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Jones B.,Sandia National Laboratories | Ampleford D.J.,Sandia National Laboratories | Vesey R.A.,Sandia National Laboratories | Cuneo M.E.,Sandia National Laboratories | And 13 more authors.
Physical Review Letters | Year: 2010

An indirect drive configuration is proposed wherein multiple compact Z-pinch x-ray sources surround a secondary hohlraum. Planar compact wire arrays allow reduced primary hohlraum surface area compared to cylindrical loads. Implosions of planar arrays are studied at up to 15 TW x-ray power on Saturn with radiated yields exceeding the calculated kinetic energy, suggesting other heating paths. X-ray power and yield scaling studied from 1-6 MA motivates viewfactor modeling of four 6-MA planar arrays producing 90 eV radiation temperature in a secondary hohlraum. © 2010 The American Physical Society.

Altman S.J.,Sandia National Laboratories | Jensen R.P.,Sandia National Laboratories | Cappelle M.A.,University of Texas at El Paso | Sanchez A.L.,Sandia National Laboratories | And 3 more authors.
Desalination | Year: 2012

A pilot study was conducted to determine whether membrane treatment on a side stream of recirculating cooling-tower water could reduce overall water usage and discharge. The treated permeate was returned to the cooling tower while the concentrate was discharged to the sanitary sewer. Flow rates, pressures and water chemistry were monitored. The pilot demonstrated potential substantial water savings. Maximum make-up water and discharge reduction were 16% and 49%, respectively. As high as possible permeate recovery is needed to maximize water conservation. Silica scaling on the membranes limited water savings in this pilot. Development of membranes with a solute-rejection capacity less than the 92% average of the membranes used in the pilot would assist in optimizing water savings. Decreased water outlays compensated for the additional energy used by membrane treatment. Scaling control is critical for economic operation. © 2011 Elsevier B.V.

Youchison D.L.,Sandia National Laboratories | Ulrickson M.A.,Sandia National Laboratories | Bullock J.H.,LMATA Government Services LLC
Proceedings - Symposium on Fusion Engineering | Year: 2011

Plasma disruptions and Edge Localized Modes (ELMS) may result in transient heat fluxes as high as 5 MW/m2 on portions of the ITER first wall (FW). To accommodate these heat loads, roughly 50% of the first wall will have Enhanced Heat Flux (EHF) panels equipped with water-cooled hypervapotron heat sinks. © 2011 IEEE.

Tandon R.,Sandia National Laboratories | Paliwal B.,Georgia Institute of Technology | Gibson C.,LMATA Government Services LLC
Philosophical Magazine | Year: 2013

Ring crack initiation loads on glass, using spherical Tungsten carbide (WC) and glass (G) indenters, are measured and analysed. Our measurements demonstrate that environmental humidity plays a key role in determining the load to fracture; experiments conducted without controlling this variable cannot be used to obtain material properties. The role of friction is explicitly considered for dissimilar (WC-G) elastic contacts. For this material pair, the stresses at fracture are well described by a boundary lubrication value of friction coefficient. The fracture loads are used in a fracture-mechanics formulation to calculate crack sizes on glass surfaces. The searched-area concept for dissimilar contacts is described, and used to provide crack density values for these surfaces. © 2013 Taylor & Francis Group, LLC.

Boye R.R.,Sandia National Laboratories | Peters D.W.,Sandia National Laboratories | Wendt J.R.,Sandia National Laboratories | Shul R.J.,Sandia National Laboratories | And 6 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010

Resonant subwavelength gratings have proven to be excellent devices for producing narrow resonances useful for filtering applications. In this paper we discuss the use of RSGs in a rotary position encoder intended for use in harsh environments. To avoid problems with routing electrical signals to the encoder, a single fiber optic connection is used to address the device with multiplexed wavelengths corresponding to position bits. Each wavelength has a corresponding RSG that is patterned in the appropriate position locations. A demonstration device utilizing RSGs with TiO2 and SiO2 films on a silicon substrate will be presented. The design and modeling effort provided several RSGs with resonances addressable by a single tunable laser source. Since multimode fiber is used to route the optical signals, the gratings were designed to be polarization insensitive. Additionally, the individual RSGs accommodate significant wavelength shifts to simplify the integration of the encoder system. The fabrication of the devices was based on electron beam lithography and details of this work will be presented. Measurements of the individual RSGs as well as a demonstration of the determination of rotary position using these gratings will be shown. © 2010 Copyright SPIE - The International Society for Optical Engineering.

Bellum J.,Sandia National Laboratories | Bellum J.,Sandia Staffing Alliance LLC | Kletecka D.,Sandia National Laboratories | Kletecka D.,LMATA Government Services LLC | And 7 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010

