Katsuhiro Miyamoto

Size Determination of Latex Particles by Electron Microscopy

The diameters of Dow latex particles in the size range from 0.085 to 0.330 μm were determined by electron microscopy. The effects of electron irradiation and the vacuum conditions in the microscope on the measured particle diameter were investigated. A comparison among latex samples was also made. The results confirmed that the measured diameters did not agree with the nominal diameters determined by the manufacturer of the latex particles. Differences lay in the range from + 6 to −18%. Standard deviations of the size distributions were also found to be different from the nominal values. Therefore, for accurate experiments, it is necessary to confirm the size of latex particles.

Size Measurements of Latex Particles by Laser Aerosol Spectrometer

Size measurements of PSL (polystyrene latex) particles in a size range from 0.109 to 0.330 μm were made by laser aerosol spectrometer (PMS, LAS-X). The results were compared with those by electron microscopy. For example, the geometric standard deviation, σg, of nominally 0.176-μm PSL particles was measured as 1.05, assuming that their sizes distribute log-normally. The value of 1.05 was very close to 1.02 measured by electron microscopy. It was found that the spectrometer had very high size resolution, although the size resolution of the light scattering type spectrometer has been said to be poor. For some samples of PSL particles, however, there were large differences between particle sizes measured by LAS-X and those by electron microscopy. It was also found that LAS-X had a problem in calibration of size response curve.

Penetration of submicron aerosols through high-efficiency air filters.

Penetration through high-efficiency air filters was measured using dioctyl phthalate (DOP) particles and ambient particles. The tested filters were a Whatman GF/A filter and a Oshitari SO filter, one of the media used in high-efficiency particulate air (HEPA) filters. The particle concentration measurements were made with an automated diffusion battery (DB)/condensation nucleus counter (CNC) submicron-sizing system and a laser-particle spectrometer. It was found that the most penetrating particle sizes through both the GF/A filter and the SO filter were in a size range from 0.10 to 0.18 micron in diam. The values of penetration through the GF/A filter by two different particle-measuring methods, the combined CNC/DB system and the laser-particle spectrometer, were consistent with each other in the limited size range from 0.12 to 0.42 micron. No significant difference between the penetration curve of DOP particles and that of ambient particles was observed.

Remote calibration of ionization chambers for radioactivity calibration

A new calibration technique, referred to as e-trace, has been developed by the National Institute of Advanced Industrial Science and Technology (AIST). The e-trace technique enables rapid remote calibration of measurement equipment and requires minimal resources. We calibrated radioisotope calibrators of the Japan Radioisotope Association (JRIA) and the Nishina Memorial Cyclotron Center (NMCC) remotely and confirmed that remote calibration provided results that are consistent with the results obtained by existing methods within the limits of uncertainty. Accordingly, e-trace has been approved as the standard calibration method at AIST. We intend to apply remote calibration to radioisotope calibrators in hospitals and isotope facilities.

The remote calibration of radioisotope calibrators

the new calibration technique ‘e-trace’ has been developed by AIST. Using e-trace, measurement equipment in remote place can be calibrated in short time and limited resources. We calibrated radioisotope calibrators of JRIA and NMCC remotely. It was confirmed that the results of remote calibration was consistent with those of former method within uncertainty. As a result, e-trace is approved as a regular calibration method at AIST. We plan to apply remote calibration to the calibration of the radioisotope calibrators in hospitals and isotope facilities.