra, ²²⁸Ra, ⁴⁰K and ¹³⁷Cs were determined by Hyper-Pure Germanium detector, and their Pearson’s coefficient correlations were calculated and to assess the effects of radiation produced from these radionuclides, their hazards indices were estimated. Pb was determined using Ionized coupled plasma optical emission spectroscopy (ICP-OES), Geo-accumulation index (I-geo) and Contamination Factor (CF) were calculated. The activity concentration of soil for ²²⁶Ra, ²²⁸Ra, ⁴⁰K and ¹³⁷Cs ranged from 2.78 to 26.88, BDL to 19.69, BDL to 382.34 and BDL to 1.14 Bq/Kg with average values 11.59, 7.53, 218.77 and 0.25 Bq/Kg respectively. The activity concentrations of shore sediment for ²²⁶Ra, ²²⁸Ra, ⁴⁰K and ¹³⁷Cs ranged from 5.48 to 15.17, BDL to 11.75, BDL to 448.48 and BDL to 1.14 Bq/Kg with average values 10.16, 6.91, 364.23 and 0.38 Bq/Kg respectively. The highest activity concentrations and values of hazard indices are around the industrial facilities in both cases of soil and shore sediment samples as a result of contamination from factories. But the average activity concentration of ²²⁶Ra, ²²⁸Ra, and ⁴⁰K in the soil and shore sediment samples are still lower than the worldwide activity concentrations average values and the Egyptian activity concentrations mean values. Also, all values of hazard indices and their average values are below recommended values by UNSCEAR 2000. Geo-accumulation Index (I-geo) and Contamination Factor (CF) for Pb indicated that more than 2 thirds of soil and 80% of shore sediment samples are moderately polluted or considerably contaminated by Pb. Pearson's Correlation indicated that pb from side and ²²⁶Ra, ²²⁸Ra and ⁴⁰K from other side may be from different sources.

Effect of Optics Contamination on X-ray Free-Electron Laser Beam Quality

Effect of Optics Contamination on X-ray Free-Electron Laser Beam Quality

Research of Fiber Optic Connector Ferrule End-Face Degradation Influence on Optical Pulse Distortion during Propagation over Indoor Multi-Gigabit Optical Network Link with Crypto-Fibers

This article presents results of approbation of developed model of piece-wise regular fiber optic link, operating in a few-mode regime, with series-connected couple of special multimode optical crypto-fibers “encryptor-decoder”. Unlike the previously developed solution, the model was modified with an ability to take into account influence of fiber optic connector end-face contamination on laser-excited optical signal launching conditions. We present comparison results of computed optical pulse response envelops, distorted during propagation over 10GBase-LX network fiber optic links, containing optical crypto-fibers, depending on various conditions of transceiver laser source connector ferrule end-face contamination.

Color-coded smoke PIV for wind tunnel experiments improved by eliminating optical and digital color contamination

Color-coded smoke PIV for wind tunnel experiments improved by eliminating optical and digital color contamination

Smart COD sensor using UV–Vis spectroscopy against optical window surface contamination

A typical method for real-time and unpolluted measurement of chemical oxygen demand (COD) is UV–Vis absorption spectroscopy, however, contamination of the measuring system’s optical window surface affects the measurement accuracy during long-term monitoring. This study proposes an optical window surface contamination (OWSC) compensation method, and a multi-wavelength smart sensor for long-term accurate COD measurement was developed.This study uses equivalent absorption spectrum (EAS) to describe OWSC, and explores its spectral characteristics. Therefore, we can predict the EAS of OWSC between 250 and 380 nm based on the measured absorption spectrum between 380 and 440 nm, and subtract the EAS of OWSC to get the absorbance of COD to complete the spectrum compensation.Furthermore, we designed a smart COD sensor which has the advantages of real-time warning and maintenance-free. We proved that the OWSC compensation has excellent applicability through experiments using the COD sensor, and long-term accurate COD measurement can be achieved.

Luciferase-Specific Coelenterazine Analogues for Optical Cross Talk-Free Bioassays.

