1,720,994 research outputs found
An open-loop front-end stage with signal compression capability and improved PSRR for mini-SDD pixel detectors
No full textIn this work we present the design and the experimental characterization of a front-end stage for X-ray pixel sensors. Our study was carried out in the framework of the DSSC detector development for the European XFEL (X-ray Free Electron Laser). The DSSC detector is going to be used in photon science applications at the European XFEL GmbH in Hamburg, Germany, and must be able to cope with an image frame rate up to 4.5 MHz. Moreover, the single photon sensitivity and a dynamic range up to 104 photons/pixel/pulse, with a photon energy of 1 keV, is required at the same time. Therefore, to achieve these requirement the front-end must provide a non-linear amplification. The non-linear response is obtained with a simple circuit that pushes the input PMOSFET into triode region as the input signal increases. However, since the readout ASIC has more than 4000 channels operating in parallel, particular care was devoted to the robustness of the implemented solution, especially with respect to power supply rejection ratio and crosstalk among channels
An open-loop front-end stage with signal compression capability and improved PSRR for mini-SDD pixel detectors
No full textStudy of PMOS front-end solution with signal compression for XFEL MiniSDD X-ray detectors
No full textIn this work we present the study and the experimental results on two different front-end stages for the MmiSDD pixel sensors of the DSSC detector for photon science applications at the European XFEL GmbH in Hamburg. The detector must be able to cope with an image frame rate up to 4.5 MHz and must achieve a dynamic range up to 104photons/pixel/pulse with a photon energy of 1 keV. In order to achieve this high dynamic range and single photon sensitivity at the same time, the front-end must provide a non-linear amplification. The non-linear response is obtained with a simple circuit that pushes the input PMOSFET into triode region as the input signal increases. Since the readout ASIC has more than 4000 channels operating in parallel, particular care was devoted to the homogeneity and the robustness of the implemented solution, especially with respect to power supply rejection ratio and the cross talk among channels
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
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
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
Characterization of the flip capacitor filter for the XFEL-DSSC project
No full textThe European X-ray Free Electron Laser (XFEL) under construction in Hamburg (Germany) will be able to deliver high intensity X-ray pulses of few tens of femto seconds of duration, at 5 MHz pulse repetition rate. Thanks to its characteristics, this instrument will open up new research opportunities for experiments in femto chemistry, structural biology and material research. A high speed focal plane detector system has been presented, based on a novel non-linear DEPFET as a detector. DEPFETs have been chosen since they can provide excellent energy resolution and high speed readout, a fundamental property to cope with the very demanding pulse time structure of XFEL. Full parallel readout is required, with every channel comprising analog filtering, data conversion and memory storage. In this paper we show results for the first prototype of the analog front end that implements the current readout of the DEPFET pixel. The circuit is based on the Flip Capacitor Filter technique, here briefly presented, and has been designed in 130 nm 1.2 V CMOS technology from IBM. Careful characterization of the individual circuit alone and also connected to a single pixel linear detector has been carried out and the measured performance is summarized. © 2006 IEEE
A front-end stage with signal compression capability for XFEL detectors
No full textIn this work, we present a front-end stage with signal compression capability to be used in detectors for the new European XFEL in Hamburg. This front-end is an alternative solution under study for the DEPFET Sensor with Signal Compression (DSSC) detection system for the European XFEL. The DEPFET sensor of the DSSC project has a high dynamic range and very good noise performance. The high gain for small collected charge and the compression for large signals will provide both desired features of single photon detection capability and wide dynamic range. However, manufacturing of the DEPFET sensor requires a sophisticated processing technology with a relatively long time fabrication process. Accordingly, an alternative solution, namely Day-0 solution, was introduced as an approach characterized not by the best performance of the DEPFET, but available in a shorter time to allow first beam tests and experiments. The alternative sensor is made of mini Silicon Drift Detector (mini-SDD) and the compression behavior is obtained from the front-end on the readout ASIC and not by the transistor integrated in the silicon sensor, as in the DEPFET. The first version of corresponding front-end of the Day-0 solution has been realized based on an input PMOSFET transistor placed on the readout chip. This simple front-end proved the working principle of the proposed compression technique and the desired noise performance. In this paper, an improved version of the Day-0 front-end is presented. In the new prototype, the current gain of the front-end stage has been increased by factor of 1.8, the total input capacitance (SDD+PMOSFET) has been reduced by factor of 2 with respect to the previous prototype and consequently the noise performance has been improved. Moreover, by introducing selectable extra branches in parallel with the main one, the compression behavior of the front-end can be tuned based on desired dynamic range
Qualification of a high-resolution on-chip injection circuit for the calibration of the DSSC X-ray imager for the European XFEL
No full textThe availability of on-chip sources with high degree of accuracy able to probe the response of the x-ray imaging detectors in all the conditions foreseen at the European XFEL is a key issue in order to implement automated procedures in order to trim gain and offset of each individual pixel channel to the desired target gain mode with the required degree of accuracy at the XFEL beamline/experiment. In the F2 readout ASIC of the DSSC instrument (DEPFET Sensor with Signal Compression) an improved 13 bit voltage DAC coupled to an electrical injection circuit has been implemented. A thorough measurement campaign to qualify the F2 DAC and the injected charge was conducted on a 64×64 miniSDD-F2 chip as a function of all relevant parameters
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