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J S Kaastra - One of the best experts on this subject based on the ideXlab platform.
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X Ray spectra of the fe l compleX
arXiv: High Energy Astrophysical Phenomena, 2019Co-Authors: A J J Raassen, J Mao, Jelle De Plaa, Chintan Shah, Ciro Pinto, N Werner, Aurora Simionescu, F Mernier, J S KaastraAbstract:The Hitomi results on the Perseus cluster lead to improvements in our knowledge of atomic physics which are crucial for the precise diagnostic of hot astrophysical plasma observed with high-resolution X-Ray Spectrometers. However, modeling uncertainties remain, both within but especially beyond Hitomi's spectral window. A major challenge in spectral modeling is the Fe-L spectrum, which is basically a compleX assembly of n>2 to n=2 transitions of Fe ions in different ionization states, affected by a range of atomic processes such as collisional eXcitation, resonant eXcitation, radiative recombination, dielectronic recombination, and innershell ionization. In this paper we perform a large-scale theoretical calculation on each of the processes with the fleXible atomic code (FAC), focusing on ions of Fe XVII to Fe XXIV that form the main body of the Fe-L compleX. The new data are found to be consistent within 20% with the recent individual R-matriX calculations for the main Fe-L lines. By further testing the new FAC calculations with the high-quality RGS data from 15 elliptical galaXies and galaXy clusters, we note that the new model gives systematically better fits than the current SPEX v3.04 code, and the mean Fe abundance decreases by 12%, while the O/Fe ratio increases by 16% compared with the results from the current code. Comparing the FAC fit results to those with the R-matriX calculations, we find a temperature-dependent discrepancy of up to ~10% on the Fe abundance between the two theoretical models. Further dedicated tests with both observed spectra and targeted laboratory measurements are needed to resolve the discrepancies, and ultimately, to get the atomic data ready for the neXt high-resolution X-Ray spectroscopy mission.
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effective area calibration of the reflection grating Spectrometers of Xmm newton ii X Ray spectroscopy of da white dwarfs
Astronomy and Astrophysics, 2009Co-Authors: J S Kaastra, T Lanz, Ivan Hubeny, F B S PaerelsAbstract:ConteXt. White dwarf spectra have been widely used as a calibration source for X-Ray and EUV instruments. The in-flight effective area calibration of the reflection grating Spectrometers (RGS) of XMM-Newton depend upon the availability of reliable calibration sources. Aims. We investigate how well these white dwarf spectra can be used as standard candles at the lowest X-Ray energies in order to gauge the absolute effective area scale of X-Ray instruments. Methods. We calculate a grid of model atmospheres for Sirius B and HZ 43A, and adjust the parameters using several constraints until the ratio of the spectra of both stars agrees with the ratio as observed by the low energy transmission grating spectrometer (LETGS) of Chandra. This ratio is independent of any errors in the effective area of the LETGS. Results. We find that we can constrain the absolute X-Ray spectrum of both stars with better than 5% accuracy. The best-fit model for both stars is close to a pure hydrogen atmosphere, and we put tight limits to the amount of helium or the thickness of a hydrogen layer in both stars. Our upper limit to the helium abundance in Sirius B is 4 times below the previous detection based on EUVE data. We also find that our results are sensitive to the adopted cut-off in the Lyman pseudo-continuum opacity in Sirius B. We get best agreement with a long wavelength cut-off. Conclusions. White dwarf model atmospheres can be used to derive the effective area of X-Ray Spectrometers in the lowest energy band. An accuracy of 3–4% in the absolute effective area can be achieved.
