John Rowley

Preparation of Conductive Buffer Architectures Based on IBAD-TiN

Ion beam assisted deposition (IBAD) was used in combination with pulsed laser deposition to develop a conductive biaxially textured buffer architecture based on IBAD-TiN for coated conductor applications. Highly textured TiN layers were prepared on Hastelloy substrates with an amorphous Y2O3 seed layer. The cube textured nucleation layer was preserved to higher thicknesses using homoepitaxial growth. A double layer of Au and Ir was used to reduce the lattice misfit between TiN and YBCO. Finally, a 120 nm thick Nb:SrTiO3 layer was deposited to ensure the epitaxial growth of the superconducting YBCO layer at higher oxygen pressures. In-situ RHEED measurements revealed an undisturbed epitaxial growth of the complete buffer layer stack. The buffered tape was successfully used for the deposition of a 300 nm thick YBa2Cu3O7-x layer, showing an in-plane FWHM value of 7.2deg and a critical temperature T c of about 88 K. The results are promising for the development of a completely electrical conductive buffer architecture based on the IBAD approach.

Experiments Using Continuous Fabrication of IBAD-MgO Based Coated Conductors

The reel-to-reel coated conductor facilities at Los Alamos National Laboratory enable electropolishing, ion-beam assist deposited (IBAD) MgO texturing, buffer layer deposition, REBaCuO pulsed laser deposition and position dependent critical current measurements, all in a continuous fashion. These systems allow development of long-length coated conductors as well as high-throughput experimentation by linear combinatorial design. We discuss how we utilize the deposition systems to obtain thickness profiles and study the properties of the films as a function of thickness. In particular we demonstrate that texture improves with thickness of epitaxial layers, whether homoepitaxial MgO or heteroepitaxial YBCO.

Stacks of YBCO Films Using Multiple IBAD Templates

In this paper we present initial results on growing YBCO/IBAD-MgO/YBCO stacks. Amorphous Y2O3 layers, deposited by sol-gel, are used to level the YBCO surface. Since the YBCO films prepared by pulsed laser deposition are relatively rough, preparing a smooth surface on top of YBCO for IBAD texturing is a major challenge for this structure. For all substrates studied-polished and unpolished metal tape and YBCO - we were able to reduce the roughness of the substrate using the sol-gel layer, with multiple coatings being more effective. First it is demonstrated that high quality YBCO films can be deposited on sol-gel-Y2O3/IBAD-MgO templates. Second it is shown that the sol-gel and the IBAD process do not affect the superconducting properties of the underlying YBCO film. Finally, a superconducting YBCO bilayer stack is demonstrated. Improvements in the properties of the top YBCO layer is expected when the surface roughness is reduced further for deposition of subsequent IBAD-textured layers. This new technology should enable novel designs of coated conductors for reduced AC losses and increased Je.

Experience from Crystalline Rock Drilling and Technology Directions for Effective Ultra-Deep Coring and Drilling

This paper sets forth the experience of sixteen selected drilling projects that have penetrated deep crystalline rocks for hot dry rock geothermal investigations, hydrothermal geothermal energy exploration, and petroleum exploration. The development of recommended directions for effective deep crustal scientific drilling projects was based on these drilling data and the views of a number of drilling technology experts.

Directional Drilling Equipment and Techniques for Deep, Hot Granite Wells

Conventional directional drilling technology has been extended and modified to drill the first well of a subsurface geothermal energy extraction system at the Fenton Hill, New Mexico, Hot dry Rock (HDR) experimental site. Completing the first of a two-wellbore HDR system has resulted in the definition of operational limitations of many conventional directional drilling tools, instrumentation and techniques. The successful completion of the first wellbore, Energy Extraction Well No. 2 (EE-2), to a measured depth of 15,300 ft (4.7 km) in granite reservoir rock with a bottomhole temperature of 530/sup 0/F (275/sup 0/C) required the development of a new high temperature downhole motor and modification of existing wireline-conveyed steering tool systems. Conventional rotary-driven directional assemblies were successfully modified to accommodate the very hard and abrasive rock encountered while drilling nearly 8500 ft (2.6 km) of directional hole to a final inclination of 35/sup 0/ from the vertical at a controlled azimuthal orientation.

