Showing papers by "Georg Weidenspointner published in 2010"

Large-format, high-speed, X-ray pnCCDs combined with electron and ion imaging spectrometers in a multipurpose chamber for experiments at 4th generation light sources

Abstract: Fourth generation accelerator-based light sources, such as VUV and X-ray Free Electron Lasers (FEL), deliver ultra-brilliant (∼1012–1013 photons per bunch) coherent radiation in femtosecond (∼10–100 fs) pulses and, thus, require novel focal plane instrumentation in order to fully exploit their unique capabilities. As an additional challenge for detection devices, existing (FLASH, Hamburg) and future FELs (LCLS, Menlo Park; SCSS, Hyogo and the European XFEL, Hamburg) cover a broad range of photon energies from the EUV to the X-ray regime with significantly different bandwidths and pulse structures reaching up to MHz micro-bunch repetition rates. Moreover, hundreds up to trillions of fragment particles, ions, electrons or scattered photons can emerge when a single light flash impinges on matter with intensities up to 1022 W/cm2. In order to meet these challenges, the Max Planck Advanced Study Group (ASG) within the Center for Free Electron Laser Science (CFEL) has designed the CFEL-ASG MultiPurpose (CAMP) chamber. It is equipped with specially developed photon and charged particle detection devices dedicated to cover large solid-angles. A variety of different targets are supported, such as atomic, (aligned) molecular and cluster jets, particle injectors for bio-samples or fixed target arrangements. CAMP houses 4π solid-angle ion and electron momentum imaging spectrometers (“reaction microscope”, REMI, or “velocity map imaging”, VMI) in a unique combination with novel, large-area, broadband (50 eV–25 keV), high-dynamic-range, single-photon-counting and imaging X-ray detectors based on the pnCCDs. This instrumentation allows a new class of coherent diffraction experiments in which both electron and ion emission from the target may be simultaneously monitored. This permits the investigation of dynamic processes in this new regime of ultra-intense, high-energy radiation—matter interaction. After an introduction into the salient features of the CAMP chamber and the properties of the redesigned REMI/VMI spectrometers, the new 1024×1024 pixel format pnCCD imaging detector system will be described in detail. Results of tests of four smaller format (256×512) devices of identical performance, conducted at FLASH and BESSY, will be presented and the concept as well as the anticipated properties of the full, large-scale system will be elucidated. The data obtained at both radiation sources illustrate the unprecedented performance of the X-ray detectors, which have a voxel size of 75×75×450 μm3 and a typical read-out noise of 2.5 electrons (rms) at an operating temperature of −50 °C.

Development of the focal plane PNCCD camera system for the X-ray space telescope eROSITA

Abstract: A so-called PNCCD, a special type of CCD, was developed twenty years ago as focal plane detector for the XMM-Newton X-ray astronomy mission of the European Space Agency ESA. Based on this detector concept and taking into account the experience of almost ten years of operation in space, a new X-ray CCD type was designed by the ‘MPI semiconductor laboratory’ for an upcoming X-ray space telescope, called eROSITA ( e xtended Ro entgen s urvey with an i maging t elescope a rray). This space telescope will be equipped with seven X-ray mirror systems of Wolter-I type and seven CCD cameras, placed in their foci. The instrumentation permits the exploration of the X-ray universe in the energy band from 0.3 up to 10 keV by spectroscopic measurements with a time resolution of 50 ms for a full image comprising 384×384 pixels. Main scientific goals are an all-sky survey and investigation of the mysterious ‘Dark Energy’. The eROSITA space telescope, which is developed under the responsibility of the ‘Max-Planck-Institute for extraterrestrial physics’, is a scientific payload on the new Russian satellite ‘Spectrum-Roentgen-Gamma’ (SRG). The mission is already approved by the responsible Russian and German space agencies. After launch in 2012 the destination of the satellite is Lagrange point L2. The planned observational program takes about seven years. We describe the design of the eROSITA camera system and present important test results achieved recently with the eROSITA prototype PNCCD detector. This includes a comparison of the eROSITA detector with the XMM-Newton detector.

Design and performance evaluations of generic programming techniques in a R&D prototype of Geant4 physics

Abstract: A R&D project has been recently launched to investigate Geant4 architectural design in view of addressing new experimental issues in HEP and other related physics disciplines. In the context of this project the use of generic programming techniques besides the conventional object oriented is investigated. Software design features and preliminary results from a new prototype implementation of Geant4 electromagnetic physics are illustrated. Performance evaluations are presented. Issues related to quality assurance in Geant4 physics modelling are discussed.

