46 research outputs found
Validation of Compton Scattering Monte Carlo Simulation Models
Several models for the Monte Carlo simulation of Compton scattering on
electrons are quantitatively evaluated with respect to a large collection of
experimental data retrieved from the literature. Some of these models are
currently implemented in general purpose Monte Carlo systems; some have been
implemented and evaluated for possible use in Monte Carlo particle transport
for the first time in this study. Here we present first and preliminary results
concerning total and differential Compton scattering cross sections.Comment: 5 pages, 3 figures, to be published in the Proceedings of IEEE
Nuclear Science Symposium 201
Background Simulations of the Wide Field Imager of the ATHENA X-Ray Observatory
The ATHENA X-ray Observatory-IXO is a planned multinational orbiting X-ray
observatory with a focal length of 11.5m. ATHENA aims to perform pointed
observations in an energy range from 0.1 keV to 15 keV with high sensitivity.
For high spatial and timing resolution imaging and spectroscopic observations
the 640x640 pixel^2 large DePFET-technology based Wide field Imager (WFI) focal
plane detector, providing a field of view of 18 arcsec will be the main
detector. Based on the actual mechanics, thermal and shielding design we
present estimates for the WFI cosmic ray induced background obtained by the use
of Monte-Carlo simulations and possible background reduction measures.Comment: IEEE NSS MIC Conference 2011, Valencia, Spai
Validation of Geant4-based Radioactive Decay Simulation
Radioactive decays are of concern in a wide variety of applications using
Monte-Carlo simulations. In order to properly estimate the quality of such
simulations, knowledge of the accuracy of the decay simulation is required. We
present a validation of the original Geant4 Radioactive Decay Module, which
uses a per-decay sampling approach, and of an extended package for Geant4-based
simulation of radioactive decays, which, in addition to being able to use a
refactored per-decay sampling, is capable of using a statistical sampling
approach. The validation is based on measurements of calibration isotope
sources using a high purity Germanium (HPGe) detector; no calibration of the
simulation is performed. For the considered validation experiment equivalent
simulation accuracy can be achieved with per-decay and statistical sampling
Radioactive Decays in Geant4
The simulation of radioactive decays is a common task in Monte-Carlo systems
such as Geant4. Usually, a system either uses an approach focusing on the
simulations of every individual decay or an approach which simulates a large
number of decays with a focus on correct overall statistics. The radioactive
decay package presented in this work permits, for the first time, the use of
both methods within the same simulation framework - Geant4. The accuracy of the
statistical approach in our new package, RDM-extended, and that of the existing
Geant4 per-decay implementation (original RDM), which has also been refactored,
are verified against the ENSDF database. The new verified package is beneficial
for a wide range of experimental scenarios, as it enables researchers to choose
the most appropriate approach for their Geant4-based application
Photon shot-noise limited transient absorption soft X-ray spectroscopy at the European XFEL
Femtosecond transient soft X-ray Absorption Spectroscopy (XAS) is a very
promising technique that can be employed at X-ray Free Electron Lasers (FELs)
to investigate out-of-equilibrium dynamics for material and energy research.
Here we present a dedicated setup for soft X-rays available at the Spectroscopy
& Coherent Scattering (SCS) instrument at the European X-ray Free Electron
Laser (EuXFEL). It consists of a beam-splitting off-axis zone plate (BOZ) used
in transmission to create three copies of the incoming beam, which are used to
measure the transmitted intensity through the excited and unexcited sample, as
well as to monitor the incoming intensity. Since these three intensity signals
are detected shot-by-shot and simultaneously, this setup allows normalized
shot-by-shot analysis of the transmission. For photon detection, the DSSC
imaging detector, which is capable of recording up to 800 images at 4.5 MHz
frame rate during the FEL burst, is employed and allows approaching the photon
shot-noise limit. We review the setup and its capabilities, as well as the
online and offline analysis tools provided to users.Comment: 11 figure
Segmented flow generator for serial crystallography at the European X-ray free electron laser
Serial femtosecond crystallography (SFX) with X-ray free electron lasers (XFELs) allows structure determination of membrane proteins and time-resolved crystallography. Common liquid sample delivery continuously jets the protein crystal suspension into the path of the XFEL, wasting a vast amount of sample due to the pulsed nature of all current XFEL sources. The European XFEL (EuXFEL) delivers femtosecond (fs) X-ray pulses in trains spaced 100 ms apart whereas pulses within trains are currently separated by 889 ns. Therefore, continuous sample delivery via fast jets wastes >99% of sample. Here, we introduce a microfluidic device delivering crystal laden droplets segmented with an immiscible oil reducing sample waste and demonstrate droplet injection at the EuXFEL compatible with high pressure liquid delivery of an SFX experiment. While achieving ~60% reduction in sample waste, we determine the structure of the enzyme 3-deoxy-D-manno-octulosonate-8-phosphate synthase from microcrystals delivered in droplets revealing distinct structural features not previously reported