Absorptance Measurements of Optical Coatings - A Round Robin (open access)

Absorptance Measurements of Optical Coatings - A Round Robin

An international round robin study was conducted on the absorption measurement of laser-quality coatings. Sets of optically coated samples were made by a ''reactive DC magnetron'' sputtering and an ion beam sputtering deposition process. The sample set included a high reflector at 514 nm and a high reflector for the near infrared (1030 to 1318 nm), single layers of silicon dioxide, tantalum pentoxide, and hafnium dioxide. For calibration purposes, a sample metalized with hafnium and an uncoated, superpolished fused silica substrate were also included. The set was sent to laboratory groups for absorptance measurement of these coatings. Whenever possible, each group was to measure a common, central area and another area specifically assigned to the respective group. Specific test protocols were also suggested in regards to the laser exposure time, power density, and surface preparation.
Date: October 26, 2000
Creator: Chow, R; Taylor, J R; Wu, Z L; Boccara, C A; Broulik, U; Commandre, M et al.
System: The UNT Digital Library
Analysis of Bulk DKDP Damage Distribution, Obscuration and Pulse Length Dependence (open access)

Analysis of Bulk DKDP Damage Distribution, Obscuration and Pulse Length Dependence

Recent LLNL experiments reported elsewhere at this conference explored the pulselength dependence of 351 nm bulk damage incidence in DKDP. The results found are consistent, in part, with a model in which a distribution of small bulk initiators is assumed to exist in the crystal and the damage threshold is determined by reaching a critical temperature. The observed pulse length dependence can be explained as being set by the most probable defect capable of causing damage at a given pulselength. Analysis of obscuration in side illuminated images of the damaged region yields estimates of the damage site distributions that are in reasonable agreement with the distributions experimentally directly estimated.
Date: December 15, 2000
Creator: Feit, M D; Rubenchik, A M & Runkel, M
System: The UNT Digital Library
Fabrication and Test Results of a Nb3Sn Superconducting Racetrack Dipole Magnet (open access)

Fabrication and Test Results of a Nb3Sn Superconducting Racetrack Dipole Magnet

A 'proof-of-principle' Nb{sub 3}Sn superconducting dual-bore dipole magnet was built from racetrack coils, as a first step in a program to develop an economical, 15 Tesla, accelerator-quality magnet. The mechanical design and magnet fabrication procedures are discussed. No training was required to achieve temperature-dependent plateau currents, despite several thermal cycles that involved partial magnet disassembly and substantial pre-load variations. Subsequent magnets are expected to approach 15 Tesla with substantially improved conductor.
Date: February 6, 2000
Creator: Chow, K.; Dietderich, D. R.; Gourlay, S. A.; Gupta, R.; Harnden, W.; Lietzke, A. F. et al.
System: The UNT Digital Library
Conductor Development for High Field Dipole Magnets (open access)

Conductor Development for High Field Dipole Magnets

Historically, improvements in dipole magnet performance have been paced by improvements in the superconductor available for use in these magnets. The critical conductor performance parameters for dipole magnets include current density, piece length, effective filament size, and cost. Each of these parameters is important for efficient, cost effective dipoles, with critical current density being perhaps the most important. Several promising magnet designs for the next hadron collider or a muon collider require fields of 12 T or higber, i.e. beyond the reach of NbTi. The conductor options include Nb{sub 3}Sn, Nb{sub 3}Al, or the high temperature superconductors. Although these conductors have the potential to provide the combination of performance and cost required, none of them have been developed sufficiently at this point to satisfy all the requirements. This paper will review the status of each class of advanced conductor and discuss the remaining problems that require solutions before these new conductors can be considered as practical. In particular, the plans for a new program to develop Nb{sub 3}Sn and Nb{sub 3}Al conductors for high energy physics applications will be presented. Also, the development of a multikiloamp Bi-2212 cable for dipole magnet applications will be reported.
Date: March 1, 2000
Creator: Scanlan, R. M.; Dietderich, D. R. & Higley, H. C.
System: The UNT Digital Library
Fabrication and testing of Rutherford-type cables for react and wind accelerator magnets (open access)

