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Scanning Hall probe microscopy of su...

Dinner, Rafael Baruch.

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Scanning Hall probe microscopy of supercurrents in YBCO films.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Scanning Hall probe microscopy of supercurrents in YBCO films./
作者:	Dinner, Rafael Baruch.
面頁冊數:	150 p.
附註:	Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6458.
Contained By:	Dissertation Abstracts International67-11B.
標題:	Physics, Electricity and Magnetism. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3242543
ISBN:	9780542983306

Scanning Hall probe microscopy of supercurrents in YBCO films.
Dinner, Rafael Baruch.

Scanning Hall probe microscopy of supercurrents in YBCO films. - 150 p.

Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6458.

Thesis (Ph.D.)--Stanford University, 2006.

High-temperature superconductors were discovered 20 years ago, inspiring dreams of levitating trains fed by superconducting power lines. The cuprates, particularly YBa2Cu3O7-delta (YBCO), still promise to fulfill such applications, but must be made to carry higher current density, Jc, which is limited by the rapid onset of dissipation. The dissipation arises from the movement of magnetic vortices in the material, driven by the magnetic field of the current. It is therefore natural to use magnetic imaging to understand these limits on the current.

ISBN: 9780542983306Subjects--Topical Terms:

1019535
Physics, Electricity and Magnetism.

Scanning Hall probe microscopy of supercurrents in YBCO films.
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245 1 0 $a Scanning Hall probe microscopy of supercurrents in YBCO films.
300 $a 150 p.
500 $a Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6458.
500 $a Adviser: M. R. Beasley.
502 $a Thesis (Ph.D.)--Stanford University, 2006.
520 $a High-temperature superconductors were discovered 20 years ago, inspiring dreams of levitating trains fed by superconducting power lines. The cuprates, particularly YBa2Cu3O7-delta (YBCO), still promise to fulfill such applications, but must be made to carry higher current density, Jc, which is limited by the rapid onset of dissipation. The dissipation arises from the movement of magnetic vortices in the material, driven by the magnetic field of the current. It is therefore natural to use magnetic imaging to understand these limits on the current.
520 $a Initially, I fix a mesoscopic ring of YBCO to a micro-Hall sensor and demonstrate that the sensor is capable of detecting small numbers of vortices. I then proceed with magnetic imaging, constructing a cryogenic scanning Hall probe microscope that combines a 1 x 4 cm scan range with 200 nm positioning resolution by coupling stepper motors to high-resolution drivers and reducing gears. It enables me to image an entire sample, then zoom in on regions of interest, down to the level of an individual quantized vortex.
520 $a Applying this capability to current-carrying YBCO strips, I generate magnetic movies of the materials' periodic response to applied ac currents. From the movies, I reconstruct current density by inverting the Biot-Savart law, and electric field by approximating dB/dt and using Faraday's law. I thereby obtain complete, space- and time-resolved characterizations of the materials, including maps of ac power losses.
520 $a After demonstrating this analysis on a single-crystal film, I image two "coated conductors"---YBCO grown on metal tape. I find relatively homogeneous flux penetration in a film grown by pulsed laser deposition (PLD) on an ion beam assisted deposition (IBAD) substrate, which contrasts with the weak-link behavior of grain boundaries in a film grown by metalorganic deposition (MOD) on rolling assisted biaxially textured substrate (RABiTS). Nonetheless, the in-plane meandering of the MOD film's boundaries allows them to sustain high currents. This observation leads me to image individual boundaries with various in-plane tilts, where I conclude that control of grain boundary orientation offers a route to higher critical current density.
590 $a School code: 0212.
650 4 $a Physics, Electricity and Magnetism. $3 1019535
650 4 $a Physics, Condensed Matter. $3 1018743
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710 2 0 $a Stanford University. $3 754827
773 0 $t Dissertation Abstracts International $g 67-11B.
790 1 0 $a Beasley, M. R., $e advisor
790 $a 0212
791 $a Ph.D.
792 $a 2006
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3242543