1,501 research outputs found
Timepix4 calibration and energy resolution evaluation with fluorescence photons
No full textThe Timepix4 is a pixelated and hybrid detection system developed by the Medipix4 Collaboration at CERN. It consist of a 448 x 512 pixel reading matrix which can be bump-bonded to a semiconductor sensor with square pixels at a pitch of 55 mu m. The Timepix4's ability to isolate individual particles and measure the energy they release in the sensor makes it a valuable tool for spectral imaging, capable of acquiring continuous energy spectrum images even in the presence of a high rate of incident events. This article presents a calibration method for the Timepix4 and evaluates the device's energy resolution using fluorescence photons produced with a micro-focus X-ray tube as a radiation source
Timepix4 characterization with monochromatic X-rays at the Elettra synchrotron facility
No full textTimepix4 is the latest generation application-specific integrated circuit (ASIC) of the Medipix family, developed by the Medipix4 Collaboration. A characterization of a Timepix4 assembly bump-bonded to a planar 300
m thick silicon pixelated sensor has been performed by using monochromatic X-rays at the Elettra synchrotron facility (Trieste, Italy). In particular, a calibration of the ToT against the energy released in the Si detector has been performed for each pixel, to optimize energy resolution. A preliminary analysis to estimate the detector photon counting linearity and pixel readout dead time was also carried out
Development of a sensor for trivalent iron: AHP fixed on mesoporous silica
No full textSince the emergence of deferiprone as an iron(iii) chelating drug, hydroxypyridinones have been intensively explored due to their high affinity for trivalent metal ions and ability to form complexes at physiological pH with low toxicity. For instance, they have been employed as carriers of La(iii) in therapy for bone diseases and to remove Gd(iii) from Gd-based contrast agents. We believe that a pyridinone-based sensor can be useful for iron(iii) monitoring. Herein, we present a novel chelating solid-phase, resulting from the functionalization of a mesoporous silica MCM-41, with the hydroxypyridinone N(3′-aminopropyl)-3-hydroxy-2-methyl-4-pyridinone (AHP) as the active site. The physico-chemical characterization of the new solid-state device, named AHP-MCM41, demonstrates that the AHP moiety is covalently anchored on the silica surface; the active site concentration was found to be around 0.4 mmol g-1. Furthermore, its sorption of Fe(iii) from aqueous solution is rather rapid. The soluble AHP forms a rich variety of complexes with iron(iii), which is typical of all analogous O,O donor ligands, and is dominated by M : L = 1 : 3 complexes. Could complexes with such high stoichiometry can be retained in the solid phase? The answer is yes. The existence of these different species in the solid phase is evidenced by the sorption isotherm results and from sorption experiments as a function of solution pH and also in the presence of a competitive ligand. Furthermore, the existence of complexes in the solid phase was demonstrated via solid vis-spectrophotometry, where these species showed identical colour variations to those formed in solution. Such complexes in the solid phase have never been reported in the literature. Additionally, the intense colour of the solid phase in the presence of iron(iii) is promising for naked eye detection
Development of a single-photon imaging detector with pixelated anode and integrated digital read-out
No full textWe present the development of a single-photon detector and the connected
read-out electronics. This `hybrid' detector is based on a vacuum tube,
transmission photocathode, microchannel plate and a pixelated CMOS read-out
anode encapsulating the analog and digital-front end electronics. This assembly
will be capable of detecting up to photons per second with simultaneous
measurement of position and time.
The pixelated read-out anode used is based on the Timepix4 ASIC
( CMOS technology) designed in the framework of the Medipix4
collaboration. This ASIC is an array of pixels distributed on a
square pitch, with a sensitive area of . It features - equivalent noise charge,
a maximum rate of , and allows to time-stamp the
leading-edge time and to measure the Time-over-Threshold (ToT) for each pixel.
The pixel-cluster position combined with its ToT information will allow to
reach - position resolution. This information can also be
used to correct for the leading-edge time-walk achieving a timing resolution of
the order of .
The detector will be highly compact thanks to the encapsulated front-end
electronics allowing local data processing and digitization. An FPGA-based data
acquisition board, placed far from the detector, will receive the detector hits
using electro-optical links operated at . The data
acquisition board will decode the information and store the relevant data in a
server for offline analysis.
