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A. Khromova

Other affiliations: University of Trieste
Bio: A. Khromova is an academic researcher from Elettra Sincrotrone Trieste. The author has contributed to research in topics: Detector & Spectrum analyzer. The author has an hindex of 2, co-authored 3 publications receiving 16 citations. Previous affiliations of A. Khromova include University of Trieste.

Papers
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Journal ArticleDOI
TL;DR: The PERCIVAL (Pixelated Energy Resolving CMOS Imager, Versatile And Large) soft X-ray 2D imaging detector is based on stitched, wafer-scale sensors possessing a thick epi-layer, which together with back-thinning and back-side illumination yields elevated quantum efficiency in the photon energy range of 125-1000 eV.
Abstract: The PERCIVAL (Pixelated Energy Resolving CMOS Imager, Versatile And Large) soft X-ray 2D imaging detector is based on stitched, wafer-scale sensors possessing a thick epi-layer, which together with back-thinning and back-side illumination yields elevated quantum efficiency in the photon energy range of 125–1000 eV. Main application fields of PERCIVAL are foreseen in photon science with FELs and synchrotron radiation. This requires high dynamic range up to 105 ph @ 250 eV paired with single photon sensitivity with high confidence at moderate frame rates in the range of 10–120 Hz. These figures imply the availability of dynamic gain switching on a pixel-by-pixel basis and a highly parallel, low noise analog and digital readout, which has been realized in the PERCIVAL sensor layout. Different aspects of the detector performance have been assessed using prototype sensors with different pixel and ADC types. This work will report on the recent test results performed on the newest chip prototypes with the improved pixel and ADC architecture. For the target frame rates in the 10–120 Hz range an average noise floor of 14e− has been determined, indicating the ability of detecting single photons with energies above 250 eV. Owing to the successfully implemented adaptive 3-stage multiple-gain switching, the integrated charge level exceeds 4 10^6 e− or 57000 X-ray photons at 250 eV per frame at 120 Hz. For all gains the noise level remains below the Poisson limit also in high-flux conditions. Additionally, a short overview over the updates on an oncoming 2 Mpixel (P2M) detector system (expected at the end of 2016) will be reported.

11 citations

Journal ArticleDOI
TL;DR: The PERCIVAL soft X-ray imager is being developed by DESY, RAL, Elettra, DLS, and PAL to address the challenges at high brilliance Light Sources such as new-generation Synchrotrons and Free Electro...
Abstract: The PERCIVAL soft X-ray imager is being developed by DESY, RAL, Elettra, DLS, and PAL to address the challenges at high brilliance Light Sources such as new-generation Synchrotrons and Free Electro ...

8 citations

Journal ArticleDOI
TL;DR: In this paper, analyzer-based imaging (ABI) was used for free-space propagation phase contrast imaging of breast tissue samples at the medical beamline of the Italian synchrotron ELETTRA.
Abstract: X-ray phase contrast imaging arises from changes of the propagation direction of the radiant wave field when traversing the object and it can yield higher contrast for soft tissues than conventional x-ray radiology based on attenuation. Commonly intermediate steps are required to transform wave front modulations into intensity modulations measurable by the detection system. One of these phase contrast techniques is analyzer-based imaging (ABI), which utilizes an analyzer crystal as angular filter with a bandwidth in the micro-radian regime placed between the sample and the detector. Furthermore employing appropriate algorithms, attenuation, refraction and scattering/dark field images can be extracted providing complementary information. The implementation of ABI requires X-ray optics with very high stability and micro-radian resolution. In return, this method possesses an extremely high sensitivity among the phase contrast techniques. At the medical beamline of the Italian synchrotron ELETTRA, a patient room has been implemented in order to perform clinical mammography with free-space propagation phase contrast. In this work we have tested the feasibility of ABI in a preclinical set-up implementing the system in the patient room. High quality images of breast tissues samples are presented and compared to images acquired at a conventional mammography unit. The system has shown excellent stability and imaging performances.

3 citations


Cited by
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Journal ArticleDOI
TL;DR: Partially coherent soft X-ray synchrotron radiation is used to obtain a quantitative image of a laterally extended, dried, and unstained fibroblast cell by ptychography and the refractive index values for two regions of the cell with respect to a reference area are obtained.
Abstract: Coherent X-ray ptychography is a tool for highly dose efficient lensless nano-imaging of biological samples. We have used partially coherent soft X-ray synchrotron radiation to obtain a quantitative image of a laterally extended, dried, and unstained fibroblast cell by ptychography. We used data with and without a beam stop that allowed us to measure coherent diffraction with a high-dynamic range of 1.7·106. As a quantitative result, we obtained the refractive index values for two regions of the cell with respect to a reference area. Due to the photon energy in the water window we obtained an extremely high contrast of 53% at 71 nm half-period resolution. The dose applied in our experiment was 9.5·104 Gy and is well below the radiation damage threshold. The concept for dynamic range improvement for low dynamic range detectors with a beam stop opens the path for high resolution nano-imaging of a variety of samples including cryo-preserved, hydrated and unstained biological cells.

