Epitaxial HTS thin films grown by PLD with a beam homogenizer

Wagner, F.; Scaggs, Michael; Koch, Alexander W.; Endert, Heinrich; Christen, H. M.; Knauss, L.A.; Harshavardhan, K. S.; Green, S.M.

doi:10.1016/s0169-4332(97)00677-6

Cited by 5 publications

(3 citation statements)

References 5 publications

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“…In one of the most effective techniques, the output laser beam is split in several sections which are then overlapped in the focal plane of an imaging lens. This technique is usually based either on microlens arrays [50], random phase plates [51], or a combination of these [52]. It is shown that these beam homogenizers can also reduce temporal fluctuations in the laser beam profiles [53].…”

Section: Flame Structure Detectionmentioning

confidence: 99%

Turbulent flame boundary and structure detection in an optical DISI engine using tracer-based two-line PLIF technique

Attar

Zhao

Herfatmanesh

et al. 2015

Experimental Thermal and Fluid Science

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"Turbulent flame boundary and structure detection in an optical DISI engine using tracer-based two-line PLIF technique", Experimental Thermal and Fluid Science, AbstractDesign and development of new combustion systems for Spark Ignition Direct Injection (DISI) engines requires thorough understanding of the combustion flame as it develops from the electric discharge and propagates across the combustion chamber. The main purpose of this work was to develop an experimental setup capable of investigating the premix turbulent flame boundary and structure inside the combustion chamber of a DISI engine. For this purpose the tracer-based two-line Planar Laser Induced Fluorescence (PLIF) technique was set up. In order to have a thermometry technique independent of the photophysical model of dopant tracer, a specially designed Constant Volume Chamber (CVC) was utilized for quasi in situ calibration measurement. The thermometry technique was evaluated by measurements of average in-cylinder charge temperature during compression stroke for both motoring and firing cycles and comparing the results with temperature values calculated from in-cylinder pressure data. The developed technique was successfully implemented to detect flame structure during combustion process in an optical engine. The present study demonstrated that as the two-line PLIF thermal images are independent of species concentration and flame luminosity they can be utilized as an accurate means for flame segmentation. The proposed technique has the potential to be utilized for study of premix flames in non-homogeneously mixed systems.

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Section: Flame Structure Detectionmentioning

confidence: 99%

Turbulent flame boundary and structure detection in an optical DISI engine using tracer-based two-line PLIF technique

Attar

Zhao

Herfatmanesh

et al. 2015

Experimental Thermal and Fluid Science

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“…Along with aging of the laser gases, these figures double to ∼10 % and ∼6 %, and the non-symmetries in the profiles of the initial output beam become more pronounced. The above-mentioned problems can be overcome by using a proper beam homogenizer, for example, a field mapper [1] or a beam integrator [5,6].…”

Section: Introductionmentioning

confidence: 99%

Pulsed laser deposition using diffractively shaped excimer-laser beams

et al. 2012

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Controlling laser-pulse parameters is an important issue in pulsed laser deposition (PLD). In particular, homogenization of laser beams improves the reproducibility of the PLD process by guaranteeing a uniform intensity distribution and a well-defined energy density of the laser spot on the target. We have integrated a beam-homogenization system into our PLD setup, and here we discuss the results and advantages of using such a system. The optical setup is based on diffractive beam-splitter gratings, which produce a 2 × 2-mm 2 flat-top distribution with fluences of the order of 3 J/cm 2 on the target. We demonstrate the applicability of this technique by depositing thin films of ferromagnetic Ni-Mn-Ga shape-memory alloys. Magnetic and structural characterization, including secondary ion mass spectrometry (SIMS), indicate that nearly stoichiometric composition and crystallization in the desired martensitic phase is obtained for films deposited on Al 2 O 3 under optimal conditions. In contrast, the formation of silicide compounds at temperatures above 500 • C is detrimental in the deposition of Ni-Mn-Ga films directly on silicon.V. Kekkonen ( ) · T. Kajava

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“…Uniform growth has been achieved by using this approach, 38 and improved target wear has been observed. 85…”

Section: Control Of the Laser Spot On The Targetmentioning

confidence: 99%

Pulsed Laser Deposition of YBa2Cu2O7−δ for Coated Conductor Applications: Current Status and Cost Issues

Christen

Second-Generation HTS Conductors

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INTRODUCTIONAmongst the numerous techniques currently being tested for the fabrication of coated conductors (i.e. high-temperature superconducting oxides deposited onto metallic tapes), pulsed laser deposition (PLD) plays a prominent role. Recent results from groups in the United States (e.g. Los Alamos National Laboratory), Europe (e.g. University of Göttingen), and Japan (e.g. Fujikura Ltd.) are most promising, yielding record numbers for J c and I c .As a method for depositing films of complex materials, such as the high-temperature superconductors (HTS) relevant to this chapter, PLD is well established and conceptually simple. Issues that have kept PLD from becoming a successful technique for devices and optical materials, namely particulate formation and thickness non-uniformities, are much less of a concern in the fabrication of HTS tapes. Nevertheless, the approach still presents ongoing challenges in the fundamental understanding of the laser-target interaction and growth from the resulting energetic plasma plume. Numerous issues related to the scale-up, control, reproducibility, and economic feasibility of PLD remain under investigation.It is clearly beyond the scope of this short chapter to give a complete treatise of such a complex subject -fortunately, several excellent reviews have already been published. 1-3 It is thus the intent of the author to introduce PLD only briefly and with a strong focus on HTS deposition, summarizing the most important developments and referring the reader to the numerous cited works. A strong emphasis is placed on issues related to scale-up.Finally, it is the goal of this chapter to introduce a preliminary cost-analysis of PLD for coated conductor fabrication. While an attempt to calculate the total cost of fabricating a length of superconducting tape would be beyond the scope of this chapter (and beyond our current knowledge of numerous issues), we can present a rather detailed analysis of the 2 cost of laser operation. The point, of course, is not to show that PLD is either cheaper or more expensive than other techniques -in fact, for most other techniques, which have not been successfully applied to long length fabrication, such a calculation cannot yet be made. It is illustrative, for example, to consider that in an industrial setting, more meters of coated tape will have to be produced per day than some other methods have produced in their entire history, and that therefore many reliability issues (including mean-time between failure of equipment) have not been addressed for many of the approaches described in this book. It is the maturity of industrial laser technology combined with the maturity of the PLD process that allows us to estimate these costs for this technique.

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Epitaxial HTS thin films grown by PLD with a beam homogenizer

Cited by 5 publications

References 5 publications

Turbulent flame boundary and structure detection in an optical DISI engine using tracer-based two-line PLIF technique

Turbulent flame boundary and structure detection in an optical DISI engine using tracer-based two-line PLIF technique

Pulsed laser deposition using diffractively shaped excimer-laser beams

Pulsed Laser Deposition of YBa2Cu2O7−δ for Coated Conductor Applications: Current Status and Cost Issues

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