We discuss recent developments in III-V multijunction solar cells, focusing on adding a fourth junction to the Ga0.5In0.5P/GaAs/Ga0.75In0.25As inverted three-junction cell. This cell, grown inverted on GaAs so that the lattice-mismatched Ga0.75In0.25As third junction is the last one grown, has demonstrated 38% efficiency, and 40% is likely in the near future. To achieve still further gains, a lower-bandgap GaxIn1-xAs fourth junction could be added to the three-junction structure for a four-junction cell whose efficiency could exceed 45% under concentration. Here, we present the initial development of the GaxIn1-xAs fourth junction. Junctions of various bandgaps ranging from 0.88 to 0.73 eV were grown, in order to study the effect of the different amounts of lattice mismatch. At a bandgap of 0.88 eV, junctions were obtained with very encouraging {approx}80% quantum efficiency, 57% fill factor, and 0.36 eV open-circuit voltage. The device performance degrades with decreasing bandgap (i.e., increasing lattice mismatch). We model the four-junction device efficiency vs. fourth junction bandgap to show that an 0.7-eV fourth-junction bandgap, while optimal if it could be achieved in practice, is not necessary; an 0.9-eV bandgap would still permit significant gains in multijunction cell efficiency while being easier to achieve than the lower-bandgap junction.

This paper describes electrical design criteria and first operational results a 140 kV, 1 MW average, 11 MW peak, zero-voltage-switching 20 kHz polyphase bridge, boost converter/modulator for klystron pulse application. The DC-DC converter derives the buss voltages from a standard 13.8 kV to 2300 Y substation cast-core transformer. Energy storage and filtering is provided by self-clearing metallized hazy polypropylene traction capacitors. Three ''H-Bridge'' Insulated Gate Bipolar Transistor (IGBT) switching networks are used to generate the polyphase 20 kHz transformer primary drive waveforms. The 20 kHz drive waveforms are chirped the appropriate duration to generate the desired klystron pulse width. PWM (pulse width modulation) of the individual 20 kHz pulses is utilized to provide regulated output waveforms with adaptive feedforward and feedback techniques. The boost transformer design utilizes amorphous nanocrystalline material that provides the required low core loss at design flux levels and switching frequencies. Resonant shunt-peaking is used on the transformer secondary to boost output voltage and resonate transformer leakage inductance. With the appropriate transformer leakage inductance and peaking capacitance, zero-voltage-switching of the IGBT's is attained, minimizing switching losses. A review of these design parameters and the first results of the performance characteristics will be presented.

This conference paper describes the GaInAsN cells that are measured to retain 933% and 894% of their original efficiency after exposure to 5 X 1014 and 1 X 1015 cm-2 1-MeV electrons, respectively. The rate of degradation is not correlated with the performance at beginning of life (BOL). The depletion width remains essentially unchanged, increasing by< 1%. Temperature-coefficient data for GaInAsN cells are also presented. These numbers are used to project the efficiency of GaInAsN-containing multijunction cells. The GaInAsN junction is not currently predicted to increase the efficiencies of the multijunction cells. Nevertheless, GaInAsN-containing multijunction cell efficiencies are predicted to be comparable to those of the conventional structures, and even small improvements in the GaInAsN cell may lead to higher multijunction cell efficiencies, especially for high-radiation applications and when cell operating temperature is low.

2-pi-photoproduction is one of the promising reactions to search for baryon resonances that have been predicted but have not yet been observed. The gamma-rho --> rho-pi{sup 0}-pi{sup 0}(CB-ELSA) and the gamma-rho --> rho-pi{sup +}-pi{sup -} (CLAS) data show interesting resonance structures. A partial wave analysis (PWA) has to be done to determine which baryon resonances contribute what their quantum numbers and their relative couplings to the different accessible rho-2-pi-channels and to the photon are. First preliminary PWA-results on the lowest energy rho-pi{sup 0}-pi{sup 0} data (sq rt s<1.8 GeV)look very promising. From an extension of this analysis to higher energies combining the rho-pi{sup 0}-pi{sup 0} and the rho-pi{sup +}-pi{sup -}-data, one can expect; interesting results on resonances decaying into Delta-pi, N-rho, N(pi-pi)s, N*-pi, and Delta*-pi.

The 3rd harmonic 3.9GHz accelerating cavity was proposed to improve the beam performance of the FLASH (TTF/DESY) facility [1]. In the frame of a collaborative agreement, Fermilab will provide DESY with a cryomodule containing a string of four cavities. In addition, a second cryomodule with one cavity will be fabricated for installation in the Fermilab photo-injector, which will be upgraded for the ILC accelerator test facility. The first 9-cell Nb cavities were tested in a vertical setup and they didn't reach the designed accelerating gradient [2]. The main problem was a multipactor in the HOM couplers, which lead to overheating and quenching of the HOM couplers. New HOM couplers with improved design are integrated in the next 9-cell cavities. In this paper we present all results of the vertical tests.

