oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Search Results: 1 - 10 of 1841 matches for " Heinz Graafsma "
All listed articles are free for downloading (OA Articles)
Page 1 /1841
Display every page Item
Simulation study of the impact of AGIPD design choices on X-ray Photon Correlation Spectroscopy utilizing the intensity autocorrelation technique
Julian Becker,Christian Gutt,Heinz Graafsma
Physics , 2011, DOI: 10.1088/1748-0221/6/11/P11005
Abstract: The European XFEL, currently under construction, will produce a coherent X-ray pulse every 222 ns in pulse trains of up to 2700 pulses. In conjunction with the fast 2D area detectors currently under development, it will be possible to perform X-ray Photon Correlation Spectroscopy (XPCS) experiments on sub-microsecond timescales with non-ergodic systems. A case study for the Adaptive Gain Integrating Pixel Detector (AGIPD) at the European XFEL employing the intensity autocorrelation technique was performed using the detector simulation tool HORUS. As optimum results from XPCS experiments are obtained when the pixel size approximates the (small) speckle size, the presented study compares the AGIPD (pixel size of (200 $\upmu$m)$^2$) to a possible apertured version of the detector and to a hypothetical system with (100 $\upmu$m)$^2$ pixel size and investigates the influence of intensity fluctuations and incoherent noise on the quality of the acquired data. The intuitive conclusion that aperturing is not beneficial as data is 'thrown away' was proven to be correct for low intensities. For intensities larger than approximately 1 photon per (100 $\upmu$m)$^2$ aperturing was found to be beneficial, as charge sharing effects were excluded by it. It was shown that for the investigated case (100 $\upmu$m)$^2$ pixels produced significantly better results than (200 $\upmu$m)$^2$ pixels when the average intensity exceeded approximately 0.05 photons per (100 $\upmu$m)$^2$. Although the systems were quite different in design they varied in the signal to noise ratio only by a factor of 2-3, and even less in the relative error of the extracted correlation constants. However the dependence on intensity showed distinctively different features for the different systems.
Optimization of radiation hardness and charge collection of edgeless silicon pixel sensors for photon science
Jiaguo Zhang,Damaris Tartarotti Maimone,David Pennicard,Milija Sarajlic,Heinz Graafsma
Physics , 2014, DOI: 10.1088/1748-0221/9/12/C12025
Abstract: Recent progress in active-edge technology of silicon sensors enables the development of large-area tiled silicon pixel detectors with small dead space between modules by utilizing edgeless sensors. Such technology has been proven in successful productions of ATLAS and Medipix-based silicon pixel sensors by a few foundries. However, the drawbacks of edgeless sensors are poor radiation hardness for ionizing radiation and non-uniform charge collection by edge pixels. In this work, the radiation hardness of edgeless sensors with different polarities has been investigated using Synopsys TCAD with X-ray radiation-damage parameters implemented. Results show that if no conventional guard ring is present, none of the current designs are able to achieve a high breakdown voltage (typically < 30 V) after irradiation to a dose of ~10 MGy. In addition, a charge-collection model has been developed and was used to calculate the charges collected by the edge pixels of edgeless sensors when illuminated with X-rays. The model takes into account the electric field distribution inside the pixel sensor, the absorption of X-rays, drift and diffusion of electrons and holes, charge sharing effect, and threshold settings in ASICs. It is found that the non-uniform charge collection of edge pixels is caused by the strong bending of electric field and the non-uniformity depends on bias voltage, sensor thickness and distance from active edge to the last pixel ("edge space"). In particular, the last few pixels close to the active edge of the sensor are not sensitive to low-energy X-rays (< 10 keV) especially for sensors with thicker Si and smaller edge space. The results from the model calculation have been compared to measurements and good agreement was obtained. The model has been used to optimize the edge design.
