Masatoshi Fujishiro

Tritium depth profiling in surface regions of solids by use of the T(d, α)n reaction

Abstract Tritium depth profiling with an incident deuteron beam by use of the T(d, α)n reaction was studied for the case where the energy spectrum of the emitted α-particles is used to evaluate the depth profile. Appropriate probing energies were considered to be from 100 keV to 1 MeV. The characteristics of this method were evaluated for a variety of experimental measurement conditions. The method was demonstrated for thin titanium layers containing tritium at probing energies of about 600 keV. The distribution of tritium obtained were almost uniform with depth, as expected, and the measured tritium content agreed well with that nominally stated.

Depth profiling of tritium in solids with the nuclear reaction induced by deuteron bombardment

A method for the measurement of depth profiles of tritium in solids has been developed in which the 3H(d,n)4He reaction is used. This method is nondestructive with relatively high depth resolution in the surface region of the solids. The validity of the present method has been supported by the examination of the depth profile measured for a tritium target as is used for a neutron source.

Depth profiling of tritium in a thin titanium layer bombarded with deuterium ions

Abstract Depth profiles of tritium in a thin titanium layer were measured using the T(d, α)n reaction. A new sample showed a nearly rectangular profile of tritium with concentrations from 1.1 to 1.2 atomic ratios (T/Ti). After the bombardment of 360 or 570 keV D 3 + ions at 20 ° C a dip was formed on the profile about the projected range of the incident ions, which indicates that tritium atoms and deuterium atoms were mixed at the implanted sites and then diffused. At a high dose rate of about 16 μA/cm 2 two dips were observable on the profile, in which a peak was formed about the projected range. For a temperature of −110 ° C the profile showed almost no change after a bombardment and the succeeding annealing at room temperature for 20 h. These results are discussed on the basis of the previous results.

Depth profiling study on the migration of tritium in titanium induced by deuterium-ion bombardment

Abstract A thin titanium layer with uniformly absorbed tritium (T/Ti ~1.0) was bombarded by 390 keV D 3 + ions (130 keV per deuteron). Bombardment was performed at low (111 K) and room temperatures up to fluences of 5.9 × 10 18 D / cm 2 and 3.0 × 10 18 D / cm 2 , respectively. Depth profiles of tritium up to a depth of 0.8 mg/cm 2 (~1.8 μm) were measured and the change of the profile with fluence was investigated by means of the T(d, α)n nuclear reaction. At both of the temperatures, a dip was formed on the depth profile of tritium at the depth around the projected range, indicating that the deuteron bombardment induced the migration of tritium against the concentration gradient. At the low temperature, the dip showed a gradual growth with fluence and saturation of the growth at the higher fluences, which could not be described by the existing model for isotope mixing. The spectrum of protons from the D(d, p)T reaction obtained in the same measurement suggested that the release of deuterium suddenly started at the final stage of the present bombardment. The dip formed at room temperature was larger than that at the low temperature. The migration of tritium induced by the bombardment is discussed on the basis of the experimental results obtained.

Tritium Depth Profiling Study on Titanium Tritide Target for Generating 14-MeV Neutrons

In-situ measurements of the depth profiles of tritium in a titanium tritide target for generating 14-MeV neutrons have been made with the method of the ion beam analysis using the T(d, α)n nuclear reaction. The initial distribution of tritium in the unirradiated target has been observed to be nearly uniform over the depths. After the irradiation of 390-keV D3 + ions at a temperature of about 10°C a dip has been found in the depth profile around the depth of the projected range of the ions. By the successive isochronal anneal-ings at temperatures below 130°C the tritium has been uniformly redistributed. The behavior of tritium in the target and the effectiveness of the depth profiling for evaluating the energy spectrum and the yield of source neutrons are discussed.

Ion beam analysis of tritium for nuclear fusion reactor materials.

