Abstract Thanks to their advantages in terms of easiness of manufacturing and reduced production costs, Monolithic Active Pixel Sensors (MAPS) represent an appealing solution for radiation imaging ...applications, which require to cover large areas with pixelated detectors. In the next upgrade of the ALICE detector, that will have to deal with the higher event rate resulting from the planned increase in the LHC luminosity, it is foreseen to include two additional sensor layers to perform Time of Flight (ToF) measurements. Trying to reach the challenging timing resolution required by the ALICE ToF layers, an internal gain layer has been included in the test structures of the third engineering run of the ARCADIA project to improve the timing performance of this MAPS technology. In the paper we will present an overview of the main results obtained from the electrical and the dynamic characterization of the fabricated devices, which have been compared with the behavior expected from the preliminary TCAD simulations carried out in the design phase. The experimental results confirmed the feasibility of embedding a gain layer in the ARCADIA 110 nm CMOS technology to develop monolithic LGADs.
Dark count rate (DCR) increase in CMOS single-photon avalanche diodes (SPADs) exposed to a nonmonochromatic neutron source is modeled, taking into accountthe source spectrum and the geometry of the ...device under test. Experimental results from the characterization of SPADs fabricated in a 150-nm technology and irradiated with 1-MeV neutron equivalent fluences up to 1011 cm-2 are found to be in good agreement with the theoretically calculated distribution of the nonionizing energy deposited in the device substrate.
Abstract
The use of a single neutron/gamma detector is an interesting solution to detect and identify gamma emitters and also special nuclear materials (SNM), being able to discriminate between the ...two kinds of particles and also to perform good-resolution gamma spectroscopy.
In this framework, we present a comprehensive characterization of a medium sized (2" × 2") CLLB (Cs
2
LiLaBr
6
:Ce) scintillation detector, in order to give the necessary information to assess its deployment in applications regarding homeland security and radiation monitoring. In particular, the parameters studied are: energy resolution, full-energy peak gamma efficiency, time resolution, thermal neutron/gamma discrimination capability, decay time of the signals, high counting rate performance and minimum detectable activities (of
137
Cs and
252
Cf sources). We employed digital nuclear electronics combined with a pulse shape discrimination algorithm to acquire and analyze the data. We compared our results with reported data for smaller CLLB scintillators, finding good agreement. Experiments were combined with Monte Carlo simulations (using GEANT4 v10.6.0 and MCNP5 v1.60) in order to complement the characterization. The obtained results suggest that the 2” × 2” CLLB detector offers better performance with respect to other scintillators of the same size such as NaI(Tl), CsI, CeBr, etc. which are commonly used in a radiation monitoring systems.
Fully depleted monolithic active pixel sensors (FD-MAPSs) represent a state-of-the-art detector technology and profit from a low material budget and cost for high-energy physics experiments and other ...fields of research like medical imaging and astro-particle physics. Compared to the MAPS currently in use, fully depleted pixel sensors have the advantage of charge collection by drift, which enables a fast and uniform response overall to the pixel matrix. The functionality of these devices has been shown in previous proof-of-concept productions. In this article, we describe the optimization of the test pixel designs that will be implemented in the first engineering run of the demonstrator chip of the ARCADIA project. These optimization procedures include radiation damage models that have been employed in Technology Computer Aided Design simulations to predict the sensors’ behavior in different working environments.
This work presents a customized 110 nm CMOS process on high-resistivity substrate tailored for the production of fully-depleted pixel sensors. Starting from n-type substrates, customized surface ...implantations have been introduced to enable fast and efficient collection of the charge generated by ionizing particles or radiation. Double-sided processing has been used to define the backside electrode and the termination structures needed to bias the sensors at high voltage. A first run showing the feasibility of 300 μm-thick fully-depleted sensors was completed, and several test devices designed for the assessment of the process were fabricated together with a 24×24 pixels array with 50 μm pitch. The main technological challenges and the customization of the process are discussed, and electrical measurements on test devices demonstrating the functionality of the termination structures, the full depletion of the substrate and the fast charge collection are presented.
Abstract
In this contribution we describe the second run of RSD (Resistive AC-Coupled Silicon Detectors) designed at INFN Torino and produced by Fondazione Bruno Kessler (FBK), Trento. RSD are
n
-in-
...p
detectors intended for 4D particle tracking based on the LGAD technology that get rid of any segmentation implant in order to achieve the 100% fill-factor. They are characterized by three key-elements, (i) a continuous gain implant, (ii) a resistive
n
-cathode and (iii) a dielectric coupling layer deposited on top, guaranteeing a good spatial reconstruction of the hit position while benefiting from the good timing properties of LGADs. We will start from the very promising results of our RSD1 batch in terms of tracking performances and then we will move to the description of the design of the RSD2 run. In particular, the principles driving the sensor design and the specific AC-electrode layout adopted to optimize the signal confinement will be addressed.