Equipment For Drilling And Fracturing Hot Granite Wells

Drilling and fracturing requirements for deep, deviated geothermal wells in very hot granite create several severe equipment problems. These problems result from the very high temperatures and extremely hard rock of the geothermal reservoir under development. Previous drilling of 2 wells to 10,000-ft (3 km) depths and 400 F (200 C) at the Fenton Hill hot-dry-rock (HDR) geothermal experimental site have defined these problems and directed efforts toward solutions. These solutions have required extensions of current drilling methods and development of new tools and hardware. This study describes the requirements for the hot hole tools, the new equipment, and status of tests of the tools that have been developed for drilling and open-hole fracturing operations for use in 14,500-ft (4.4 km) deep, 527 F (275 C) bottom-hole temperature wells. The relationships and potential applications of these drilling equipment advances to drilling of natural (hydrothermal) geothermal reservoirs are presented. 17 references.

The application of visible absorption spectroscopy to the analysis of uranium in aqueous solutions

Through assay analysis into an excess of 1M H2SO4 at fixed temperature a technique has been developed for uranium concentration analysis by visible absorption spectroscopy over an assay concentration range of 1.8-13.4mgU/g. Once implemented for a particular spectrophotometer and set of spectroscopic cells this technique promises to provide more rapid results than a classical method such as Davies-Gray (DG) titration analysis. While not as accurate and precise as the DG method, a comparative analysis study reveals that the spectroscopic method can analyze for uranium in well characterized uranyl(VI) solution samples to within 0.3% of the DG results. For unknown uranium solutions in which sample purity is less well defined agreement between the developed spectroscopic method and DG analysis is within 0.5%. The technique can also be used to detect the presence of impurities that impact the colorimetric analysis, as confirmed through the analysis of ruthenium contamination. Finally, extending the technique to other assay solution, 1M HNO3, HCl and Na2CO3, has also been shown to be viable. Of the four aqueous media the carbonate solution yields the largest molar absorptivity value at the most intensely absorbing band, with the least impact of temperature.

Development of conducting buffer architectures using cube textured IBAD-TiN layers

Ion-beam assisted deposition (IBAD) offers the possibility to prepare thin textured films on amorphous or non-textured substrates. In particular, the textured nucleation of TiN is promising for the development of a conducting buffer layer architecture for YBCO coated conductors based on the IBAD approach. Accordingly, cube textured IBAD-TiN layers have been deposited reactively using pulsed laser deposition on Si/Si 3 N 4 substrates as well as on polished Hastelloy tapes using different amorphous seed layers. Metallic buffer layers such as Au, Pt or Ir were grown epitaxially on top of the TiN layer showing texture values similar to the IBAD layer. Smooth layers were obtained using a double layer of Au/Pt or Au/Ir. Biaxially textured YBCO layers were achieved using SrRuO 3 or Nb-doped SrTiO 3 as a conductive oxide cap layer. Finally, different amorphous conducting seed layers were applied for the IBAD-TiN process. Highly textured TiN films were achieved on amorphous Ta 0.75 Ni 0.25 layers showing a similar in-plane orientation of about 8° as on standard seed layers.

Deep Drilling Technology for Hot Crystalline Rock

This paper recounts the experience of deep drilling into hot crystalline rock by the Fenton Hill HDR project (Fig. 1) to illustrate that such operations for scientific purposes are indeed possible. The discussion is intended to provide general guidance for project planning for future scientific drilling operations. The discussion also supports the thesis that experience from past ambitious drilling projects can aid in the design of the strategy of drilling and coring programs and help reduce costs and risks of such efforts in order to maximize the likelihood of success and scientific yield.