1,721,006 research outputs found
Defects studies towards more-radiation-tolerant Silicon Photomultipliers
No full textSilicon photomultipliers (SiPMs) are single-photon sensitive large-area detectors widely used in many applications. Among them, they are used in several radiation-harsh applications, like high-energy physics and experiments in space, where they receive a significant radiation dose. The effect of ionizing and non-ionizing radiation dose on their performance is very interesting for those applications.We irradiated several Silicon Photomultipliers with protons and X-ray. We investigated the noise increment and directly compared per performance worsening on several SiPM technologies produced sat FBK (Trento, Italy). We also characterized the temperature dependence of the noise down to cryogenic levels, extracting the activation energy. We investigated in depth the defects created by protons within the microcells of the SiPMs, with emission microscopy measurements. We also investigated the effect of ionizing-energy-loss in the SiPM microcells, showing a relevant effect of charge accumulation in the dielectrics and in the trenches. Some technologies demonstrated a worse radiation tolerance with an internal modification of electric fields that increases the primary noise and afterpulsing. This have been directly confirmed with a dedicated irradiation campaign comparing SiPMs with different materials inside the deep trenches between microcells.All these considerations are useful to develop new SiPM technologies that are more radiation hard, both in terms of bulk damage and ionizing-energy-loss effects
Characterization of radiation damages on Silicon photomultipliers by X-rays up to 100 kGy
No full textSilicon photomultipliers (SiPMs) are highly-sensitive photodetectors emerging as the technology of choice for many applications, including among the others, large high-energy physics experiments and detectors for space instruments, where they are often exposed to a large amount of radiation. In recent years, there has been an increasing interest in assessing the performance deterioration of such detectors after ionizing and non-ionizing radiation, such as protons, neutrons and X or gamma rays. It is therefore interesting to characterize the effect of irradiation on such Geiger-mode detectors, differentiating between the ionizing and non-ionizing energy-loss effects. Moreover, it is interesting to compare the radiation damage effects on several types of SiPMs, to assess the main phenomena and the deterioration mechanisms, aiming to a more radiation tolerant SiPM design.
In this work we irradiated several types of SiPM structures, produced in FBK (Trento, Italy), with 40 keV X-rays, at several doses, up to 100 kGy (in silicon), performing both online measurements (after each irradiation step) and offline functional characterization, after one month of room temperature annealing. The SiPMs are made with many different technologies, in particular different layouts, junction polarities, internal structures and starting materials. We studied the variation in the reverse current–voltage curves, distinguishing the effects on multiplied and not-multiplied current components, the primary dark count rate, the correlated noise probabilities and photon detection efficiency. Comparing all the measurement results, knowing the internal structure and the fabrication processes, we were able to extract and distinguish different deterioration mechanisms, also supported by TCAD simulations on the different effects of ionizing radiation inside the microcells
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
First Demonstration of the Use of LG-SiPMs for Optical Readout of a TPC
Full text linkThis paper describes a new method for optical readout of Time Projection Chambers (TPCs), based on the Linearly Graded Silicon Photomultiplier (LG-SiPM). This is a single photon-sensitive detector with excellent timing and 2D position resolution developed at Fondazione Bruno Kessler, Trento (FBK). The LG-SiPM produces time-varying voltage signals that are used to reconstruct the 3D position and energy of ionisation tracks generated inside the TPC. The TPC used in this work contained room-temperature CF4 gas at a pressure of 100 mbar, with two THGEMs to produce secondary scintillation light. A collimated 241Am source (Qα = 5.486 MeV) was used to produce the ionisation tracks. The successful reconstruction of these tracks is demonstrated, and the consistency of the methodology characterised through varying the geometry of the tracks within the TPC. Energy reconstruction and deposition studies are also described, demonstrating the feasibility of the LG-SiPM as a potential option for optical TPC readout
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
First demonstration of the use of LG-SiPMs for optical readout of a TPC
Full text linkThis paper describes a new method for optical readout of Time Projection Chambers
(TPCs), based on the Linearly Graded Silicon Photomultiplier (LG-SiPM). This is a single photonsensitive detector with excellent timing and 2D position resolution developed at Fondazione Bruno
Kessler, Trento (FBK). The LG-SiPM produces time-varying voltage signals that are used to
reconstruct the 3D position and energy of ionisation tracks generated inside the TPC.
The TPC used in this work contained room-temperature CF4 gas at a pressure of 100 mbar,
with two THGEMs to produce secondary scintillation light. A collimated 241Am source (Qα =
5.486 MeV) was used to produce the ionisation tracks. The successful reconstruction of these tracks
is demonstrated, and the consistency of the methodology characterised through varying the geometry
of the tracks within the TPC. Energy reconstruction and deposition studies are also described,
demonstrating the feasibility of the LG-SiPM as a potential option for optical TPC readout
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Radiation damage on SiPMs for Space Applications
No full textSilicon Photomultipliers (SiPMs) are very sensitive photo-detectors that experienced a big development in the last years in several applications, like LIDAR, astrophysics, medical imaging and high energy physics (HEP) experiments. In HEP experiments, in particular, they are often exposed to significant radiation doses. The main purpose of this manuscript is the characterization of several FBK SiPM technologies when exposed to 74 MeV protons with a total fluence comparable to the one that they would experience in space along circular Polar, Low Earth Orbits (LEO) during a five years mission.
In this work, we estimated the expected proton fluences along the selected orbit, by means of the SPENVIS software. Several fluence steps were chosen to consider dense fluence intervals and have a more accurate sight on the whole damage process. We estimated a maximum fluence achieved during the tests of
. Based on such simulations, we irradiated several SiPM technologies. We developed a custom experimental setup, which was used to perform online reverse voltage–current, right after each irradiation step, to minimize the effect of the annealing on the measurement.
The results are then displayed, in particular the currents, the noise and the Photon Detection Efficiency. Also a 30-days study on the annealing of the devices was performed.
Lastly, the conclusions are drawn on the basis of the Signal-to-Noise Ratio (SNR), taking into account the standard parameters of famous satellites using similar orbits as the ones considered into this work
Radiation damage effects of protons and X-rays on silicon photomultipliers
No full textSilicon photomultipliers (SiPMs) are highly-sensitive photodetectors emerging as the technology of choice for many applications. In high-energy physics experiments and as the detectors for space instruments they are often exposed to a large amount of irradiation. In recent years, there has been an increasing interest in assessing the performance deterioration of such detectors after ionizing and non-ionizing radiation, such as protons, neutrons and X or gamma rays. It is interesting to compare the radiation damage effects on several types of SiPMs, to assess the main deterioration mechanisms on SiPM performances.
In this work we report on the irradiation by protons and X-rays of several types of small-area (1 mm2) SiPMs, produced in FBK with different technologies. We show and compare the most interesting results of the online measurements, taken just after each irradiation step, for both irradiations. We performed and monitored the current variation during a room temperature annealing. Finally we characterized all the main functional performance of the irradiated SiPMs, highlighting the most interesting variations
- …
