Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “soft”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

Continuous-time photon-stimulated desorption spectroscopy studies on soft x-ray-induced reactions of CF{sub 3}Br adsorbed on Si(111)-7x7

Continuous-time core-level photon-stimulated desorption (PSD) spectroscopy was used to study the soft x-ray-induced reactions of CF{sub 3}Br molecules adsorbed on Si(111)-7x7 near the Si(2p) edge (98-110 eV). The monochromatic synchrotron radiation was employed as a soft x-ray light source in the photon-induced reactions and also as a probe for investigating the produced fluorination states of the bonding surface Si atom in the positive-ion PSD spectroscopy. Several different surface coverages were investigated. The PSD spectra from the low-CF{sub 3}Br-covered surfaces show the production of surface SiF species, while those from the high-CF{sub 3}Br-covered surfaces depict the formation of surface SiF, SiF{sub 2}, and SiF{sub 3} species. The photolysis cross section of the submonolayer CF{sub 3}Br-covered surface is determined as {approx}4.3x10{sup -18} cm{sup 2}. A comparison with the results on CF{sub 3}Cl/Si(111)-7x7 surface is discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2012

The soft x-ray instrument for materials studies at the linac coherent light source x-ray free-electron laser

The soft x-ray materials science instrument is the second operational beamline at the linac coherent light source x-ray free electron laser. The instrument operates with a photon energy range of 480-2000 eV and features a grating monochromator as well as bendable refocusing mirrors. A broad range of experimental stations may be installed to study diverse scientific topics such as: ultrafast chemistry, surface science, highly correlated electron systems, matter under extreme conditions, and laboratory astrophysics. Preliminary commissioning results are presented including the first soft x-ray single-shot energy spectrum from a free electron laser.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Soft x-ray scattering facility at the Advanced Light Source with real-time data processing and analysis

We present the development and characterization of a dedicated resonant soft x-ray scattering facility. Capable of operation over a wide energy range, the beamline and endstation are primarily used for scattering from soft matter systems around the carbon K-edge ({approx}285 eV). We describe the specialized design of the instrument and characteristics of the beamline. Operational characteristics of immediate interest to users such as polarization control, degree of higher harmonic spectral contamination, and detector noise are delineated. Of special interest is the development of a higher harmonic rejection system that improves the spectral purity of the x-ray beam. Special software and a user-friendly interface have been implemented to allow real-time data processing and preliminary data analysis simultaneous with data acquisition.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

Central electron temperature estimations of TJ-II neutral beam injection heated plasmas based on the soft x ray multi-foil technique

The core electron temperature (T{sub e0}) of neutral beam heated plasmas is determined in TJ-II stellarator by using soft x ray detectors with beryllium filters of different thickness, based on the method known as the foil absorption technique. T{sub e0} estimations are done with the impurity code IONEQ, making use of complementary information from the TJ-II soft x ray tomography and the VUV survey diagnostics. When considering the actual electron density and temperature profile shapes, an acceptable agreement is found with Thomson scattering measurements for 8 different magnetic configurations. The impact of the use of both neutral beam injectors on the T{sub e0} measurements is addressed. Also, the behaviour of T{sub e0} during spontaneous profile transitions is presented.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2012

A multi-frame soft x-ray pinhole imaging diagnostic for single-shot applications

For high energy density magnetized target fusion experiments at the Air Force Research Laboratory FRCHX machine, obtaining multi-frame soft x-ray images of the field reversed configuration (FRC) plasma as it is being compressed will provide useful dynamics and symmetry information. However, vacuum hardware will be destroyed during the implosion. We have designed a simple in-vacuum pinhole nosecone attachment, fitting onto a Conflat window, coated with 3.2 mg/cm{sup 2} of P-47 phosphor, and covered with a thin 50-nm aluminum reflective overcoat, lens-coupled to a multi-frame Hadland Ultra intensified digital camera. We compare visible and soft x-ray axial images of translating ({approx}200 eV) plasmas in the FRX-L and FRCHX machines in Los Alamos and Albuquerque.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

