Vacuum-compatible photon-counting hybrid pixel detector for wide-angle x-ray scattering, x-ray diffraction, and x-ray reflectometry in the tender x-ray range.

A vacuum-compatible photon-counting hybrid pixel detector has been installed in the ultra-high vacuum reflectometer of the four-crystal monochromator beamline of the Physikalisch-Technische Bundesanstalt at the electron storage ring BESSY II in Berlin, Germany. The setup is based on the PILATUS3 100K module. The detector can be used in the entire photon energy range accessible at the beamline from 1.75 keV to 10 keV. Complementing the already installed vacuum-compatible PILATUS 1M detector used for small-angle x-ray scattering (SAXS) and grazing incidence SAXS, it is possible to access larger scattering angles. The water-cooled module is located on the goniometer arm and can be positioned from -90° to 90° with respect to the incoming beam at a distance of about 200 mm from the sample. To perform absolute scattering experiments, the linearity, homogeneity, and angular dependence of the quantum efficiency, including their relative uncertainties, have been investigated. In addition, the first results of the performance in wide-angle x-ray scattering, x-ray diffraction, and x-ray reflectometry are presented.

Two-channel high-resolution quasi-monochromatic X-ray imager for Al and Ti plasma.

High-resolution, high-sensitivity X-ray imaging is a real challenge in high-energy density plasma experiments. We present an improved design of the Fresnel ultra high-resolution imager instrument. Using an Ultra-High-Intensity (UHI) laser to generate hot and dense plasma in a small volume of an Al-Ti mixed target provides simultaneous imaging of both Al and Ti X-ray emission. Specifically, the Al Heß (or Lyß) and the Ti Heα lines are imaged with a resolution of (2.7 ± 0.3) µm and (5.5 ± 0.3) µm, respectively. It features two transmission Fresnel phase zone plates fabricated on the same substrate, each associated with a multilayer mirror for spectral selection. Their spatial resolution has been measured on the PTB synchrotron radiation facility laboratory at BESSY II and on the EQUINOX laser facility. Results obtained on an UHI experiment highlight the difference of emission zone sizes between Al and Ti lines and the versatility of this instrument.

Hollow organosilica beads as reference particles for optical detection of extracellular vesicles.

Essentials Standardization of extracellular vesicle (EV) measurements by flow cytometry needs improvement. Hollow organosilica beads were prepared, characterized, and tested as reference particles. Light scattering properties of hollow beads resemble that of platelet-derived EVs. Hollow beads are ideal reference particles to standardize scatter flow cytometry research on EVs. SUMMARY: Background The concentration of extracellular vesicles (EVs) in body fluids is a promising biomarker for disease, and flow cytometry remains the clinically most applicable method to identify the cellular origin of single EVs in suspension. To compare concentration measurements of EVs between flow cytometers, solid polystyrene reference beads and EVs were distributed in the first ISTH-organized interlaboratory comparison studies. The beads were used to set size gates based on light scatter, and the concentration of EVs was measured within the size gates. However, polystyrene beads lead to false size determination of EVs, owing to the mismatch in refractive index between beads and EVs. Moreover, polystyrene beads gate different EV sizes on different flow cytometers. Objective To prepare, characterize and test hollow organosilica beads (HOBs) as reference beads to set EV size gates in flow cytometry investigations. Methods HOBs were prepared with a hard template sol-gel method, and extensively characterized for morphology, size, and colloidal stability. The applicability of HOBs as reference particles was investigated by flow cytometry with HOBs and platelet-derived EVs. Results HOBs proved to be monodisperse with a homogeneous shell thickness. Two-angle light-scattering measurements by flow cytometry confirmed that HOBs have light-scattering properties similar to those of platelet-derived EVs. Conclusions Because the structure and light-scattering properties HOBs resemble those of EVs, HOBs with a given size will gate EVs of the same size. Therefore, HOBs are ideal reference beads with which to standardize optical measurements of the EV concentration within a predefined size range.

