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Description: The Sub-Picosecond Accelerator (SPA) at the Los Alamos National Laboratory is an L-band photoinjector. Using magnetic compression, the SPA routinely compresses 8 MeV, 1 nC per bunch electron beams from an initial temporal FWHM bunch length of 20 ps to less than 1 ps. In recent plasma wakefield accelerator experiments, we have compressed a 2 nC per bunch electron beam to an approximate temporal length of 1 ps.
Date: February 2001
Creator: Russell, S.; Carlsten, B. & Goettee, J.
Partner: UNT Libraries Government Documents Department

High-magnetic-field research collaborations

Description: This is the final report of a two-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The purpose of this project was to develop collaborations with the academic community to exploit scientific research potential of the pulsed magnetic fields that might be possible with electrically pulsed devices, as well as magneto-cumulative generators. The author started with a campaign of experiments using high-explosive-driven flux compression generators. The campaign's objective was to explore completely novel ideas in condensed-matter physics and chemistry. The initiative was very successful in pulling together top researchers from around the world.
Date: December 31, 1998
Creator: Goettee, J.
Partner: UNT Libraries Government Documents Department

A High-Voltage Pulse Transformer for Explosive Pulsed-Power Devices

Description: It is often necessary to use a high-voltage pulse transformer for impedance matching an explosive generator to a higher impedance load. Also, a particular application may require high-voltage rather than the high current which flux compressor generators (FCGs) normally deliver when driving suitable low impedance loads. We have designed and built transformers for use with FCGs. They are air-core transformers with measured coupling coefficients in the range of 0.88 to 0.94. The turns ratio for these transformers vary from 10 to 40. We have used these transformers in FCG shots and have measured 250 kV and 250 kA on the secondary, simultaneously and without breakdown. So far the FCG and not the transformer have limited the voltage. Experiments to determine a voltage limit are ongoing. Our design and results are presented.
Date: October 1, 1998
Creator: Fortgang, C.; Erickson, G.A. & Goettee, J.
Partner: UNT Libraries Government Documents Department

Complex microwave conductivity of YBa{sub 2}Cu{sub 3}O{sub 7} in magnetic fields up to 500T

Description: We have measured the complex conductivity of thin films of YBa{sub 2}cu{sub 3}O{sub 7} (YBCO) superconductor down to temperatures of 4K and magnetic fields up to 500T. The highly oriented films were probed by 94 GHz radiation, with the external magnetic field applied perpendicular to the c-axis. These measurements allowed us to assign a value of 340 {plus_minus} 40 for the upper critical field at T=O. The measurements were recently carried out at the pulsed field facility of the National High Magnetic Field Laboratory at Los Alamos using both Russian and American magnetic flux compression generators.
Date: July 1, 1994
Creator: Goettee, J. D.; Zerwekh, W. D. & Kudasov, Y. B.
Partner: UNT Libraries Government Documents Department

Dirac: A campaign of experiments to study physics and chemistry at ultrahigh magnetic fields

Description: We present an overview of the Dirac experimental campaign conducted at Los Alamos in spring of 1996. The name was chosen in recognition of P.A.M. Dirac`s monumental contributions to quantum theory, which affected every aspect of the science we planned to investigate. We show how the various collaborations were put together, discuss some of the difficulties of collecting data in rapidly changing magnetic fields, describe the motivation, packaging, and integration of experiments, and give an exceedingly preliminary discussion of some of the results.
Date: December 1, 1996
Creator: Solem, J.C.; Fowler, C.M.; Goettee, J.D.; Rickel, D.; Campbell, L.J. & Veeser, L.
Partner: UNT Libraries Government Documents Department

Explosively produced megagauss fields and recent solid state applications

Description: Large magnetic fields may be generated by compression of an initial magnetic flux generated over a large area at relatively low magnetic field into a region of smaller area. Following a discussion of flux compression principles, the authors discuss megagauss field systems in use at Los Alamos where chemical explosives are used to compress the flux. Their use in some solid state experiments will be discussed briefly, including a planned set of experiments on YBCO to be done jointly with a Russian team, whose aim is to determine the low temperature, critical magnetic field of YBCO.
Date: December 31, 1993
Creator: Fowler, C. M.; Freeman, B. L.; Hults, W. L.; King, J. C.; Mueller, F. M.; Rickel, D. G. et al.
Partner: UNT Libraries Government Documents Department

The Dirac Experiments - Results and Challenges

Description: The 1997 international Dirac II Series held at Los Alamos National Laboratory involved low temperature electrical transport and optical experiments in magnetic fields exceeding 800%, produced by explosive flux compression using Russian MC-1 generators. An overview of the scientific and technical advances achieved in this Series is given, together with a strategy for future work in this challenging experimental environment. A significant outcome was achieved in transport studies of microfabricated thin-film YBCO structures with the magnetic field in the CuO plane. Using a GHz transmission line technique at an ambient temperature of 1.6 K, an onset of dissipation was observed at 150 T (a new upper bound for superconductivity in any material), with a saturation of resistivity at 240 T. Comparison with the Pauli limit expected at B=155 T in this material suggests that the critical field in this geometry is limited by spin paramagnetism. In preparation for a Diract III series, a systematic temperature-dependent transport study of YBCO using in-plane magnetic fields of 150 T generated by single-turn coils, at temperatures over the range 10-100 K, has been undertaken in collaboration with the Japanese Megagauss Laboratory. The objective is to map out the phase diagram for this geometry, which is expected to be significantly different than the Werthamer-Helfand-Hohenberg model, due to the presence of paramagnetic limiting. Nanofabricated magnetometers have also been developed in a UNSW-LANL collaboration for use in Dirac III for Fermi surface measurements of YBCO in megagauss fields, which are described.
Date: October 24, 1998
Creator: Clark, R.G.; O'Brien, J.L.; Dzurak, A.S.; Kane, B.E.; Lumpkin, N.E.; Reilley, D.J. et al.
Partner: UNT Libraries Government Documents Department