753 research outputs found
First experiences with the H-maser EFOS 1
The results are given on the performance measurements, on the dependence on external temperature, and on external magnetic field of a hydrogen maser. It is compared with another hydrogen maser. Details of the transportation and installation of the maser are given. The hydrogen maser frequency is compared with cesium oscillators to derive long-term behavior
Study made of corrosion resistance of stainless steel and nickel alloys in nuclear reactor superheaters
Experiments performed under conditions found in nuclear reactor superheaters determine the corrosion rate of stainless steel and nickel alloys used in them. Electropolishing was the primary surface treatment before the corrosion test. Corrosion is determined by weight loss of specimens after defilming
Superconductor-Insulator Phase Separation Induced by Rapid Cooling in kappa-(ET)_2Cu[N(CN)_2]Br
We present measurements of the low temperature specific heat of single
crystals of kappa-(ET)_2Cu[N(CN)_2]Br as a function of the cooling rate through
the glasslike structure transition at 80K. We find that rapid cooling
produces a small (< 4%) decrease in the superconducting transition temperature
accompanied by a substantial (up to 50%) decrease in the normal-state
electronic specific heat. A natural explanation of our data is that there is a
macroscopic phase separation between superconducting and insulating regions in
rapidly cooled samples.Comment: 4 pages, to appear in Phys. Rev. B (Rapid Comm
Kondo Lattice without Nozieres Exhaustion Effect
We discuss the properties of layered Anderson/Kondo lattices with metallic
electrons confined in 2D xy planes and local spins in insulating layers forming
chains in z direction. Each spin in this model possesses its own 2D Kondo
cloud, so that the Nozieres' exhaustion problem does not occur. The excitation
spectrum of the model is gapless both in charge and spin sectors. The
disordered phases and possible experimental realizations of the model are
briefly discussed.Comment: 4 pages, 3 figure
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Design of the Main Dipoles and Quadrupoles for the SSC Low Energy Booster
Anisotropic charge dynamics in the quantum spin-liquid candidate -(BEDT-TTF)Cu(CN)
We have in detail characterized the anisotropic charge response of the dimer
Mott insulator -(BEDT-TTF)\-Cu(CN) by dc conductivity, Hall
effect and dielectric spectroscopy. At room temperature the Hall coefficient is
positive and close to the value expected from stoichiometry; the temperature
behavior follows the dc resistivity . Within the planes the dc
conductivity is well described by variable-range hopping in two dimensions;
this model, however, fails for the out-of-plane direction. An unusually broad
in-plane dielectric relaxation is detected below about 60 K; it slows down much
faster than the dc conductivity following an Arrhenius law. At around 17 K we
can identify a pronounced dielectric anomaly concomitantly with anomalous
features in the mean relaxation time and spectral broadening. The out-of-plane
relaxation, on the other hand, shows a much weaker dielectric anomaly; it
closely follows the temperature behavior of the respective dc resistivity. At
lower temperatures, the dielectric constant becomes smaller both within and
perpendicular to the planes; also the relaxation levels off. The observed
behavior bears features of relaxor-like ferroelectricity. Because
heterogeneities impede its long-range development, only a weak tunneling-like
dynamics persists at low temperatures. We suggest that the random potential and
domain structure gradually emerge due to the coupling to the anion network.Comment: 14 pages, 13 figure
Upper critical field study in the organic superconductor -(ET)SFCHCFSO : Possibility of Fulde-Ferrell-Larkin-Ovchinnikov state
We report upper critical field measurements in the metal-free-all-organic
superconductor -(ET)SFCHCFSO obtained
from measuring the in-plane penetration depth using the tunnel diode oscillator
technique. For magnetic field applied parallel to the conducting planes the low
temperature upper critical fields are found to exceed the Pauli limiting field
calculated by using a semi-empirical method. Furthermore, we found a signature
that could be the phase transition between the superconducting vortex state and
the Fulde-Ferrell-Larkin-Ovchinnikov state in the form of a kink just below the
upper critical field and only at temperatures below 1.23 K.Comment: 4 pages, 6 figure
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