Due to be launched in late 2021, the imaging X-ray polarimetry explorer (IXPE) is a NASA Small Explorer mission designed to perform polarization measurements in the 2-8-keV band, complemented with ...imaging, spectroscopy, and timing capabilities. At the heart of the focal plane, there are a set of three polarization-sensitive gas pixel detectors, each based on a custom-integrated circuit acting as a charge-collecting anode, with their readout electronics. We designed an integrated test equipment based on the VMEbus protocol to characterize the performance of such detectors, debug the IXPE readout electronics, and perform stable data acquisitions to study the whole system. The test campaign was conducted to validate the readout processor against the mission requirements in more demanding conditions than the worst case foreseen for in-orbit operations. The test showed that the device under test could sustain an event rate with a 5.9-keV source, nearly twice the worst case of 300 Hz at 3 keV, with a dead time down to 1.1 ms. Additionally, we performed various scans in the readout electronics parameter space to optimize its performance in observing celestial sources. The success of the test campaign proved the robustness and reliability of the system in these conditions, legitimating its adoption for the IXPE mission.
The aim of the SYRMA-CT collaboration is to set-up the first clinical trial of phase-contrast breast CT with synchrotron radiation (SR). In order to combine high image quality and low delivered dose ...a number of innovative elements are merged: a CdTe single photon counting detector, state-of-the-art CT reconstruction and phase retrieval algorithms. To facilitate an accurate exam optimization, a Monte Carlo model was developed for dose calculation using GEANT4. In this study, high isotropic spatial resolution (120 μm)(3) CT scans of objects with dimensions and attenuation similar to a human breast were acquired, delivering mean glandular doses in the range of those delivered in clinical breast CT (5-25 mGy). Due to the spatial coherence of the SR beam and the long distance between sample and detector, the images contain, not only absorption, but also phase information from the samples. The application of a phase-retrieval procedure increases the contrast-to-noise ratio of the tomographic images, while the contrast remains almost constant. After applying the simultaneous algebraic reconstruction technique to low-dose phase-retrieved data sets (about 5 mGy) with a reduced number of projections, the spatial resolution was found to be equal to filtered back projection utilizing a four fold higher dose, while the contrast-to-noise ratio was reduced by 30%. These first results indicate the feasibility of clinical breast CT with SR.
The DMAPS upgrade of the Belle II vertex detector Babeluk, M.; Barbero, M.; Baudot, J. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
07/2024, Letnik:
1064
Journal Article
Recenzirano
The Belle II experiment at KEK in Japan considers an upgrade for the vertex detector system in line with the accelerator upgrade for higher luminosity at long shutdown 2 planned for 2028.
One ...proposal for the upgrade of the vertex detector called VTX aims to improve background robustness and reduce occupancy using small and fast pixels. VTX accommodates the OBELIX depleted monolithic active CMOS pixel sensor (DMAPS) on all five proposed layers. OBELIX is specifically developed for the VTX application and based on the TJ-Monopix2 chip initially developed to meet the requirements of the outer layers of the ATLAS inner tracker (ITk).
This paper will review recent tests of the TJ-Monopix2 chip as well as various design aspects of the OBELIX-1 chip currently under development.
Assembly and test of the gas pixel detector for X-ray polarimetry Li, H.; Feng, H.; Muleri, F. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2015, Letnik:
804
Journal Article
Recenzirano
Odprti dostop
The gas pixel detector (GPD) dedicated for photoelectric X-ray polarimetry is selected as the focal plane detector for the ESA medium-class mission concept X-ray Imaging and Polarimetry Explorer ...(XIPE). Here we show the design, assembly, and preliminary test results of a small GPD for the purpose of gas mixture optimization needed for the phase A study of XIPE. The detector is assembled in house at Tsinghua University following a design by the INFN-Pisa group. The improved detector design results in a good uniformity for the electric field. Filled with pure dimethyl ether (DME) at 0.8atm, the measured energy resolution is 18% at 6keV and inversely scales with the square root of the X-ray energy. The measured modulation factor is well consistent with that from simulation, up to ~0.6 above 6keV. The residual modulation is found to be 0.30±0.15% at 6keV for the whole sensitive area, which can be translated into a systematic error of less than 1% for polarization measurement at a confidence level of 99%. The position resolution of the detector is about 80μm in FWHM, consistent with previous studies and sufficient for XIPE requirements.
X-rays are particularly suited to probing the physics of extreme objects. However, despite the enormous improvements of X-ray astronomy in imaging, spectroscopy, and timing, polarimetry remains ...largely unexplored. We propose the photoelectric polarimeter Gas Pixel Detector (GPD) as a candidate instrument to fill the gap created by more than 30 yr without measurements. The GPD, in the focus of a telescope, will increase the sensitivity of orders of magnitude. Moreover, since it can measure the energy, the position, the arrival time, and the polarization angle of every single photon, it allows us to perform polarimetry of subsets of data singled out from the spectrum, the light curve, or an image of the source. The GPD has an intrinsic, very fine imaging capability, and in this work we report on the calibration campaign carried out in 2012 at the PANTER X-ray testing facility of the Max-Planck-Institut fur extraterrestrische Physik of Garching (Germany) in which, for the first time, we coupled it with a JET-X optics module with a focal length of 3.5 m and an angular resolution of 18 arc sec at 4.5 keV. This configuration was proposed in 2012 aboard the X-ray Imaging Polarimetry Explorer (XIPE) in response to the ESA call for a small mission. We derived the imaging and polarimetric performance for extended sources like pulsar wind nebulae and supernova remnants as case studies for the XIPE configuration and also discuss possible improvements by coupling the detector with advanced optics that have a finer angular resolution and larger effective areas to study extended objects with more detail.
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