This paper presents the measurements on first very thin Ultra-Fast Silicon Detectors (UFSDs) produced by Fondazione Bruno Kessler; the data have been collected in a beam test setup at the CERN PS, ...using beam with a momentum of 12 GeV/c. UFSDs with a nominal thickness of 25 and 35
μ
m and an area of 1
×
1
mm
2
have been considered, together with an additional HPK 50-
μ
m thick sensor, taken as reference. Their timing performances have been studied as a function of the applied voltage and gain. A time resolution of about 25 ps and of 22 ps at a voltage of 120 and 240 V has been obtained for the 25 and 35
μ
m thick UFSDs, respectively.
Monolithic Active Pixel Sensors (MAPS) represent one of the most promising technologies for the next generation of radiation detectors. The ARCADIA project aims at the development of Fully Depleted ...(FD) MAPS employing a production process compatible with a 110 nm commercial CMOS technology. The first engineering run of the project included matrices of active pixels with embedded analog and digital frontend electronics and passive test structures such as passive pixel arrays, MOS capacitors and backside diodes. Although the produced samples were already characterized from the electrical point of view, a thorough study of the charge collection dynamics of the passive pixel arrays was still missing. In this paper we show the results of the dynamic characterization of a group of passive pixel arrays with different pixel pitches (50, 25 and 10
μ
m) and different pixel layouts. The tested samples have been illuminated from the backside with an infrared and a red laser with wavelengths equal to 1,060 nm and 660 nm, respectively. The pixel arrays have been mounted on a custom readout PCB connected to an external amplifier with 1 GHz bandwidth and the signals have been acquired through a fast digital oscilloscope. We employed both focused and unfocused laser spots to evaluate the change in the measured signal as a function of the laser spot position and the average response of the pixel arrays. An excellent agreement has been demonstrated by comparing the measured signals with the results of transient TCAD simulations and a time for 50% charge collection of 7.8, 4.2 and 2.6 ns has been predicted and experimentally validated in pixels with 50, 25 and 10
μ
m pitch, respectively.
Next generation Low Gain Avalanche Diodes (LGAD) produced by Hamamatsu photonics (HPK) and Fondazione Bruno Kessler (FBK) were tested before and after irradiation with ~1MeV neutrons at the JSI ...facility in Ljubljana. Sensors were irradiated to a maximum 1-MeV equivalent fluence of 2.5E15 N
eq
/cm
2
. The sensors analysed in this paper are an improvement after the lessons learned from previous FBK and HPK productions that were already reported in precedent papers. The gain layer of HPK sensors was fine-tuned to optimize the performance before and after irradiation. FBK sensors instead combined the benefit of Carbon infusion and deep gain layer to further the radiation hardness of the sensors and reduced the bulk thickness to enhance the timing resolution. The sensor performance was measured in charge collection studies using β-particles from a 90Sr source and in capacitance-voltage scans (C-V) to determine the bias to deplete the gain layer. The collected charge and the timing resolution were measured as a function of bias voltage at -30C. Finally a correlation is shown between the bias voltage to deplete the gain layer and the bias voltage needed to reach a certain amount of gain in the sensor. HPK sensors showed a better performance before irradiation while maintaining the radiation hardness of the previous production. FBK sensors showed exceptional radiation hardness allowing a collected charge up to 10 fC and a time resolution of 40 ps at the maximum fluence.
Orthodontic treatment is highly popular for restoring functional and facial esthetics in juveniles and adults. However, the prevalence of biofilm-related complications remains high. The objectives of ...this review are to 1) identify which of the two professional prophylaxis systems analyzed, rubber cup polishing (RCP) and air-powder polishing (APP), is the most effective in removing bacterial biofilm in patients undergoing fixed orthodontic treatment, and 2) the comfort expressed by the patient and any damage caused to the orthodontic device. The search yielded 23 scientific articles, 14 of which were excluded, and 6 met the inclusion criteria. From the studies analyzed, it is, therefore, possible to state that the APP technique is more effective than the RCP technique in removing dental plaque, and treatment is less time-consuming and safer concerning orthodontic devices, as none of the scientific articles examined did APP cause any damage to the orthodontic device or debonding of the brackets.
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