Hiroshi Ebihara

Domain Orientation Imaging of PbTiO3 Single Crystals by Vertical and Lateral Piezoresponse Force Microscopy

Four kinds of domain structures (180° c-c, 180° a-a, 90° a-a and 90° a-c domains) on grown surfaces of PbTiO3 single crystals were imaged successfully using vertical and lateral piezoresponse force microscopy (PFM). Domain orientations (i.e., polarization vector distributions) at the surface of each domain structure are presented. These domain images are compared with simultaneously observed surface topographic images decorated by an acid etching treatment.

Determination of disintegration rates of a 60Co point source and volume sources by the sum-peak method

The disintegration rates of 60Co as a point source (<2 mm in diameter on a thin plastic disc) and volume sources (10–100 mL solutions in a polyethylene bottle) are determined by the sum-peak method. The sum-peak formula gives the exact disintegration rate for the point source at different positions from the detector. However, increasing the volume of the solution results in enlarged deviations from the true disintegration rate. Extended sources must be treated as an amalgam of many point sources.

Performance test of PDM-101 electronic pocket dosimeters using a 60Co source

The performance tests of one type (named PDM-101) of silicon semiconductor dosimeter were carried out by using a 60Co point source (approximately 500 kBq). The dosimeter responds to dose equivalents on the order of 0.02 microSv although measured data show a large error for values < 0.08 microSv. The deviation of measured dose equivalents from calculated ones was < 10% in the region > or = 0.08 microSv. The deviation of measured dose equivalent rates from calculated ones was generally < 10%. The average value of measured dose equivalents for 31 directional exposures without underside exposure was 0.92 +/- 0.06 of the calculated value. The difference of measured data for the front and back exposure was < 10%. The background and noise level of the dosimeter was 0.092 +/- 0.005 microSv h-1. All measured data showed that dosimeter response for radiation was symmetric between the front (left) and the back (right) sides of the dosimeter within 10% tolerance.

Error estimation for the sum-peak method by use of two 60Co point sources in place of extended sources

Abstract The sum-peak method had been applied to determination of disintegration rates of extended sources composed of two 60 Co point sources. It was concluded that, when a detector had an equal efficiency for both point sources, the absolute disintegration rate could be determined, and when not equally efficiency, under-estimated. We had examined an error which occurred in the extended source, and theoretical results perfectly coincided with experimental results. These results were found to be effective for an arbitrary extended source.

Measurement of disintegration rates of small [60Co]Co sources in lead containers by the sum-peak method

Abstract The sum-peak method has been applied to determine the disintegration rates of two small [60Co]Co sources (30 and 350 kBq) in lead containers with several thicknesses (3, 6, 9, 15, 21, 27 and 33 mm) by using a NaI(Tl) detector. The experimental results showed that the sum-peak method was perfectly effective for the determination of the disintegration rates (unrelated to the thicknesses of the containers) of the 350 kBq source. The sum-peak method was also absolutely effective for the 30 kBq source in the case of containers with thicknesses of 15 mm and less, but in the cases of those with thicknesses of 21, 27 and 33 mm, the disintegration rates were under-estimated and the deviations from the true disintegration rate increased rapidly with increasing thicknesses of the containers. We presume that the under-estimation of the disintegration rates was the result of the over-estimation of the areas under the sum peaks, caused by the interference of the γ-ray (2614 keV) emitted from the naturally occurring radionuclide 208Tl.

Visualization of the Domain Orientation in Relaxor Ferroelectric Single Crystals by Piezoresponse Force Microscopy

Domain structures on (001) plates of PZN-9%PT and PMN-32%PT were visualized by piezoresponse force microscopy (PFM) at various sample temperatures ranging from 25°C to 200°C. Zebra pattern domain structures were observed on both relaxors at various temperatures ranging from 25°C to the Curie temperatures and above. It was found that these domain boundaries did not move at these temperatures excluding the case of domain switching by PFM modulation voltage.

Chemical effects of β− decay in 99Mo(CO)6

Abstract The chemical consequences following β − decay of 99 Mo in Mo(CO) 6 have been investigated. The yields of 99m Tc species in solid state and in solution of n -pentane were determined by various separation methods. The 99m Tc species are identified as 99m Tc(CO) 5 radicals, 99m Tc 2 (CO) 10 and 99m Tc 2+ ions. The product yields were 73,7 and 7% respectively for the solid and 31, 0 and 39% respectively for the solution. These results are discussed on the basis of the energy distribution of recoiling 99m Tc atoms and the charge effects owing to perturbation of electron shells.

Solvent Effects on the Reactions of Recoil Species in the Group VI Metal Carbonyls in Solution

Solvent effects on recoil reactions following neutron capture have been studied in hexacarbonyls of the Group VI metals, CrCCO),, Mo(CO), and W(CO)j in hydrocarbon solutions. The retentions basically increased with an increase in the number of carbon atoms of n-aUcane. By comparison with radiolytic reactions it was assumed that radiolysis products such as olefins and alkyl radicals in saturated hydrocarbon solvents brought about a signiJficant decrease in retention. A fairly low retention was observed in olefin solutions such as 1-hexene, cyclohexene. Further, the retentions were drastically affected by the addition of iodine as a radical scavenger. It could be deduced from these results that the solvent effects on recoil reactions in the Group VI metal carbonyl solutions are influenced by the physical parameters (molecular weight and/or viscosity), scavenger effect and formation of radical scavenger by radiolysis of the solvents.

Transfer of60Co from midwater squid to sperm whales

Sperm whales are notable squid-eaters. They feed mainly on medium to large-sized cephalopods at midwater levels and defecate near the surface. This suggests the existence of an upward transport of60Co by sperm whales from the mesopelagic zone (150–1,200 m). To elucidate this squid-whale route for this artificial radionuclide,60Co content was determined in squid and in predator whales captured by commercial whaling. In the Cephalopoda livers60Co levels of 30–500 mBq kg−1 wet were found and in the viscera of Odontoceti (toothed whales) 15–40 mBq kg−1 wet. About 0.3% of80Co ingested was estimated to be retained in a 23-year-old male sperm whale. In the livers of Brydes whales,60Co levels of 40–80 mBq kg−1 wet were detected, but not in euphausiids and sardines, their possible prey. The level of Co in sperm whales was nearly the same as in Brydes whales. Specific radioactivity60Co/59Co in mBq µg−1 was several times higher in sperm whale (1.1–1.6) than in cephalopods (0.19–0.77). Eating prey with a high content of60Co in the 1960s may have contributed to the present body burden in sperm whales with a long-life span. However, the origin of60Co in Brydes whales is unknown.

Chemical effect of iron recoil atoms in ferrocene

The chemical consequences of neutron capture in solid ferrocene were investigated. Initial retentions of 55Fe and 59Fe recoil atoms were determined by various separation methods. Slight differences in retention between recoil atoms of 55Fe and 59Fe were observed. The results are discussed and interpreted in comparison with other compounds on the basis of difference in recoil energies of the product nuclides. Temperature sensitivity of the retention is also discussed.