scholarly journals The interpretation of protoplanetary disc wind diagnostic lines from X-ray photoevaporation and analytical MHD models

2020 ◽  
Vol 496 (1) ◽  
pp. 223-244 ◽  
Author(s):  
Michael L Weber ◽  
Barbara Ercolano ◽  
Giovanni Picogna ◽  
Lee Hartmann ◽  
Peter J Rodenkirch
Keyword(s):  
Trace Gas ◽  
Line Profiles ◽  
Line Broadening ◽  
Low Velocity ◽  
X Ray ◽  
Double Peaks ◽  
Multiple Components ◽  
Spectral Profiles ◽  
Extended Mhd ◽  
Gaussian Decomposition

ABSTRACT High-resolution spectra of typical wind diagnostics ([O i] 6300 Å and other forbidden emission lines) can often be decomposed into multiple components: high-velocity components with blueshifts up to several 100 km s−1 are usually attributed to fast jets, while narrow (NLVC) and broad (BLVC) low-velocity components are believed to trace slower disc winds. Under the assumption that the line broadening is dominated by Keplerian rotation, several studies have found that the BLVCs should trace gas launched between 0.05 and 0.5 au and correlations between the properties of BLVCs and NLVCs have been interpreted as evidence for the emission tracing an extended magnetohydrodynamics (MHD) wind and not a photoevaporative wind. We calculated synthetic line profiles obtained from detailed photoionization calculations of an X-ray photoevaporation model and a simple MHD wind model and analysed the emission regions of different diagnostic lines and the resulting spectral profiles. The photoevaporation model reproduces most of the observed NLVCs but not the BLVCs or HVCs. The MHD model is able to reproduce all components but produces Keplerian double peaks at average inclinations that are rarely observed. The combination of MHD and photoevaporative winds could solve this problem. Our results suggest that the Gaussian decomposition does not allow for a clear distinction of flux from different wind regions and that the line broadening is often dominated by the velocity gradient in the outflow rather than by Keplerian rotation. We show that observed correlations between BLVC and NLVC do not necessarily imply a common origin in an extended MHD wind.

Flat Crystal X-Ray Optics

1957 ◽  
Vol 1 ◽  
pp. 193-206 ◽  
Author(s):  
William J. Campbell ◽  
Melvin Leon ◽  
John Thatcher
Keyword(s):  
Wave Length ◽  
Pulse Height ◽  
Line Profiles ◽  
Line Broadening ◽  
Crystal Surfaces ◽  
X Ray ◽  
Line Intensities ◽  
Long Wave ◽  
On Line ◽  
College Park

AbstractAn investigation was undertaken by the Bureau of Mines at College Park, Md., to determine the effect of various combinations of collimators, analyzing crystals and detectors on line intensities, line-to-backgrouhd ratios, and spectral resolution. The research showed that line broadening due to mosaic crystal surfaces was greatly reduced and line splitting from faults was eliminatedby the use of two fine collimators (0.005 inch, spacing, 4 inch length). Line intensities were reduced, but lineto- background ratios arid line profiles were substantially improved with double collimators. Pulse height discrimination resulted in marked improvement in the line-to-background ratio in the long-wave length region, 2 to 10 A, but was much less effective for shorter wave lengths.

Evaluation of Straight and Curved Braun Position-Sensitive Proportional Counters on a Huber-Guinier X-Ray Diffraction System

1983 ◽  
Vol 27 ◽  
pp. 261-266 ◽  
Author(s):  
R.A. Newman ◽  
P. Moore Kirchhoff ◽  
T.G. Fawcett
Keyword(s):  
Scintillation Counter ◽  
Line Profiles ◽  
Line Broadening ◽  
X Ray Diffraction ◽  
Camera System ◽  
X Ray ◽  
Proportional Counters ◽  
On Line ◽  
Position Sensitive ◽  
Gas Chamber