CCD detector development for the eROSITA space telescope

Abstract: The German X-ray telescope eROSITA is the core instrument on the Russian satellite Spectrum-Roentgen-Gamma (SRG). Its scientific goal is the exploration of the X-ray Universe in the energy band from about 0.3 keV up to 10 keV with excellent energy, time and spatial resolution and large effective telescope area. The launch of the SRG satellite is scheduled for 2013. The observational program divides the planned mission duration of seven years into an all-sky survey and pointed observations. For detection of the single X-ray photons with high resolution, adequate frame transfer pnCCDs and the associated front-end electronics have been developed. The back-illuminated, 450 μm thick and fully depleted pnCCDs with a 3 cm × 3 cm large image area have been produced in the MPI Halbleiterlabor in the course of further development of the XMM-Newton X-ray pnCCDs. By means of the concept of back-illumination and full depletion of the chip thickness, high quantum efficiency is obtained over the entire energy band of interest. The performance of each eROSITA CCD was tested on chip level using a so-called ‘cold chuck probe station’. A special feature of this setup is that it allows spectroscopic measurements with a 55Fe source. Based on these results, we will select the seven best CCDs for the eROSITA focal plane cameras. An analog signal processor with 128 parallel channels has been developed for readout of the pnCCD signals. This ASIC permits fast and low-noise signal filtering. For a detailed characterization of the CCD detectors an appropriate control, supply and data acquisition electronics system was developed. We achieve a read noise of 2 electrons rms and an energy resolution of 135 eV FWHM for photons with energy of 5.9 keV. Even at the low X-ray energy of 280 eV, we measure a spectrum of Gaussian shape with a FWHM of 52 eV. However, the energy resolution will degrade during the seven years in space due to radiation damage caused by protons. The radiation damage effect was studied and quantified for the eROSITA CCDs in an experiment. After successful development and verification of the CCD and its signal processor chip, we have started to assemble a flight-like eROSITA camera.

New models for PIXE simulation with Geant4

Abstract: Particle induced X-ray emission (PIXE) is a physical effect that is not yet adequately modelled in Geant4. The current status as in Geant4 9.2 release is reviewed and new developments are described. The capabilities of the software prototype are illustrated in application to the shielding of the X-ray detectors of the eROSITA telescope on the upcoming Spectrum-X-Gamma space mission.

New physics data libraries for Monte Carlo transport

Abstract: The role of data libraries as a collaborative tool across Monte Carlo codes is discussed. Some new contributions in this domain are presented; they concern a data library of proton and alpha ionization cross sections, the development in progress of a data library of electron ionization cross sections and proposed improvements to the EADL (Evaluated Atomic Data Library), the latter resulting from an extensive data validation process.

Radioactive decay simulation with Geant4: experimental benchmarks and developments for X-ray astronomy applications

Abstract: We present {\gamma} spectroscopy validation measurements for the Geant4 radioactive decay simulation for a selected range of isotopes using a simple experimental setup. Using these results we point out problems in the decay simulation and where they may originate from.

Environmental Adaptability and Mutants: Exploring New Concepts in Particle Transport for Multi-Scale Simulation

Abstract: Ongoing investigations to introduce software techniques suitable to support new experimental requirements for multi-scale simulation are discussed.

Environmental adaptability and mutants: Exploring new concepts in particle transport for multi-scale simulation

Abstract: Ongoing investigations to introduce software techniques suitable to support new experimental requirements for multi-scale simulation are discussed.

New Physics Data Libraries for Monte Carlo Transport

Abstract: The role of data libraries as a collaborative tool across Monte Carlo codes is discussed. Some new contributions in this domain are presented; they concern a data library of proton and alpha ionization cross sections, the development in progress of a data library of electron ionization cross sections and proposed improvements to the EADL (Evaluated Atomic Data Library), the latter resulting from an extensive data validation process.

New models for PIXE simulation with Geant4

Abstract: Particle induced X-ray emission (PIXE) is a physical effect that is not yet adequately modelled in Geant4. The current status as in Geant4 9.2 release is reviewed and new developments are described. The capabilities of the software prototype are illustrated in application to the shielding of the X-ray detectors of the eROSITA telescope on the upcoming Spectrum-X-Gamma space mission.

Design and performance evaluations of generic programming techniques in a R&D prototype of Geant4 physics

Abstract: A R&D project has been recently launched to investigate Geant4 architectural design in view of addressing new experimental issues in HEP and other related physics disciplines. In the context of this project the use of generic programming techniques besides the conventional object oriented is investigated. Software design features and preliminary results from a new prototype implementation of Geant4 electromagnetic physics are illustrated. Performance evaluations are presented. Issues related to quality assurance in Geant4 physics modelling are discussed.