Pixel readout IC for CdTe detectors operating in single photon counting mode with interpixel communication

This paper presents a readout integrated circuit (IC) of pixel architecture called MPIX (Multithreshold PIXels), designed for CdTe pixel detectors used in X-ray imaging applications. The MPIX IC area is 9.6 mm × 20.3 mm and it is designed in a CMOS 130 nm process. The IC core is a matrix of 96 × 192 square-shaped pixels of 100 µm pitch. Each pixel contains a fast analog front-end followed by four independently working discriminators and four 12-bit ripple counters. Such pixel architecture allows photon processing one by one and selecting the X-ray photons according to their energy (X-ray colour imaging). To fit the different range of applications the MPIX IC has 8 possible different gain settings, and it can process the X-ray photons of energy up to 154 keV. The MPIX chip is bump-bonded to the CdTe 1.5 mm thick pixel sensor with a pixel pitch of 100 µm. To deal with the charge sharing effect coming from a thick semiconductor pixel sensor, multithreshold pattern recognition algorithm is implemented in the readout IC. The implemented algorithm operates both in the analog domain (to recover the total charge spread between neighboring pixels, when a single X-ray photon hits the border of the pixel) and in the digital domain (to allocate a hit position to a single pixel).

3D TSV hybrid pixel detector modules with ATLAS FE-I4 readout electronic chip

The through silicon via (TSV) technology has been introduced in a wide range of electronic packaging applications. Hybrid pixel detectors for X-ray imaging and for high-energy physics (HEP) can benefit from this technology as well. A 3D TSV prototype using the ATLAS FE-I4 readout electronic chip is described in this paper. This type of readout chip is already prepared for the TSV backside process providing a TSV landing pad in the first metal layer of the backend-of-line (BEOL) layer stack. Based on this precondition a TSV backside via-last process is developed on ATLAS FE-I4 readout chip wafer. The readout chip wafers were thinned to 100 µm and 80 µm final thickness and straight sidewall vias with 60 µm in diameter has been etched into the silicon from wafer backside using deep reactive ion etching (DRIE). The filling of the TSVs and the formation of the wafer backside interconnection were provided by a copper electroplating process. ATLAS FE-I4 readout chips with through silicon vias has been successfully tested, tuned and operated. In addition, hybrid pixel detector modules have been flip chip bonded using ATLAS FE-I4 TSV readout chips and planar sensor chips. After mounting the bare modules onto a support PCB, its full functionality has been verified with a source scan.

Electron detection with CdTe and GaAs sensors using the charge integrating hybrid pixel detector JUNGFRAU

Speed, dynamic range, and radiation hardness make hybrid pixel detectors suitable image detectors for diffraction experiments. At synchrotrons and X-ray free electron lasers they are ubiquitous. However, for electron microscopy their spatial resolution is limited by multiple scattering in the sensor layer. In this paper we examine the use of two high Z sensor materials: CdTe and GaAs, as a way to mitigate this problem. The sensors were bonded to a JUNGFRAU readout chip which is a charge integrating hybrid pixel detector developed for use at X-ray free electron lasers. Using in-pixel gain switching, it can detect single particles down to 2 keV while maintaining a dynamic range of 120 MeV/pixel/frame. The characteristics of JUNGFRAU, besides being a capable detector, make it a good tool for sensor characterization since we can measure dark current and energy deposition per pixel. The high Z material shows better spatial resolution than silicon at 200 and 300 keV, however, their practical use with integrating detectors is still limited by material defects.

Compositionally Disordered Doped with Cerium Crystalline Garnet Type Materials for Brighter and Faster Scintillations

Ce-doped tetracationic garnets (Gd, M)3Al2Ga3O12(M = Y, Lu) form a family of new multipurpose promising scintillation materials. The aim of this work was to evaluate the scintillation yield in the materials of quaternary garnets activated by cerium ions with partial isovalent substitution of the matrix-forming gadolinium ions by yttrium or lutetium ions.Materials were obtained in the form of polycrystalline ceramic samples, and the best results were shown by samples obtained from the raw materials produced by the coprecipitation method. It was found that ceramics obtained from coprecipitated raw materials ensure a uniform distribution of activator ions in the multi-cationic matrices, which enables the high light yield and fast scintillation kinetics of the scintillation. It was demonstrated that the superstoichiometric content of lutetium/gadolinium in the material is an effective method to suppress phosphorescence accompanied scintillation. For ceramics with the composition (Gd, Lu)3Al2Ga3O12 , a scintillation yield of more than 50.000 ph/MeV was achieved. The scintillation kinetics was measured to be close to the kinetics with a decay constant of 50 ns.In terms of the set of the parameters, the developed scintillation materials are close to the recently developed alkali halide materials LaBr3:Ce, GdBr3:Ce. Moreover, they have high mechanical hardness, are characterized by the absence of hygroscopicity, and are better adapted to the manufacture of pixel detectors used in modern devices for medical diagnostics.