Absolute radiant power measurement for the Au M lines of laser-plasma using a calibrated broadband soft X-ray spectrometer with flat-spectral response.

CEA implemented an absolutely calibrated broadband soft X-ray spectrometer called DMX on the Omega laser facility at the Laboratory for Laser Energetics (LLE) in 1999 to measure radiant power and spectral distribution of the radiation of the Au plasma. The DMX spectrometer is composed of 20 channels covering the spectral range from 50 eV to 20 keV. The channels for energies below 1.5 keV combine a mirror and a filter with a coaxial photo-emissive detector. For the channels above 5 keV the photoemissive detector is replaced by a conductive detector. The intermediate energy channels (1.5 keV < photon energy < 5 keV) use only a filter and a coaxial detector. A further improvement of DMX consists in flat-response X-ray channels for a precise absolute measurement of the photon flux in the photon energy range from 0.1 keV to 6 keV. Such channels are equipped with a filter, a Multilayer Mirror (MLM), and a coaxial detector. We present as an example the development of channel for the gold M emission lines in the photon energy range from 2 keV to 4 keV which has been successfully used on the OMEGA laser facility. The results of the radiant power measurements with the new MLM channel and with the usual channel composed of a thin titanium filter and a coaxial detector (without mirror) are compared. All elements of the channel have been calibrated in the laboratory of the Physikalisch-Technische Bundesanstalt, Germany's National Metrology Institute, at the synchrotron radiation facility BESSY II in Berlin using dedicated well established and validated methods.

Innovation in detection of microparticles and exosomes.

Cell-derived or extracellular vesicles, including microparticles and exosomes, are abundantly present in body fluids such as blood. Although such vesicles have gained strong clinical and scientific interest, their detection is difficult because many vesicles are extremely small with a diameter of less than 100 nm, and, moreover, these vesicles have a low refractive index and are heterogeneous in both size and composition. In this review, we focus on the relatively high throughput detection of vesicles in suspension by flow cytometry, resistive pulse sensing, and nanoparticle tracking analysis, and we will discuss their applicability and limitations. Finally, we discuss four methods that are not commercially available: Raman microspectroscopy, micro nuclear magnetic resonance, small-angle X-ray scattering (SAXS), and anomalous SAXS. These methods are currently being explored to study vesicles and are likely to offer novel information for future developments.

Broad-band efficiency calibration of ITER bolometer prototypes using Pt absorbers on SiN membranes.

The energy resolved efficiency of two bolometer detector prototypes for ITER with 4 channels each and absorber thicknesses of 4.5 µm and 12.5 µm, respectively, has been calibrated in a broad spectral range from 1.46 eV up to 25 keV. The calibration in the energy range above 3 eV was performed against previously calibrated silicon photodiodes using monochromatized synchrotron radiation provided by five different beamlines of Physikalische Technische Bundesanstalt at the electron storage rings BESSY II and Metrology Light Source in Berlin. For the measurements in the visible range, a setup was realised using monochromatized halogen lamp radiation and a calibrated laser power meter as reference. The measurements clearly demonstrate that the efficiency of the bolometer prototype detectors in the range from 50 eV up to ≈6 keV is close to unity; at a photon energy of 20 keV the bolometer with the thick absorber detects 80% of the photons, the one with the thin absorber about 50%. This indicates that the detectors will be well capable of measuring the plasma radiation expected from the standard ITER scenario. However, a minimum absorber thickness will be required for the high temperatures in the central plasma. At 11.56 keV, the sharp Pt-L3 absorption edge allowed to cross-check the absorber thickness by fitting the measured efficiency to the theoretically expected absorption of X-rays in a homogeneous Pt-layer. Furthermore, below 50 eV the efficiency first follows the losses due to reflectance expected for Pt, but below 10 eV it is reduced further by a factor of 2 for the thick absorber and a factor of 4 for the thin absorber. Most probably, the different histories in production, storage, and operation led to varying surface conditions and additional loss channels.

Measurement of the mass energy-absorption coefficient of air for x-rays in the range from 3 to 60 keV.