Development of a soft x-ray diffractometer for a wideband multilayer grating with a novel layer structure in the 2-4 keV range

We have been developing a wavelength-dispersive soft x-ray spectrograph covering an energy region of 50-4000 eV to attach to a conventional electron microscope. Observation of soft x-ray emission in the 2-4 keV range needs a multilayer coated grating. In order to evaluate the performance of the optical component in the energy region, a goniometric apparatus has been newly developed and the preliminary performance has been tested using synchrotron radiation.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

A beam intensity monitor for the evaluation beamline for soft x-ray optical elements

Evaluation Beamline for Soft X-Ray Optical Elements (BL-11) at the SR Center of Ritsumeikan University has been operated to measure the wavelength and angular characteristics of soft x-ray optical components in a wavelength range of 0.65-25 nm using a reflecto-diffractometer (RD). The beam intensity monitor that has been equipped in BL-11 has observed the signal of the zero-th order light. For the purpose of more accurate evaluation of the performance of optical components, a new beam intensity monitor to measure the intensity of the first order light from the monochromator in BL-11 has been developed and installed in just front of RD. The strong positive correlation between the signal of the beam monitor and a detector equipped in the RD is shown. It is successful that the beam intensity of the first order light can be monitored in real time.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Interaction of soft x-ray laser pulse radiation with aluminum surface: Nano-meter size surface modification

Interaction of soft x-ray laser radiation with material and caused modification of the exposed surface has both physical and practical interests. We irradiated the focusing soft x-ray laser (SXRL) pulses having a wavelength of 13.9 nm and the duration of 7 ps to aluminum (Al) surface. After the SXRL irradiation process, the irradiated Al surface was observed with a scanning electron microscope. The surface modifications caused by SXRL single pulse exposure were clearly seen. In addition, it was found that the conical structures having around 100 nm in diameters were formed in the shallow features. The nano-meter size modified structures at Al surface induced by SXRL pulse is interesting as the newly surface structure. Hence, the SXRL beam would be a candidate for a tool of micromachining. We also provide a thermomechanical modeling of SXRL interaction with Al briefly to explain the surface modification.

36 MATERIALS SCIENCE↗
DOE OSTI2012

End station for nanoscale magnetic materials study: Combination of scanning tunneling microscopy and soft X-ray magnetic circular dichroism spectroscopy

We have constructed an end station for nanoscale magnetic materials study at the soft X-ray beamline HiSOR BL-14 at Hiroshima Synchrotron Radiation Center. An ultrahigh-vacuum scanning tunneling microscope (STM) was installed for an in situ characterization of nanoscale magnetic materials in combination with soft X-ray magnetic circular dichroism (XMCD) spectroscopy experiment. The STM was connected to the XMCD experimental station via damper bellows to isolate it from environmental vibrations, thus achieving efficient spatial resolution for observing Si(111) surface at atomic resolution. We performed an in situ experiment with STM and XMCD spectroscopy on Co nanoclusters on an Au(111) surface and explored its practical application to investigate magnetic properties for well-characterized nanoscale magnetic materials.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2013

Bayesian soft X-ray tomography using non-stationary Gaussian Processes

In this study, a Bayesian based non-stationary Gaussian Process (GP) method for the inference of soft X-ray emissivity distribution along with its associated uncertainties has been developed. For the investigation of equilibrium condition and fast magnetohydrodynamic behaviors in nuclear fusion plasmas, it is of importance to infer, especially in the plasma center, spatially resolved soft X-ray profiles from a limited number of noisy line integral measurements. For this ill-posed inversion problem, Bayesian probability theory can provide a posterior probability distribution over all possible solutions under given model assumptions. Specifically, the use of a non-stationary GP to model the emission allows the model to adapt to the varying length scales of the underlying diffusion process. In contrast to other conventional methods, the prior regularization is realized in a probability form which enhances the capability of uncertainty analysis, in consequence, scientists who concern the reliability of their results will benefit from it. Under the assumption of normally distributed noise, the posterior distribution evaluated at a discrete number of points becomes a multivariate normal distribution whose mean and covariance are analytically available, making inversions and calculation of uncertainty fast. Additionally, the hyper-parameters embedded in the model assumption can be optimized through a Bayesian Occam's Razor formalism and thereby automatically adjust the model complexity. This method is shown to produce convincing reconstructions and good agreements with independently calculated results from the Maximum Entropy and Equilibrium-Based Iterative Tomography Algorithm methods.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Boundary displacement measurements using multi-energy soft x-rays

