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| Author | Amigó, M.L.; Herrera, T.; Neñer, L.; Peralta Gavensky, L.; Turco, F.; Luzuriaga, J. | ||||
| Title | A quantitative experiment on the fountain effect in superfluid helium | Type | Journal Article | ||
| Year | 2017 | Publication | European Journal of Physics | Abbreviated Journal | Eur. J. Phys. |
| Volume | 38 | Issue | 5 | Pages  |
055103 |
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| Abstract | Superfluid helium, a state of matter existing at low temperatures, shows many remarkable properties. One example is the so called fountain effect, where a heater can produce a jet of helium. This converts heat into mechanical motion; a machine with no moving parts, but working only below 2 K. Allen and Jones first demonstrated the effect in 1938, but their work was basically qualitative. We now present data of a quantitative version of the experiment. We have measured the heat supplied, the temperature and the height of the jet produced. We also develop equations, based on the two-fluid model of superfluid helium, that give a satisfactory fit to the data. The experiment has been performed by advanced undergraduate students in our home institution, and illustrates in a vivid way some of the striking properties of the superfluid state. | ||||
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| ISSN | 0143-0807 | ISBN | Medium | ||
| Area | Expedition | Conference | |||
| Notes | Approved | no | |||
| Call Number | BT @ pedrazp @ | Serial | 780 | ||
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| Author | Luzuriaga, J.; Badía-Majós, A.; Nieva, G.; Giordano, J.L.; Lopez, C.; Serquis, A.; Serrano, G. | ||||
| Title | Magnetic relaxation induced by transverse flux shaking in MgB2 superconductors | Type | Journal Article | ||
| Year | 2009 | Publication | Superconductor Science and Technology | Abbreviated Journal | Supercond. Sci. Technol. |
| Volume | 22 | Issue | Pages |
15021 | |
| Keywords | MgB2 | ||||
| Abstract | We report on measurements and numerical simulations of the behavior of MgB2 superconductors when magnetic field components are applied along mutually perpendicular directions. By closely matching the geometry in simulations and measurements, full quantitative agreement is found. The critical state theory and a single phenomenological law, i.e. the field dependence of the critical current density Jc(B), are sufficient for a full quantitative description of the measurements. These were performed in thick strips of carbon nanotube doped MgB2 samples. Magnetization was measured in two orthogonal directions using a SQUID magnetometer. Magnetic relaxation effects induced by the application of an oscillatory perpendicular field were observed and simulated numerically. The measurements confirm the numerical predictions, that two relaxation regimes appear, depending on the amplitude of the applied magnetic field. The overall agreement constitutes a convincing validation of the critical state model and the numerical procedures used. | ||||
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| Notes | Approved | no | |||
| Call Number | BT @ gnieva @ | Serial | 421 | ||
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| Author | Luzuriaga, J.; Andre, M.-O.; Benoit, W. | ||||
| Title | Mechanical response of the flux lines in ceramic YBa2Cu3O7- | Type | Journal Article | ||
| Year | 1992 | Publication | Physical Review B | Abbreviated Journal | |
| Volume | 45 | Issue | 21 | Pages |
12492-12497 |
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| Abstract | We have studied the mechanical response of the flux-line lattice (FLL) in ceramic samples of YBa2Cu3O7 by means of a low-frequency forced pendulum. The internal friction and elastic modulus variation of the FLL have been measured as a function of temperature for different values of the applied stress. A somewhat different behavior was observed whether a zero-field-cooling or field-cooling procedure was followed. Measurements of the internal friction and elastic modulus as a function of the applied stress at constant temperature show amplitude-dependent dissipation, with a maximum dissipation at intermediate values of the stress. This dependence is well fitted by a rheological model of extended dry friction, if we restrict ourselves to the dissipation and modulus at fixed temperature. The agreement is not so good when attempting to extend the model to fit the temperature dependence. | ||||
