Physical Model of Nernst Element

Generation of electric power by the Nernst effect is a new application of a semiconductor. A key point of this proposal is to find materials with a high thermomagnetic figure-of-merit, which are called Nernst elements. In order to find candidates of the Nernst element, a physical model to describe its transport phenomena is needed. As the first model, we began with a parabolic two-band model in classical statistics. According to this model, we selected InSb as candidates of the Nernst element and measured their transport coefficients in magnetic fields up to 4 Tesla within a temperature region from 270K to 330K. In this region, we calculated transport coefficients numerically by our physical model. For InSb, experimental data are coincident with theoretical values in strong magnetic field.Comment: 4 pages, Latex, This article was presented in the XVII International Conference on Thermoelectrics, Nagoya, Japan(1998

Transport Coefficients of InSb in a Strong Magnetic Field

Improvement of a superconducting magnet system makes induction of a strong magnetic field easier. This fact gives us a possibility of energy conversion by the Nernst effect. As the first step to study the Nernst element, we measured the conductivity, the Hall coefficient, the thermoelectric power and the Nernst coefficient of the InSb, which is one of candidates of the Nernst elements. From this experiment, it is concluded that the Nernst coefficient is smaller than the theoretical values. On the other hand, the conductivity, the Hall coefficient ant the thermoelectric power has the values expected by the theory.Comment: 6 pages, Latex, This article was presented in the XVI International Conference on Thermoelectrics, Dresden, Germany (1997

Observation of the thermosiphon effect in the circulation of liquid nitrogen in HTS cable cooling system

AbstractIt is traditionally considered that superconducting technology is just the way that will help to overcome the energy crisis and improve the environmental safety of the electricity production. However, real achievements in this field still insufficient to build commercial long power transmission lines. In particular, cooling systems constructed using expensive coolant circulation pumps have to be improved. Our previous calculations show that the use of a thermosiphon effect may reduce both the heat load and the required coolant circulation pump power and, ideally, would completely abandon the forced circulation. Direct experimental verification of this approach has been carried out at the new 200-meter HTS DC experimental facility of the Chubu University. The thermosiphon effect was clearly observed in satisfactory agreement with theory, although the change in elevation of the cryopipe was small. Our results will be used to design an effective HTS cable cooling system based on natural circulation of the coolant

Stability test results on the aluminum stabilized superconductor for the helical coils of LHD

Stability tests have been carried out on short samples of the aluminum/copper stabilized composite-type superconductors developed and used for the pool-cooled helical coils of the Large Helical Device. The waveform of the longitudinal voltage initiated by resistive heaters shows a short-time rise before reaching a final value, which seems to correspond to the diffusion process of transport current into the pure aluminum stabilizer. The propagation velocity has a finite value even for the transport current being lower than the recovery current, and it differs depending on the direction with respect to the transport current

Impurity emission characteristics of long pulse discharges in Large Helical Device

Line spectra from intrinsic impurity ions have been monitored during the three kinds of long-pulse discharges (ICH, ECH, NBI). Constant emission from the iron impurity shows no preferential accumulation of iron ion during the long-pulse operations. Stable Doppler ion temperature has been also measured from Fe XX, C V and C III spectra

One Dimensional Simulation for Peltier Current Leads

Current leads, which connect superconducting magnets at the liquid helium temperature and power supplies at the room temperature, are the major source of heat leaking into cryostats, and therefore largely determines the running cost of magnet systems. Heat leak can be reduced by using high-temperature superconductors as the lowtemperature (4 K--77 K) segments of current leads. Another method to reduce heat leak, recently proposed by one of us (S. Y.), uses Peltier thermoelectric elements as the high-temperature (200 K--300 K) segments of current leads. These thermoelements effectively pump heat out of cryostats without using separate sources of electricity. We carried out experiments and numerical calculations with such Peltier current leads and found out that they reduce heat leak at 77 K by 20--30 percent. I. Introduction In 1834 Peltier observed that heat is absorbed or generated when an electric current crosses a junction between two different materials. This phenomenon, called th..

Current density profiles of BSCCO tapes in the stacked conductor under different current feeding modes

Some applications of high-temperature superconductors (HTS) will require stacked HTS tapes. Previous studies have revealed that the vertical component of the self-magnetic field affects the current transport properties in HTS tapes. In the present work, we examined the current density profiles in a stacked conductor that consists of two identical BSCCO tapes placed, in parallel, one above the other at the distance of 50 μm2. We measured the vertical component of the magnetic field by a Hall probe with an active area of 0.05 × 0.05 mm2 above the stacked conductor at the height of 0.3 mm. The magnetic field profile was measured at different current feeding modes for analysis of its behavior. MATLAB code was developed to calculate current density profiles from measured data. The calculation results showed the flattening of current density profile in the top tape during various current feeding modes that is expected to be followed by increasing critical current. The critical current (Ic) increased in one tape of the stacked conductors and may be attributed to self-field influence of antiparallel currents in the second HTS tape. Measured Ic is enhanced on the top tape of stacked conductors by antiparallel currents, and this may be as a result of strong interaction between HTS tapes