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effective area calibration of the reflection grating Spectrometers of Xmm newton ii X Ray spectroscopy of da white dwarfs
arXiv: High Energy Astrophysical Phenomena, 2009Co-Authors: J S Kaastra, T Lanz, Ivan Hubeny, F B S PaerelsAbstract:White dwarf spectra have been widely used as a calibration source for X-Ray and EUV instruments. The in-flight effective area calibration of the reflection grating Spectrometers (RGS) of XMM-Newton depend upon the availability of reliable calibration sources. We investigate how well these white dwarf spectra can be used as standard candles at the lowest X-Ray energies in order to gauge the absolute effective area scale of X-Ray instruments. We calculate a grid of model atmospheres for Sirius B and HZ 43A, and adjust the parameters using several constraints until the ratio of the spectra of both stars agrees with the ratio as observed by the low energy transmission grating spectrometer (LETGS) of Chandra. This ratio is independent of any errors in the effective area of the LETGS. We find that we can constrain the absolute X-Ray spectrum of both stars with better than 5 % accuracy. The best-fit model for both stars is close to a pure hydrogen atmosphere, and we put tight limits to the amount of helium or the thickness of a hydrogen layer in both stars. Our upper limit to the helium abundance in Sirius B is 4 times below the previous detection based on EUVE data. We also find that our results are sensitive to the adopted cut-off in the Lyman pseudo-continuum opacity in Sirius B. We get best agreement with a long wavelength cut-off. White dwarf model atmospheres can be used to derive the effective area of X-Ray Spectrometers in the lowest energy band. An accuracy of 3-4 % in the absolute effective area can be achieved.
Vasiledan Hodoroaba - One of the best experts on this subject based on the ideXlab platform.
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check of the energy dispersive X Ray Spectrometers eds performance with the bam test material eds tm001 2 and bam software eds spectrometer test
2018Co-Authors: Vasiledan Hodoroaba, M ProcopAbstract:The test material EDS-TM001 together with an accompanying software package, “EDX spectrometer check”, have been made available in 2009 by BAM to be employed by EDS (energy-dispersive X-Ray spectrometer) users to check the performance of an EDS attached to the SEM. Particularly for test laboratories operating under accreditation schemes like ISO/IEC 17025, a periodical control of the critical instrumental parameters in end-user laboratories is required. With EDS-TM001 or EDS-TM002 (second generation) test material, this periodical check is simplified to the acquisition of only one 10 kV spectrum. The software “EDX spectrometer check” is destined to evaluate automatically this spectrum and determine the performance of the EDS in terms of energy resolution and calibration, as well as possible alteration of low-energy Efficiency due to detector contamination. Energy resolution can be compared with the specified values according to the international ISO standard ISO 15632:2012. EDS-TM is a synthetic material consisting of a 6 μm thick layer of C, Al, Mn, Cu and Zr deposited on a steel (in case of EDS-TM001) or silicon (in case of EDS-TM002) substrate. The chemical composition of EDS-TM was chosen such as to give nearly equal intensities of the low energy lines in a 10 kV spectrum, thus, making it very sensitive against spectrometer efficiency changes. Meanwhile, about 150 laboratories use the EDS-TM001 or EDS-TM002 test material for the periodical check of their EDS. A detailed description of the test material and software together with eXamples of application was published recently. New results and gained eXperiences will be presented as well. When the FWHM of the X-Ray lines in the EDS-TM spectrum are determined, the spectrum background must be subtracted accurately. The applied physical background subtraction procedure is robust and takes into account the transmission of the detector window. While the previous version considers only MoXtek AP windows, the new version includes selection of silicon Nitride window and the case of windowless detector. Moreover, the new version allows importing of spectra in Bruker spX-format and EMSA/MSA files from EDAX TEAM software. Windowless detectors have been also tested demonstrating long-term stability after repeated heating and cooling cycles. In this case, the appropriate Background subtraction is decisive for accurate detector characterization. Detailed results will be presented.
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determination of the effective detector area of an energy dispersive X Ray spectrometer at the scanning electron microscope using eXperimental and theoretical X Ray emission yields
Microscopy and Microanalysis, 2016Co-Authors: M Procop, Vasiledan Hodoroaba, Ralf Terborg, Dirk BergerAbstract:A method is proposed to determine the effective detector area for energy-dispersive X-Ray Spectrometers (EDS). Nowadays, detectors are available for a wide range of nominal areas ranging from 10 up to 150 mm2. However, it remains in most cases unknown whether this nominal area coincides with the "net active sensor area" that should be given according to the related standard ISO 15632, or with any other area of the detector device. Moreover, the specific geometry of EDS installation may further reduce a given detector area. The proposed method can be applied to most scanning electron microscope/EDS configurations. The basic idea consists in a comparison of the measured count rate with the count rate resulting from known X-Ray yields of copper, titanium, or silicon. The method was successfully tested on three detectors with known effective area and applied further to seven Spectrometers from different manufacturers. In most cases the method gave an effective area smaller than the area given in the detector description.