Sandia's Large Optics Coating Operation has extensive results of laser induced damage threshold (LIDT) testing of its anti-reflection (AR) and high reflection coatings on substrates pitch polished using ceria and washed in a process that includes an alumina wash step. The purpose of the alumina wash step is to remove residual polishing compound to minimize its role in laser damage. These LIDT tests are for multi longitudinal mode, ns class pulses at 1064 nm and 532 nm (NIF-MEL protocol) and mode locked, sub-ps class pulses at 1054 nm (Sandia measurements), and show reasonably high and adequate laser damage resistance for coatings in the beam trains of Sandia's Z-Backlighter terawatt and petawatt lasers. An AR coating in addition to coatings of our previous reports confirms this with LIDTs of 33.0 J/cm2 for 3.5 ns pulses and 1.8 J/cm2 for 350 fs pulses. In this paper, we investigate both ceria and zirconia in doublesided polishing (common for large flat Z-Backlighter laser optics) as they affect LIDTs of an AR coating on fused silica substrates washed with or without the alumina wash step. For these AR coated, double-sided polished surfaces, ceria polishing in general affords better resistance to laser damage than zirconia polishing and laser damage is less likely with the alumina wash step than without it. This is supported by specific results of laser damage tests with 3.5 ns, multi longitudinal mode, single shot pulses at 1064 nm and 532 nm, with 7.0 ns, single and multi longitudinal mode, single and multi shot pulses at 532 nm, and with 350 fs, mode-locked, single shot pulses at 1054 nm. © 2010 Copyright SPIE - The International Society for Optical Engineering.

Youchison D.L.,Sandia National Laboratories | Ulrickson M.A.,Sandia National Laboratories | Bullock J.H.,LMATA Government Services LLC
IEEE Transactions on Plasma Science | Year: 2012

Plasma disruptions and edge localized modes can result in transient heat fluxes as high as 5 MW/m 2 on portions of a tokamak reactor first wall (FW). To accommodate these heat loads, the FW will likely use water-cooled hypervapotron heatsinks to enhance the heat transfer. In this article, we present the results of a computational fluid dynamics (CFD) study using 70 °C inlet water at 2.7 MPa to investigate the tooth height and backchannel depth of 50-mm-wide hypervapotrons with 6-mm-pitch and 3-mm side slots. We compare a popular design with 4-mm-high teeth and a 5-mm backchannel to a more optimal case with 2-mm-high teeth and a 3-mm backchannel under nominal heat loads (0.5 MW/m 2) on a 100-mm-heated length and under single-phase flow conditions. Better heat transfer in the latter case and the smaller backchannel permit a factor of two reduction in the required mass flow while maintaining the same beryllium armor surface temperatures near 130°C. The shallow teeth and smaller backchannel allow the 40 fingers in a typical panel to flow in parallel and simplify the water circuit. A comparison of the two hypervapotron designs during off-normal loading (5.0 MW/m 2) and two-phase flow then follows. The design with 2-mm teeth has a 3.5% higher beryllium surface temperature of 648°C and reduces the critical heat flux (CHF) by ∼2%. Hypervapotron width also plays a role in heat transfer and CHF. CFD results for 36 and 70 mm wide hypervapotrons compared to the 50-mm case reveal similar thermal performance at low heat flux, but a reduction in CHF with increasing width. This study highlights the necessary compromise between design margin during transient events, effective heat transfer under nominal conditions, limitations on finger width, and the simplicity needed in the water circuit design. © 2012 IEEE.

Skogen E.J.,Sandia National Laboratories | Vawter G.A.,Sandia National Laboratories | Tauke-Pedretti A.,Sandia National Laboratories | Peake G.M.,Sandia National Laboratories | And 4 more authors.
2010 23rd Annual Meeting of the IEEE Photonics Society, PHOTINICS 2010 | Year: 2010

We demonstrate an optical gate architecture using electro-absorption modulator/photodiode pairs to perform AND and NOT functions. Optical bandwidth for both gates reach 40 GHz. Also shown are AND gate waveforms at 40 Gbps. ©2010 IEEE.

Altman S.J.,Sandia National Laboratories | McGrath L.K.,LMATA Government Services LLC | Jones H.D.T.,Sandia National Laboratories | Sanchez A.,LMATA Government Services LLC | And 4 more authors.
Water Research | Year: 2010

Micromixers, UV-curable epoxy traces printed on the surface of a reverse osmosis membrane, were tested on a cross-flow system to determine their success at reducing biofouling. Biofouling was quantified by measuring the rate of permeate flux decline and the median bacteria concentration on the surface of the membrane (as determined by fluorescence intensity counts due to nucleic acid stains as measured by hyperspectral imaging). The micromixers do not appear to significantly increase the pressure needed to maintain the same initial permeate flux and salt rejection. Chevrons helped prevent biofouling of the membranes in comparison with blank membranes. The chevron design controlled where the bacteria adhered to the membrane surface. However, blank membranes with spacers had a lower rate of permeate flux decline than the membranes with chevrons despite having greater bacteria concentrations on their surfaces. With better optimization of the micromixer design, the micromixers could be used to control where the bacteria will adhere to the surface and create a more biofouling resistant membrane that will help to drive down the cost of water treatment. © 2010 Elsevier Ltd.

Tauke-Pedretti A.,Sandia National Laboratories | Vawter G.A.,Sandia National Laboratories | Skogen E.J.,Sandia National Laboratories | Peake G.,Sandia National Laboratories | And 6 more authors.
IEEE Photonics Technology Letters | Year: 2011

We present a photonic integrated circuit (PIC) composed of two strongly coupled distributed Bragg reflector (DBR) lasers. This PIC utilizes the dynamics of mutual injection locking to increase the relaxation resonance frequency from 3 GHz to beyond 30 GHz. Mutual injection-locking and external injection-locking operation are compared. © 2011 IEEE.

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