Spectral overlaps in fluorescence (FL) and bioluminescence (BL) commonly cause optical cross talks. The present protocol introduces five different lineages of coelenterazine (CTZ) analogues, which have selectivity to a specific luciferase, and thus cross talk-free. For example, some CTZ analogues with ethynyl or styryl groups display dramatically biased BL to specific luciferases and pH by modifying the functional groups at the C-2 and C-6 positions of the imidazopyridinne backbone of CTZ. The optical cross talk-free feature is exemplified with the multiplex system, which simultaneously illuminated antiestrogenic and rapamycin activities without optical cross talks. This unique protocol contributes to specific and high-throughput BL imaging of multiple optical readouts in mammalian cells without optical contamination.

In situ XPS analysis of the electronic structure of silicon and titanium thin films exposed to low-pressure inductively-coupled RF plasma

Carbon contamination of synchrotron and free-electron lasers beamline optics continues to be a major nuisance due to the interaction of the intense photon beams with the surfaces of the optical elements in the presence of residual gases even in ultrahigh vacuum (UHV) conditions. Among the available in situ cleaning strategies, low-pressure radio frequency (RF) plasma treatment has emerged as a useful and relatively simple approach to remove such carbon contamination. However, the irreversible damage that the plasma may induce in such critical surfaces has to be carefully characterized before its general application. In this study, we focus on reducing the amount of carbon from UHV chamber inside surfaces via silicon and titanium coatings using a low-pressure inductively-coupled downstream plasma source and we characterize the surface alterations by in situ X-ray photoemission spectroscopy (XPS). The in situ mirror cleaning is simulated by means of silicon wafers. We observe upward band bending, which translates into lower binding energies of the photoemission lines, that we attribute to the generation of vacancies and trapped charges in the oxide layers.

Ratio-cut background removal method and its application in near-wall PTV measurement of a turbulent boundary layer

Optical contamination due to wall reflection creates limitations for near-wall velocity field measurement via either particle image velocimetry (PIV) or particle tracking velocimetry (PTV). In this paper, a simple image pre-processing method, i.e. the ratio cut method, is proposed to deal with this problem. It is based on the ratio between the grayscale intensities of tracer particles and those of the laser-illuminated background, on which a direct minimum cut is applied on the basis of a non-dimensional threshold for background removal. To evaluate its performance in near-wall measurement, this ratio cut method, along with two other typical pre-processing methods, i.e. the minimum removal method and the proper orthogonal decomposition (POD) filtering method, are applied to particle images in the near-wall region of turbulent boundary layers over an opaque roughness wall (ORW), whose characteristic roughness height is small enough to be regarded as hydraulically smooth, but still gives rise to severe wall reflection. Results for a case involving a transparent smooth wall, which suffers less from wall reflection issues, and direct numerical simulation (DNS) data at a similar Reynolds number are employed as reference baselines for performance evaluation. The examination of pre-processed particle images, as well as the probability density function (PDF) of grayscale intensities, indicates that the ratio cut method is capable of eliminating time-dependent flare, reducing noise level, and retaining low-intensity particles in the ORW case. These features are almost completely absent in both the minimum removal method and the POD filtering method. In addition, PTV-obtained velocity statistics for an ORW, pre-processed by the ratio cut method, including data relating to fluctuating intensity and the PDF distribution of fluctuating velocity, are shown to be more consistent with those relating to baseline cases than data obtained by either of the the other two methods used for comparison. Moreover, evidence is also provided regarding the superiority and robustness of this approach, in terms of estimating the mean skin friction from the near-all mean velocity profile.