| Address | Institut de Genie Atomique, Ecole Politechnique Federal de Lausanne, (1015) Ecublens, Switzerland | ||||
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| ISSN | 01631829 (ISSN) | ISBN | Medium | ||
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| Notes | Export Date: 28 April 2009; Source: Scopus; doi: 10.1103/PhysRevB.45.12492; Language of Original Document: English; Correspondence Address: Luzuriaga, J.; Institut de Genie Atomique; Ecole Politechnique Federal de Lausanne (1015) Ecublens, Switzerland | Approved | no | ||
| Call Number | BT @ luzuriag @ | Serial | 522 | ||
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| Author | Zemma, E.; Luzuriaga, J.; Babuin, S. | ||||
| Title | Analysis of motion of solid hydrogen tracer particles in oscillating superfluid flows | Type | Conference Article | ||
| Year | 2014 | Publication | Journal of Physics: Conference Series | Abbreviated Journal | J. Phys.: Conf. Ser. |
| Volume | 568 | Issue | Pages |
012029 | |
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| Abstract | We have developed a relatively simple cryostat which allows us to image turbulent flows in superfluid helium at temperatures below 2 K, using frozen H2 particles. We analyze the statistics of the velocities of these solid tracers, which follow the turbulent flow generated by oscillating bodies. We have also studied one of the oscillators working in air at room temperature, and traced the flow with solid talcum particles for comparison. Images were recorded by a digital camera at 240 frames per second, while frequencies of the oscillators are between 20 to 45 Hz. The flow is characterized by a modified Reynolds number Reδ based on the viscous penetration depth δ. Software in a dedicated particle tracking velocimetry code allows us to compute the trajectories and velocities of tens of thousands of particles. We have obtained the number of particles for equally spaced intervals of the velocity modulus. For the oscillators in the superfluid, the probability of finding particles at higher velocities has an exponential decay. Within our resolution the statistics in the superfluid for oscillating objects with sharp borders is largely independent of Reδ, while the logarithmic decay at low velocities seems faster than for high velocities for rounded objects. On the other hand, for data taken in air the result is closer to a classical Gaussian distribution of velocities. | ||||
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| Area | Expedition | Conference | 27th International Conference on Low Temperature Physics (LT27) | ||
| Notes | Approved | no | |||
| Call Number | BT @ pedrazp @ | Serial | 735 | ||
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| Author | Luzuriaga, J.; Badía-Majós, A.; Nieva, G.; Giordano, J.L.; Lopez, C.; Serquis, A.; Serrano, G. | ||||
| Title | Experimental and numerical study of transverse flux shaking in MgB2 superconductors | Type | Conference Article | ||
| Year | 2009 | Publication | Journal of Physics: Conference Series | Abbreviated Journal | J. Phys.: Conf. Ser. |
| Volume | 167 | Issue | Pages |
012009 | |
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| Abstract | Magnetization measurements in the mixed state of thick strips of carbon nanotube doped MgB 2 in crossed fields configurations are reported, together with numerical simulations performed with a geometry equivalent to the sample shape. The samples were subjected to magnetic field components along mutually perpendicular directions, an oscillatory field in one direction and a remanent magnetization in the perpendicular direction. The magnetic response along the oscillatory field and the magnetic relaxation perpendicular to it are observed and simulated using the critical state theory. A remarkable quantitative agreement between the experiment and the theory was obtained. |
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| Area | Expedition | Conference | XIX Latin American Symposium on Solid State Physics (SLAFES XIX) | ||
| Notes | Approved | no | |||
| Call Number | BT @ pedrazp @ | Serial | 737 | ||
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| Author | Herbsommer, J.A.; Nieva, G.; Luzuriaga, J. | ||||
| Title | Interaction of vortices with oriented twin boundaries in single-crystal YBa2Cu3O7-delta | Type | Journal Article | ||
