Position resolution of a position-sensitive proportional counter developed for neutron detection has been studied. The counter is based on the tilted-wire position reading method and consists of a pair of position sensing wires being extended in parallel each other but tilted against the anode wire. Natural boron and boron nitride in solid phase and of about 1 mm width are employed as neutron converters. The counting gas is PR gas and the pressure of the gas is varied from 1.00 to 1.44-atm. The two-dimensional spectra of position vs. energy for the emitted charged particles are observed and boron-related neutron events can be clearly identified. The position spectra are deduced from the two-dimensional data, and the effect of gas pressure and particle energy on the position resolution is discussed. The position resolution of about 2 mm full width at half maximum (FWHM) is obtained at 1.44 atm for low-energy events.
Whole black pepper packed in multilayers of 1 cm thick (0.6g/cm3) was irradiated with 5 MeV electron beam (EB) in a downward direction (surface dose, 15 kGy) . The absorbed dose in the sample was maximal at a depth of 0.9g/cm2 (120% of the surface dose) and decreased towards the deepest layer. The total amount of aerobic bacteria in the black pepper before irradiation was 2.1×107 per gram and spore-formation after irradiation was decreased to below 1.0×103 per gram within a depth of 1.5 g/cm2. After irradiation, the electron spin resonance (ESR) signal at g=2.004 accompanied satellites. Furthermore, we also found minor signals such as cellulose radicals in the irradiated black pepper. The amount of radicals induced by EB was dose-dependent. Satellites and minor signals remained detectable for over 9 months in black pepper that had been irradiated to the level of sterilization.
To elucidate the various characteristic and their availabilities of the radioactivity and negative air ion originated from an artificial thoron hot spring, we simulated a hot spring condition using a monazite powder and measured the negative air ions and radioactivities in the condition. In the result, the radioactivity of the thorium series nuclide (208Tl) in monazite was 5.3 times of that of the uranium series nuclide (214Bi) . For the pH (3.5-12.5) dependence of the leaching nuclides from monazite in water, the thorium series nuclides (228Ac, 212Pb) were well leached on the strong acid side because the monazite includes the rare earth element (REE) which was high ionization tendency and was substituted by the radioactive nuclide. On the other side, the uranium series nuclides (214Bi, 214Pb) leached in water were not detected because the specific activities of the uranium series nuclide are lower relative to those of the thorium series nuclide. Moreover, there were many negative air ions originated from monazite in the place within 10 cm away from the monazite surface. This is suggested that most negative ions exist within the range of the radiated α rays. Negative air ions increased with increasing atmospheric relative humidity (35-60%) . This is suggested that negative air ions stably existed in the hydration type such as O-2 (H2O) n. Furthermore, for the hydrous rate dependence of the negative air ions originated from monazite, the negative air ions without supernatant fluid were larger than those with supernatant fluid, because a rays ionized water on the surface of monazite.
Penetration range and depth-dose distribution of 10 MeV electrons within commercial packages of experimental animal feeds were examined with a high power electron accelerator for verification of the application of high energy electron beam irradiation to sterilize experimental animal feeds. Optimum packaging sizes were proposed based on the experimental results. The change of the vitamins and the efficacy of the sterilization by the irradiation were also studied. It is confirmed that the sterilization of experimental animal feeds by 10 MeV electron beam has been completely practical.