Yoshiro Saji

The Superheat-Limit of Liquid Oxygen and Nitrogen at 1 atm

The superheating of bimolecular cryogenic liquids (oxygen, nitrogen) was measured at one atmospheric pressure. The maximum superheating data obtained here were compared with the results of calculation based on the Becker-Doring-Zeldovich homogeneous nucleation theory. Good agreement between theory and experiment was found, and the magnitude of the super-heat-limit Tnucleation-Tcoexist was well represented as a function of the temperature gap Tcritical-Tcoexist, as Tnucleation-Tcoexist0.68 (Tcritical-Tcoexist) at 1 atm.

Superheat Limit of 4He and Its Quantum Deviation from Classical Behavior

The superheating of normal liquid 4 He was investigated by means of continuous heating of liquid specimen in a small glass capillary over a temperature range 2.26 K to 4.88 K. The maximum superheating data obtained were compared with the prediction from the homogeneous nucleation theory and the data for various liquids in terms of the reduced coordinates. It is confirmed that the agreement between the homogeneous nucleation theory and experiment on 4 He is satisfactory, and the scaled superheating depends parametrically on the quantum parameter \(\varLambda^{*}\), i.e., the deviations of the data for quantum liquids from the classical behavior become pronounced as the parameter is increased.

Nucleation in Superheated 3He

The superheating of liquid 3He has been carefully measured by means of the continuous heating of a liquid specimen in a small glass capillary. Experiments covered the pressure range 0.05 to 0.85 atm. Maximum superheating temperatures (Ts) obtained were compared with the prediction from the fluctuation theory of homogeneous nucleation. It was found that the agreement between the theory and experiment on 3He was satisfactory. Analysis of the Ts data with respect to the scaled pressure and temperature confirmed the quantum effects in the superheating limit. The surface tension for critical nucleus bubbles was also determined using the experimental Ts data and homogeneous nucleation theory.

Temperature changes of the photoelastic effect of NaCl, KCl, and KBr

The Brillouin spectra of NaCl, KCl, and KBr were observed in the temperature range ∼50–300 °K. From the measurements of scattered light intensity and the frequency shift, the temperature change of the photoelastic effect were determined. From these results and thermodynamical calculations, the temperature change of ∂n/∂TP of these crystals were also determined. The result showed the same shapes as NaF, obtained from the measurements of the refractive index by previous workers.

A New Superconducting Planer Magnet Development from a Magnetic Shielding Device Made of NbTi-Cu Films

We have studied the magnetizing characteristics of large scale sheets (300×1000 mm) of various tickness with superconducting NbTi-Cu multilayer films up to 100 layers in vertical magnetic field: The number of NbTi layer (n) dependence on the maximum value of trapped flux density (BTM) were investigated. In region of 0.1 µm < the thickness of a NbTi layer (d) < 1 µm at the total thickness of NbTi layers (nd)=10 µm, BTM increased in proportion to the logarithm of n value. In case of d=0.1 µm and n=100, the value of BTM was 3 times larger than that of the multilayer film with d=1.0 µm and n=10.

High Magnetic Field Shielding Devices with Superconducting NbTi-Cu Multilayer Films

We have studied the magnetic shielding effects of various hollow disks with superconducting NbTi-Cu multilayer films in vertical magnetic field. The hollow disk has an outer diameter(O.D.) of 60mm and an inner diameter(I.D.) ranging from 0 to 40mm by using the multilayer films composed of two NbTi-Cu layers which NbTi or Cu layer is 5.0um thick, respectively. As the increasing I.D. of the disks from 0 to 40mm, ΔBm (maximum magnetic shielding effects) decreased from 0.11 to 0.024-T. These studies have developed for high magnetic shielding devices which were formed by piling the hollow superconducting disks and A1 disks alternately. The device provided a space free from high magnetic field up to 0.8T.

MAGNETIC SHIELD EFFECTS OF SUPERCONDUCTING NbTi-Cu MULTI-LAYER FILMS

We have carried out the experimental study on magnetic shield effects of NbTi-Cu multilayers film deposited alternately NbTi and Cu films of various thickness. The thickness dependence of ΔBm/nd (ΔBm:max. magnetic shield effect, [d]:film thickness) with the parameter of the number of NbTi layers (n) for the multilayers film are investigated. In the region of [nd]>3μm and in any case of [n]=1,2,3,ΔBm/nd increases exponentially with decreasing [nd] and increasing [n].The relation between ΔBm/nd and [nd] is given the following formula in(ΔBm/nd)=α-βin(nd), α,β (constant). From these results, it is possible to completely seal off a magnetic field of a tesla or more by laminating NbTi-Cu multilayers film of reasonable thickness.

Turbulence Dependence of Vaporous Cavitation in Oxygen Jet

For the purpose of clarifying the cavitation characteristics and the effect of turbulence on the inception of hydraulic cavitation, liquid oxygen and oxygen-argon solution were cavitated in an immersed jet in the temperature range from 70°K to the normal boiling point under various hydrostatic pressures between vapor pressure and ordinary pressure. A good reproducibility in the inception of cavitation was obtained under the same hydrodynamic conditions. A simple relation was found among the critical velocity, the static pressure around the jet and the temperature of specimens. The result was discussed and the conclusion has been reached that the cavitation inception may be caused spontaneously in a flowing liquid by the turbulence with sufficient intensity.