The Multi-Energy Soft X-ray (ME-SXR) system on NSTX provides radial profiles of soft X-ray emission, measured through a set of filters with varying thickness, which have been used to reconstruct the electron temperature on fast time scales (∼10 kHz). In addition to this functionality, here we show that the ME-SXR system can be used to measure the boundary displacement of the NSTX plasma with a few mm spatial resolution during magnetohydrodyamic (MHD) activity. Boundary displacement measurements can serve to inform theoretical predictions of neoclassical toroidal viscosity, and will be used to investigate other edge phenomena on NSTX-U. For example, boundary measurements using filtered SXR measurements can provide information on pedestal steepness and dynamic evolution leading up to and during edge localized modes (ELMs). Future applications include an assessment of a simplified, filtered SXR edge detection system as well as its suitability for real-time non-magnetic boundary feedback for ELMs, MHD, and equilibrium position control.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Design and initial operation of a two-color soft x-ray camera system on the Compact Toroidal Hybrid experiment

A multi-camera soft x-ray diagnostic has been developed to measure the equilibrium electron temperature profile and temperature fluctuations due to magnetohydrodynamic activity on the Compact Toroidal Hybrid experiment. The diagnostic consists of three separate cameras each employing two 20-channel diode arrays that view the same plasma region through different beryllium filter thicknesses of 1.8 μm and 3.0 μm allowing electron temperature measurements between 50 eV and 200 eV. The Compact Toroidal Hybrid is a five-field period current-carrying stellarator, in which the presence of plasma current strongly modifies the rotational transform and degree of asymmetry of the equilibrium. Details of the soft x-ray emission, effects of plasma asymmetry, and impurity line radiation on the design and measurement of the two-color diagnostic are discussed. Preliminary estimates of the temperature perturbation due to sawtooth oscillations observed in these hybrid discharges are given.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Use of soft x-ray diagnostic on the COMPASS tokamak for investigations of sawteeth crash neighborhood and of plasma position using fast inversion methods

The soft x-ray diagnostic is suitable for monitoring plasma activity in the tokamak core, e.g., sawtooth instability. Moreover, spatially resolved measurements can provide information about plasma position and shape, which can supplement magnetic measurements. In this contribution, fast algorithms with the potential for a real-time use are tested on the data from the COMPASS tokamak. In addition, the soft x-ray data are compared with data from other diagnostics in order to discuss possible connection between sawtooth instability on one side and the transition to higher confinement mode, edge localized modes and productions of runaway electrons on the other side.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Note: Effect of photodiode aluminum cathode frame on spectral sensitivity in the soft x-ray energy band

Silicon photodiodes used for soft x-ray detection typically have a thin metal electrode partially covering the active area of the photodiode, which subtly alters the spectral sensitivity of the photodiode. As a specific example, AXUV4BST photodiodes from International Radiation Detectors have a 1.0 μm thick aluminum frame covering 19% of the active area of the photodiode, which attenuates the measured x-ray signal below ∼6 keV. This effect has a small systematic impact on the electron temperature calculated from measurements of soft x-ray bremsstrahlung emission from a high-temperature plasma. Although the systematic error introduced by the aluminum frame is only a few percent in typical experimental conditions on the Madison Symmetric Torus, it may be more significant for other instruments that use similar detectors.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Installation of soft X-ray array diagnostics and its application to tomography reconstruction using synthetic KSTAR X-ray images