For the first time the absolute photon mass energy-absorption coefficient of air in the energy range of 10 to 60 keV has been measured with relative standard uncertainties below 1%, considerably smaller than those of up to 2% assumed for calculated data. For monochromatized synchrotron radiation from the electron storage ring BESSY II both the radiant power and the fraction of power deposited in dry air were measured using a cryogenic electrical substitution radiometer and a free air ionization chamber, respectively. The measured absorption coefficients were compared with state-of-the art calculations and showed an average deviation of 2% from calculations by Seltzer. However, they agree within 1% with data calculated earlier by Hubbell. In the course of this work, an improvement of the data analysis of a previous experimental determination of the mass energy-absorption coefficient of air in the range of 3 to 10 keV was found to be possible and corrected values of this preceding study are given.

Applications of non-periodic multilayer optics for high-resolution x-ray microscopes below 30 keV.

Multilayer mirrors with enhanced bandwidth were developed with special performances for dense plasma diagnostics and mainly for high spatial resolution x-ray imaging. The multilayer coatings are designed to provide broadband x-ray reflectance at low grazing incidence angles. They are deposited onto toroidal mirror substrates. Our research is directed at the development of non-periodic (depth graded) W∕Si multilayer specifically designed for use in the 1 to 30 keV photon energy band. First, we present a study for a 5 to 22 keV x-ray spectral window at 0.45° grazing angle. The goal is to obtain a high and constant reflectivity. Second, we have modeled a broadband mirror coating for harder x-rays in the range from 10 to 30 keV, with a non-periodic structure containing 300 W∕SiC layers with periods in the range from 0.8 to 4 nm, designed for 0.35° grazing incidence angle.

Determination of the Avogadro constant by counting the atoms in a 28Si crystal.

The Avogadro constant links the atomic and the macroscopic properties of matter. Since the molar Planck constant is well known via the measurement of the Rydberg constant, it is also closely related to the Planck constant. In addition, its accurate determination is of paramount importance for a definition of the kilogram in terms of a fundamental constant. We describe a new approach for its determination by counting the atoms in 1 kg single-crystal spheres, which are highly enriched with the 28Si isotope. It enabled isotope dilution mass spectroscopy to determine the molar mass of the silicon crystal with unprecedented accuracy. The value obtained, NA = 6.022,140,78(18) × 10(23) mol(-1), is the most accurate input datum for a new definition of the kilogram.

Measurement of the x-ray mass energy-absorption coefficient of air using 3 keV to 10 keV synchrotron radiation.

For the first time absolute photon mass energy-absorption coefficients of air in the energy range 3 keV to 10 keV have been measured with relative standard uncertainties less than 1%, significantly smaller than those of up to 5% assumed hitherto for calculated data. Monochromatized synchrotron radiation was used to measure both the total radiant energy by means of silicon photodiodes calibrated against a cryogenic radiometer and the fraction of radiant energy that is deposited in dry air by means of a free air ionization chamber. The measured ionization charge was converted into energy absorbed in air by calculated effective W values of photons as a function of their energy based on new measurements of the W values in dry air for electron kinetic energies between 1 keV and 7 keV, also presented in this work. The measured absorption coefficients were compared with state-of-the art calculations and found to agree within 0.7% with data calculated earlier by Hubbell at energies above 4 keV but were found to differ by values up to 2.1% at 10 keV from more recent calculations of Seltzer.

Is there reliable experimental evidence for different dicentric yields in human lymphocytes produced by mammography X-rays free-in-air and within a phantom?

