1,721,119 research outputs found
Internal charge injection for the calibration of DEPFETs with non-linear amplification
No full textWithin the DSSC (DEPFET Sensor with Signal Compression) project a new active pixel sensor based on a Depleted P-Channel Field Effect Transistor (DEPFET) has been developed for the use at the European X-ray Free Electron Laser (EuXFEL). A DEPFET is an integrated detector amplifier combining internal amplification, full sensitivity over the whole bulk thickness, analog data storage, readout on demand, low serial noise, and absence of reset noise. To cope with the EuXFEL detector requirements the new developed DSSC-DEPFET has a non-linear amplification, i.e. a high gain for small signals in order to provide single photon resolution of low energy X-rays and a reduced gain for large signals to have a high dynamic range of several thousand photons per pixel and frame. For a pixel by pixel calibration of the final DSSC system the new feature of internal charge injection in every pixel has been introduced and investigated in detail using existing DSSC-prototype structures. This paper illustrates the principle of the injection mechanism and demonstrates its capability for calibration purposes
Methods for calibrating the gain and offset of the DSSC detector for the European XFEL using X-ray line sources
No full textThe DSSC (DEPFET Sensor with Signal Compression) will be a silicon based, 2d 1 Mpx imaging detector for the European X-ray Free Electron Laser Facility (XFEL.EU) in Hamburg, Germany. The DSSC is foreseen for soft X-radiation from 0.5 keV up to 6 keV. Driven by its scientific requirements, the design goals of the detector system are single photon detection, high dynamic range and a high frame rate of up to 4.5 MHz. Signal compression and amplification will be performed in the silicon sensor pixels yielding a low signal noise. Utilizing an in-pixel active filtering stage and an 8/9-bit ADC, the detector will provide parallel read-out of all pixels. In order to calibrate offset and gain, the procedure currently under investigation relies on determining peak positions in measurements with calibration line sources such as 55Fe. Here the status of studies of the stability and performance of a parameterized fit function designed for this task will be presented
Methods for calibrating the gain and offset of the DSSC detector for the European XFEL
No full textThe DEPFET Sensor with Signal Compression (DSSC) will be a 2d 1Mpx imaging detector for the European X-ray Free Electron Laser facility (XFEL.EU), that is currently under construction in Hamburg. The DSSC is foreseen as a photon counting detector for soft X-ray radiation from 0.5 keV up to 6 keV. Driven by its scientific requirements, the design goals of the detector system are foremost low noise, a high dynamic range and a high frame rate of up to 4.5 MHz. Signal compression, amplification and digitization will be performed in the focal plane. Utilizing an in-pixel active filtering stage and an 8/9-bit ADC, the detector will provide parallel readout of all pixels. A critical step of calibrating the detector is the determination of the system gain and offset based on peak energies of X-ray calibration line sources such as 55 Fe. This is demanding due to the intrinsically low spectral resolution of the DSSC. The results of studies on the stability and performance of automated procedures for peak fitting in single pixel spectra with a low energy resolution were presented on a poste
Calibration Sources and Techniques for Large Format X-Ray Imagers at XFEL
No full textIn this work we compare different calibration sources and focus on their combination to optimize the calibration of large-format X-ray imagers over a wide range. This activity is carried out in the framework of the DSSC project and the primary aim is the calibration of the DSSC camera. We considered pulsed IR laser, radioactive sources, X-ray tube, electrical injection devices, X-ray synchrotron beam, low-energy protons, LED sources. The relevant features (deposited energy and pulse width) are critically summarized and calibration strategies will be discussed
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
Study of charge collection effects in the DSSC sensor
No full textThe DePFET Sensor with Signal Compression (DSSC) instrument is a 1 Mpixel camera under development at the European XFEL for the detection of low-energy X-rays (<;6 keV). In this work an experimental study of charge collection effects has been carried out as a function of the deposited charge in order to extract the true time profile of the collected charge cloud in a wide range of experimental conditions. A preliminary set of results is presented and discussed
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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