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new reference and test materials for the characterization of energy dispersive X Ray Spectrometers at scanning electron microscopes
Analytical and Bioanalytical Chemistry, 2015Co-Authors: Vanessa Rackwitz, Frank Scholze, Michael Krumrey, Christian Laubis, Vasiledan HodoroabaAbstract:Checking the performance of energy dispersive X-Ray Spectrometers as well as validation of the results obtained with energy dispersive X-Ray spectrometry (EDX) at a scanning electron microscope (SEM) involve the use of (certified) reference and dedicated test materials. This paper gives an overview on the test materials mostly employed by SEM/EDX users and accredited laboratories as well as on those recommended in international standards. The new BAM reference material EDS-CRM, which is currently in the process of certification, is specifically designed for the characterization of EDS systems at a SEM through calibration of the spectrometer efficiency in analytical laboratories in a simple manner. The certification of the spectra by means of a reference EDS is described. The focus is on the traceability of EDS efficiency which is ensured by measurements of the absolute detection efficiency of silicon drift detectors (SDD) and Si(Li) detectors at the laboratory of the PTB using the electron storage ring BESSY II as a primary X-Ray source standard. A new test material in development at BAM for testing the performance of an EDS in the energy range below 1 keV is also briefly presented.
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a method to test the performance of an energy dispersive X Ray spectrometer eds
Microscopy and Microanalysis, 2014Co-Authors: Vasiledan Hodoroaba, M ProcopAbstract:A test material for routine performance evaluation of energy-dispersive X-Ray Spectrometers (EDS) is presented. It consists of a synthetic, thick coating of C, Al, Mn, Cu, and Zr, in an elemental composition that provides interference-free characteristic X-Ray lines of similar intensities at 10 kV scanning electron microscope voltage. The EDS energy resolution at the C-K, Mn-Lα, Cu-Lα, Al-K, Zr-Lα, and Mn-Kα lines, the calibration state of the energy scale, and the Mn-Lα/Mn-Kα intensity ratio as a measure for the low-energy detection efficiency are calculated by a dedicated software package from the 10 kV spectrum. Measurements at various input count rates and processor shaping times enable an estimation of the operation conditions for which the X-Ray spectrum is not yet corrupted by pile-up events. Representative eXamples of EDS systems characterized with the test material and the related software are presented and discussed.
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performance of high resolution sem edX systems equipped with transmission mode tsem for imaging and measurement of size and size distribution of spherical nanoparticles
Microscopy and Microanalysis, 2014Co-Authors: Vasiledan Hodoroaba, C Motzkus, T Mace, Sophie VaslinreimannAbstract:The analytical performance of high-resolution scanning electron microscopy/energy dispersive X-Ray spectroscopy (SEM/EDX) for accurate determination of the size, size distribution, qualitative elemental analysis of nanoparticles (NPs) was systematically investigated. It is demonstrated how powerful high-resolution SEM is by using both mono- and bi-modal distributions of SiO 2 airborne NPs collected on appropriate substrates after their generation from colloidal suspension. The transmission mode of the SEM (TSEM) is systematically employed for NPs prepared on thin film substrates such as transmission electron microscopy grids. Measurements in the transmission mode were performed by using a “single-unit” TSEM transmission setup as manufactured and patented by Zeiss. This alternative to the “conventional” STEM detector consists of a special sample holder that is used in conjunction with the in-place Everhart–Thornley detector. In addition, the EDX capabilities for imaging NPs, highlighting the promising potential with respect to eXploitation of the sensitivity of the new large area silicon drift detector energy dispersive X-Ray Spectrometers were also investigated. The work was carried out in the frame of a large prenormative VAMAS (Versailles Project on Advanced Materials and Standards) project, dedicated to finding appropriate methods and procedures for traceable characterization of NP size and size distribution.
