Characterization of Carbon-Contaminated B4C-Coated Optics after Chemically Selective Cleaning with Low-Pressure RF Plasma

Boron carbide (B4C) is one of the few materials that is expected to be mostly resilient with respect to the extremely high brilliance of the photon beam generated by free electron lasers (FELs) and is thus of considerable interest for optical applications in this field. However, as in the case of many other optics operated at modern light source facilities, B4C-coated optics are subject to ubiquitous carbon contaminations. These contaminations represent a serious issue for the operation of high performance FEL beamlines due to severe reduction of photon flux, beam coherence, creation of destructive interference, and scattering losses. A variety of B4C cleaning technologies were developed at different laboratories with varying success. We present a study regarding the low-pressure RF plasma cleaning of carbon contaminated B4C test samples via inductively coupled O2/Ar, H2/Ar, and pure O2 RF plasma produced following previous studies using the same IBSS GV10x downstream plasma source. Results regarding the chemistry, morphology as well as other aspects of the B4C optical coating before and after the plasma cleaning are reported. We conclude from these comparative plasma processes that pure O2 feedstock plasma only exhibits the required chemical selectivity for maintaining the integrity of the B4C optical coating.Comment: 27 pages, 15 figure

Pressure evaluation of spray induced flow by means of URANS and time-resolved Stereo Particle Image Velocimetry

In the present work, pressure distributions of spray-induced flow are obtained by means of time-resolved stereo Particle Image Velocimetry. Revealing an extensive insight in the nature of spray transport, the characterization of pressure, material acceleration and instantaneous velocity provides a comprehensive description of spray induced flow dynamics. The pressure evaluation is conducted by an extended formulation based on the Unsteady Reynolds Averaged Navier-Stokes Equations and ensemble averaging. Assuming adiabatic flow and perfect gas the effect of compressibility is taken into account. In order to achieve phase discrimination and image contrast enhancement, optical filtering is applied by doping the gaseous phase with fluorescent tracer particles. The measurements are performed with gasoline direct injection 2-hole research samples. Demonstrating the capacity of pressure evaluation, pressure fields of spray-induced flow are successfully obtained. The investigations reveal characteristic flow patterns in accordance to air entrainment and fluid displacement. In respect to single spray plumes, high pressure regions are identified in front of the spray and the wake flow, whereas low pressure regions are present at central position. The pressure evaluation exposes minimal pressure differences

Analysis of spray induced flow of gasoline direct injection (GDI) nozzle by means of time-resolved Fluorescence-Particle Image Velocimetry

The development of modern gasoline direct injection (GDI) nozzles demands profound knowledge about the mechanisms of spray transport in order to minimize emissions and maximize fuel efficiency. To receive a fundamental understanding about spray transport, the present study investigates spray induced flow of a two-hole research nozzle. Air entrainment, spray-air interaction and jet-to-jet interaction are analyzed by means of timeresolved Fluorescence-Particle Image Velocimetry (FPIV). In order to achieve phase discrimination, optical filtering is applied by doping the gaseous phase with fluorescent seeding particles. The investigation considers near field and global spray characteristics by using different field of views and optical magnifications. Flow features such as displacement and entrainment are identified and localized, providing a description of strength, growth and propagation. The exchange of momentum between spray and gas indicates jet-to-jet interaction by attraction of separate spray plumes. The investigation demonstrates a dependency between spray hole inclination angle and entrainment flow. Spray plumes with smaller inclination angels tend to be more attracted than spray plumes with higher inclination angels. A disparity of momentum exchange is observed

An assessment of the correlation-based particle identification (CPI) method in the framework of Dual-Plane Stereo-Astigmatism (DPSA)

A synthetic study is conducted to assess the performance of the correlation-based particle identification method (CPI). As a technique developed in the context of Dual-Plane StereoAstigmatism (DPSA), the CPI method allows the identification of particle image shapes by utilizing image cross-correlation. The performance assessment addresses the influence of noise, particle density, particle image size and particle image deformation. The study shows viable results for low to moderate particle densities. Generally, a stronger performance of the CPI method is observed for small particle image sizes and pronounced particle image deformations. However, in the absence of particle overlapping, such as in the case of small particle densities, bigger particle images show a stronger performance, since a finer numerical discretization of the particle image provides a more accurate computation of the image cross-correlation. A stronger incorporation of particle overlapping increases the rate of particle identification, however it diminishes the accuracy of particle localization and particle allocation

Expression Patterns of TNFα, MAdCAM1, and STAT3 in Intestinal and Skin Manifestations of Inflammatory Bowel Disease.

Pathogenesis of cutaneous extraintestinal manifestations [EIM] in inflammatory bowel disease [IBD] remains elusive. Efficacy of anti-TNF agents suggests TNF-dependent mechanisms. The role of other biologics, such as anti-integrins or JAK-inhibitors, is not yet clear. We performed immunohistochemistry for TNFα, NFκB, STAT1/STAT3, MAdCAM1, CD20/68, caspase 3/9, IFNγ, and Hsp-27/70 on 240 intestinal [55 controls, 185 IBD] and 64 skin biopsies [11 controls, 18 erythema nodosum [EN], 13 pyoderma gangenosum [PG], 22 psoriasis]. A semiquantitative score [0-100%] was used for evaluation. TNFα was upregulated in intestinal biopsies from active Crohn`s disease [CD] vs controls [36.2 vs 12.1, p < 0.001], but not ulcerative colitis [UC: 17.9]. NFκB, however, was upregulated in intestinal biopsies from both active CD and UC [43.2 and 34.5 vs 21.8, p < 0.001 and p = 0.017, respectively]. TNFα and NFκB were overexpressed in skin biopsies from EN, PG, and psoriasis. No MAdCAM1 overexpression was seen in skin tissues, whereas it was upregulated in active UC vs controls [57.5 vs 35.4, p = 0.003]. STAT3 was overexpressed in the intestinal mucosa of active and non-active IBD, and a similar upregulation was seen in skin biopsies from EN [84.7 vs 22.3, p < 0.001] and PG [60.5 vs 22.3, p = 0.011], but not in psoriasis. Caspase 3 and CD68 overexpression in skin biopsies distinguished EN/PG from psoriasis and controls. Upregulation of TNFα/NFκB in EN and PG is compatible with the efficacy of anti-TNF in EIM management. Data on overexpressed STAT3, but not MAdCAM1, support a rationale for JAK-inhibitors in EN and PG, while questioning the role of vedolizumab