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International audience; The success of the Belle II experiment in Japan relies on the very high instantaneous luminosity, close to 6 × 1035cm−2s−1, expectedfrom the SuperKEKB collider. The corresponding beam conditions at such luminosity levels generate large rates of backgroundparticles and creates stringent constraints on the vertex detector, adding to the physics requirements. Current prospects for theoccupancy rates in the present vertex detector (VXD) at full luminosity fall close to the acceptable limits and bear large uncertainties.In this context, the Belle II collaboration is considering the possibility to install an upgraded VXD system around 2027 to providea sufficient safety margin with respect to the expected background rate and possibly enhance tracking and vertexing performance.The VTX collaboration has started the design of a fully pixelated VXD, called VTX, based on fast and highly granular DepletedMonolithic Active Pixel Sensors (DMAPS) integrated on light support structures.The two main technical features of the VTX proposal are the usage of a single sensor type over all the layers of the system and theoverall material budget below 2 % of radiation length, compared to the current VXD which has two different sensor technologiesand about 3 % of radiation length. A dedicated sensor (OBELIX), taylored to the specific needs of Belle II, is under development,evolving from the existing TJ-Monopix2 sensor. The time-stamping precision below 100 ns will allow all VTX layers to take part inthe track finding strategy contrary to the current situation. The first two detection layers are designed according to a self-supportedall-silicon ladder concept, where 4 contiguous sensors are diced out of a wafer, thinned and interconnected with post-processedredistribution layers. The outermost detection layers follow a more conventional approach with a cold plate and carbon fibresupport structure, and light flex cables interconnecting the sensors.This document will review the context, technical details and development status of the proposed Belle II VTX.

While the successful launch and operation in space of the Gas Pixel Detectors onboard the PolarLight cubesat and the Imaging X-ray Polarimetry Explorer demonstrate the viability and the technical soundness of this class of detectors for astronomical X-ray polarimetry, it is clear that the current state of the art is not ready to meet the challenges of the next generation of experiments, such as the enhanced X-ray Timing and Polarimetry mission, designed to allow for a significantly larger data throughput. In this paper we describe the design and test of a new custom, self-triggering readout ASIC, dubbed XPOL-III, specifically conceived to address and overcome these limitations. While building upon the overall architecture of the previous generations, the new chip improves over its predecessors in several, different key areas: the sensitivity of the trigger electronics, the flexibility in the definition of the readout window, as well as the maximum speed for the serial event readout. These design improvements, when combined, allow for almost an order of magnitude smaller dead time per event with no measurable degradation of the polarimetric, spectral, imaging or timing capability of the detector, providing a good match for the next generation of X-ray missions., accepted for publication at Nuclear Inst. and Methods in Physics Research Section A

The Imaging X-Ray Polarimetry Explorer IXPE mission will perform polarization measures of 2–8 keV X-rays. Imaging, spectroscopy, and timing will complement this measurement for a comprehensive study of soft X-rays. The launch of the IXPE NASA small explorer mission to a low earth orbit is due late 2021. We designed a subsystem of the scientific payload, which has three identical telescopes based on the detector unit. The Gas Pixel Detector and its back-end electronics are the core of these units, performing data acquisition and processing, event sequencing, and on-line data compression. The back-end electronics processes the auto-triggered output of the detector of 300 photons per second with 30% of dead-time. A radiation-tolerant FPGA implements the electronics custom algorithms, including two digital serial interfaces with a central on-board computer. One interface is used for command and control of the unit, while the other for scientific data transmission. We also designed comprehensive test equipment to emulate the on-board computer and to operate the electronics. This equipment uses an FPGA on a VMEbus board as the electrical interface for the electronics, transferring data to a personal computer with dedicated software infrastructure. In this paper, we shall discuss the design process of the back-end electronics and the results of laboratory tests and measurements with X-ray sources.

International audience; The RD53A large scale pixel demonstrator chip has been developed in 65 nm CMOS technology by the RD53 collaboration, in order to face the unprecedented design requirements of the pixel 2 phase upgrades of the CMS and ATLAS experiments at CERN. This prototype chip is designed to demonstrate that a set of challenging specifications can be met, such as: high granularity (small pixels of 50×50 or 25× 100 µm2) and large pixel chip size (~2x2 cm2), high hit rate (3 GHz/cm2), high readout speed, very high radiation levels (500 Mrad - 1 Grad) and operation with serial powering. Furthermore, coping with the long latency of the trigger signal (~12.5 µs), used to select only events of interest in order to achieve sustainable output data rates, requires increased buffering resources in the limited pixel area. The RD53A chip has been fabricated in an engineer run. It integrates a matrix of 400×192 pixels and features various design variations in the analog and digital pixel matrix for testing purposes. This paper presents an overview of the chip architecture and of the methodologies used for efficient design of large complex mixed signal chips for harsh radiation environments. Experimental results obtained from the characterization of the RD53A chip are reported to demonstrate that design objectives have been achieved. Moreover, design improvements and new features being developed in the RD53B framework for final ATLAS and CMS production chips are discussed

High-energy physics experiments at the high-intensity frontier place ever-greater demands on detectors, and in particular on tracking devices. In order to compare the performance of many possible small-size tracking prototypes, a high-resolution cosmic ray tracker may be used as an external track reference. We have constructed a telescope by assembling four spare ladders of the external layers of the Silicon Vertex Tracker of the BaBar experiment. This test facility, operating at INFN Sezione di Pisa, provides the detector under test with an external track with an intrinsic resolution of 15–30 $~\mu\hbox{m}$ . The DAQ originally used in the BaBar experiment was replaced by custom-designed boards coupled with an acquisition front-end personal computer through commercial field-programmable gate array evaluation boards. We show that the facility is operative, and we present the performance in terms of tracking resolution and efficiency. A first device has been characterized, and some plots from the analysis demonstrating the telescope performance are shown.

We present a method that enables performing x-ray phase-contrast imaging (XPCI) computed tomography with a laboratory setup using a single image per projection angle, eliminating the need to move optical elements during acquisition. Theoretical derivation of the method is presented, and its validity conditions are provided. The object is assumed to be quasihomogeneous, i.e., to feature a ratio between the refractive index and the linear attenuation coefficient that is approximately constant across the field of view. The method is experimentally demonstrated on a plastics phantom and on biological samples using a continuous rotation acquisition scheme achieving scan times of a few minutes. Moreover, we show that such acquisition times can be further reduced with the use of a high-efficiency photon-counting detector. Thanks to its ability to substantially simplify the image-acquisition procedure and greatly reduce collection times, we believe this method represents a very important step towards the application of XPCI to real-world problems.

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-theart 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 mu m)(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.

International audience; This paper is a review of recent progress of RD53 Collaboration. Results obtained onthe study of the radiation effects on 65 nm CMOS have matured enough to define first strategies toadopt in the design of analog and digital circuits. Critical building blocks and analog very frontend chains have been designed, tested before and after 5–800 Mrad. Small prototypes of 64 64pixels with complex digital architectures have been produced, and point to address the main issuesof dealing with extremely high pixel rates, while operating at very small in-time thresholds in theanalog front end. The collaboration is now proceeding at full speed towards the design of a largescale prototype, called RD53A, in 65 nm CMOS technology