Spinor condensates and light scattering from Bose-Einstein condensates

These notes discuss two aspects of the physics of atomic Bose-Einstein condensates: optical properties and spinor condensates. The first topic includes light scattering experiments which probe the excitations of a condensate in both the free-particle and phonon regime. At higher light intensity, a new form of superradiance and phase-coherent matter wave amplification were observed. We also discuss properties of spinor condensates and describe studies of ground--state spin domain structures and dynamical studies which revealed metastable excited states and quantum tunneling.Comment: 58 pages, 33 figures, to appear in Proceedings of Les Houches 1999 Summer School, Session LXXI

The NPS-FEL Injector Upgrade

The Naval Postgraduate School (NPS) has begun the design and assembly of the NPS Free-Electron Laser (NPS-FEL). As part of this effort, the original DC gunbased injector system from the Stanford Superconducting Accelerator has been moved to NPS and is being refurbished and upgraded to operate as a photoinjector. Design work has begun on a new, SRF, quarter-wave resonator based cavity that can serve as either an energy booster or photocathode gun. The overall NPS-FEL design parameters are for 40- MeV beam energy, 1 nC bunch charge, and 1 mA average beam current, built as an energy-recovery linac in its final configuration [1]. As we move towards this goal, the injector system will be incrementally upgraded to add photocathode capability, have a higher final beam energy, and improve the beam brightness, to meet the needs of the overall experimental program

Design and operation of a superconducting quarter-wave electron gun

The article of record as published may be found at: http://dx.doi.org10.1103/PhysRevSTAB.14.053501Superconducting radio-frequency electron guns are viewed by many as the preferred technology for generating the high-quality, high-current beams needed for future high power-free-electron lasers and energy recovery linacs. All previous guns of this type have employed elliptical cavities, but there are potential advantages associated with other geometries. Here we describe the design, commissioning, and initial results from a superconducting radio-frequency electron gun employing a quarter-wave resonator configuration, the first such device to be built and tested. In initial operation, the gun has generated beams with bunch charge is excess in 78 pC, energy of 469 keV, and normalized rms emittances of about 4.9 um. Currently, bunch charge is limited by the available drive laser energy, and beam energy is limited by x-ray production and the available rf power. No fundamental limits on beam charge or energy have been encountered, and no high-field quenching events have been observed.Office of Naval Research and the High Energy Laser Joint Technology Office.Approved for public release; distribution is unlimited

NPS prototype superconducting 500 MHz quarter-wave gun update

Proceedings of FEL2010, Malmö, SwedenThe Naval Postgraduate School (NPS) Beam Physics Laboratory, Niowave, Inc., and The Boeing Company have completed construction of a superconducting 500 MHz quarter-wave gun and photocathode drive laser system. This prototype gun went from conception to initial operation in just under one calendar year. Such rapid progress is due in part to the decision to develop the gun as a prototype, deliberately omitting some features, such as tuners and a cathode loadlock, desired for a linac beam source. This will enable validation of the basic concept for the gun, including high-charge bunch dynamics, as rapidly as possible, with lessons learned applied to the next generation gun. This paper presents results from initial testing of the gun, technical challenges of the prototype design, and improvements that would enhance capabilities in future versions of this novel design

Network Improvement for Equilibrium Routing

In routing games, agents pick routes through a network to minimize their own delay. A primary concern for the network designer in routing games is the average agent delay at equilibrium. A number of methods to control this average delay have received substantial attention, including network tolls, Stackelberg routing, and edge removal. A related approach with arguably greater practical relevance is that of making investments in improvements to the edges of the network, so that, for a given investment budget, the average delay at equilibrium in the improved network is minimized. This problem has received considerable attention in the literature on transportation research. We study a model for this problem introduced in transportation research literature, and present both hardness results and algorithms that obtain tight performance guarantees. – In general graphs, we show that a simple algorithm obtains a 4/3-approximation for affine delay functions and an O(p/ log p)- approximation for polynomial delay functions of degree p. For affine delays, we show that it is NP-hard to improve upon the 4/3 approximation. – Motivated by the practical relevance of the problem, we consider restricted topologies to obtain better bounds. In series-parallel graphs, we show that the problem is still NP-hard. However, we show that there is an FPTAS in this case. – Finally, for graphs consisting of parallel paths, we show that an optimal allocation can be obtained in polynomial time

Equity portfolio construction and selection using multiobjective mathematical programming

Portfolio optimization, Multiobjective mathematical programming, ε-Constraint method, Equities,