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The two-fluid description is a very successful phenomenological representation of the properties of Helium II. A 3-D model suitable for numerical analysis based on the Landau-Khalatnikov description of Helium II is proposed. In this paper we introduce a system of partial differential equations that is both complete and consistent as well as practical, to be used for a 3-D solution of the flow of Helium II. The development of a 3-D numerical model for Helium II is motivated by the need to validate experimental results obtained by observing the normal component velocity distribution in a Helium II thermal counter-flow using the Particle Image Velocimetry (PIV) technique.

Distributed memory AMR codes provide a special challenge for laser ray-trace modeling. For RAGE we follow the energy-carrying rays through each cell, checking for crossings which require collection a new cell index (1 of 9 in 2D). Density gradients for ray deflections can be calculated 'on the fly.' Substantial excursions must be made from the legacy PIC particle area-weighting approach, but this serves as a useful 1st step. Similarly, IDL now offers a quick graphical rendering, while ENSIGHT graphics beautifully captures the 3D light refraction and deposition.

Interferometric SAR (IFSAR) can be shown to be a special case of 3-D SAR image formation. In fact, traditional IFSAR processing results in the equivalent of merely a super-resolved, under-sampled, 3-D SAR image. However, when approached as a 3-D SAR problem, a number of IFSAR properties and anomalies are easily explained. For example, IFSAR decorrelation with height is merely ordinary migration in 3-D SAR. Consequently, treating IFSAR as a 3-D SAR problem allows insight and development of proper motion compensation techniques and image formation operations to facilitate optimal height estimation. Furthermore, multiple antenna phase centers and baselines are easily incorporated into this formulation, providing essentially a sparse array in the elevation dimension. This paper shows the Polar Format image formation algorithm extended to 3 dimensions, and then proceeds to apply it to the IFSAR collection geometry. This suggests a more optimal reordering of the traditional IFSAR processing steps.

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The DOE Advanced Fuel Cycle Initiative and Generation IV reactor programs are developing new fuel types for use in the current Light Water Reactors and future advanced reactor concepts. The Advanced Gas Reactor program is planning to test fuel to be used in the Next Generation Nuclear Plant (NGNP) nuclear reactor. Preliminary information for assessing performance of the fuel will be obtained from irradiations performed in the Advanced Test Reactor large “B” experimental facility. A test configurations has been identified for demonstrating fuel types typical of gas cooled reactors or fast reactors that may play a role in closing the fuel cycle or increasing efficiency via high temperature operation Plans are to have 6 capsules, each containing 12 compacts, for the test configuration. Each capsule will have its own temperature control system. Passing a helium-neon gas through the void regions between the fuel compacts and the graphite carrier and between the graphite carrier and the capsule wall will control temperature. This design with three compacts per axial level was evaluated for thermal performance to ascertain the temperature distributions in the capsule and test specimens with heating rates that encompass the range of initial heat generation rates.

We report three new structures of mitochondrial respiratory Complex II (succinate ubiquinone oxidoreductase, E.C. 1.3.5.1) at up to 2.1 {angstrom} resolution, with various inhibitors. The structures define the conformation of the bound inhibitors and suggest the residues involved in substrate binding and catalysis at the dicarboxylate site. In particular they support the role of Arg297 as a general base catalyst accepting a proton in the dehydrogenation of succinate. The dicarboxylate ligand in oxaloacetate-containing crystals appears to be the same as that reported for Shewanella flavocytochrome c treated with fumarate. The plant and fungal toxin 3-nitropropionic acid, an irreversible inactivator of succinate dehydrogenase, forms a covalent adduct with the side chain of Arg297. The modification eliminates a trypsin cleavage site in the flavoprotein, and tandem mass spectroscopic analysis of the new fragment shows the mass of Arg 297 to be increased by 83 Da and to have potential of losing 44 Da, consistent with decarboxylation, during fragmentation.

The LHC Schottky observation system is based on traveling wave type high sensitivity pickup structures operating at 4.8 GHz. The choice of the structure and operating frequency is driven by the demanding LHC impedance requirements, where very low impedance is required below 2 GHz, and good sensitivity at the selected band at 4.8 GHz. A sophisticated filtering and triple down -mixing signal processing chain has been designed and implemented in order to achieve the specified 100 dB instantaneous dynamic range without range switching. Detailed design aspects for the complete systems and test results without beam are presented and discussed.

Tevatron Run-II upgrade requires a significant increase of the efficiency and speed of the antiproton transfers from the Accumulator to the Recycler. The goal for the total transfer time is challenging a reduction from 1 hour down to a few minutes. Here we discuss the beam line optics aspects of this project. Results of lattice measurements and optimization are analyzed in terms of transport efficiency and stability.

Fermilab is working on the design of an 8 GeV superconducting RF H{sup -} linac called the Proton Driver. The energy of H{sup -} beam will be an order of magnitude higher than the existing ones. This brings up a number of technical challenges to transport and injection of H{sup -} ions. This paper will focus on the subjects of stripping losses (including stripping by blackbody radiation, field and residual gas) and carbon foil stripping efficiency, along with a brief discussion on other issues such as Stark states lifetime of hydrogen atoms, single and multiple Coulomb scattering, foil heating and stress, radiation activation, collimation and jitter correction, etc.

