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Ultrafast Magnetism Dynamics Measure Using Tabletop Ultrafast EUV Sources

Description: In our work to date, we made two significant advances. First we demonstrated element-selective demagnetization dynamics for the first time, with a record time resolution for x-ray probing of 55 fs. Second, in new work, we were able to probe the timescale of the exchange interaction in magnetic materials, also for the first time. Our measurements were made using the transverse magneto-optic Kerr effect (T-MOKE) geometry, since the reflectivity of a magnetic material changes with the direction of the magnetization vector of a surface. In our experiment, we periodically reversed the magnetization direction of a grating structure made of Permalloy (Ni80Fe20) using an external magnetic field. To achieve maximum contrast, we used HHG light spanning the M-shell (3p) absorption edges of Fe and Ni. Our characterization of the static magnetization of a Permalloy sample shows high magnetic asymmetry at photon energies just above and below the absorption edges at 55 eV and 65 eV, respectively. This result is in excellent agreement with measurements done on the same using a synchrotron source.
Date: August 21, 2013
Creator: Silva, Thomas J. & Murnane, Margaret
Partner: UNT Libraries Government Documents Department

Variable-Temperature Critical-Current Measurements

Description: This is the final report of a three year contract that covered 09/19/2005 to 07/14/2008. We requested and received a no cost time extension for the third year, 07/15/2007 to 07/14/2008, to allow DoE to send us funds if they became available during that year. It turned out that we did not receive any funding for the third year. The following paper covers our variable-temperature critical-current measurements. We made transport critical-current (Ic) measurements on commercial multifilamentary Nb3Sn strands at temperatures (T) from 4 to 17 K and magnetic fields (H) from 0 to 14 T. One of the unique features of our measurements is that we can cover a wide range of critical currents from less than 0.1 A to over 700 A.
Date: May 19, 2009
Creator: Goodrich, L. F. & Stauffer, T. C.
Partner: UNT Libraries Government Documents Department

Characterization of Nb3Sn Strand for ITER

Description: We have an ongoing research program for characterization of superconductor composite strands, the principal output of which is sensitive measurements of critical current Ic over a broad range of the essential parameters: longitudinal strain ε, temperature T, and magnetic field B. This features a new apparatus for integrated measurement of Ic(ε,T,B) on the same, long-conductor sample without remounting.
Date: May 3, 2012
Creator: Cheggour, Najib & Goodrich, Loren F.
Partner: UNT Libraries Government Documents Department