Tsuyoshi Tomiyama

Discrimination and determination of gases utilizing adsorption luminescence

Thermoluminescence caused by adsorbates (adsorption thermoluminescence) appears in the process of heating Al2O3 powder that had previously adsorbed the vapour of an organic solvent, such as ethanol or acetone, at room temperature. The profiles of the thermoluminescence spectrum and glow curve depend on the kind of adsorbed vapour. The total amount of emitted light L depends on the concentration of the vapour in air, and L increases with an increase in the duration of adsorption. The adsorbates that act as the origin of the thermoluminescence are accumulated through a Langmuir-type adsorption process of very low activation energy (about 0.02 eV). These characteristics of the adsorption thermoluminescence enable us to discriminate and determine very low concentrations of these vapours. For example, L is proportional to the concentration of acetone vapour below 20 ppm for an adsorption time of 10 min, and the 1 ppm of vapour can be measured with good reproducibility.

Continuous determination and discrimination of mixed odour vapours by a new chemiluminescence-based sensor system

Abstract A gas sensor that utilizes chemiluminescence (CL) during the catalytic oxidation of odour vapours on a sintered aluminium oxide (γ-Al 2 O 3 ) layer is proposed. A new technique is applied to determine continuously the concentration of each constituent in a mixed vapour by a single CL-based sensor. The sensor is heated and cooled periodically in a temperature cycle between 200 and 740 °C at constant heating and cooling rates of ±9 °C s −1 . By measuring the total CL intensities in the heating and cooling courses, we can obtain the concentration of each constituent for a mixed vapour of ethanol and acetone in air. The lowest detection limit of the concentration of these vapours is of the order of 1 ppm.

In vivo measurement of spatial dose distribution with thermoluminescent sheet around high dose-rate intracavitary source: application to rectal cancer.

For intracavitary high dose-rate radiation therapy, a thermoluminescent [TL] sheet for in vivo measurement of spatial dose distribution around source has been recently developed. The TL sheet was found to have a linear response with a very wide dynamic range from at least 0.002 cGy to 5000 cGy for 60Co gamma-rays. This TL sheet (40 cm x 50 cm x 200 microns), which is composed of Teflon mixed with BaSO4:Eu doped powder, is very flexible and can be cut to the desired size. In addition, this sheet is easy to handle because of its insensitivity to room light. The spatial dose distribution is displayed in a color mode by using a newly developed TL sheet readout system. For a clinical application, the TL sheet was wrapped on an applicator for intracavitary radiation therapy of a rectal cancer and was inserted into the rectum. The location of the TL sheet could be confirmed with diagnostic X ray film. After irradiation with high dose-rate 60Co source, the in vivo relative dose distribution on the surface of the rectum was determined. This TL sheet provided a convenient means of measuring the relative dose distributions around 60Co sources of various patterns in intracavitary radiation therapy.

Screening out obstructive radiation from thermoluminescence sheets (BaSO4:Eu) exposed to cosmic rays

Abstract The effects of filtering the light and of N2 gas in use of the thermoluminescence sheet (BaSO4:Eu) for cosmic rays are reported.

Coordinate measurement system supported by image processor for emulsion plates

Abstract Central collisions of 32S and 16O with Pb at 200 GeV amu have been studied by the emulsion spectrometer in the CERN-EMU05 experiment. The emission angles, momenta and charge signs of the secondary particles are measured. The position of a track in an emulsion plate should be measured by using a microscope to determine the momenta of more than 500 charged secondaries in an event. A new coordinate measurement system has been developed by using a video image processor connected to the microscope. In this system, the position, direction and length of a track in a coated emulsion are expressed as a vector which is linked with the motion of micro X-Y stage and is superimposed on an emulsion image on a TV monitor. By using this system, the data acquisition rate has become about ten times faster than that by using only an emulsion image and the momentum resolution has become higher than that. Moreover, this system is effective for identifying tracks emitted in more than 45°.

Photoluminescence study of adsorption-luminescent Al2O3 sensor for determining odor substances in air

An adsorption-luminescent sensor enables us to discriminate and determine the vapor of odor substances by measuring temperature dependence of luminescence from the sensor (powder of (gamma) -Al2O3) which previously adsorbed odor vapor in the air. Profiles of the adsorption luminescence (AL) spectra as a function of temperature for butanol, acetone, and n- butyric acid are apparently different from each other, and these vapors of 1 to 100 ppm in concentration in the air can be determined from the total luminescence intensity. The study of photoluminescence (PL) observed for the sensor after contact with these odor vapors implies that AL is peculiar chemiluminescence during catalytic oxidation of odor vapor which produces water and surface hydroxide.

A pure single particle detecting counter telescope to search for fractionally charged particles

Abstract This paper gives an outline of the PSPD (pure single particle detecting) telescope which is being used in a search for fractionally charged particles in cosmic rays at sea level. A special feature of this experiment is the accurate d E /d x measurement and the detecting of pure single particles. For this purpose, multicell proportional chambers and the PSPD counters are used. The procedures and systems for data selection are also described.

A cosmic-ray counter telescope to search for fractionally charged particles

Abstract A cosmic-ray counter telescope (Okayama Telescope) has been operated at various zenith angles in order to look for fractionally charged particles at sea level. Several millions of clear single events have been analyzed. At zenith angles around 40°, several candidates of ( 4 3 )e charged particles were found, while at other zenith angles few candidates were found. To examine these results, we have constructed an improved telescope to measure d E /d x and to trace the track in crossed planes. This paper gives the characteristics and the first analysis of the data obtained with the improved telescope.

The arrival direction of (4/3)e-lepton candidates in celestial coordinates

SummaryA cosmic-ray counter telescope (OKAYAMA telescope) has been operated at several zenith angles at sea level. Several millions of clean single events have been analysed. About thirty candidates of (4/3)e charged leptons were found at around 40° zenith angles. The distribution of the arrival directions of these candidates in the celestial sphere was found to be anisotropic.