S H Moseley - One of the best experts on this subject based on the ideXlab platform.
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improved energy resolution of X Ray single photon imaging Spectrometers using superconducting tunnel junctions
Journal of Applied Physics, 2001Co-Authors: Luigi Frunzio, C M Wilson, D E Prober, Andrew Szymkowiak, S H MoseleyAbstract:We present measurements of the energy resolution of improved single-photon imaging X-Ray Spectrometers based on superconducting tunnel junctions. The devices have a Ta film absorber with an Al/AlOX/Al tunnel junction on each end. Recent device designs optimized for better quasiparticle cooling in the Al trap obtain an energy resolution of 13 eV full width at half maXimum for a photon energy E=5.9 keV, an improvement of a factor of two over earlier devices. We also determined that the niobium contact used in previous devices degraded the energy resolution in the center section of the absorber. With a different contact configuration, we have eliminated this spatial broadening.
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single photon imaging X Ray Spectrometers
IEEE Transactions on Applied Superconductivity, 1999Co-Authors: K Segall, Michael C Gaidis, C M Wilson, D E Prober, Andrew Szymkowiak, A K Davies, Richard E Lathrop, S H MoseleyAbstract:We have developed superconducting, single-photon imaging X-Ray detectors with an energy resolution of 26 eV FWHM at 6 keV and a spatial resolution of 0.5 /spl mu/m over an effective area of 18 /spl mu/m/spl times/100 /spl mu/m. The energy resolution is among the best reported for this kind of detector and is within a factor of /spl ap/4 of its theoretical limit. The calculated absorption efficiency of the detector is 28%. Scaling to larger areas and higher quantum efficiency appear possible. We discuss the device design and readout along with possible sources of resolution broadening.
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single photon imaging X Ray Spectrometers using low noise current preamplifiers with dc voltage bias
IEEE Transactions on Applied Superconductivity, 1997Co-Authors: S Friedrich, K Segall, Michael C Gaidis, C M Wilson, D E Prober, P J Kindlmann, Andrew Szymkowiak, S H MoseleyAbstract:We have developed superconducting single-photon imaging X-Ray detectors with an energy resolution of 54 eV at 6 keV and a spatial resolution of 1 /spl mu/m over an effective length of 40 /spl mu/m. They utilize a current-sensitive low-noise preamplifier with a dc voltage bias. It has a signal bandwidth of 300 kHz, current noise of i/sub n/=0.26 pA//spl radic/(Hz) and voltage noise of e/sub n/=0.5 nV//spl radic/(Hz) with an input capacitance of 200 pF under operating conditions. Injected pulses with a charge Q=3.7/spl middot/10/sup 6/ electrons have been measured with a standard deviation /spl sigma/Q=3400 electrons, corresponding to an electronic noise of 13 eV at 6 keV.
F B S Paerels - One of the best experts on this subject based on the ideXlab platform.
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effective area calibration of the reflection grating Spectrometers of Xmm newton ii X Ray spectroscopy of da white dwarfs
Astronomy and Astrophysics, 2009Co-Authors: J S Kaastra, T Lanz, Ivan Hubeny, F B S PaerelsAbstract:ConteXt. White dwarf spectra have been widely used as a calibration source for X-Ray and EUV instruments. The in-flight effective area calibration of the reflection grating Spectrometers (RGS) of XMM-Newton depend upon the availability of reliable calibration sources. Aims. We investigate how well these white dwarf spectra can be used as standard candles at the lowest X-Ray energies in order to gauge the absolute effective area scale of X-Ray instruments. Methods. We calculate a grid of model atmospheres for Sirius B and HZ 43A, and adjust the parameters using several constraints until the ratio of the spectra of both stars agrees with the ratio as observed by the low energy transmission grating spectrometer (LETGS) of Chandra. This ratio is independent of any errors in the effective area of the LETGS. Results. We find that we can constrain the absolute X-Ray spectrum of both stars with better than 5% accuracy. The best-fit model for both stars is close to a pure hydrogen atmosphere, and we put tight limits to the amount of helium or the thickness of a hydrogen layer in both stars. Our upper limit to the helium abundance in Sirius B is 4 times below the previous detection based on EUVE data. We also find that our results are sensitive to the adopted cut-off in the Lyman pseudo-continuum opacity in Sirius B. We get best agreement with a long wavelength cut-off. Conclusions. White dwarf model atmospheres can be used to derive the effective area of X-Ray Spectrometers in the lowest energy band. An accuracy of 3–4% in the absolute effective area can be achieved.