| Year | 2000 | Publication | Physical Review B | Abbreviated Journal | Phys. Rev. B |
| Volume | 61 | Issue | 17 | Pages |
11745-11751 |
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| Abstract | We have studied the response of the vortex lattice (VL) in a YBa2Cu3O7-delta sample with oriented twin boundaries (TB's) and in an untwinned sample. In the twinned sample the density of twin boundaries is estimated from decoration experiments. The TB's affect the liquid-to-solid transition in the vortex structure, which is of first order in the twin free crystal and to a Bose glass in the twinned sample. We measure the ac susceptibility, and find that the response strongly depends on the orientation of the probing ac field with respect to the TB's. The ac field produces a tilting stress on the vortices. With the applied de magnetic field H-dc parallel to the c axis, the response of the VL is weaker when the tilt is parallel to the TB's than when it is perpendicular or at 45 degrees to the TB's. The results are explained by the fact that the VL is locked to the twin boundaries for small deviations of H-dc from the c axis and is partially pinned to them for larger angles. By measuring over the whole angular range we estimate the angles over which each regime is realized for different temperatures. The results of the detwinned sample are used for comparison. | ||||
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| ISSN | 1098-0121 | ISBN | Medium | ||
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| Notes | ISI:000086937700090 | Approved | no | ||
| Call Number | BT @ hernan @ | Serial | 228 | ||
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| Author | Rodriguez, E.; Luzuriaga, J.; Dovidio, C.A.; Esparza, D.A. | ||||
| Title | Softening of the flux-line structure in La1.8Sr0.2CuO4 measured by a vibrating reed | Type | Journal Article | ||
| Year | 1990 | Publication | Physical Review B | Abbreviated Journal | Phys. Rev. B |
| Volume | 42 | Issue | 16 | Pages |
10796-10799 |
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| Abstract | Vibrating-reed measurements in La1.8Sr0.2CuO4 in a magnetic field show that the flux-line structure (FLS) becomes uncoupled from the material at a temperature TH of 23 K, much below the critical temperature of the sample, which is 32 K. The behavior is similar to that found in Bi2Sr2CaCu2O8 but shows some significant differences, the most important being that TH changes little with magnetic field throughout the measured field range (0.01 TH1 T). For low fields, TH is below the reversibility line of the magnetization. This seems to imply that the reversibility line and the line at which the FLS softens have to be considered as distinct physical phenomena. It is argued that neither flux-lattice melting nor giant flux creep considered separately can account for the data in a wholly satisfactory manner. | ||||
| Address | Centro Atmico Bariloche, (8400) Bariloche, Argentina | ||||
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| ISSN | 01631829 (ISSN) | ISBN | Medium | ||
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| Notes | Cited By (since 1996): 2; Export Date: 28 April 2009; Source: Scopus; doi: 10.1103/PhysRevB.42.10796; Language of Original Document: English; Correspondence Address: Rodrguez, E.; Centro Atmico Bariloche (8400) Bariloche, Argentina | Approved | no | ||
| Call Number | BT @ luzuriag @ | Serial | 489 | ||
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| Author | Esquinazi, P.; Luzuriaga, J. | ||||
| Title | Annealing effects on the sound velocity and internal friction in the superconducting and normal states of the Cu30Zr70 amorphous alloy | Type | Journal Article | ||
| Year | 1988 | Publication | Physical Review B | Abbreviated Journal | |
| Volume | 37 | Issue | 13 | Pages |
7819-7831 |
| Keywords | Zr70Cu30 | ||||
