Radiation induced luminescence phenomena, such as thermoluminescence (TL) and radioluminescence (RL), have been observed, when quartz grains are irradiated with ionizing radiations. Nowadays, the usefulness of red TL (RTL) -dating techniques to burnt archaeological materials and volcanic ash layers is widely recognized. In these luminescence studies, an artificial irradiator, which serves as a dose-simulator to natural radiations, is necessary for the determination of naturally accumulated doses. The authors have initially proposed the preferable use of a small X-ray generator as a reference radiation source instead of radioisotopes (RI) (90Sr-90Y source) . The X-ray generator exhibits the following excellent properties : (i) good linear relationship between tube current and dose rate, (ii) widely dynamic range of applicable doses up to 105 orders, and (iii) highly uniform irradiation property to sample area. On the other hand, since the X-ray spectra from an X-ray tube consist of continuous energy, a part of low energies below a few keV cannot pass through the whole of a quartz grain due to their short path length within quartz to cause homogeneous radiation effects. Therefore, the optimal irradiation conditions with the X-ray generator were studied with the aid of X-ray spectrometry by applying various thickness of aluminum-absorbers to exclude low-energy components. Concerning the reproducibility of the luminescence intensities, it was confirmed that Al-absorbers are available to dosimetry owing to an atomic number almost equivalent to Si. Finally, the thickness of the optimal aluminum absorber was found to be usable beyond 50μm thickness.
The separation factor of chlorine isotopes was precisely determined by using anion-exchange chromatographic technique, which employed a 1.5 m-long column. Hydrochloric acid (0.1 mol/L) solution was fed into the column with the flow rate of 1.5 mL/min. The magnitude of the factor obtained was 1.00023±0.00006 (1δ) at 25 °C. The result was in good agreement with the results obtained in previous works, and showed that the lighter isotope (35Cl) was preferentially fractionated into the resin phase, while the heavier one (37Cl) was enriched into the aqueous phase. This trend suggested that Cl-ions hydrated in the aqueous phase were slightly more stable than the hydrated Cl-ions interacting with the ion-exchange sites of the resin.
We present the effect of X-ray irradiation of buckwheat seeds on the growth of seedlings. The highest growth was observed when irradiation dose was 200 mGy, after two weeks, where the dose was changed from 20 to 1000 mGy. When the number of the seeds for the experiment was increased from 10 to 50 200 mGy irradiation also showed the growth promotion of the seedlings (T-test showed p = 0.02) .