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effective area calibration of the reflection grating Spectrometers of Xmm newton ii X Ray spectroscopy of da white dwarfs
arXiv: High Energy Astrophysical Phenomena, 2009Co-Authors: J S Kaastra, T Lanz, Ivan Hubeny, F B S PaerelsAbstract:White dwarf spectra have been widely used as a calibration source for X-Ray and EUV instruments. The in-flight effective area calibration of the reflection grating Spectrometers (RGS) of XMM-Newton depend upon the availability of reliable calibration sources. We investigate how well these white dwarf spectra can be used as standard candles at the lowest X-Ray energies in order to gauge the absolute effective area scale of X-Ray instruments. We calculate a grid of model atmospheres for Sirius B and HZ 43A, and adjust the parameters using several constraints until the ratio of the spectra of both stars agrees with the ratio as observed by the low energy transmission grating spectrometer (LETGS) of Chandra. This ratio is independent of any errors in the effective area of the LETGS. We find that we can constrain the absolute X-Ray spectrum of both stars with better than 5 % accuracy. The best-fit model for both stars is close to a pure hydrogen atmosphere, and we put tight limits to the amount of helium or the thickness of a hydrogen layer in both stars. Our upper limit to the helium abundance in Sirius B is 4 times below the previous detection based on EUVE data. We also find that our results are sensitive to the adopted cut-off in the Lyman pseudo-continuum opacity in Sirius B. We get best agreement with a long wavelength cut-off. White dwarf model atmospheres can be used to derive the effective area of X-Ray Spectrometers in the lowest energy band. An accuracy of 3-4 % in the absolute effective area can be achieved.
Simo Huotari - One of the best experts on this subject based on the ideXlab platform.
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Improving the energy resolution of bent crystal X-Ray Spectrometers with position-sensitive detectors
Journal of Synchrotron Radiation, 2014Co-Authors: Ari-pekka Honkanen, R Verbeni, Giulio Monaco, Laura Simonelli, Marco Moretti Sala, Ali Al-zein, Michael Krisch, Simo HuotariAbstract:Wavelength-dispersive high-resolution X-Ray Spectrometers often employ elastically bent crystals for the wavelength analysis. In a preceding paper [Honkanen et al. (2014). J. Synchrotron Rad. 21, 104-110] a theory for quantifying the internal stress of a macroscopically large spherically curved analyser crystal was presented. Here the theory is applied to compensate for the corresponding decrease of the energy resolution. The technique is demonstrated with a Johann-type spectrometer using a spherically bent Si(660) analyser in near-backscattering geometry, where an improvement in the energy resolution from 1.0 eV down to 0.5 eV at 9.7 keV incident photon energy was observed
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improving the performance of high resolution X Ray Spectrometers with position sensitive piXel detectors
Journal of Synchrotron Radiation, 2005Co-Authors: Simo Huotari, G Vanko, F Albergamo, C Ponchut, H Graafsma, C Henriquet, R Verbeni, Giulio MonacoAbstract:A dispersion-compensation method to remove the cube-size effect from the resolution function of diced analyzer crystals using a position-sensitive two-dimensional piXel detector is presented. For demonstration, a resolution of 23 meV was achieved with a spectrometer based on a 1 m Rowland circle and a diced Si(555) analyzer crystal in a near-backscattering geometry, with a Bragg angle of 88.5°. In this geometry the spectrometer equipped with a traditional position-insensitive detector provides a resolution of 190 meV. The dispersion-compensation method thus allows a substantial increase in the resolving power without any loss of signal intensity.