These performance will allow significant advances in particle physics, life
sciences, quantum optics or other emerging fields where the detection of single
photons with excellent timing and position resolutions are simultaneously
required.Comment: 5 pages, 1 figure, Proceedings of the 12th International Conference
on Position Sensitive Detectors, 12 - 17 September 2021, University of
Birmingham, Birmingham, U
Energy calibration of a Timepix4 detector assembly with a compact quasi-monochromatic X-ray system
No full textTimepix4 is an application-specific integrated circuit (ASIC) developed by the Medipix4 international collaboration. It features a 448 × 512 pixel matrix that can be bump-bonded to pixelated sensors of various materials and thicknesses optimized for specific uses. Among its potential applications, Timepix4 can be utilized for spectral imaging, provided that an accurate energy calibration is performed to ensure precise measurements across all pixels. This calibration procedure was previously carried out using synchrotron X-ray beams, which provide a monochromatic and high-statistics source essential for pixel-by-pixel calibration. Building on this established protocol, which combines X-ray measurements with the detector internal test pulses, we introduce an alternative approach that employs a quasi-monochromatic (QM) X-ray beam generated by an X-ray tube in conjunction with a mosaic crystal. This configuration enables flexible implementation under standard laboratory conditions, minimizing the need for accelerator facilities with limited access. To validate this method, data acquired with an additional X-ray fluorescence (XRF) system were analyzed, demonstrating that the mixed calibration approach (combining QM data and test pulses) reduces discrepancy between measured and nominal energies to within 5%, compared to about 20% when relying solely on test pulses and less than 2% when using synchrotron radiation. Moreover, this improvement is accompanied by a significant decrease in the standard deviation of the measured photopeak, reflecting enhanced consistency across the pixel matrix. These findings highlight the potential of QM-based calibration as an effective and accessible alternative for achieving accurate Timepix4 energy calibration for a wide variety of spectral imaging applications
Timepix4 spatial response characterization with X-ray monochromatic synchrotron beam
No full textThe Timepix4 is a readout ASIC developed by the Medipix4 collaboration, designed to work with various semiconductor sensors to form detection systems with 448×512 pixels with a pitch of 55 μm. Its ability to simultaneously measure the Time of Arrival (ToA) and the Time over Threshold (ToT) of the signal makes it particularly suitable for spectral imaging applications. The ToT allows to measure the hit's energy, while the ToA enables to cluster the acquired events, recomposing the signal of the detected photons. The ability to cluster events allows to limit the degradation of the detector's spatial response caused by charge sharing effects, a common issue that affect conventional single-photon-counting detectors. This work aims to characterize the spatial response of a Timepix4-based detection system, in terms of the Edge Spread Function (ESF) and Line Spread Function (LSF), using a monochromatic X-ray beam. The characterization was performed at different energies (10 keV and 20 keV) using the moving edge method; different clustering methods were applied and compared during the analysis
Validation of Timepix4 energy calibration procedures with synchrotron X-ray beams
No full textThe Timepix4 is an application-specific integrated circuit developed by the Medipix4 collaboration. The chip is a 448x512 matrix that can be connected, via bump-bonding, to pixelated sensors of various materials and thicknesses, forming application specific detection systems. Among the Timepix4 operating modes, the data-driven Time-of-Arrival - Time-Over-Treshold is a particularly promising mode for spectral imaging applications: data packets are generated every time the charge created by the incoming radiation goes above a pre-defined threshold, allowing the count of the detected particles and their energy measurement. This article investigates the spectroscopic characteristics of a Timepix4 assembly equipped with a 300
m Si sensor, using monochromatic X-ray beams in the energy range 8.5 keV - 40 keV working at the SYRMEP beamline of the Elettra synchrotron. The accuracy and the energy resolution of the reconstructed energy spectra, together with an energy resolution model, will be presented
Validation of Timepix4 energy calibration procedures with synchrotron X-ray beams
No full textThe Timepix4 is an application-specific integrated circuit developed by the Medipix4 collaboration. The chip is a 448 x 512 matrix that can be connected, via bump-bonding, to pixelated sensors of various materials and thicknesses, forming application specific detection systems. Among the Timepix4 operating modes, the data-driven Time-of-Arrival - Time-Over-Threshold is a particularly promising mode for spectral imaging applications: data packets are generated every time the charge created by the incoming radiation goes above a pre-defined threshold, allowing the count of the detected particles and their energy measurement. This article investigates the spectroscopic characteristics of a Timepix4 assembly equipped with a 300 mu m Si sensor, using monochromatic X-ray beams in the energy range 8.5 keV-40 keV working at the SYRMEP beamline of the Elettra synchrotron. The accuracy and the energy resolution of the reconstructed energy spectra, together with an energy resolution model, will be presented
Optimum extraction process of polyphenols from Bridelia grandis stem bark using experimental design
No full textEuphorbiaceae barks are known to contain an appreciable amount of polyphenolic
compounds responsible for several biological activities. Preliminary extraction from
Bridelia grandis stem bark afforded high content of polyphenols, determined by spectrophotometric
methods such as Folin–Ciocalteu (for total phenols, TP) and n-butanol-HCl
(for condensed tannins, CT). A preliminary Plackett–Burman screening design was used
to identify the key factors that influence the TP and CT extraction. Between all the
variables known to influence the extraction from vegetable matrixes, six were selected;
maceration was chosen as traditional extraction methodology. To investigate the effect of
solvents and extraction method, methanol, acetone 70% (v/v in water), centrifugation and
ultrasound were chosen. A full factorial design 23 was applied to optimize the extraction
procedure. The responses were obtained analyzing the extracts for their TP and CT
contents determined by the above-mentioned spectrophotometric methods. The results
confirm that, within the explored domain, the optimum solvent is methanol and the
optimum method is one-cycle centrifugation. Finally, it was also compared with the effect
of maceration on the considered responses. It has never given results better than
centrifugation, whereas in the case of CT it represents an advantage to employ a threecycle
centrifugation instead of one
Sorption of chrysoidine by row cork and cork entrapped in calcium alginate beads
No full textAzo-dyes, molecules characterised by the presence of the azo-group (–NN–), are widely used in textile, leather, rubber, plastic, and food industries. Water-soluble azo-dyes are greatly resistant to biodegradation, and are characterised by a high thermal and photo stability due to their complex structures. The release of these molecules into the environment is of crucial concern due to their toxic, mutagenic and carcinogenic characteristics. Biosorption has been demonstrated an effective method to remove pollutants from wastewaters thus solving ecological tasks, being a low cost process and the sorbent biodegradable. The main requirements of an efficient sorbent are thermal, chemical and mechanical stability, and rapid sorption.
In this work, the ability of both row cork and the same sorbent entrapped in a biopolymeric gel of calcium alginate, on the removal of chrysoidine from aqueous solutions was examined.
The influence on the sorption of pH, initial dye concentration, and particle size, as well as the efficiency of the entrapment, have been investigated. The maximum sorption was found for cork samples of fine particle size (FC), in both row and entrapped forms, at pH 7; conversely, at pH 4 the difference is significant (0.12 mmol/g for row cork and 0.20 mmol/g for entrapped cork), evoking a cooperation of alginate in binding the positively charged chrysoidine molecule
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