Study of X-ray radiation damage in the AGIPD sensor for the European XFEL
Jiaguo Zhang,Eckhart Fretwurst,Heinz Graafsma,Robert Klanner,Ioannis Kopsalis,Joern Schwandt
Physics , 2013, DOI: 10.1088/1748-0221/9/05/C05022
Abstract: The European X-ray Free Electron Laser (XFEL), currently being constructed in Hamburg and planning to be operational in 2017 for users, will deliver 27,000 fully coherent, high brilliance X-ray pulses per second with duration less than 100 fs. The unique features of the X-ray beam pose major challenges for detectors used at the European XFEL for imaging experiments, in particular a radiation tolerance of silicon sensors for doses up to 1 GGy for 3 years of operation at an operating voltage above 500 V. One of the detectors under development at the European XFEL is the Adaptive Gain Integrating Pixel Detector (AGIPD), which is a hybrid detector system with ASICs bump-bonded to p+n silicon pixel sensors. We have designed the silicon sensors for the AGIPD, which have been fabricated by SINTEF and delivered in the beginning of February of 2013. To demonstrate the performance of the AGIPD sensor with regard to radiation hardness, mini-sensors with the same pixel and guard-ring designs as the AGIPD together with test structures have been irradiated at the beamline P11 of PETRA III with 8 keV and 12 keV monoenergetic X-rays to dose values up to 10 MGy. The radiation hardness of the AGIPD sensor has been proven and all electrical properties are within specification before and after irradiation. In addition, the oxide-charge density and surface-current density from test structures have been characterized as function of the X-ray dose and compared to previous measurements for test structures produced by four vendors.
The single photon sensitivity of the Adaptive Gain Integrating Pixel Detector
Julian Becker,Dominic Greiffenberg,Ulrich Trunk,Xintian Shi,Roberto Dinapoli,Aldo Mozzanica,Beat Henrich,Bernd Schmitt,Heinz Graafsma
Physics , 2012, DOI: 10.1016/j.nima.2012.08.008
Abstract: Single photon sensitivity is an important property of certain detection systems. This work investigated the single photon sensitivity of the Adaptive Gain Integrating Pixel Detector (AGIPD) and its dependence on possible detector noise values. Due to special requirements at the European X-ray Free Electron Laser (XFEL) the AGIPD finds the number of photons absorbed in each pixel by integrating the total signal. Photon counting is done off line on a thresholded data set. It was shown that AGIPD will be sensitive to single photons of 8 keV energy or more (detection efficiency $\gg$ 50%, less than 1 count due to noise per 10$^6$ pixels). Should the final noise be at the lower end of the possible range (200 - 400 electrons) single photon sensitivity can also be achieved at 5 keV beam energy. It was shown that charge summing schemes are beneficial when the noise is sufficiently low. The total detection rate of events is increased and the probability to count a single event multiple times in adjacent pixels is reduced by a factor of up to 40. The entry window of AGIPD allows 3 keV photons to reach the sensitive volume with approximately 70% probability. Therefore the low energy performance of AGIPD was explored, finding a maximum noise floor below 0.035 hits/pixel/frame at 3 keV beam energy. Depending on the noise level and selected threshold this value can be reduced by a factor of approximately 10. Even though single photon sensitivity, as defined in this work, is not given, imaging at this energy is still possible, allowing Poisson noise limited performance for signals significantly above the noise floor.
The Misleading Use of “Enthalpy” in an Energy Conversion Analysis  [PDF]
Heinz Herwig
Natural Science (NS) , 2014, DOI: 10.4236/ns.2014.611085
Abstract: The frequently used thermodynamic state quantity enthalpy H turns out to be very problematic when applied in an energy conversion analysis. Due to the fact that H combines two terms, the internal energy U and the product pV, the interpretation of what H means in physical terms is often obscure and leads to various misinterpretations. Several examples are given and interpreted twice,i.e.with and without referring to enthalpy.
A Phenomenological Extension of the Newtonian Gravity  [PDF]
Heinz Dehnen
International Journal of Astronomy and Astrophysics (IJAA) , 2019, DOI: 10.4236/ijaa.2019.91006
Abstract: Following the idea of our previous paper we distinguish also in the case of Newtonian gravity as in the electrodynamics between extensive and intensive field quantities. Between both, a “material’’ quantity produced e.g. by vacuum polarisations induced by the gravitational field strength itself is mediated. It acts in such a way that it amplifies the field strength in weak gravitational fields and reduces the field strength in strong gravitational fields following Lenz’s rule. Newton’s gravity is valid only in a very large intermediate range of middle field strength F\"\", F0? and F1critical field strengths). In this way dark matter and black holes may be avoidable.
