117757554
Advanced numerical methods in astrophysical fluid dynamics
Computational gas dynamics has become a prominent research field both in astrophysics and cosmology. In the first part of this review we intend to briefly describe several of the numerical methods used in this field, discuss their range of application and present strategies for converting conditionally-stable numerical methods into unconditionally-stable solution procedures. The underlying aim of the conversion is to enhance the robustness and unification of numerical methods and subsequently enlarge their range of applications considerably. In the second part Fabian Heitsch presents and discusses the implementation of a time-explicit MHD Boltzmann solver.
343060
An implicit numerical algorithm for solving the general relativistic hydrodynamical equations around accreting compact objects
Abstract An implicit algorithm for solving the equations of general relativistic hydrodynamics in conservative form in three-dimensional axi-symmetry is presented. This algorithm is a direct extension of the pseudo-Newtonian implicit radiative magnetohydrodynamical solver – IRMHD – into the general relativistic regime. We adopt the Boyer–Lindquist coordinates and formulate the hydrodynamical equations in the fixed background of a Kerr black hole. The set of equations are solved implicitly using the hierarchical solution scenario (HSS). The HSS is efficient, robust and enables the use of a variety of solution procedures that range from a purely explicit up to fully implicit schemes. The discretization of the HD-equations is based on the finite volume formulation and the defect-correction iteration strategy for recovering higher order spatial and temporal accuracies. Depending on the astrophysical problem, a variety of relaxation methods can be applied. In particular the vectorized black-white Line-Gauss–Seidel relaxation method is most suitable for modeling accretion flows with shocks, whereas the Approximate Factorization Method is for weakly compressible flows. The results of several test calculations that verify the accuracy and robustness of the algorithm are shown. Extending the algorithm to enable solving the non-ideal MHD equations in the general relativistic regime is the subject of our ongoing research.
219570988
THE PSI "VPC" BOARD-FIRST APPLICATIONS OF A COMMON DIGITAL BACK-END FOR ELECTRON AND PROTON BEAM INSTRUMENTATION AT PSI
This report gives an overview of the design concept and applications of the VME PMC Carrier board (VPC), a VME64x board that was developed at PSI as a common digital back-end for beam instrumentation at the PSI electron and proton accelerators. The two Xilinx Virtex2Pro FPGAs of the VPC allow the implementation of the complete digital section of a beam instrumentation system on a single chip ("SOC"), including detector frontend interface, filters, interlocks, feedback links, high-level data analysis like FFTs, and a generic control system interface. In addition to the two on-chip PowerPC processors of the FPGAs, the VPC provides a DSP, RAM, and multi-gigabit fibre optic links for distributed feedbacks and synchronisation. First applications of the VPC include digital proton beam position monitors (DBPMs) and beam profile monitors for the PSI proton accelerators, the readout of several thousand detector channel waveforms for a muon decay experiment, and the integration of photon BPMs into the SLS fast orbit feedback (FOFB). In addition to a status report and first results for these applications, an outlook on possible future applications of the VPC will be given.
219569964
The “Generic VME PMC Carrier Board”: A Common Digital Hardware Platform for Beam Diagnostics and Feedbacks at PSI
Rapid progress in digital electronics allows digitisation of monitor signals at a very early stage of the signal processing chain, providing optimum performance and maximum flexibility for today’s accelerator instrumentation. While the analog front-ends of such systems are usually specific for each monitor type, the subsequent digital part of the processing chain can be unified for many different measurement tasks. The “generic VME PMC Carrier board” (VPC) [1] was developed to achieve this unification for the PSI electron and proton accelerator diagnostics and fast data acquisition and feedback systems. The core of the VME64x board consists of two Virtex2Pro FPGAs with two PowerPCs each, a floating point DSP and RAM. The FPGAs can acquire and process measurement data from the VMEbus P0/P2 connectors or from two applicationdependent PMC mezzanine modules. Two 2 GBaud fibre optics transceivers may also be used to acquire or distribute measurement data. Envisaged applications include digital beam position (DBPM) and current monitors for proton beams, data processing for a muon decay experiment, and general beam diagnostics as well as global feedbacks at SLS accelerators and beamlines.
45605429
THE EVOLUTION OF THE DELTA CONTROL SYSTEM
Since January 1999 the Dortmunder Elektronen Testspeicherring Anlage (DELTA) control system has changed from a non-standard hand-made system to the standard Experimental Physics and Industrial Control System (EPICS) [1]. The complete 80 MeV LINAC and transfer-line, the asymmetric 5.5 T multipole wiggler magnet (SAW) and main parts of the 1.5 GeV electron storage ring are now under EPICS control. Additional hardware upgrades like a fast 100baseTX/FX Ethernet network, Linux-PCs, PowerPC-IOCs, and reengineered device I/O-interface cards have been installed. Moreover, a self-made VME DSP-board is in the final test phase to control the booster ramping process. Generic stream device drivers for the IEEE/GPIB and CAN fieldbusses have been developed and have already been in use for one year [2]. The number of high level software tools for data acquisition and evaluation as well as for remote device control and complex software feedback is increasing continuously. The availability of a wide variety of interfaces to the EPICS Channel Access (CA) protocol makes it possible to include state of the art software platforms and architectures like the CORBA middleware, Java, Delphi, Tcl/Tk etc. very easily. Furthermore, the integration of complex simulation, design and modeling tools together with database archiving and Web-based accelerator monitoring is in progress.
62399469
Intra bunch train feedback system for the European X-FEL
32963428
Correction of Insertion Device Induced Orbit Distortions at the SLS
Corrections of insertion device (ID) induced orbit distortions at the SLS are performed by means of feed forward schemes down to the micron level at the corresponding photon beam position monitors (XBPMs). The remaining orbit fluctuations are suppressed by XBPM feedbacks which are an integral part of the fast orbit feedback system. As a result, sub-μm RMS stability at the XBPMs is achieved while the ID settings are varied.