Surface Cleanliness Level Research Articles

A New Method for Monitoring Scattered Stray Light of an Inner-occulted Coronagraph

The scattered stray light of a coronagraph is a type of stray light that is generated by the objective lens as its surface defects are irradiated by sunlight. The defects mainly include dust and blemishes on the lens surface, microroughness of the lens surface, and impurity and inhomogeneity of the glass. Unlike the other types of relatively stable defects introduced when the objective lens is being manufactured, the scattered stray light caused by dusts on the lens surface is difficult to quantify accurately due to the disorder and randomness of the dust accumulation. The contribution of this type of stray light to the overall stray light level is difficult to determine through simulations and experiments. This can result in continuous deterioration of the stray light level of a coronagraph and thus affect the observation capabilities of the instrument. To solve this issue, through analyzing the forming mechanism of scattered stray light and ghost image generated by the inner-occulted coronagraph, we propose a novel method to monitor the scattered stray light from dusts by utilizing different stray light correlation coefficients. In this method, we first simulate and measure the level of stray light from the ghost image of the objective lens, and then determine the flux ratio of scattered light and ghost image on the conjugate plane. Although the flux ratio varies with the accumulation of dusts on the lens surface, it remains constant on the image plane. Therefore, the level of dust scattering light on the image plane can be obtained by using this ratio together with the level of ghost image stray light. The accuracy of this method has been validated in a laboratory by applying the objective lens with numerous surface cleanliness levels.

Modelling of particulate contamination redistribution inside purged cavities

Sophisticated instruments on-board most of satellite payloads, especially scientific ones, are sensitive to particulate contamination since their performance can be affected in terms of straylight or surface obscuration. The surface cleanliness levels have to be minimized on ground. However, even if the deposition rate is controlled in cleanroom, the hardware is continuously exposed to particles and fibers, moving in the airflow and settling according to their various sizes and matter compositions. Thus, depending on the initial surface cleanliness level, the redistribution of particulate contamination can be a concern during integration and tests activities until launch, when venting and/or vibrations occur which results in more or less random fallout of particles. Previous studies identified different steps for the transfer mechanism such as detachment, transport and interaction with the surface (with or without bounce). Therefore, it is paramount to understand the physical phenomena of particle resuspension that happens either inside purged cavities of spacecraft or under fairing in order to be able to model them as for molecular contamination. After performing a state of the art of the existing detachment models, a Computational Fluid Dynamics software, scSTREAM, has been chosen among the most relevant ones for a feasibility study to simulate particles redistribution. This tool was particularly interesting due to the possibility to add specific functions for computation. For the purpose, the Rock’n’Roll (R’n’R) model has been implemented to consider particle resuspension. In parallel, some simple test configurations have been defined and a mock-up with several adjacent cavities has been used to compare theory and experiment when a purging under dry nitrogen was applied in the vicinity of a pre-contaminated surface. The relocation of FluoDust particles, as the source of contamination, deposited on a specific substrate has been evaluated thanks to many collector plates disseminated in one or two cavities and the levels quantified. The impact of different test conditions (flow rate, material of the substrate, presence of leakage, initial contamination level…) has been investigated. This paper presents the comparative results that confirmed the redistribution of the particulate contamination with similar trajectories but also some discrepancies due to the limitations of the R’n’R model and depending on experimental parameters such as initial distribution of particles, adherence force to the substrate…

Using a simplified ATP algorithm to improve data reliability and improve cleanliness standards for surface and medical device hygiene.

An algorithm has been improved to mitigate variability in cleanliness measurements of various surfaces using rapid Adenosine Triphosphate (ATP) testing. A cleaning intervention step (CIS) verifies the cleanability of those surfaces. ATP testing was performed on surfaces which were pre-approved as "clean" and ready for re-use. Adjacent (duplicate) ATP sampling was undertaken on 421 environmental surfaces, medical devices and other implements. The CIS was conducted on 270 surfaces using an aseptic technique and disposable cleaning wipes. The two initial ATP results were plotted against each other with a 100 RLU threshold grading the results as clean (2x<100RLU), dirty (2x>100RLU) or equivocal (1x<100RLU and 1x>100RLU). Of the surfaces sampled, 68.5% were clean (288/421), 13.5% were dirty (57/421) and 18% were equivocal (76/421). The duplicate testing demonstrated a false negative rate of 10% (44/421) where the first swab was <100 RLU and the second swab >100 RLU. For the equivocal group, the gap between the two swabs was >100 RLU for 7.5% of surfaces (33/421). The CIS was conducted on 270 of the surfaces tested and showed that cleaning could be improved (P=<0.001) on 88.5% of surfaces (239/270). The simplified ATP testing algorithm provides real-time discrimination between surface cleanliness levels and improved certainty over surface hygiene. The duplicate swab sampling approach mitigates uncontrolled variability in the results and the CIS provides a nuanced understanding of the measurable cleanliness of any surface.