AbstractThe interfacing of both straight and curved Braun Position- Sensitive Proportional Counters (PSPC's) to a high resolution Huber-Guinier camera system has been accomplished, resulting in a 10 to 100-fold decrease in data collection times when compared to conventional Guinier (film or scintillation counter) detector techniques.Various factors causing line broadening were evaluated for both PSPC Guinier systems. The depth of the PSPC gas chamber was found to Have the greatest influence on line profiles. An R0% increase in peak half-widths was observed for PSPC-Guinier data compared to our highest resolution Guinier film data, but still yielded significantly better resolution than conventional powder diffractometer data obtained in our laboratory.

Analytical formulation of the variance method of line-broadening analysis for Voigtian X-ray diffraction peaks

2006 ◽  
Vol 39 (4) ◽  
pp. 598-600 ◽  
Author(s):  
Florentino Sánchez-Bajo ◽  
Angel L. Ortiz ◽  
Francisco L. Cumbrera
Keyword(s):  
Square Lattice ◽  
Polycrystalline Materials ◽  
Alternative Formulation ◽  
Line Profiles ◽  
Line Broadening ◽  
X Ray Diffraction ◽  
X Ray ◽  
Variance Method ◽  
Instrumental Line ◽  
Diffraction Peaks

An alternative formulation of the variance method for the line-broadening analysis of polycrystalline materials is presented. It maintains the theoretical basis of the earlier formulations of the variance method, but differs in the manner of calculating the variance coefficients of the line profiles. In the proposed formulation, these are evaluated analytically in terms of the shape parameters of Voigt functions fitted to the X-ray diffraction data. Explicit expressions are thus derived for calculating the (surface-weighted) crystal sizes and (root-mean-square) lattice microstrains from the integral breadths of the Gauss and Lorentz components of the Voigt functions that model the experimental and instrumental line profiles.

scholarly journals X-Ray Line Broadening and Pure Diffraction Contours

1954 ◽  
Vol 7 (1) ◽  
pp. 77 ◽  
Author(s):  
RI Garrod ◽  
JF Brett ◽  
JA MacDonald
Keyword(s):  
Particle Size ◽  
Fourier Series ◽  
Polycrystalline Materials ◽  
Line Profiles ◽  
Line Broadening ◽  
X Ray ◽  
Experimental Line

In analysing the data from experiments designed to distinguish between particle size and distortion broadening from polycrystalline materials, it is customary either to employ correction formulae to obtain the true broadening �, or to derive the pure diffraction contour in terms of a Fourier series whose coefficients may be evaluated from the experimental line profiles.

Asymmetric X-ray line broadening of plastically deformed crystals. II. Evaluation procedure and application to [001]-Cu crystals

1989 ◽  
Vol 22 (1) ◽  
pp. 26-34 ◽  
Author(s):  
T. Ungár ◽  
I. Groma ◽  
M. Wilkens
Keyword(s):  
Dislocation Density ◽  
Dislocation Structure ◽  
Cell Structure ◽  
Dislocation Cell ◽  
Line Profiles ◽  
Line Broadening ◽  
Spatial Fluctuation ◽  
X Ray ◽  
Dislocation Cell Structure ◽  
Dipole Polarization

In paper I [Groma, Ungár & Wilkens (1988). J. Appl. Cryst. 21, 47–53] a theory was developed to interpret the asymmetric X-ray line broadening of plastically deformed crystals. It was shown that the dislocation structure can be described by five distinct parameters, namely the dislocation density, the mean quadratic spatial fluctuation of the dislocation density, the effective outer cut-off radius, the dipole polarization and the spatial fluctuation of the dipole polarization of the dislocation structure. In this paper a procedure is developed to evaluate these parameters from the Fourier transform of the line profiles. The theory and this procedure are tested by applying it to the asymmetric line profiles of tensile-deformed Cu single crystals orientated for ideal multiple slip. The asymmetry of these profiles is assigned to the dipole polarization of the dislocation cell structure and is directly correlated to residual long-range internal stresses. It is shown that the data can be interpreted in terms of the quasi-composite model of the dislocation cell structure developed earlier for the same material.