Study on the Prevention of Optics Contamination in Photo-Lithography

In semiconductor manufacturing technology, photolitho exposure tools have advanced scaling of integrated circuit (IC) chips for decades. The tools enable illumination optics to expose the patterns of photo-mask onto wafers coated with photo-resist (PR). As the line width of the chip has been scaled down below 20 nm, the contamination of optics degrades the uniformity of light so that it reduces the accuracy of optical patterns. Thus, contamination in the optic system is crucial to enhance wafer pattern scaling.The level of contamination in optics can be identified with light scattering (i.e., Straylight index). By tracing the Straylight index for years, we determined REMA (Reticle Masking) lens, which is one of the lens element, was contaminated by the chemical ions of FAB air. We implemented destructive inspection with the contaminated lenses to identify degradation mechanisms and detected plenty of positive ions (i.e., Si+) (Table.1) and negative ions (i.e., Silicon Oxide) (Table.2) on REMA Lens. (Fig.1). The humidity in FAB air which is attach to the polar surface of optics, light exposure transforms it to hydroxide ions or highly reactive radical (OH*, H*, O*) by the DUV light. And then the highly reactive radical is easy to combine with non-cleanable contamination (e.g., silicon, sulfur, and nitrogen). Although Photolithographic tools have a purging system using inert N2, XCDA (Extreme clean dry air), CA (Clean Air) to prevent contamination. Each optic has a different purge system and environment, so contamination has been strongly concentrated on the last lens element of REMA.In this paper, we performed three main tests to slow the rate of lens contamination. First of all, literally hundreds of tools in the factory have measured with the efficiency of the chemical filters for pollutions. Then, we exchanged types of chemical filters based on the different contamination speed. This test helps us to identify contamination sources. Secondly, we changed the air mixing ratio (i.e., Dilution factor). Despite the similar structure of the tool, the air mixing ratio is different respectively as the time of each tools is released. After investigating the three different values, we found an optimized value to slow down the contamination speed. Lastly, we reform the structure of tools to avoid mixing the pollution air. Overall, these test results tell a remedy of how to manage the lens contamination in optics. Figure 1

Avaliação da contaminação ótica de analisadores de gás CO2 de caminho aberto em medições sobre uma superfície de água doce

Avaliação da contaminação ótica de analisadores de gás CO2 de caminho aberto em medições sobre uma superfície de água doce

Optical-trapping of particles in air using parabolic reflectors and a hollow laser beam.

We present an advanced optical-trapping method that is capable of trapping arbitrary shapes of transparent and absorbing particles in air. Two parabolic reflectors were used to reflect the inner and outer parts of a single hollow laser beam, respectively, to form two counter-propagating conical beams and bring them into a focal point for trapping. This novel design demonstrated high trapping efficiency and strong trapping robustness with a simple optical configuration. Instead of using expensive microscope objectives, the parabolic reflectors can not only achieved large numerical aperture (N.A.) focusing, but were also able to focus the beam far away from optical surfaces to minimize optics contamination. This design also offered a large free space for flexible integration with other measuring techniques, such as optical-trapping Raman spectroscopy, for on-line single particle characterization.

Extreme UV secondary electron yield measurements of Ru, Sn, and Hf oxide thin films

Background: The secondary electron yield (SEY) of materials is important for topics as nanoparticle photoresists and extreme ultraviolet (EUV) optics contamination. Aim: Experimentally measure SEY and secondary electron energy distributions for Ru, Sn, and Hf oxide. Approach: The SEY and energy distribution resulting from 65 to 112 eV EUV radiation are measured for thin-film oxides or films with native oxide. Results: The total SEY can be explained by EUV absorption in the topmost nanometer of (native) oxide of the investigated materials. Conclusions: Although the relative SEY of Ru and Sn is well-explained by the difference in EUV absorption properties, the SEY of HfO2 is almost a factor 2 higher than expected. Based on the energy distribution of secondary electrons, this may be related to a lower barrier for secondary electron emission.

Experimental investigation of surface adhesion of Titan analog materials: Mitigation by dust-repellent coatings

We report an experimental investigation of organic Titan regolith simulant interactions with transparent surfaces. In the absence of prior triboelectrification of the particles and surface, the area coverage of sprinkled particles increases with increasing substrate surface energy, as expected. Bare sapphire, sapphire coated with indium tin oxide (ITO), and sapphire coated with ITO and fluorosilane collected 20%, 10%, and 5% particles, respectively. Under turbulent conditions that promote triboelectric charging, the adhesion of Titan regolith analogs is enhanced. Bare sapphire occluded by more than 60% in some cases. However, conductive ITO generally reduced the area coverage below 10% when electrically grounded, and the fluorosilane treatment reduced it slightly further. The surface coatings tested, and anti-static measures more generally, therefore provide significant mitigation of optical window contamination.