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Weber, G

Publications and source records attributed to Weber, G.

Compton polarimeters for the study of hard X-rays arising from energetic collisions of electrons and ions with matter

Novel position-sensitive x-ray detectors are presented that, when applied as Compton polarimeters, enable precise and efficient linear polarization studies of hard x-rays up to several 100 keV. We give an analytical formula which yields a rough estimate of the polarimeter efficiencies of such detector systems. Moreover, we briefly summarize a recent linear polarization measurement of the Lyman-{alpha}{sub 1} radiation in a H-like high-Z system, namely U91+.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

VisIt: An End-User Tool for Visualizing and Analyzing Very Large Data

VisIt is a popular open source tool for visualizing and analyzing data. It owes its success to its foci of increasing data understanding, large data support, and providing a robust and usable product, as well as its underlying design that fits today's supercomputing landscape. In this short paper, we describe the VisIt project and its accomplishments. The VisIt project's three focal points - understanding data, large data, and delivering a product - together form a powerful environment for analyzing data from HPC simulations. It is used in varied ways: it enables visualization scientists, computational code developers, and the physicists that run these codes to perform a broad range of data understanding activities, including debugging, making movies, and exploring data. The user interface portion of its design provides a powerful paradigm for analyzing data while the data processing portion of its design is well suited for big data. This in turn has led to many successes: in scaling up to high levels of concurrency and large data sizes, in providing a 'home' for large data algorithms, in understanding how to best use supercomputers, and, most importantly, in helping users understand their data. Further, despite significant upcoming changes in supercomputing architecture, VisIt's future appears bright, as it enjoys vibrant user and developer communities.

99 GENERAL AND MISCELLANEOUS↗

Higher charges and regularized quantum trace identities in su(1,1) Landau-Lifshitz model

We solve the operator ordering problem for the quantum continuous integrable su(1,1) Landau-Lifshitz model, and give a prescription to obtain the quantum trace identities, and the spectrum for the higher-order local charges. We also show that this method, based on operator regularization and renormalization, which guarantees quantum integrability, as well as the construction of self-adjoint extensions, can be used as an alternative to the discretization procedure, and unlike the latter, is based only on integrable representations.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Direct Determination of the Magnetic Quadrupole Contribution to the Lyman-{alpha}{sub 1} Transition in a Hydrogenlike Ion

We report the observation of an interference between the electric dipole (E1) and the magnetic quadrupole (M2) amplitudes for the linear polarization of the Ly-{alpha}{sub 1} (2p{sub 3/2}{yields}1s{sub 1/2}) radiation of hydrogenlike uranium. This multipole mixing arises from the coupling of the ion to different multipole components of the radiation field. Our observation indicates a significant depolarization of the Ly-{alpha}{sub 1} radiation due to the E1-M2 amplitude mixing. It proves that a combined measurement of the linear polarization and of the angular distribution enables a very precise determination of the ratio of the E1 and the M2 transition amplitudes and the corresponding transition rates without any assumptions concerning the population mechanism for the 2p{sub 3/2} state.

74 ATOMIC AND MOLECULAR PHYSICS↗