Ion beam technique using the T (d, α) n nuclear reaction was applied to depth profiling of tritium in a deuterium implanted titanium sample simulating nuclear fusion reactor materials. The energy distribution of the α-particles from the T (d, α) n reaction was converted to the depth profile of tritium. The impurities of D, 3He, C and O were found to give no significant influence on the depth profiling. From the backscattered deuteron spectrum measured the amounts of the impurity atoms of O and C were estimated. According to the present results the applicability of the ion beam techniques to depth profiling of tritium in nuclear fusion reactor materials is discussed.

Cyclotron-based Real-Time Neutron Radiography System

A real-time neutron radiography system was installed by using a sub-compact cyclotron as a neutron generator. We utilized the neutron radiography facilities of Sumitomg Heavy Industries, Ltd. in which nominal neutron flux is 1.1 × 106 n/cm2 /sec at L/D = 30 with field size of 14″ × 17″.

The Gamma-Ray Dose-rate Effect in the Sprout Inhibitionof Potato Tubers

The gamma-ray dose and dose-rate effects and the loss of weight in the sprout inhibition of potato tubers were studied. The potato tubers used for this experiments were “Danshaku” variety which were yielded in October in Hokkaido.The irradiation was carried out in the dose-rate range from 5 × 102 R/h to 5 × 105 R/h changing the dose from 3 kR to 15 KR in December of 1975 and 1976. 60Co-source used for those irradiation were 7300 Ci and 13000 Ci of a rod type one (1.4 cm ∅ × 30 cm), respectively. The irradiated potato tubers were stored for 5 to 7 months in dark natural condition, and their sprouting and their weight variation were observed.The obtained results are summarized as follows:1) The time of sprouting of the irradiated potato tubers is delayed compared to that of non-irradiated ones (control). The more the dose and the higher the dose-rate, the delayed time becomes larger. The potatoe tubers irradiated to 6 kR under 5 × 104 R/h are late about 60 days in sprouting from non-irradiated ones (Fig. 1).2) The sprout inhibition is more effective not only by heavier irradiation dose, but also by irradiation under higher exposurerate (Fig. 2 and Fig. 3).3) The necessary and sufficient dose for the sprout inhibition is estimated to be about 10.5 kR for exposure-rate of 5 × 103 R/h, and it increases rapidly for the lower exposure-rate, while it decreases with the rate of about 2 kR per one order of magnitude of exposure-rate for the higher exposure-rate (Fig. 4).4) The rate of weight loss of irradiated potato tubers is small compared to that of non-irradiated ones, and ones more irradiatedshow less rate of weight loss (Fig. 5 and Fig. 6). The exposure-rate dependence in weight loss is not apparent (Fig. 7).

The Gamma-Ray Dose-Rate Effect in the Sprout Inhibition of Onion Bulbs

防止の線量率効果に関する研究も少ない。筆者等は60Co.線源 (1.4φ×30cm、棒状約8000Ci) を用いて昭和50年と昭和51年に102～105R/hの範囲で種々の線量に対する発芽防止の線量率効果を観察した。試料の玉ねぎは “泉州甲高” (6月中旬採取) 、照射は7月下旬～8月上旬に実施し、照射後、自然状態で保存、10～20日毎に発芽を観測した。線量率を変えるには線源と試料との距離を調整して変えた。高線量率照射の場合は試料が線源に近接するので、玉ねぎ2～3個を紙筒に入れ、底盤部と頂部が円筒軸に一致するように重ね、線量のパラッキを少なくするようにした。低線量率照射の場合はプラスチック製籠に一重に並べて照射した。発芽は照射線量が低い程早く、日が経つにつれて発芽率は高くなる (Fig.3) 。また、照射線量率が高いほど発芽しにくい (Fig.5) 。発芽防止の限界線量は、照射線量率が1×103R/hのとき約2000Rで、これより低い線量率では急速に高くなり、高い線量率ではゆるやかに低下する (Fig.7) 発芽率の観察を終了後 (照射後8ケ月後) 、発芽しなかった玉ねぎを切断して内芽の褐変を観察し、その長さを測定し、褐変の長さの分布曲線を求めた (Fig.8) 。その結果、褐変の長さは照射線量率に依存しており、低線量率で低線量照射したものの褐変は太く長く、高線量率で高線量照射したものは短いことが判明した (Fig.10) 。