Fabrication and testing of Rutherford-type cables for react and wind accelerator magnets

A common coil design for a high-field accelerator dipole magnet using a Nb{sub 3}Sn cable with the React-and-Wind approach is pursued by a collaboration between Fermilab and LBNL. The design requirements for the cable include a high operating current so that a field of 10-11 T can be produced, together with a low critical current degradation due to bending around a 90 mm radius. A program, using ITER strands of the internal tin type, was launched to develop the optimal cable design for React-and-Wind common coil magnets. Three prototype cable designs, all 15 mill wide, were fabricated: a 41-strand cable with 0.7 mm diameter strands; a 57-strand cable with 0.5 mm diameter strands; and a 259 strand multi-level cable with a 6-around-1 sub-element using 0.3 mm diameter wire. Two versions of these cables were fabricated: one with no core and one with a stainless steel core. Additionally, the possibility of a wide (22 mm) cable made from 0.7 mm strand was explored. This paper describes the first results of the cable program including reports on cable fabrication and reaction, first winding tests and first results of the measurement of the critical current degradation due to cabling and bending.
Date: September 11, 2000
Creator: Bauer, P.; Ambrosio, G.; Andreev, N.; Barzi, E.; Dietderich, D.; Ewald, K. et al.
System: The UNT Digital Library
AZU-1: A Candidate Breast Tumor Suppressor and Biomarker for Tumor Progression (open access)

AZU-1: A Candidate Breast Tumor Suppressor and Biomarker for Tumor Progression

To identify genes misregulated in the final stages of breast carcinogenesis, we performed differential display to compare the gene expression patterns of the human tumorigenic mammary epithelial cells, HMT-3522-T4-2, with those of their immediate premalignant progenitors, HMT-3522-S2. We identified a novel gene, called anti-zuai-1 (AZU-1), that was abundantly expressed in non- and premalignant cells and tissues but was appreciably reduced in breast tumor cell types and in primary tumors. The AZU-1 gene encodes an acidic 571-amino-acid protein containing at least two structurally distinct domains with potential protein-binding functions: an N-terminal serine and proline-rich domain with a predicted immunoglobulin-like fold and a C-terminal coiled-coil domain. In HMT-3522 cells, the bulk of AZU-1 protein resided in a detergent-extractable cytoplasmic pool and was present at much lower levels in tumorigenic T4-2 cells than in their nonmalignant counterparts. Reversion of the tumorigenic phenotype of T4-2 cells, by means described previously, was accompanied by the up-regulation of AZU-1. In addition, reexpression of AZU-1 in T4-2 cells, using viral vectors, was sufficient to reduce their malignant phenotype substantially, both in culture and in vivo. These results indicate that AZU-1 is a candidate breast tumor suppressor that may exert its effects by promoting correct tissue morphogenesis.
Date: February 4, 2000
Creator: Chen, Huei-Mei; Schmeichel, Karen L; Mian, I. Saira; Lelie`vre, Sophie; Petersen, Ole W & Bissell, Mina J
System: The UNT Digital Library
Design of Racetrack Coils for High Field Dipole Magnets (open access)

Design of Racetrack Coils for High Field Dipole Magnets

The magnet group at LBNL is currently in the process of developing high-field accelerator magnets for use in future colliders. One of the primary challenges is to provide a design which is cost-effective and simple to manufacture, at the same time resulting in good training performance and field quality adequate for accelerator operation. Recent studies have focused on a racetrack geometry that has the virtues of simplicity and conductor compatibility. The results have been applied to the design of a series of prototype high-field magnets based on Nb{sub 3}Sn conductor.
Date: September 8, 2000
Creator: Sabbi, G.; Caspi, S.; Gourlay, S. A.; Hafalia, R.; Jackson, A.; Lietzke, A. et al.
System: The UNT Digital Library
Semileptonic Form-factors from B-> K* gamma Decays in the Large Energy Limit (open access)