Lipophilic Optical Supramolecular Nano Devices in the Aqueous Phase  [PDF]
Heinz Langhals, Tim Pust
Green and Sustainable Chemistry (GSC) , 2011, DOI: 10.4236/gsc.2011.11001
Abstract: Nano micelles of sodium dodecyl sulphate in water were prepared as local lipophilic media for the organisation of interacting chromophores. Such arrangements were controlled by peripheric substituents to operate either as isolated chromophores or as skew oriented pairs where H-type transitions cause hysochromic absorption and J-type transitions bathochromic fluorescence. As a consequence, large Stokes' shift could be obtained.
A Concept for a Novel Test for Chemical Parity  [PDF]
Heinz Langhals, Oswald Krotz
Green and Sustainable Chemistry (GSC) , 2018, DOI: 10.4236/gsc.2018.84021
Abstract: Deviations from chemical parity (PV) were evaluated with the search for very small enantiomeric excesses in a racemate prepared from non chiral materials and were detected by means of the circular dichroism (CD). Thus, intensely light-absorbing perylenebiscarboximides were attached to axially chiral biphenyls for the amplification of CD effects by exciton interactions of the adjacent chromophores. A rapidly racemising system was applied for the exclusion of artifacts and compared with an analogous with locked chirally. A very slight enantiomeric excess was detected for the (M) enantiomer. Application of the method for other systems was suggested and relations to natural products discussed.
Do Near-Solar-System Supernovae Enhance Volcanic Activities on Earth and Neighbouring Planets on Their Paths through the Spiral Arms of the Milky Way, and What Might Be the Consequences for Estimations of Earth’s History and Predictions for Its Future?  [PDF]
Heinz-Juergen Brink
International Journal of Geosciences (IJG) , 2019, DOI: 10.4236/ijg.2019.105032
Abstract: Recent observations of young volcanism on the near-Earth terrestrial planets require a new understanding. Magmatic/volcanic episodes on Venus, Mars and Mercury, as well as on Earth’s Moon, are apparently contemporaneous thermal events that accompanied increased magmatic/volcanic activity on Earth, following a 300-Myr cycle. A collateral galactic thermal source in the Milky Way appears to be needed that would predominantly affect the interior of the planets and, perhaps indirectly, Earth’s biosphere, compared to other galactic sources, such as intense cosmic rays or large, rocky bolides. The search for such a source leads to near-Earth supernovae, with their neutrino output, and to the question of whether those neutrinos could act as energy transmitters to heat up the body of Earth, and also enhance its short-term magmatic processes; for example, Cenozoic anorogenic volcanism. This observation challenges present assumptions and paradigms about Earth’s history, and requires the following reconsiderations: 1) the real origin of the end-Cretaceous mass extinction; 2) the general radioactive age determinations of rocks; and 3) geodynamic modelling using additional, external heat sources.
Periodic Signals of the Milky Way Concealed in Terrestrial Sedimentary Basin Fills and in Planetary Magmatism?  [PDF]
Heinz-Jürgen Brink
International Journal of Geosciences (IJG) , 2015, DOI: 10.4236/ijg.2015.68067
Abstract: Long periodic geodynamic processes with durations between 150 and 600 Million years appear to be in phase with similar galactic cycles, caused by the path of the solar system through the spiral arms of the Milky Way. This path is assumed by some authors to cause climate change due to cosmic ray fluctuations, affecting the cloud formation and the related albedo of the Earth, which periodically lead to glaciations every 150 Ma. With the glaciations, the sea level fluctuates accordingly. Subsequently, the varying sizes of shallow seas are causing periodic changes of the Moon’stidal dissipation, which affects presumably other geodynamic processes on the Earth. The Moonmay therefore synchronize directly or indirectly long periodic Phanerozoic cycles (sea level, orogeny, magmatism, sedimentation, etc.) with the Milky Way. As sea level fluctuations, orogeny, sedimentation and magmatism can be described as members of a geodynamic feedback system; no apparent reasons appear to be required to assign a cause of the cyclicity to agents outside of thegalactic-climatically synchronized Earth-Moon system. However, recent observations of youngvolcanism on the near Earth terrestrial planets may require a new understanding. Magmatic/volcanic episodes on Venus, Mars and Mercury as well as on the Earth’s Moon are apparently contemporaneous thermal events accompanying increased magmatic/volcanic activities on theEarth,following a 300 myr cycle. Therefore, a collateral galactic thermal source within the Milky Way
Page 1 /1841
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.