Performance of Ti/Zr and silane coating pretreatments on adhesive bonding of an automotive aluminium alloy produced using the Hot Form Quench (HFQ®) process

Surface pretreatments of an automotive aluminium alloy delivered in F temper and subsequently processed using Hot Form Quench (HFQ®), a novel press forming technique combining solution heat treatment, press forming and in-die quenching to produce high-strength aluminium alloys, for adhesive bonding have been explored. The performance of two commercial pretreatments including Ti/Zr and silane coatings, with either acid spray or alkaline immersion cleaning, was investigated. Scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM) were employed to characterize the surface chemistry and topography of the alloy after pretreatments. Adhesively bonded aluminium-aluminium single lap shear joints and double cantilever beam specimens were tested to evaluate the performance of the pretreatments on the bonding strength and fracture resistance, respectively. The FTIR and TEM techniques show that the natural oxides and near-surface deformed layer have been successfully removed, but the surface cleanliness level was sensitive to the cleaning approach adopted. New Ti/Zr oxide layers or silane films have been built upon the aluminium surfaces, which confirms that sound surface conditions for adhesive bonding can be obtained for parts produced using HFQ® from F temper input material.

Scatter studies for visible emission line coronagraph on board ADITYA-L1 mission

Visible emission line coronagraph (VELC) on board ADITYA-L1 mission is an internally occulted mirror coronagraph designed for solar coronal observations over a field of view (FOV) of 1.05 R o to 3 R o . To achieve the proposed science goals, instrument background should be less than 5 ppm over the FOV of VELC. Major contributor toward instrument background is scatter from surface microroughness and particulate contamination over the primary mirror (M1). Hence, a detailed study of scatter through simulations is carried out to arrive at the surface microroughness specifications and surface cleanliness level requirements of M1. Estimation of RMS microroughness correction factor due to finite band width of the profilometer is very important while specifying the RMS microroughness of M1. This paper discusses in detail about scatter simulations, results, and analysis. All simulations are carried out using Advanced System Analysis Program, developed by Breault Research Organization.

The efficacy of ATP removal on gym contact surfaces with disinfectant wipes

&#x0D; Background: Gym equipment surfaces are known to harbor a range of contaminants due to the wide range of community use of the equipment. Certain gym equipment undergoes daily sanitation, however many other equipment surfaces do not. This study measures the levels of contamination on certain gym equipment surfaces at an educational institute gym facility and determines the contamination levels after disinfectant wipes are applied. Methods: The method to obtain the data was determined by the use of the Hygiena Systemsure II ATP analyzer in conjunction with Hygiena Ultrasnap ATP surface swabs. Gym equipment (barbells, dumbbells, machine handles, cable attachments) and other surfaces (benches, floor mats) were swabbed subsequently after a random gym patron had used the equipment to capture an accurate representation of the cleanliness of the surfaces. Disinfectant wipes were then applied to the same area before being swabbed again to determine contamination levels after disinfection. Results: The results demonstrated a statistically significant difference in the reduction of ATP levels with the use of disinfectant wipes with a p-value of 0.00001 at α=0.05. Alpha error was highly unlikely with a p-value being that low. Power was 99.9%, therefore there is a strong likelihood that we are correctly rejecting the null hypothesis. Conclusion: The study can conclude that disinfectant wipes do make a significant difference in surface cleanliness levels. Equipment that does not undergo routine cleaning such as the equipment used by the hands carry a much higher contamination rate than the body contact surfaces. Gym patrons should disinfect all body contact surfaces prior to use to reduce the risk of getting an infectious disease.&#x0D;