scholarly journals Relativistic Fe Kα line in the composite X-ray spectra of radio-loud active galactic nuclei

2019 ◽  
Vol 488 (3) ◽  
pp. 4378-4388
Author(s):  
Jingwei Hu ◽  
Zhu Liu ◽  
Chichuan Jin ◽  
Weimin Yuan
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Precise Measurement ◽  
Galactic Nuclei ◽  
Relativistic Effects ◽  
Line Profiles ◽  
X Ray ◽  
Wide Range ◽  
Average Spin ◽  
Spectral Profiles

ABSTRACT While a broad Fe Kα emission line is generally found in the X-ray spectra of radio quiet (RQ) active galactic nuclei (AGNs), this feature, commonly thought to be broadened by the relativistic effects near the central black hole, appears to be rare in their radio loud (RL) counterparts. In this paper, we carry out a detailed study of the ensemble property of the X-ray spectra, focusing on the Fe line, of 97 RL AGNs by applying the spectral stacking method to the spectra obtained with XMM–Newton. For comparison, the same analysis is also performed for 193 RQ AGNs. Both a narrow and a broad component of the Fe Kα line are detected at high significance in the stacked spectra of both samples. The broad lines can be well fitted with relativistically broadened line profiles. Our results suggest that, as in their RQ counterparts, a relativistic Fe line component is commonly present in RL AGNs, though it may not be detected unambiguously in individual objects with spectra of relatively low signal to noise. We try to constrain the average spin of the black holes for both the RL and RQ AGN samples by modelling their composite Fe line spectral profiles with relativistic disc line models. For the RL sample, the average spin is loosely constrained and a wide range is allowed except for very fast spins (<0.78, 90 per cent confidence), while for the RQ sample, it is constrained to be low or moderate (<0.24). We conclude that the more precise measurement of the black hole spins in RL AGNs has to await for the advent of future high-throughput X-ray telescopes.

Asymmetric X-ray line broadening of plastically deformed crystals. I. Theory

1988 ◽  
Vol 21 (1) ◽  
pp. 47-54 ◽  
Author(s):  
I. Groma ◽  
T. Ungár ◽  
M. Wilkens
Keyword(s):  
Dislocation Density ◽  
Mean Square ◽  
Line Profiles ◽  
Line Broadening ◽  
X Ray Diffraction ◽  
X Ray ◽  
Average Dislocation Density ◽  
Mean Square Fluctuation ◽  
The Mean ◽  
Dipole Polarization

X-ray diffraction line profiles of plastically deformed Cu single crystals orientated for ideal multiple slip were recently found to be markedly asymmetric. A theory is developed to interpret this kind of asymmetric line broadening in terms of the average dislocation density, the dipole polarization of the dislocation structure and the mean square fluctuation of the dislocation density.

Nondestructive Inspection of Thin, Low-Z Samples using Multiplexed Compton Scatter Tomography

1997 ◽  
Vol 503 ◽  
Author(s):  
B. L. Evans ◽  
J. B. Martin ◽  
L. W. Burggraf
Keyword(s):  
Signal To Noise Ratio ◽  
Reconstruction Algorithm ◽  
Filtered Backprojection ◽  
Line Broadening ◽  
Compton Scatter ◽  
X Ray ◽  
Tomography System ◽  
Transmission Computed Tomography ◽  
High Purity Germanium ◽  
Scattered Energy

