Critical current test results of 13 T-46 kA Nb3Al cable-in-conduit conductor

In the framework of ITER-EDA, a 13 T-46 kA Nb₃Al conductor with stainless steel jacket has been developed in order to demonstrate applicability of an Nb₃Al conductor with react-and-wind technique to ITER-TF coils. Using a 3.5 m sample consisting of a pair of conductors with 0% and 0.4% bending strain, the critical current performances of the Nb₃Al conductors were studied to verify that the conductor achieves the expected performance and the bending strain of 0.4% does not originate degradation. The critical currents were measured at background magnetic fields of 7, 9, 10 and 11 T at temperatures from 6 to 9 K. The expected critical currents were evaluated taking into account the variation of the strain in the cross-section due to the bending strain as well as self-field and non-uniform current distribution as results of an imbalance in the joint resistance and inductances. The calculation results indicate that the current distribution is almost uniform and the experimental results showed good agreement with the expected critical currents. Accordingly, we can conclude that the fabrication process of this conductor is appropriate and the react-and-wind technique using the Nb₃Al conductor is applicable to ITER-TF coils. In addition, the critical current of the Nb₃Al conductor is expected to be 108 kA at 13 T and 4.5 K, resulting in a sufficient margin against the nominal current of 46 kA. Furthermore, it was found that the decrease in the critical current by thermal strain can be made small by applying the bending strain to the conductor so as to reduce the compressive strain at higher fields, i.e. inner side of the coil, in the conductor cross-section.     

Layer-by-Layer Growth of 4He Adsorbed on One-dimensional 18Å-Pores

We have measured vapor pressures (P) of ⁴ He adsorbed on one-dimensional pores of 18 Å diameter with a sensitivity of 2×10 ^–3 mbar as a function of coverage down to 1.2 K. The isothermal compressibility (_T) calculated from P isotherm has two minima, which are associated with the completion of the first and the second layer. The adsorption energy was obtained quantitatively from an Arrhenius type temperature dependence of P. As the coverage is increased, the adsorption energy at T=0 per atom ( ₀ /k_B) decreases from 180 K to 35 K, followed by a clear step associated with a second layer promotion. After second layer completion, ₀ /k_B is constant. The magnitude is the same value as the latent heat of the bulk ⁴ He liquid (7 K). These results give us a clear picture that ⁴ He film grows in a layer-by-layer fashion up to the second layer on one-dimensional pore walls.     

Vertical-cavity surface-emitting laser active regions for enhanced performance with optical pumping

We have developed an improved active region design for optically pumped vertical-cavity surface-emitting lasers. The design makes use of carrier-blocking layers to segment the absorber and promote uniform carrier populations in the quantum wells with pump efficiencies near 75%. A model to calculate the carrier distribution in the active region and a design methodology are presented along with a metric to describe the carrier uniformity in the quantum wells. Experimental verification of the performance improvements shows an over 50% reduction in device thresholds and an increase of 20/spl deg/C in maximum operating temperatures.     

Long-wavelength two-dimensional WDM vertical cavity surface-emitting laser arrays fabricated by nonplanar wafer bonding

We demonstrate the first long-wavelength two-dimensional wavelength-division-multiplexed vertical cavity surface-emitting laser array. The eight-channel single-mode array covers the C-band from 1532 to 1565 nm. The devices are fabricated using two separate active regions laterally integrated using nonplanar wafer bonding. We achieved single-mode powers up to 0.8 mW, 2-dB output power uniformity across the array, and sidemode suppression ratios in excess of 43 dB. This fabrication technique can be used to maintain the gain-peak and cavity-mode alignment across wide-band arrays and, with the use of nontraditional mirrors, can be extended to the fabrication of arrays covering the entire C-, S-, and L-bands as well as the 1310-nm transmission band.     

