Studies of irradiated AMS H35 CMOS detectors for the ATLAS tracker upgrade

Silicon detectors based on the HV-CMOS technology are being investigated as possible candidate for the outer layers of the ATLAS pixel detector for the High Luminosity LHC. In this framework the H35Demo ASIC has been produced in the 350 nm AMS technology (H35). The H35Demo chip has a large area ($18.49 \times 24.40 \, \mathrm{mm^2}$) and includes four different pixel matrices and three test structures. In this paper the radiation hardness properties, in particular the evolution of the depletion region with fluence is studied using edge-TCT on test structures. Measurements on the test structures from chips with different substrate resistivity are shown for non irradiated and irradiated devices up to a cumulative fluence of $2 \cdot 10^{15} \, \mathrm{1\,MeV\, n_{eq} / cm^{2}}$

Radiation hard Depleted Monolithic Active Pixel Sensors with high-resistivity substrates

High Voltage/High resistivity Depleted Monolithic Active Pixel Sensors (HV/HR-DMAPS) is a technology which is becoming of great interest for high energy physics applications.With respect to hybrid pixel detectors the monolithic approach offers the main advantages of reduced material budget and production costs due to the absence of the bump bonding process. This aspect is important especially when large areas need to be covered as in the tracking detectors of the LHC experiments. Thus, the possibility of employing this technology in the outermost layers of the upgraded ATLAS pixel detector at the HL-LHC is being investigated.Different HR/HV-DMAPS prototypes have been recently developed for the future ATLAS Inner Tracker (ITk) with the aim of studying their radiation hardness and the feasibility of producing large area devices.The H35DEMO is a large area demonstrator chip for the ITk designed by KIT, IFAE and University of Liverpool and produced in AMS 350 nm HV-CMOS technology with an engineering run on four different substrate resistivities: 20, 80, 200 and 1000 $\mathrm{\Omega cm}$. It consists of four large matrices, two of which include digital electronics and are thus fully monolithic. One, called CMOS matrix, has comparators made of CMOS transistors in the periphery only, while the other, called NMOS matrix, includes also comparators made of NMOS transistors directly in the pixels. The other two matrices have only analog front-end electronics and are meant to be coupled to ATLAS FE-I4 chips. All matrices feature pixels with a size of $\mathrm{(50\times250)\;\mu m^2}$ in which the analog electronics are embedded in a Deep N-WELL (DNWELL) also acting as collecting electrode.A Data Acquisition (DAQ) system was developed at IFAE to read out and test the monolithic matrices of the H35DEMO both in the laboratory and with beam test experiments. H35DEMO chips with a resistivity of 200 $\mathrm{\Omega cm}$ have been irradiated with reactor neutrons to a particle fluence of $1\times10^{15}$ $\mathrm{1\;MeV\;n_{eq}/cm^2}$, the expected fluence for the outermost pixel layer of ITk. The monolithic CMOS matrix of the H35DEMO chip was extensively characterised before and after irradiation in beam tests at Fermilab and DESY, with proton and electron beams, respectively.Results after irradiation show good performance in terms of hit efficiency with thresholds of about 1800 e and a bias voltage of 150 V.Another production of monolithic HV-CMOS prototypes in LFoundry 150 nm technology (LF2) has been recently completed. It includes sensors with a similar DNWELL concept as the H35DEMO but with a smaller pixel size of $\mathrm{(50\times50)\;\mu m^2}$. Preliminary measurements of leakage current of the LF2 chips have been preformed showing good agreement with what expected from the foundry process

Calcium Imaging In Electrically Stimulated Flat-Mounted Retinas

Retinal dystrophies are a leading cause of blindness worldwide. Extensive efforts are underway to develop advanced retinal prostheses that can bypass the impaired light-sensing photoreceptor cells in the degenerated retina, aiming to partially restore vision by inducing visual percepts. One common avenue of investigation involves the design and production of implantable devices with a flexible physical structure, housing a high number of electrodes. This enables the efficient and precise generation of visual percepts. However, with each technological advancement, there arises a need for a reliable and manageable ex vivo method to verify the functionality of the device before progressing to in vivo experiments, where factors beyond the device's performance come into play. This article presents a comprehensive protocol for studying calcium activity in the retinal ganglion cell layer (GCL) following electrical stimulation. Specifically, the following steps are outlined: (1) fluorescently labeling the rat retina using genetically encoded calcium indicators, (2) capturing the fluorescence signal using an inverted fluorescence microscope while applying distinct patterns of electrical stimulation, and (3) extracting and analyzing the calcium traces from individual cells within the GCL. By following this procedure, researchers can efficiently test new stimulation protocols prior to conducting in vivo experiments

Design and characterization of the monolithic matrices of the H35DEMO chip

The H35DEMO chip is a HV/HR-MAPS demonstrator of 18.49 mm x 24.4 mm, fabricated with a 0.35 µm HVCMOS process from AMS in four different substrate resistivities. The chip is divided into four independent matrices with a pixel size of 50 µm x 250 µm. Two of the matrices are fully monolithic and include the digital readout electronics at the periphery. This contribution describes the two standalone matrices of the H35DEMO chip and presents results of the beam tests carried out with unirradiated and irradiated samples with different substrate resistivities

Measurement of mobility and lifetime of electrons and holes in a Schottky CdTe diode

We report on the measurement of drift properties of electrons and holes in a CdTe diode grown by the travelling heating method (THM). Mobility and lifetime of both charge carriers has been measured independently at room temperature and fixed bias voltage using charge integration readout electronics. Both electrode sides of the detector have been exposed to a 241 Am source in order to obtain events with full contributions of either electrons or holes. The drift time has been measured to obtain the mobility for each charge carrier. The Hecht equation has been employed to evaluate the lifetime. The measured values for μτ (mobility-lifetime product) are in agreement with earlier published data

Calcium Imaging In Electrically Stimulated Flat-Mounted Retinas

Retinal dystrophies are a leading cause of blindness worldwide. Extensive efforts are underway to develop advanced retinal prostheses that can bypass the impaired light-sensing photoreceptor cells in the degenerated retina, aiming to partially restore vision by inducing visual percepts. One common avenue of investigation involves the design and production of implantable devices with a flexible physical structure, housing a high number of electrodes. This enables the efficient and precise generation of visual percepts. However, with each technological advancement, there arises a need for a reliable and manageable ex vivo method to verify the functionality of the device before progressing to in vivo experiments, where factors beyond the device's performance come into play. This article presents a comprehensive protocol for studying calcium activity in the retinal ganglion cell layer (GCL) following electrical stimulation. Specifically, the following steps are outlined: (1) fluorescently labeling the rat retina using genetically encoded calcium indicators, (2) capturing the fluorescence signal using an inverted fluorescence microscope while applying distinct patterns of electrical stimulation, and (3) extracting and analyzing the calcium traces from individual cells within the GCL. By following this procedure, researchers can efficiently test new stimulation protocols prior to conducting in vivo experiments.The funding entities that supported this work are: Fundació CELLEX; Fundació Mir-Puig; Ministerio de Economía y Competitividad - Severo Ochoa program for Centres of Excellence in R&D (CEX2019-000910-S, [MCIN/AEI/10.13039/501100011033]); Generalitat de Catalunya through CERCA program; Laserlab-Europe (EU-H2020 GA no. 871124); La Caixa Foundation (LCF/HR19/52160003); and Fondo Social Europeo (PRE2020-095721, M.C.).With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000910-S)Peer reviewe