The Correlation Between Percent Area Coverage and Surface Cleanliness Level Owing to Particulate Accretion

The Correlation Between Percent Area Coverage and Surface Cleanliness Level Owing to Particulate Accretion

A modular approach for the design of the Alicia3 climbing robot for industrial inspection

The system proposed in this paper is the Alicia3 robot, which is based on the Alicia II module. Its aim is to inspect non‐porous vertical walls like those of aboveground petrochemical tanks, with a wide range of surface materials and cleanliness levels. To meet this aim, pneumatic‐like adhesion has been selected for the system. The system is also required to move over the surface at a suitable speed, to pass over obstacles and to have a suitable payload to carry mission‐specific instrumentation. The robot design mainly aimed at finding a solution with a high degree of modularity, so that it can easily be disassembled for maintenance purposes and to replace consumable parts such as the wheels and the sealing, making its design easier. Some onboard control algorithms have also been introduced to increase system reliability and reduce energy consumption.

Surface Cleaning and Carbonaceous Film Removal Using High Pressure, High Temperature Water, and Water/ CO 2 Mixtures

Silicon surface cleaning was investigated using water and water/ mixtures at elevated temperature (100 to 170°C) and elevated pressure [10.3 bar (150 psi) to 137.9 bar (2000 psi)]. Several “model” carbon‐containing materials were invoked to determine the ability of the fluids to remove different forms of carbonaceous layers. Polymethylmethacrylate, amorphous carbon, photoresist (KTI 820), and laboratory contamination were studied using X‐ray photoelectron spectroscopy (XPS) to evaluate removal. A model was developed to assist quantitative XPS data interpretation by mathematical simulation of sample surfaces. Results demonstrated that water removed hydrocarbon contamination and polymeric films, but could not remove amorphous carbon layers; water/ mixtures removed all of these materials. Surface cleanliness levels achievable by treating RCA‐cleaned silicon and thermally grown silicon dioxide samples with water and water/ were determined via XPS analysis. Native oxide levels and metal contamination resulting from the cleaning cycles were also evaluated.

Scatter from particulate-contaminated mirrors. part 4: properties of scatter from dust for visible to far-infrared wavelengths

It is shown that the far-infrared scatter from smooth mirrors can be dominated by the scatter from just a few very small particles or defects. This emphasizes the necessity for good cleaning techniques and good clean-room procedures. Several effects of this finding are discussed, as well as several other related topics: the cleanliness required for the scatter to be dominated by a mirror's surface microroughness; a proposed specification for low-scatter infrared mirrors; incident angle invariance of clean and contaminated mirrors; the shape ofthe bidirectional reflectance distribution function (BRDF) curves; and the relation between surface cleanliness level, clean-room cleanliness class, and BRDF.

Contamination Control Program for the Cosmic Background Explorer: An Overview

Each of the three state-of-the-art instruments flown aboard NASA's Cosmic Background Explorer (COBE)2 were designed, fabricated, and integrated using unique contamination control procedures to ensure accurate characterization of the diffuse radiation in the universe. The most stringent surface level cleanliness specifications ever attempted by NASA were required by the diffuse infrared background experiment (DIRBE) which is located inside a liquid helium cooled dewar along with the far infrared absolute spectrophotometer (FIRAS). The DIRBE instrument required complex stray radiation suppression that defined a cold primary optical baffle system surface cleanliness level of 100A.1.3 The cleanliness levels of the cryogenic instrument and the differential microwave radiometers (DMR) which were positioned symmetrically around the dewar were less stringent, ranging from level 300A to 500A. To achieve these instrument cleanliness levels, the entire flight spacecraft was maintained at level 500A throughout each phase of development. This paper describes the COBE contamination control program and the difficulties experienced in maintaining the cleanliness quality of personnel and flight hardware throughout instrument assembly, spacecraft integration, flight environmental qualification, and launch-site operations.

Role of scattering distribution functions in spacecraft contamination control practices

A method for spacecraft contamination monitoring based on the measurement of scattering distribution functions is described. Optical surfaces scattering properties are related to surface cleanliness levels making possible the definition of new contamination control criteria that can be included in spacecraft contamination control plans.