| Abstract | By means of the vibrating-reed technique we have measured the evolution upon low-temperature annealing of the internal friction Q-1 and sound velocity v of the Cu30Zr70 amorphous alloy between 0.1 and 10 K. With an applied magnetic field of 5.6 T we measured also the normal-state behavior of both properties. Upon annealing, the internal friction and the slope of the logarithmic temperature dependence of v in the superconducting state decrease, in agreement with the standard tunneling model. Our results indicate that with thermal treatments, the coupling constant between tunneling systems (TSs) and phonons decreases, and the density of states of the TS remains constant or decreases, at most 25%, in the fully relaxed state, which is in agreement with published specific-heat results in these materials. From our data we conclude that the coupling constant between the TS and phonons should be very sensitive to the relaxed state of the disordered structure. The sound-velocity behavior strongly indicates that relaxation processes up to 10 K involve the interaction with the TS. A well-defined change of slope in v at the superconducting critical temperature Tc is observed in the as-quenched and the first relaxed state, which cannot be explained with the standard tunneling model and the Korringa-like relaxation rate between the TS and electrons. Several features observed in the superconducting and normal states lead to the conclusion that the TS-electron interaction problem remains unsolved. | ||||
| Address | Centro Atómico Bariloche, Instituto Balseiro, 8400 Bariloche, Argentina | ||||
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| ISSN | 01631829 (ISSN) | ISBN | Medium | ||
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| Notes | Cited By (since 1996): 9; Export Date: 28 April 2009; Source: Scopus; doi: 10.1103/PhysRevB.37.7819; Language of Original Document: English; Correspondence Address: Esquinazi, P.; Centro Atmico Bariloche; Instituto Balseiro 8400 Bariloche, Argentina | Approved | no | ||
| Call Number | BT @ luzuriag @ | Serial | 494 | ||
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| Author | Safar, H.; Durán, C.; Guimpel, J.; Civale, L.; Luzuriaga, J.; Rodriguez, E.; de la Cruz, F.; Fainstein, C.; Schneemeyer, L.F.; Waszczak, J.V. | ||||
| Title | Logarithmic-to-nonlogarithmic flux-creep transition and magnetic-flux hardening in Bi-Sr-Ca-Cu-O superconducting ceramics | Type | Journal Article | ||
| Year | 1989 | Publication | Physical Review B | Abbreviated Journal | Phys. Rev. B |
| Volume | 40 | Issue | 10 | Pages |
7380 |
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| Abstract | A sharp temperature- and field-dependent transition from a logarithmic to a nonlogarithmic flux-creep behavior has been found in Bi-Sr-Ca-Cu-O superconductors. The transition is not followed by any noticeable change in the magnetization. However, vibrating-reed measurements show that it coincides with a strong hardening of the magnetic structure. The transition occurs at fields and temperatures well below the reversibility line. The possible relation to the recently proposed flux lattice melting is discussed. | ||||
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| Publisher | American Physical Society | Place of Publication | Editor | ||
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| Call Number | BT @ jguimpel @ 10.1103/PhysRevB.40.7380 | Serial | 627 | ||
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| Author | De La Cruz, F.; Luzuriaga, J.; Martinez, E.N.; Osquiguil, E.J. | ||||
| Title | Current-voltage characteristics in collective pinning | Type | Journal Article | ||
| Year | 1987 | Publication | Physical Review B | Abbreviated Journal | |
| Volume | 36 | Issue | 13 | Pages |
6850-6852 |
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| Abstract | The critical-current curves of amorphous samples which exhibit collective flux pinning have been analyzed, and it was found that the nonlinear part can be fitted by an expression of the form V(I)[(I-IK)/IK]. This form, which could be due to critical behavior, is consistent with an interpretation of the unpinning of vortices in the collective regime as a phase transition between the static flux-line lattice (FLL) and the FLL in steady-state movement as has been proposed by Fisher. | ||||
| Address | Centro Atomico Bariloche, Instituto Balseiro, 8400 Bariloche, Argentina | ||||
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| ISSN | 01631829 (ISSN) | ISBN | Medium | ||
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| Notes | Cited By (since 1996): 2; Export Date: 17 April 2009; Source: Scopus; doi: 10.1103/PhysRevB.36.6850; Language of Original Document: English; Correspondence Address: De La Cruz, F.; Centro Atomico Bariloche; Instituto Balseiro 8400 Bariloche, Argentina | Approved | no | ||
| Call Number | BT @ osquigui @ | Serial | 417 | ||
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