In over-irradiated imaging plates(IPs) with X-ray, quite stable latent images remain unerasable after fully erasing with visible light. Emission from unerasable latent images was verified to be photostimulated luminescence(PSL). A model of the excitation of deeply trapped electrons and PSL processes was proposed. Deeply trapped electrons spread in relatively longer wavelength would be the cause of PSL in unerasable latent images. Dose-response curves as a function of X-ray dose were obtained before and after fully erasing in three types of IP samples(BAS-TR, BAS-MS, and ST-VI). In all types of IPs, dosimetric characteristics such as linear relationship between irradiated dose and PSL density were found to be the same before and after erasing except quite smaller PSL density observed in unerasable latent images. Comprehensive results indicate that deep electron centers may act as competitive trap centers to the F centers but their capture cross section is fairly smaller than that of F centers.
Dose-rate distribution in irradiation field of 60Co gamma-ray was calculated using Monte Carlo photon transport code named as EGS4-SPG code. The dose rate values measured by the ionization chamber and the alanine dosimeter were compared with calculated ones for the evaluation of the validity of the calculation. As a result, the difference between measurements and the calculation value was within ± a few% except for a position very near the source for a wide board radiation source. The dose-rate distribution can be estimated using these numerical results at the beforehand planning of a board radiation source arrangement although dose-rate measurement should be done only for a position very near the radiation source, where calculated value disagreed. The dose rate distribution measurement after the radiation source arrangement enables us to save number of the dosimeter and measurement time.
It became to be ruled to check the concentration of formaldehyde as the estimation of airborne concentration in working environment since March, 2009 and then, liquid chromatography and easily analyzing equipment methods, mainly gas detector tube method, are given as the official methods. When we estimate the airborne formaldehyde concentration in a work place where only formalin is used as a formaldehyde emission source such as a room for pathological examination, it is not necessary to separate formaldehyde and therefore not very reasonable to use liquid chromatography including troublesome procedures. On the other hand, gas detector tube method is convenient but has possibility of causing errors by individual differences. The errors might cause the additional differences of the control classes and of the measures to prevent workers from being exposed to harmful materials. In order to solve these problems and to exam alternative analyzing method for formaldehyde, we tried to measure the concentration by using 14C-labelled one. After 14C-labelled formaldehyde solution is put into the emission source of formaldehyde(formalin solution), the vaporized samples are taken by silica gel tubes quantitatively as usual at the estimation of airborne concentration in working environment. By counting the desorpted amount of radioactivity from silica gel, it was revealed that the obtained concentrations of formaldehyde are correspond to both the calculated values and the values indicated on the gas detector tubes at various concentrations. In this study, we used the amount below the lower activity limits of radioactive material. Except the users who have radioisotope controlled area, we are allowed to use 14C-labeled materials below 10MBq without being regulated under the Law Concerning Prevention of Radiation Hazards. When we use a little amount of 14C-formaldehyde at formaldehyde using area to check the concentration of vaporized formaldehyde, this method was found to be practically useful for the estimation of airborne concentration in working environment.
We studied a method to measure low level radon concentration in the argon gas using a high sensitivity radon detector. Radon is collected by activated charcoal in a column with cooling system. It is confirmed that collection efficiency of radon in argon gas is higher than 90% with the activated charcoal cooled at −105°C. The measured release efficiency of radon in argon gas is higher than 99% at 85°C of the charcoal temperature. The background level of this system for argon is 14±1(stat.) ±1(sys.)mBq/m3. As a result, we estimate that the radon concentration of 14μBq/m3 in argon can be measured after 0.5 days of collection with flow rate 3.0L/min.
Frontiers of antimatter physics are reviewed, with a focus on our ASACUSA collaboration, doing research on “Atomic Spectroscopy And Collisions Using Slow Antiprotons” at the “Antiproton Decelerator” facility at CERN. Antiprotonic helium atoms give a unique test ground for testing CPT invariance between particles and antiparticles. Laser spectroscopy of this exotic atom has reached a precision of a few parts per billion in determation of the antiproton mass. We also have developed techniques to decelerate antiprotons and cool them to sub-eV energies in an electromagnetic trap at ultra-high vacuum and extract them as an ultra-slow beam at typically 250eV. This unique low-energy beam opens up the possibility to study ionization and formation of antiprotonic atoms. The antihydrogen has been synthesized at low temperature in nested Penning traps by ATRAP and ATHENA(presently ALPHA) collaborations. Confinement of this neutral anti-atoms in a trap with magnetic field gradient is being studied, with an aim of 1S-2S laser spectroscopy in the future. ASACUSA has prepared a cusp trap for production of antihydrogen atoms, and aims at microwave spectroscopy between the hyperfine states of spin-polarized antihydrogen. A wide variety of low-energy antiproton physics also includes measurement of nuclear scattering, radiational biological effects, and gravity test of antimatter.
[11C]flumazenil, which selectively binds to the central benzodiazepine receptors, is a PET tracer to visualize GABAA receptors in the central nervous system. In this review, a brief summary of the tracer and its clinical applications are discussed. Because of its unique pharmacokinetic characteristics, various practical quantitative methods have been proposed. [11C]flumazenil PET study is useful for epileptic foci detection in the clinical situations, and many other applications such as detecting ischemic penumbra, prognosis prediction, dose-finding trial have been reported.
The basic idea of the crystal physics and diffraction technique is given as an introduction for neutron diffraction. X-ray and neutron diffraction techniques are compared, and also the principle of the technique to use pulse neutron is explained. Reciprocal lattice, which is essentially important to consider the diffraction phenomena, is emphasized in the lecture. Powder diffraction technique is explained based on the single crystal diffraction. The introduction of crystal structure analysis is given with a simple example having a base-centered-tetragonal cell. In addition, the formalism of the magnetic structure analysis is discussed and the simple example of the antiferromagnetic case with the same unit cell is given.