Semileptonic Form-factors from B-> K* gamma Decays in the Large Energy Limit

Making use of the measurement of the $B\to K^*\gamma$ branching ratio together with the relations following from the limit of high recoil energy, we obtain stringent constraints on the values of the form-factors entering in heavy-to-light $B\to V\ell\ell'$ processes such as $B\to K^*\ell^+\ell^-$, $B\to K^*\nu \bar\nu$ and $B\to \rho\ell\nu$ decays. We show that the symmetry predictions, when combined with the experimental information on radiative decays, specify a severely restricted set of values for the vector and axial-vector form-factors evaluated at zero momentum transfer, $q^2=0$. These constraints can be used to test model calculations and to improve our understanding of the $q^2$-dependence of semileptonic form-factors. We stress that the constraints remain stringent even when corrections are taken into account.
Date: November 21, 2000
Creator: Burdman, Gustavo & Hiller, Gudrun
System: The UNT Digital Library
Anti-B-B Mixing Constrains Topcolor-Assisted Technicolor (open access)

Anti-B-B Mixing Constrains Topcolor-Assisted Technicolor

We argue that extended technicolor augmented with topcolor requires that all mixing between the third and the first two quark generations resides in the mixing matrix of left-handed down quarks. Then, the anti-B_d--B_d mixing that occurs in topcolor models constrains the coloron and Z' boson masses to be greater than about 5 TeV. This implies fine tuning of the topcolor couplings to better than 1percent.
Date: December 6, 2000
Creator: Burdman, Gustavo; Lane, Kenneth & Rador, Tonguc
System: The UNT Digital Library
Dynamics of Supersymmetric SU(n_c) and USp(2n_c) Gauge Theories (open access)

Dynamics of Supersymmetric SU(n_c) and USp(2n_c) Gauge Theories

We study dynamical flavor symmetry breaking in the context of a class of N=1 supersymmetric SU(n_c) and USp(2 n_c) gauge theories, constructed from the exactly solvable N=2 theories by perturbing them with small adjoint and generic bare hypermultiplet (quark) masses. We find that the flavor U(n_f) symmetry in SU(n_c) theories is dynamically broken to $U(r)\times U(n_f-r)$ groups for $n_f \leq n_c$. In the r=1 case the dynamical symmetry breaking is caused by the condensation of monopoles in the $\underlinen_f$ representation. For general r, however, the monopoles in the $\underline_n_fC_r$ representation, whose condensation could explain the flavor symmetry breaking but would produce too-many Nambu--Goldstone multiplets, actually"break up'' into"magnetic quarks'' which condense and induce confinement and the symmetry breaking. In USp(2n_c) theories with $n_f\leq n_c + 1$, the flavor SO(2n_f) symmetry is dynamically broken to U(n_f), but with no description in terms of a weakly coupled local field theory. In both SU(n_c) and USp(2 n_c) theories, with larger numbers of quark flavors, besides the vacua with these properties, there exist also vacua with no flavor symmetry breaking.
Date: January 7, 2000
Creator: Carlino, Giuseppe; Konishi, Kenichi & Murayama, Hitoshi
System: The UNT Digital Library
MSW Effects in Vacuum Oscillations (open access)

MSW Effects in Vacuum Oscillations

We point out that for solar neutrino oscillations with the mass-squared difference of Delta m^2 ~;; 10^-10 - 10^-9 eV^2, traditionally known as"vacuum oscillation'' range, the solar matter effects are non-negligible, particularly for the low energy pp neutrinos. One consequence of this is that the values of the mixing angle theta and pi/2-theta are not equivalent, leading to the need to consider the entire physical range of the mixing angle 0<=theta<=pi/2 when determining the allowed values of the neutrino oscillation parameters.
Date: February 6, 2000
Creator: Friedland, Alexander
System: The UNT Digital Library
Revealing myths about people, energy and buildings (open access)