26 citations

Journal ArticleDOI
TL;DR: The capabilities and performance of a camera equipped with a newly commercialized backside-illuminated scientific CMOS (sCMOS-BSI) sensor, integrated in a vacuum environment, for soft X-ray experiments at synchrotron sources are described.
Abstract: Huge progress have been done with the 3 rd generation storage ring, and more recently the ultimate storage ring under development suggest an unprecedent increase of x-ray brightness. Unfortunately, as far as the detectors are concerned, progress has not been as fast and even more so in the range of soft x-rays. In particular for 2D detector the most commonly used detector are based on old CCD technology and the recent development of CMOS detector will be certainly crucial for 2D detector in the soft x-rays. With this goal we explore the possibilities and the the performance of a camera equipped with new mass-marketed scientific Complementary Metal Oxide Semiconductor Back Side Illuminated (sCMOS-BSI) integrated in vacuum environment for soft X-ray experiment at synchrotron. The 4 Mpix sensor reaches a frame rate up to 48 fps while suiting the necessary performances needed for X-ray experiments, in term of linearity (98 %), homogeneity (PRNU <1%) charge capacity (up to 80 ke-), readout noise (down to 2 e-rms) and adequate dark current (3 e-/s/px). The sensor performances tests in the X-ray range have been performed at the SOLEIL METROLOGIE beamline. The Quantum Efficiency, the spatial resolution (24 lp/mm), the energy resolution (< 100 eV) and the radiation damage versus the X-ray dose (< 200 Gy) have been evaluated in the energy range from 40 eV to 2000 eV. In order to illustrate the capabilities of this new sCMOS-BSI sensor, several experiments have been performed at three soft x-ray beamline of the SOLEIL synchrotron: diffraction pattern from a pinhole at 186 eV, scattering experiment from nanostructured Co/Cu multilayer at 700 eV and Ptychoraphy imaging in transmission at 706 eV.

24 citations

Journal ArticleDOI
TL;DR: A novel algorithm is reported on, which allows the robust separation of absorption, refraction and scattering effects from three measured x-ray images and allows precise assessment of local scattering distributions at biocompatible radiation doses, which in turn might yield a quantitative characterization tool with sufficient structural sensitivity on a submicron length scale.
Abstract: Unlike conventional x-ray attenuation one of the advantages of phase contrast x-ray imaging is its capability of extracting useful physical properties of the sample. In particular the possibility to obtain information from small angle scattering about unresolvable structures with sub-pixel resolution sensitivity has drawn attention for both medical and material science applications. We report on a novel algorithm for the analyzer based x-ray phase contrast imaging modality, which allows the robust separation of absorption, refraction and scattering effects from three measured x-ray images. This analytical approach is based on a simple Gaussian description of the analyzer transmission function and this method is capable of retrieving refraction and small angle scattering angles in the full angular range typical of biological samples. After a validation of the algorithm with a simulation code, which demonstrated the potential of this highly sensitive method, we have applied this theoretical framework to experimental data on a phantom and biological tissues obtained with synchrotron radiation. Owing to its extended angular acceptance range the algorithm allows precise assessment of local scattering distributions at biocompatible radiation doses, which in turn might yield a quantitative characterization tool with sufficient structural sensitivity on a submicron length scale.

19 citations

Journal ArticleDOI
TL;DR: The PERCIVAL (Pixelated Energy Resolving CMOS Imager, Versatile And Large) soft X-ray 2D imaging detector is based on stitched, wafer-scale sensors possessing a thick epi-layer, which together with back-thinning and back-side illumination yields elevated quantum efficiency in the photon energy range of 125-1000 eV.
Abstract: The PERCIVAL (Pixelated Energy Resolving CMOS Imager, Versatile And Large) soft X-ray 2D imaging detector is based on stitched, wafer-scale sensors possessing a thick epi-layer, which together with back-thinning and back-side illumination yields elevated quantum efficiency in the photon energy range of 125–1000 eV. Main application fields of PERCIVAL are foreseen in photon science with FELs and synchrotron radiation. This requires high dynamic range up to 105 ph @ 250 eV paired with single photon sensitivity with high confidence at moderate frame rates in the range of 10–120 Hz. These figures imply the availability of dynamic gain switching on a pixel-by-pixel basis and a highly parallel, low noise analog and digital readout, which has been realized in the PERCIVAL sensor layout. Different aspects of the detector performance have been assessed using prototype sensors with different pixel and ADC types. This work will report on the recent test results performed on the newest chip prototypes with the improved pixel and ADC architecture. For the target frame rates in the 10–120 Hz range an average noise floor of 14e− has been determined, indicating the ability of detecting single photons with energies above 250 eV. Owing to the successfully implemented adaptive 3-stage multiple-gain switching, the integrated charge level exceeds 4 10^6 e− or 57000 X-ray photons at 250 eV per frame at 120 Hz. For all gains the noise level remains below the Poisson limit also in high-flux conditions. Additionally, a short overview over the updates on an oncoming 2 Mpixel (P2M) detector system (expected at the end of 2016) will be reported.

11 citations

Journal ArticleDOI
TL;DR: The back-side-illuminated Percival 2-Megapixel (P2M) detector is presented, along with its characterization by means of optical and X-ray photons, and for the first time the response of the system to soft X-rays is presented.
Abstract: In this paper the back-side-illuminated Percival 2-Megapixel (P2M) detector is presented, along with its characterization by means of optical and X-ray photons. For the first time, the response of the system to soft X-rays (250 eV to 1 keV) is presented. The main performance parameters of the first detector are measured, assessing the capabilities in terms of noise, dynamic range and single-photon discrimination capability. Present limitations and coming improvements are discussed.

9 citations