ABSTRACTThe viability of a Compton scattering tomography system for nondestructively inspecting thin, low Z samples for corrosion is examined. This technique differs from conventional x-ray backscatter NDI because it does not rely on narrow collimation of source and detectors to examine small volumes in the sample. Instead, photons of a single energy are backscattered from the sample and their scattered energy spectra are measured at multiple detector locations, and these spectra are then used to reconstruct an image of the object. This multiplexed Compton scatter tomography technique interrogates multiple volume elements simultaneously. Thin samples less than 1 cm thick and made of low Z materials are best imaged with gamma rays at or below 100 keV energy. At this energy, Compton line broadening becomes an important resolution limitation. An analytical model has been developed to simulate the signals collected in a demonstration system consisting of an array of planar high-purity germanium detectors. A technique for deconvolving the effects of Compton broadening and detector energy resolution from signals with additive noise is also presented. A filtered backprojection image reconstruction algorithm with similarities to that used in conventional transmission computed tomography is developed. A simulation of a 360–degree inspection gives distortion-free results. In a simulation of a single-sided inspection, a 5 mm × 5 mm corrosion flaw with 50% density is readily identified in 1-cm thick aluminum phantom when the signal to noise ratio in the data exceeds 28.

scholarly journals Fingerprinting shock-induced deformations via diffraction

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Avanish Mishra ◽  
Cody Kunka ◽  
Marco J. Echeverria ◽  
Rémi Dingreville ◽  
Avinash M. Dongare
Keyword(s):  
High Speed ◽  
Shock Loading ◽  
Dislocation Slip ◽  
Line Profiles ◽  
X Ray Diffraction ◽  
Final State ◽  
X Ray ◽  
Shock Testing ◽  
Local Pressures ◽  
Deformation Modes

AbstractDuring the various stages of shock loading, many transient modes of deformation can activate and deactivate to affect the final state of a material. In order to fundamentally understand and optimize a shock response, researchers seek the ability to probe these modes in real-time and measure the microstructural evolutions with nanoscale resolution. Neither post-mortem analysis on recovered samples nor continuum-based methods during shock testing meet both requirements. High-speed diffraction offers a solution, but the interpretation of diffractograms suffers numerous debates and uncertainties. By atomistically simulating the shock, X-ray diffraction, and electron diffraction of three representative BCC and FCC metallic systems, we systematically isolated the characteristic fingerprints of salient deformation modes, such as dislocation slip (stacking faults), deformation twinning, and phase transformation as observed in experimental diffractograms. This study demonstrates how to use simulated diffractograms to connect the contributions from concurrent deformation modes to the evolutions of both 1D line profiles and 2D patterns for diffractograms from single crystals. Harnessing these fingerprints alongside information on local pressures and plasticity contributions facilitate the interpretation of shock experiments with cutting-edge resolution in both space and time.

Temperature-induced structural phase transitions in RERhSn (RE = Y, Gd-Tm, Lu)

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Simon Engelbert ◽  
Rolf-Dieter Hoffmann ◽  
Jutta Kösters ◽  
Steffen Klenner ◽  
Rainer Pöttgen
Keyword(s):  
Rare Earth ◽  
Phase Transitions ◽  
Driving Force ◽  
Room Temperature ◽  
Structural Phase ◽  
Structural Phase Transitions ◽  
Line Broadening ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
X Ray

Abstract The structures of the equiatomic stannides RERhSn with the smaller rare earth elements Y, Gd-Tm and Lu were reinvestigated on the basis of temperature-dependent single crystal X-ray diffraction data. GdRhSn crystallizes with the aristotype ZrNiAl at 293 and 90 K. For RE = Y, Tb, Ho and Er the HP-CeRuSn type (approximant with space group R3m) is already formed at room temperature, while DyRhSn adopts the HP-CeRuSn type below 280 K. TmRhSn and LuRhSn show incommensurate modulated variants with superspace groups P31m(1/3; 1/3; γ) 000 (No. 157.1.23.1) (γ = 3/8 for TmRhSn and γ = 2/5 for LuRhSn). The driving force for superstructure formation (modulation) is a strengthening of Rh–Sn bonding. The modulation is expressed in a 119Sn Mössbauer spectrum of DyRhSn at 78 K through line broadening.

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