An 8 GeV superconducting linear accelerator (SCL) has been proposed [1] as a single stage H{sup -} injector into the Main Injector (MI) synchrotron . This would be the highest energy H{sup -} multi-turn injection system in the world. The conceptual design of an injection system has been further refined by addressing transverse phase space painting issues, chicane dipole fields and foil location, foil temperature issues, and initial longitudinal phase space painting simulations. We present the current state of design.

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We report on the serendipitous discovery of the brightest Lyman Break Galaxy (LBG) currently known, a galaxy at z = 2.73 that is being strongly lensed by the z = 0.38 Luminous Red Galaxy (LRG) SDSS J002240.91+143110.4. The arc of this gravitational lens system, which we have dubbed the ''8 o'clock arc'' due to its time of discovery, was initially identified in the imaging data of the Sloan Digital Sky Survey Data Release 4 (SDSS DR4); followup observations on the Astrophysical Research Consortium (ARC) 3.5m telescope at Apache Point Observatory confirmed the lensing nature of this system and led to the identification of the arc's spectrum as that of an LBG. The arc has a spectrum and a redshift remarkably similar to those of the previous record-holder for brightest LBG (MS 1512-cB58, a.k.a ''cB58''), but, with an estimated total magnitude of (g,r,i) = (20.0,19.2,19.0) and surface brightness of ({mu}{sub g}, {mu}{sub r}, {mu}{sub i}) = (23.3, 22.5, 22.3) mag arcsec{sup -2}, the 8 o'clock arc is thrice as bright. The 8 o'clock arc, which consists of three lensed images of the LBG, is 162{sup o}(9.6'') long and has a length-to-width ratio of 6:1. A fourth image of the LBG--a counter-image--can …

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Thin hydrogenated amorphous silicon (a-Si:H) layers deposited by hot-wire chemical vapor deposition (HWCVD) are used as both emitters and back contacts in silicon heterojunction solar cells. Low interface recombination velocity and high open-circuit voltage are achieved by a low substrate temperature (<150 deg C) intrinsic a-Si:H deposition which ensures immediate amorphous silicon deposition. This is followed by deposition of doped a-Si:H at a higher temperature (>200 deg C) which appears to improve dopant activation. With an i/n a-Si:H emitter, we obtain a confirmed efficiency of 17.1% on textured p-type float-zone (FZ) silicon with a screen-printed aluminum back-surface-field (Al-BSF) contact. Employing a-Si:H as both the front emitter and the back contact, we achieve a confirmed efficiency of 17.5%, the highest reported efficiency for a p-type c-Si based heterojunction solar cell.

Muon decay rings are under study as part of an International Scoping Study (ISS) for a future Neutrino Factory. Both isosceles triangle- and racetrack-shaped rings are being considered for a 20 GeV muon energy, but with upgrade potentials of 40 or 50 GeV. Both rings are designed with long straights to optimize directional muon decay. The neutrinos from muon decay pass to one or two distant detectors; the racetrack ring has one very long production straight aligned with one detector while the triangular ring has two straights which can be aligned with two detectors. Decay ring specifications and lattice studies are the primary topic of this paper. Injection, collimation, and the RF system are covered in a second contribution to these proceedings.

This paper summarizes findings during a one-week (27-31 October 2003) site visit to the Thin-Film Technology Test Bed at India's Solar Energy Centre (SEC) near New Delhi. The U.S. and Indian governments signed a Memorandum of Understanding in March 2000 to undertake a 50-50 cost-shared 21-kW thin-film PV technology validation project to evaluate the performance of thin-film photovoltaic (PV) modules under Indian climatic conditions. This project benefits Indian researchers by giving them experience with cost-effective PV materials, and it benefits the United States because data will be sent to the appropriate U.S. thin-film PV manufacturers for evaluation and analysis. During the visit, NREL personnel engaged in technical discussions regarding thin-film PV technologies with Ministry of Non-Conventional Energy Sources engineers and scientists. Issues included inspecting the newly constructed arrays, discussing better methods of electrically loading the PV arrays, taking I-V traces, and gathering baseline I-V data.

The radio frequency quadrupole (RFQ) accelerator began as 'The ion linear accelerator with space-uniform strong focusing' conceived by I. M. Kapchinskii and V. A. Teplyakove. In 1979, R. H. Stokes, K. R. Crandall, J. E. Stovall and D. A. Swenson gave this concept the name RFQ. And by 1983, at least 15 laboratories throughout the world were working on various FWQ designs. In the early years, there were many types of geometry considered for the RFQ, but only a few types have survived. The two cavity geometries now used in almost all RFQs are the 4-vane and 4-rod structures. The 4-vane structure is the most popular because its operating frequency range (80 to -500 MHz) is suitable for light ions. Heavy ions require low frequencies (below 200 MHz). Because the 4-rod structure has smaller transverse dimensions than a 4-vane RFQ at the same frequency, the 4-rod RFQ is often preferred for these applications. This paper will describe how the RFQ accelerates and focuses the beam. The paper also discusses some of the important technical advances in designing and building RFQs.