Anti-drug-related antibodies in nonthrombocytopenic cardiac patients

Drug-related antibodies (quinidine, hydrochlorothiazide, and digoxin) were studied using the 51Cr platelet lysis test and a recently introduced simplified platelet factor 3 assay in a total of 109 patients admitted to a coronary care unit. Quinidine antibodies were found in 16 (14.7%), hydrochlorothiazide antibodies in six (5.5%) and digoxin antibodies in two (1.8%) of 109 patients. All patients had normal hematologic data, including platelet counts. There was a significantly high incidence of quinidine antibodies in male patients (p less than 0.02), despite the previous report that quinidine-induced purpura was seen predominantly in female patients. Ten patients (9.2%) had antiplatelet antibodies. The simplified platelet factor 3 assay can easily be done in most laboratories and appears as sensitive as the 51Cr platelet lysis test. The high incidence of drug-related or antiplatelet antibodies in hematologically asymptomatic patients may indicate the presence of an insidious, compensated thrombolytic state in many patients.     

Low loss and high extinction ratio strictly nonblocking 16×16thermooptic matrix switch on 6-in wafer using silica-based planarlightwave circuit technology

We describe a silica-based 16×16 strictly nonblocking thermooptic matrix switch with a low loss and a high extinction ratio. This matrix switch, which employs a double Mach-Zehnder interferometer (MZI) switching unit and a matrix arrangement to reduce the total waveguide length, is fabricated with 0.75% refractive index difference waveguides on a 6-in silicon wafer using silica-based planar lightwave circuit (PLC) technology. We obtained an average insertion loss of 6.6 dB and an average extinction ratio of 53 dB in the worst polarization case. The operating wavelength bandwidth completely covers the gain band of practical erbium-doped fiber amplifiers (EDFAs). The total power consumption needed for operation is reduced to 17 W by employing a phase-trimming technique which eliminates the phase-error in the interferometer switching unit     

Separation of Am(III) from Eu(III) by extraction based on in situ extractant formation of dithiocarbamate derivatives

A new solvent-extraction technique based on in situ formation of dithiocarbamate derivatives in order to separate Am(III) from Eu(III) was carried out. In this technique, the extractant is formed during the extraction course by the reaction between the organic materials, which are needed to synthesize the extractant. The synthesis of extractant in in situ extractant-formation method was carried out as follows. Di-substituted amine, such as dioctylamine (DOA), dibenzylamine (DBzA) and so on, and carbon disulfide (CS₂) were mixed in organic solvents, such as nitrobenzene, to produce dioctylammonium dioctyldithiocarbamate (DOA⁺·DODTC⁻), dibenzylammonium dibenzyldithiocarbamate (DBzA⁺·DODTC⁻), or so on. These organic solutions are also the organic phase in the solvent extraction, whereas the aqueous phase is 1.00 mol/dm³ (H, Na)NO₃ solution. The elements of Am(III) and Eu(III) were extracted into organic phase from different hydrogen ion concentrations of aqueous phase. The SF of Am(III)/Eu(III) is 3.2 × 10⁴ at pH_eq = 6.25 in DOA–CS₂/nitrobenzene system. This separation technique of Am(III) from Eu(III) by extraction based on in situ extractant formation has the following advantages. (a) It is unnecessary to take the chemical stability of extractant into account for storage purpose, and (b) Am(III) can be completely separated from Eu(III) by a single extraction procedure.     

Active reduction of the end effect by local installation of neutron absorbers

In the burnup credit analyses of interim or long-term spent fuel (SF) storage facilities and transport casks, when the average burnup value is greater than approximately 30 GWd/t, the neutron multiplication factor becomes greater if we consider the axial burnup distribution of the spent fuel assembly rather than assuming an average burnup. This phenomenon is called the “end effect” and it is one of the main technical issues in burnup credit research. The end effect is characterized by an increase of the neutron flux around the end regions of the spent fuel assemblies in the criticality calculation. However, such increase of the neutron flux has not been observed in experiments using actual spent fuel assemblies.     

Robust and efficient determination of saturation pressure from constant mass expansion data

This article presents an improved method for the determination of saturation pressure from pressure-volume data of constant-mass expansion (CME) for hydrocarbon mixtures. The conventional methods rely on the direct observation of an incipient phase and/or the change in total compressibility of the fluid sample near the saturation pressure in CME; however, they are unreliable for volatile oils, gas condensates, and near-critical fluids. The method developed in this research is to capture the expansion behavior of the overall fluid through the attraction and covolume parameters of the Peng–Robinson equation of state. The reliability of the new method is demonstrated by comparing it with the conventional methods in the case studies using 59 different fluids. It was the only method that could reliably identify saturation pressures for five volatile oils, 11 gas condensates, and one near-critical fluid among the datasets tested.