Comparisons Between Modeling and Measured Performance of the BNL Linac

Quite good agreement has been achieved between computer modeling and actual performance of the Brookhaven 200 MeV Linac. We will present comparisons between calculated and measured performance for the beam transport through the RFQ, the 6 meter transport from RFQ to the linac and meching and transport through the linac.Comment: 3 page

A Super-Conducting Linac Driver for the HFBR

This paper reports on the feasibility study of a proton Super-Conducting Linac (SCL) as a driver gor the High-Flux Breader Reactor (HFBR) at Brookhaven National Laboratory (BNL). The Linac operates in Continuos Wave (CW) mode to produce an average 10 MW of beam power. The Linac energy is 1.0 GeV. The average proton beam intensity is 10 mA.Comment: 3 page

The NSNS High Energy Beam Transport Line

In the National Spallation Neutron Source (NSNS) design, a 180 meter long transport line connects the 1 GeV linac to an accumulator ring. The linac beam has a current of 28 mA, pulse length of 1 ms, and 60 Hz rep rate. The high energy transport line consists of sixteen 60 degrees FODO cells, and accommodates a 90 degrees achromatic bend, an energy compressor, collimators, part of injection system, and enough diagnostic devices to measure the beam quality before injection. To reduce the uncontrolled beam losses, this line has nine beam halo scrapers and very tight tolerances on both transverse and longitudinal beam dynamics under space charge conditions. The design of this line is presented.Comment: 3 pages, transfer line desig

The relevance of point defects in studying silica-based materials from bulk to nanosystems

The macroscopic properties of silica can be modified by the presence of local microscopic modifications at the scale of the basic molecular units (point defects). Such defects can be generated during the production of glass, devices, or by the environments where the latter have to operate, impacting on the devices’ performance. For these reasons, the identification of defects, their generation processes, and the knowledge of their electrical and optical features are relevant for microelectronics and optoelectronics. The aim of this manuscript is to report some examples of how defects can be generated, how they can impact device performance, and how a defect species or a physical phenomenon that is a disadvantage in some fields can be used as an advantage in others

The dynamical structure of the MEO region: long-term stability, chaos, and transport

It has long been suspected that the Global Navigation Satellite Systems exist in a background of complex resonances and chaotic motion; yet, the precise dynamical character of these phenomena remains elusive. Recent studies have shown that the occurrence and nature of the resonances driving these dynamics depend chiefly on the frequencies of nodal and apsidal precession and the rate of regression of the Moon's nodes. Woven throughout the inclination and eccentricity phase space is an exceedingly complicated web-like structure of lunisolar secular resonances, which become particularly dense near the inclinations of the navigation satellite orbits. A clear picture of the physical significance of these resonances is of considerable practical interest for the design of disposal strategies for the four constellations. Here we present analytical and semi-analytical models that accurately reflect the true nature of the resonant interactions, and trace the topological organization of the manifolds on which the chaotic motions take place. We present an atlas of FLI stability maps, showing the extent of the chaotic regions of the phase space, computed through a hierarchy of more realistic, and more complicated, models, and compare the chaotic zones in these charts with the analytical estimation of the width of the chaotic layers from the heuristic Chirikov resonance-overlap criterion. As the semi-major axis of the satellite is receding, we observe a transition from stable Nekhoroshev-like structures at three Earth radii, where regular orbits dominate, to a Chirikov regime where resonances overlap at five Earth radii. From a numerical estimation of the Lyapunov times, we find that many of the inclined, nearly circular orbits of the navigation satellites are strongly chaotic and that their dynamics are unpredictable on decadal timescales.Comment: Submitted to Celestial Mechanics and Dynamical Astronomy. Comments are greatly appreciated. 28 pages, 15 figure