We examined the production of dicentrics in human lymphocytes irradiated with 29 kV X-rays to a depth of 13.5 mm in a PMMA phantom. For these irradiation conditions, which are appropriate for the diagnostic application of mammography X-rays, a coefficient alpha of (5.88+/-0.66) x 10(-2) Gy(-1) of the linear quadratic dose-response relationship was determined. This value does not differ significantly from the coefficient alpha of (6.55+/-0.97) x 10(-2) Gy(-1) obtained earlier for a free-in-air set-up using blood of the same donor. The results are interpreted in terms of both the energy distributions of the photon fluence of mammography X-rays free-in-air and those in the PMMA phantom. Based on earlier results of experiments with monochromatic X-rays in the energy range 1.83-40 keV (completed here by an additional measurement at 25 keV), a fit function alpha(E) to the measured alpha coefficients as a function of the energy E of monochromatic X-rays was used to calculate weighted mean values alpha for both the mammography X-ray spectra free-in-air and in the phantom. As a result, weighted mean values of (4.9+/-1.0) x 10(-2) Gy(-1) and (4.5+/-1.0) x 10(-2) Gy(-1) were obtained, respectively. Although the measured alpha coefficients for mammography X-rays appear to be systematically higher than those calculated as weighted mean values alpha, it can be concluded that the modification of the mammography X-ray spectrum to a depth of 13.5 mm in a PMMA phantom compared with the free-in-air spectrum has no significant influence on the dicentric yields in human lymphocytes.

Near monochromatic X-rays for digital slot-scan mammography: initial findings.

X-ray spectra are composed of a broad bremsspectrum and anode-characteristic emission lines. In mammography typically molybdenum (Mo), rhodium (Rh) or tungsten (W) anodes are used in combination with Mo, Rh or aluminium filters. Only the photons with energies between 17 and 22 keV of the resulting spectrum are suitable for the soft tissue imaging needed for mammography. The aim of this article is to present first results obtained with a monochromator module mounted at the exit of the X-ray tube of a conventional clinical mammography unit. The experimental setup consists of a Siemens Mammomat 300, an X-ray monochromator module and a linear array detector for image acquisition. The technique is similar to the slot-scan technique known from digital mammography. The experimental machine allows to obtain images both with polychromatic and monochromatic X-rays. Initial evaluation of the system was performed by examination of a contrast-detail phantom (CD-MAM-phantom, Nijmegen, The Netherlands). Images done with the new monochromatic technique were compared to images of the phantom done with polychromatic spectra, with film-screen mammography as well as with digital mammography. The new technique with monochromatic slot-scan mammography resulted in correct identification of 93% of the phantom. Digital slot-scan mammography with polychromatic beam resulted in correct identification of 87%, digital full-field mammography in 83% and conventional film-screen mammography in 70% of the phantom. The results suggest that monochromatization has a potential for improving image quality or decreasing dose in X-ray mammography.

Dicentric chromosomes in monolayers of human lymphocytes produced by monochromatized synchrotron radiation with photon energies from 1.83 keV to 17.4 keV.

A systematic approach was used to examine the induction of dicentric chromosomes in human lymphocytes irradiated in vitro with monochromatized synchrotron radiation produced with photon energies in the range from 1.83 keV to 17.4 keV. To avoid potential confounding factors that could influence the outcome of the experiments, only blood from one individual was used. Since for the irradiation experiments with these low photon energies the local dose variations would become unacceptable, monolayers of lymphocytes attached within 3 h PHA stimulation have been used. The culture conditions ensured that the chromosome analysis could be performed exclusively in metaphases of the first cell cycle in vitro. There is a strong indication for a systematic change of the alpha coefficient of the linear quadratic dose-response relationship from 1.83 keV (alpha=1.26+/-0.28) with increasing energy up to 6.9 keV (alpha=8.24+/-0.41) and a decrease with further increase of energy up to 17.4 keV (alpha=3.83+/-1.72). A tendency for a systematic change of the beta coefficient seems to be present at energies of 6.9 keV (beta=8.04+/-0.40) and 4.8 keV (beta=9.48+/-1.57) as well as at energies of 3.10 keV (beta=2.99+/-0.51) and 1.83 keV (beta=0.40+/-0.25). These results agree in essence with the previously published large data set from Sasaki's laboratory.

The maximum low-dose RBE of 17.4 and 40 keV monochromatic X rays for the induction of dicentric chromosomes in human peripheral lymphocytes.