Measurements and analysis of different front-end configurations for monolithic SiGe BiCMOS pixel detectors for HEP applications

This paper presents a small-area monolithic pixel detector ASIC designed in 130 nm SiGe BiCMOS technology for the upgrade of the pre-shower detector of the FASER experiment at CERN. The purpose of this prototype is to study the integration of fast front-end electronics inside the sensitive area of the pixels and to identify the configuration that could satisfy at best the specifications of the experiment. Self-induced noise, instabilities and cross-talk were minimised to cope with the several challenges associated to the integration of pre-amplifiers and discriminators inside the pixels. The methodology used in the characterisation and the design choices will also be described. Two of the variants studied here will be implemented in the pre-production ASIC of the FASER experiment pre-shower for further tests.

Beam test results of silicon sensor module prototypes for the Phase-2 Upgrade of the CMS Outer Tracker

The start of the High-Luminosity LHC (HL-LHC) in 2027 requires upgrades to the Compact Muon Solenoid (CMS) experiment. In the scope of the upgrade program the complete silicon tracking detector will be replaced. The new CMS Tracker will be equipped with silicon pixel detectors in the inner layers closest to the interaction point and silicon strip detectors in the outer layers. The new CMS Outer Tracker will consist of two different kinds of detector modules called PS and 2S modules. Each module will be made of two parallel silicon sensors (a macro-pixel sensor and a strip sensor for the PS modules and two strip sensors for the 2S modules). Combining the hit information of both sensor layers, it is possible to estimate the transverse momentum of particles in the magnetic field of 3.8 T at the full bunch-crossing rate of 40 MHz directly on the module. This information will be used as an input for the first trigger stage of CMS. It is necessary to validate the Outer Tracker module functionality before installing the modules in the CMS experiment. Besides laboratory-based tests several 2S module prototypes have been studied at test beam facilities at CERN, DESY and FNAL. This article concentrates on the beam tests at DESY during which the functionality of the module concept was investigated using the full final readout chain for the first time. Additionally the performance of a 2S module assembled with irradiated sensors was studied. By choosing an irradiation fluence expected for 2S modules at the end of HL-LHC operation, it was possible to investigate the particle detection efficiency and study the trigger capabilities of the module at the beginning and end of the runtime of the CMS experiment.

Radiation Hardness Property of Ultra-Fast 3D-Trench Electrode Silicon Detector on N-Type Substrate

The radiation fluence of high luminosity LHC (HL-LHC) is predicted up to 1 × 1016 1 MeV neq/cm2 in the ATLAS and CMS experiments for the pixel detectors at the innermost layers. The increased radiation leads to the degradation of the detector properties, such as increased leakage current and full depletion voltage, and reduced signals and charge collection efficiency, which means it is necessary to develop the radiation hard semiconductor devices for very high luminosity colliders. In our previous study about ultra-fast 3D-trench electrode silicon detectors, through induced transient current simulation with different minimum ionizing particle (MIP) hitting positions, the ultra-fast response times ranging from 30 ps to 140 ps were verified. In this work, the full depletion voltage, breakdown voltage, leakage current, capacitance, weighting field and MIP induced transient current (signal) of the detector after radiation at different fluences will be simulated and calculated with professional software, namely the finite-element Technology Computer-Aided Design (TCAD) software frameworks. From analysis of the simulation results, one can predict the performance of the detector in heavy radiation environment. The fabrication of pixel detectors will be carried out in CMOS process platform of IMECAS based on ultra-pure high resistivity (up to 104 ohm·cm) silicon material.

Luminosity Measurements at the LHC at CERN Using Medipix, Timepix and Timepix3 Devices

The precise determination of the luminosity is essential for many analyses in physics based on the data from the particle accelerator Large Hadron Collider (LHC) at CERN. There are different types of detectors used for the luminosity measurements. The focus of this review is on luminosity measurements with hybrid-pixel detectors and the progress made over the past decade. The first generations of detectors of the Medipix and Timepix families had frame-based readout, while Timepix3 has a quasi-continuous readout. The applications of the detectors are manifold, and in particular, the detectors have been operated in the harsh environment of the LHC. The excellent performance in detecting high fluxes of elementary particles made these detectors ideal tools to measure the delivered luminosity resulting from proton–proton collisions. Important aspects of this review are the performance improvements in relative luminosity measurements from one detector generation to another, the long-term stability of the measurements, absolute luminosity measurements, material activation (radiation-induced) corrections, and the measurement of luminosity from neutron counting. Rather than bunch-average luminosity provided by previous detector generations, owing to the excellent time-resolution, Timepix3 measured the luminosity of individual proton bunches that are 25 ns apart. This review demonstrates the large progress in the precision of luminosity measurements during LHC Run-1 and Run-2 operations using hybrid-pixel detectors, and thus their importance for luminosity measurements in the future of LHC operations.