Revealing myths about people, energy and buildings

In this essay we take a closer look at some energy myths, focusing on the ways energy professionals and the public alike, talk, write and teach about how energy affects the way in which we design, operate, retrofit and inhabit buildings. What myths about people, energy and buildings are current today? Who tells these myths and why do we believe them? How do myths affect our behavior? Myths are a way of understanding the world we live in. They may represent incomplete understanding, or be based on premises that are scientifically not valid, but they help us understand and explain how the world works, and we shape our behavior accordingly.
Date: May 1, 2000
Creator: Diamond, R. & Moezzi, M.
System: The UNT Digital Library
BAs-GaAs Semiconductor Alloys as a Photovoltaic Alternative to Nitride Alloys (open access)

BAs-GaAs Semiconductor Alloys as a Photovoltaic Alternative to Nitride Alloys

Nitrogen alloyed III-V semiconductor compounds have been intensely studied in recent years due to unusual effects caused by nitrogen alloying. These effects are exploited in band gap engineering for specific applications such as solar cells and blue lasers.
Date: January 1, 2000
Creator: Hart, G. L. W. & Zunger, A.
System: The UNT Digital Library
Small-Angle Neutron Scattering Studies of a-Si:H and a-Si:D (open access)

Small-Angle Neutron Scattering Studies of a-Si:H and a-Si:D

The heterogeneity of hydrogen and deuterium on the nanometer scale has been probed by samll-angle neutron scattering (SANS) from a-Si:H and a-Si:D films. Films were depsoited by two techniques, plasma-enhanced chemical vapor deposition (PECVD) and hot-wire chemical vapor deposition (HWCVD) using conditions that yield high quality films and devices.
Date: January 1, 2000
Creator: Williamson, D. L.; Marr, D. W. M.; Nelson, B. P.; Iwaniczko, E.; Yang, J.; Yan, B. et al.
System: The UNT Digital Library
Structural Ordering and its Correlation to the Optoelectronic Properties of a-Si:H Films (open access)

Structural Ordering and its Correlation to the Optoelectronic Properties of a-Si:H Films

Magnetic susceptibility was suggested theoretically to be sensitive to the overall structural order of a-Si:H and is measured precisely for various a-Si:H thin films using a new technique.
Date: January 1, 2000
Creator: Baugh, J.; Han, D.; Kleinhammes, A.; Wang, Q. & Wu, Y.
System: The UNT Digital Library
Procedures at NREL for Evaluating Multijunction Concentrator Cells (open access)

Procedures at NREL for Evaluating Multijunction Concentrator Cells

The procedures for evaluating the performance of multijunctiion-concentrator cells at the National Renewable Energy Laboratory are described. The accurate measurement of the performance of multijunction cells requires accurate relative-quantum-efficiency-measurements, "matched" reference cells, and a spectrally adjustable solar simulator.
Date: January 1, 2000
Creator: Moriarty, T. & Emery, K.
System: The UNT Digital Library
Research Needs of c-Si Technology Required to Meet Roadmap Milestones (open access)

Research Needs of c-Si Technology Required to Meet Roadmap Milestones

In this paper, we examine the areas in c-Si growth, materials, and processing that require improvement through research to overcome barriers to the implementation of the PV Roadmap's Si goals.
Date: January 1, 2000
Creator: Ruby, D. S.; Ciszek, T. & Sopori, B.
System: The UNT Digital Library
Performance Assessment Analyses Unique to Department of Energy Spent Nuclear Fuel (open access)

Performance Assessment Analyses Unique to Department of Energy Spent Nuclear Fuel