Schmid et al. recently reported on the maximum low-dose RBE for mammography X rays (29 kV) for the induction of dicentrics in human lymphocytes. To obtain additional information on the RBE for this radiation quality, experiments with monochromatized synchrotron radiation were performed. Monochromatic 17.4 keV X rays were chosen for comparison with the diagnostic mammography X-ray spectrum to evaluate the spectral influence, while monochromatic 40 keV X rays represent a higher-energy reference radiation, within the experiment. The induction of dicentric chromosomes in human lymphocytes from one blood donor irradiated in vitro with 17.4 keV and 40 keV monochromatic X rays resulted in alpha coefficients of (3.44 +/- 0.87) x 10(-2) Gy(-1) and (2.37 +/- 0.93) x 10(-2) Gy(-1), respectively. These biological effects are only about half of the alpha coefficients reported earlier for exposure of blood from the same donor with the broad energy spectra of 29 kV X rays (mean energy of 17.4 keV) and 60 kV X rays (mean energy of 48 keV). A similar behavior is evident in terms of RBEM. Relative to weakly filtered 220 kV X rays, the RBEM for 17.4 and 40 keV monochromatic X rays is 0.86 +/- 0.23 and 0.59 +/- 0.24, respectively, which is in contrast to the RBEM of 1.64 +/- 0.27 for 29 kV X rays and 1.10 +/- 0.19 for 60 kV X rays. It is evident that the monochromatic radiations are less effective in inducing dicentric chromosomes than broad-spectrum X rays with the corresponding mean energy value. Therefore, it can be assumed that, for these X-ray qualities with broad energy spectra, a large fraction of the effects should be attributed predominantly to photons with energies well below the mean energy.

Electron probe microanalysis (EPMA) measurement of thin-film thickness in the nanometre range.

The thickness of thin films of platinum and nickel on fused silica and silicon substrates has been determined by EPMA using the commercial software STRATAGEM for calculation of film thickness. Film thickness ranged in the order 10 nm. An attempt was made to estimate the confidence range of the method by comparison with results from other methods of analysis. The data show that in addition to the uncertainty of the spectral intensity measurement and the complicated fitting routine, systematic deviation caused by the underlying model should be added. The scattering in the results from other methods does not enable specification of a range of uncertainty, but deviations from the real thickness are estimated to be less than 20%.

Components for the X-ray radiometry beamline at BESSY II.

Optical components for the X-ray radiometry beamline of the Physikalisch-Technische Bundesanstalt at BESSY II were investigated at BESSY I. Reflectometry measurements on different mirror coatings were used to calculate their capability to suppress higher-order radiation. An MgF(2) coating proved to be best suited for photon energies below 4 keV. The reflectance of silicon (111) monochromator crystals at low photon energies around 2 keV was homogeneous within +/-1%. In a test at a superconducting wavelength shifter the cooling system for the first crystal was shown to cope with the absorbed power of 14 W.

Design of a four-crystal monochromator beamline for radiometry at BESSY II.

A four-crystal monochromator beamline will be part of the radiometry laboratory that the Physikalisch-Technische Bundesanstalt will install at the new storage ring BESSY II. The most important design criteria for the beamline are the tunability of the photon energy in a wide spectral range from 1.75 to 10 keV, the high spectral purity of the radiation, as well as the good reproducibility of the absolute photon flux.

Adaptive Silicon Monochromators for High-Power Insertion Devices. Tests at CHESS, ESRF and HASYLAB.

X-ray wigglers which produce tens of kilowatts of photon power within the white beam will soon become available at third-generation sources of synchrotron radiation. Insertion devices that produce several kilowatts already exist and we have used those at CHESS, ESRF and HASYLAB to test adaptive 111 silicon water-jet-cooled monochromators at up to 2 kW total incident beam power. This development from earlier work at the Brookhaven National Synchrotron Light Source (NSLS) uses the pressure in the water coolant to provide active compensation of the strain field in the thermal footprint, nulling its effect to within residual variations in Bragg angle of only a few arc s. The design is robust, vacuum compatible and uses no moving mechanical parts.