Four-array system of soft X-ray diagnostics was installed on KSTAR tokamak. Each array has 32 viewing chords of two photo-diode array detectors with spatial resolution of 2 cm. To estimate signals from the soft X-ray radiation power, typical n{sub e}, T{sub e}, and argon impurity line radiation profiles in KSTAR are chosen. The photo-diodes were absolutely calibrated as a function of the incident photon energy in 2–40 keV range with a portable X-ray tube. Two-dimensional T{sub e} image properties by multi-energy method were simulated and visualized with six combinations of beryllium filter sets within the dynamic range of signal ratio.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

In operando observation system for electrochemical reaction by soft X-ray absorption spectroscopy with potential modulation method

In order to investigate local structures of electrolytes in electrochemical reactions under the same scan rate as a typical value 100 mV/s in cyclic voltammetry (CV), we have developed an in operando observation system for electrochemical reactions by soft X-ray absorption spectroscopy (XAS) with a potential modulation method. XAS spectra of electrolytes are measured by using a transmission-type liquid flow cell with built-in electrodes. The electrode potential is swept with a scan rate of 100 mV/s at a fixed photon energy, and soft X-ray absorption coefficients at different potentials are measured at the same time. By repeating the potential modulation at each fixed photon energy, it is possible to measure XAS of electrochemical reaction at the same scan rate as in CV. We have demonstrated successful measurement of the Fe L-edge XAS spectra of aqueous iron sulfate solutions and of the change in valence of Fe ions at different potentials in the Fe redox reaction. The mechanism of these Fe redox processes is discussed by correlating the XAS results with those at different scan rates.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

The simultaneous measurement of energy and linear polarization of the scattered radiation in resonant inelastic soft x-ray scattering

Resonant Inelastic X-ray Scattering (RIXS) in the soft x-ray range is an element-specific energy-loss spectroscopy used to probe the electronic and magnetic excitations in strongly correlated solids. In the recent years, RIXS has been progressing very quickly in terms of energy resolution and understanding of the experimental results, but the interpretation of spectra could further improve, sometimes decisively, from a full knowledge of the polarization of incident and scattered photons. Here we present the first implementation, in a high resolution soft-RIXS spectrometer used to analyze the scattered radiation, of a device allowing the measurement of the degree of linear polarization. The system, based on a graded W/B{sub 4}C multilayer mirror installed in proximity of the CCD detector, has been installed on the AXES spectrometer at the ESRF (European Synchrotron Radiation Facility); it has been fully characterized and it has been used for a demonstration experiment at the Cu L{sub 3} edge on a high-T{sub c} superconducting cuprate. The loss in efficiency suffered by the spectrometer equipped with this test facility was a factor 17.5. We propose also a more advanced version, suitable for a routine use on the next generation of RIXS spectrometers and with an overall efficiency up to 10%.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Direct observation of ferromagnetism in grain boundary phase of Nd-Fe-B sintered magnet using soft x-ray magnetic circular dichroism

We have investigated the magnetism of the grain boundary (GB) phase in a Nd{sub 14.0}Fe{sub 79.7}Cu{sub 0.1}B{sub 6.2} sintered magnet using soft x-ray magnetic circular dichroism (XMCD) at the Fe L{sub 2,3}-edges. Soft XMCD spectra were measured from the fractured surface that was confirmed to be covered with a thin GB phase by Auger electron spectroscopy. The magnetic moment of Fe in the GB phase was estimated to be m{sub GB}=1.4 μ{sub B} at 30 °C using the sum rule analysis for XMCD spectra, which is 60% of that of Fe in the Nd{sub 2}Fe{sub 14}B compound. The temperature dependence of m{sub GB} evaluated with reference to Fe in the Nd{sub 2}Fe{sub 14}B phase indicated that the Curie temperature of the GB phase is more than 50 °C lower compared to that of Nd{sub 2}Fe{sub 14}B.

36 MATERIALS SCIENCE↗