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Poster presentation by a high-school student Eric Buchanan on developing of an AC susceptometer.

Topological Hysteresis in Type-I Superconductors Ruslan Prozorov, Ames Laboratory and Iowa State University, DMR 0553285.

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Poster presentation by a high-school student Eric Buchanan on developing of an AC susceptometer.

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  1. Topological Hysteresis in Type-I SuperconductorsRuslan Prozorov, Ames Laboratory and Iowa State University,DMR 0553285 Lead (Pb) is one of the first and most studied elemental superconductors. Yet, NSF has sponsored this project almost 100 years after the discovery of superconductivity in this compound. Why? Because low-temperature magneto-optical imaging used by our group on very clean Pb single crystals revealed unusual magnetic structures.The basic principle of physics of free energy minimization Intermediate state in single crystals of lead in shape of a disc. Boh images are obtained a the same temperature (T=5 K) and applied magnetic field (H 190 Oe). Yet, the striking diffence in morphology is observed between flux penetration (left) and flux exit (right). fails to determine the equilibrium pattern of the intermediate state (when magnetic flux partially penetrates the sample). Yet, it is possible to analyze the situation in terms of physics of coarsening froths and foams (work under review in Nature). We call the observed phenomenon a topological hysteresis – when in a structurally perfect and pinning-free superconductor shows a macroscopic hysteresis in its bulk rersponse, such a magnetization. Moreover, these observations depend on a shape of a specimen as described in a recent publication: Ruslan Prozorov, Phys. Rev. Lett. 98, 257001 (2007) Ames Laboratory is operated for the U.S. Department of Energy by Iowa State University under Contract No. W-7405-ENG-82. This work was supported by the NSF Grant Number DMR-0553285, the Alfred P. Sloan Foundation, and by the Director for Energy Research, Office of Basic Energy Sciences.

  2. Topological Hysteresis in Type-I SuperconductorsRuslan Prozorov, Ames Laboratory and Iowa State University,DMR 0553285 Our group is heavily involved in outreach activities. We engage high-school students (SPRI program – high school students in research), undergraduate students (SULI program – similar to REU, but for National Laboratories) and general public to disseminate our results. We were involved in many very different projects ranging from developing a magnetic fish bait to assessing pork quality using advanced ultrasonic and electromagnetic techniques. Every year a flock of students passes through the laboratory and some choose to stay. We currently have six graduate and two undergraduate students. With combined recourses of the National Science Foundation and the Department of Energy Basic Science, we offer a unique opportunity to all beginning researchers to become engaged in a well-funded world-class research. Poster presentation by a high-school student Eric Buchanan on developing of an AC susceptometer.

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