This paper describes the iterative process of grouping and performance assessment that has led to the current grouping of the U.S. Department of Energy (DOE) spent nuclear fuel (SNF). The unique sensitivity analyses that form the basis for incorporating DOE fuel into the total system performance assessment (TSPA) base case model are described. In addition, the chemistry that results from dissolution of DOE fuel and high level waste (HLW) glass in a failed co-disposal package, and the effects of disposal of selected DOE SNF in high integrity cans are presented.
Date: June 1, 2000
Creator: Loo, Henry Hung Yiu & Duguid, J. O.
System: The UNT Digital Library
Effects of Surface Composition on CdTe/CdS Device Performance (open access)

Effects of Surface Composition on CdTe/CdS Device Performance

The atomic composition of the back surface of the CdTe layer in a CdTe/CdS photovoltiac (PV) device has a significant influence on the quality of the electrical contact to this layer. This paper reports the results of a systematic study that correlates the composition of the back surface with pre-contact processing and device performance.
Date: January 1, 2000
Creator: Levi, D.; Albin, D. & King, D.
System: The UNT Digital Library
Micro-PL Studies of Polycrustalline CdS/CdTe Interfaces (open access)

Micro-PL Studies of Polycrustalline CdS/CdTe Interfaces

We describe a technique of photoluminescence measurements with a resolutiion of microns. This technique is applied to examine the CdS/CdTe interface of CdTe solar cells.
Date: January 1, 2000
Creator: Dhere, R.; Cheong, M.; Smith, S.; Albin, D.; Mascarenhas, A. & Gessert, T. A.
System: The UNT Digital Library
Photothermal Stability of Various Module Encapsulants and Effects of Superstrate and Substrate Materials Studied for PVMaT Sources (open access)

Photothermal Stability of Various Module Encapsulants and Effects of Superstrate and Substrate Materials Studied for PVMaT Sources

This paper briefs the photothermal reliability studies we conducted on different encapsulation materials for some U.S. PV companies that are subcontractors of the Photovoltaic Manufacturing Technology (PVMaT) program.
Date: January 1, 2000
Creator: Pern, F. J. & Glick, S. H.
System: The UNT Digital Library
Procedures for Determining the Performance of Stand-Alone Photovoltaic Systems (open access)

Procedures for Determining the Performance of Stand-Alone Photovoltaic Systems

Standard test procedures are being developed to assess the performance of stand-alone photovoltaic (PV) systems. This paper will present an overview of the latest procedure.
Date: January 1, 2000
Creator: McNutt, P.; Kroposki, B.; Hansen, R. & DeBlasio, R.
System: The UNT Digital Library
Comparison of Dye-Sensitized Rutile- and Anatase-Based TiO2 Solar Cells (open access)

Comparison of Dye-Sensitized Rutile- and Anatase-Based TiO2 Solar Cells

The objective of this work is to develop and optimize the new dye-sensitized solar cell technology. In view of the infancy of rutile material development for solar cells, the PV response of the dye-sensitized rutile-based solar cell is remarkably close to that of the anatase-based cell.
Date: January 1, 2000
Creator: Park, N. G.; van de Lagemaat, J. & Frank, A. J.
System: The UNT Digital Library
Confinement and flavor symmetry breaking via monopolecondensation (open access)

Confinement and flavor symmetry breaking via monopolecondensation

We discuss dynamics of N=2 supersymmetric SU(n_c) gaugetheories with n_f quark hypermultiplets. Upon N=1 perturbation ofintroducing a finite mass for the adjoint chiral multiplet, we show thatthe flavor U(n_f) symmetry is dynamically broken to U(r) times U(n_f-r),where r\leq [n_f/2]is an integer. This flavor symmetry breaking occursdue to the condensates of magnetic degrees of freedom which acquireflavor quantum numbers due to the quark zero modes. We briefly comment onthe USp(2n_c) gauge theories. This talk is based on works with GiuseppeCarlino and Ken Konishi, hep-th/0001036 and hep-th/0005076.
Date: September 19, 2000
Creator: Murayama, Hitoshi
System: The UNT Digital Library