2,523 research outputs found
Optimization of RF Coupling to Produce High-Density Homogenous Plasma for Negative Ion Sources
Optimization of RF Coupling to Produce High-Density Homogenous Plasma for Negative Ion Sources
Kinetically-balanced Gaussian Basis Set Approach to Relativistic Compton Profiles of Atoms
Atomic Compton profiles (CPs) are a very important property which provide us
information about the momentum distribution of atomic electrons. Therefore, for
CPs of heavy atoms, relativistic effects are expected to be important,
warranting a relativistic treatment of the problem. In this paper, we present
an efficient approach aimed at ab initio calculations of atomic CPs within a
Dirac-Hartree-Fock (DHF) formalism, employing kinetically-balanced Gaussian
basis functions. The approach is used to compute the CPs of noble gases ranging
from He to Rn, and the results have been compared to the experimental and other
theoretical data, wherever possible. The influence of the quality of the basis
set on the calculated CPs has also been systematically investigated.Comment: 31 pages, 12 figure
Building A High Performance Parallel File System Using Grid Datafarm and ROOT I/O
Sheer amount of petabyte scale data foreseen in the LHC experiments require a
careful consideration of the persistency design and the system design in the
world-wide distributed computing. Event parallelism of the HENP data analysis
enables us to take maximum advantage of the high performance cluster computing
and networking when we keep the parallelism both in the data processing phase,
in the data management phase, and in the data transfer phase. A modular
architecture of FADS/ Goofy, a versatile detector simulation framework for
Geant4, enables an easy choice of plug-in facilities for persistency
technologies such as Objectivity/DB and ROOT I/O. The framework is designed to
work naturally with the parallel file system of Grid Datafarm (Gfarm).
FADS/Goofy is proven to generate 10^6 Geant4-simulated Atlas Mockup events
using a 512 CPU PC cluster. The data in ROOT I/O files is replicated using
Gfarm file system. The histogram information is collected from the distributed
ROOT files. During the data replication it has been demonstrated to achieve
more than 2.3 Gbps data transfer rate between the PC clusters over seven
participating PC clusters in the United States and in Japan.Comment: Talk from the 2003 Computing in High Energy and Nuclear Physics
(CHEP03), La Jolla, Ca, USA, March 2003, 4 pages, PDF. PSN TUDT01
A multi-instrument approach to determining the source‐region extent of EEP-driving EMIC Waves
Recent years have seen debate regarding the ability of electromagnetic ion cyclotron (EMIC) waves to drive EEP (energetic electron precipitation) into the Earth's atmosphere. Questions still remain regarding the energies and rates at which these waves are able to interact with electrons. Many studies have attempted to characterize these interactions using simulations; however, these are limited by a lack of precise information regarding the spatial scale size of EMIC activity regions. In this study we examine a fortuitous simultaneous observation of EMIC wave activity by the RBSP‐B and Arase satellites in conjunction with ground‐based observations of EEP by a subionospheric VLF network. We describe a simple method for determining the longitudinal extent of the EMIC source region based on these observations, calculating a width of 0.75 hr MLT and a drift rate of 0.67 MLT/hr. We describe how this may be applied to other similar EMIC wave events
A Bright Spatially-Coherent Compact X-ray Synchrotron Source
Each successive generation of x-ray machines has opened up new frontiers in
science, such as the first radiographs and the determination of the structure
of DNA. State-of-the-art x-ray sources can now produce coherent high brightness
keV x-rays and promise a new revolution in imaging complex systems on nanometre
and femtosecond scales. Despite the demand, only a few dedicated synchrotron
facilities exist worldwide, partially due the size and cost of conventional
(accelerator) technology. Here we demonstrate the use of a recently developed
compact laser-plasma accelerator to produce a well-collimated,
spatially-coherent, intrinsically ultrafast source of hard x-rays. This method
reduces the size of the synchrotron source from the tens of metres to
centimetre scale, accelerating and wiggling a high electron charge
simultaneously. This leads to a narrow-energy spread electron beam and x-ray
source that is >1000 times brighter than previously reported plasma wiggler and
thus has the potential to facilitate a myriad of uses across the whole spectrum
of light-source applications.Comment: 5 pages, 4 figure
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