K. Ashida, K. Ichimura, K. Watanabe

Abstract

    A study was made on the effect of iron impurities on the trapping-detrapping processes of hydrogen isotopes implanted to graphite by using XPS and thermal desorption spectroscopies. XPS measurements revealed that the deposited iron changed its state to iron-carbide (Fe₃C) type by vacuum heating at above 800℃ and increased the electron density of graphitic carbon atoms. The modified graphite surface showed considerably different thermal desorption spectra (TDS) from those observed for clean graphite surfaces. Namely, the iron caused to disappear the desorption peak Ⅰ (the lowest desorption peak for the clean graphite), and to appear a new desorption peak ([Fe/C] peak) in TDS. The new peak was found to be equivalent to the desorption peak Ⅱ for the clean graphite. Its desorption mechanism was explained by the second order surface recombination of trapped hydrogen isotope atoms. The rate constants for three hydrogen isotopes were determined as

K(H₂) = (7×10^-4) exp (-59×10³/RT)

K(D₂) = (4×10^-4) exp (-59×10³/RT)

K(T₂) = (1×10^-4) exp (-59×10³/RT)

    Where the frequency factor and activation energy are in [/molec. s] and [cal/mol] units, respectively. The results indicate that the impurity effect on the trapping-detrapping processes is due to the increase in electronic change on carbon atoms caused by iron dopant.

Kiyoshi Kusabiraki, Takashi Kubo, Takayuki Oaka, Masao Matsuyama, Kuniaki Watanabe

Abstract

    The tritium thermal desorption analysis for iron was carried out in order to elucidate the trapping sites of hydrogen and to obtain the activation energy of tritium desorption from each trapping site in iron.
    The results obtained in this study are as follows:

1. Four desorption peaks of tritium with maxima at about 500, 620, 900 and 1100 K, which were designated as peaks 1, 2, 3 and 4, respectively, were detected in both cold-rolled and annealed iron in the thermal analyses. This result suggests that there are at least four kinds of tritium trapping sites in iron.
2. The intensity of peak 1 which appears remarkably in the cold-rolled iron decreases by annealing the specimen.
3. The total amount of desorbed tritium, namely the total amount of absorbed tritium, in the cold-rolled iron is much larger than that in the annealed one.
4. The activation energies for desorption of tritium from the trapping sites were estimated. Peaks 1, 2 and 3 in the cold-rolled iron, they were estimated to be 56.5, 75.3 and 17.6 kJ/mol, respectively. Peaks 2 and 3 in the annealed iron, they were estimated to be 31.0 and 14.2 kj/mol, respectively. Peaks 1 and 2 can be assigned as tritium release from dislocation and/or vacancy and iron nitride precipitate, respectively.

K. Ashida, K. Ichimura, M.Matsuyama, K.Watanabe

Tritium Research Center, Toyama University, Gofuku 3190, Toyama 930, Japan

Abstract

    The thermal desorption of deuterium implanted into graphite with iron dopant was studied by means of mass analyzed thermal desorption spectroscopy. Deuterium ions were implanted into the sample at room temperature with 5 keV using a conventional ion gun. An impurity modification phenomenon was found for the mass analyzed thermal desorption spectra (MATDSs). Namely, a new desorption peak (denoted as [Fe/C]-peak) appeared at 970 K in the MATDS for the graphite doped with iron (3 at%), whereas a broad spectrum ranging from 750 to 1275 K was observed for pure graphite. The desorption mechanism for the [Fe/C]-peak was explained by the second order surface association reaction. The rate constant was determined as

K_[Fe/C] (D₂) = (5×10^-4)exp(-59×10³/RT),

where the frequency factor and activation energy are in [/molecule s] and [cal/mol], respectively. The broad spectrum for pure graphite was deconvoluted into three component peaks, [Ⅰ] and [Ⅱ]. The rate constants for them are determined as

K_[Ⅰ] (D₂) = (2×10^-7)exp(-46×10³/RT),

K_[Ⅱ] (D₂) = (8×10^-5)exp(-61×10³/RT).

Katsunori MoriI^a, Kiichiro Kasai^b, Yosikau Isikawa^a, Kiyoo Sato^b, Kan Ashida^c, Kuniaki Watanabe^c

^a College of Liberal Arts, Toyama University, 3190 Gofuku, Toyama 930 Japan

^b Faculty of Science, Toyama University, 3190 Gofuku, Toyama 930 Japan

^c Tritium Research Center, Toyama University, 3190 Gofuku, Toyama 930 Japan

Abstract

    The variation of the superconducting transition temperature, Tc in NbH_x and NbD_x films, which were prepared by a method of hydrogen (deuterium) - reactive sputtering at room temperature, was investigated. The effect of hydrogen or deuterium absorption reduced Tc and a pronounced normal isotope effect was observed.

Kenji Ichimura, Masao Matsuyama, Kuniaki Watanabe

Tritium Research Center, Toyama University, Gofuku 3190, Toyama 930, Japan

Abstract

    Gettering materials, most of which are alloys, have wide applicability to tritium processing function in fusion and fission reactors such as storage, supply, recovery, separation, and so on. However, required getter properties differ depending on unit process conditions. To develop suitable getters for each unit process, it is important to investigate fundamentals of alloying effects on their properties. Therefore, we studied the activation processes of three Zr-alloy getters (Zr-Al, Zr-Ni, and Zr-V-Fe) by means of x-ray photoelectron spectroscopy-secondary ion mass spectrometry and thermal desorption spectroscopy. It was observed that the formation of a metallic Zr surface is the principal process for activation, by which the getters show pumping action for various gases. A considerable effect was observed on the activation processes of the three getters. The activation temperature varied with alloying elements: 800℃ for Zr-Al, 700℃ for Zr-Ni, and 400℃ for Zr-V-Fe. It was concluded that the activation temperature is determined by the balance between the stability of corresponding oxides and carbides present on the surface and the diffusivity of oxygen and carbon from the surface into the bulk.

Hitoshi Miyake, Masao Matsuyama, Kuniaki Watanabe1987_06

Abstract

    To evaluate the absolute pressure of hydrogen isotopes with ionization gauges and quadrupole mass spectrometers in tritium handling systems as well as thermonuclear fusion devices, we determined the relative sensitivities of two kind of Bayard-Alpert (B-A) gauges and a quadrupole mass spectrometer among hydrogen isotope molecules. The relative sensitivities of the B-A gauges (normalized to H₂) were R^HD_B = 1.08, R^D2_B = 0.99, R^HT_B = 1.03, R^DT_B = 0.97, and R^T2_B = 0.95. In the case of the quadrupole mass spectrometer, they were R^HD_M = 1.09, R^D2_M = 0.99, R^HT_M = 1.06, R^DT_M = 0.96, and R^T2_M = 0.88. These values

Kuniaki Watanabe, Hitoshi Miyake, Masao Matsuyama

Tritium Research Center, Toyama University, Gofuku 3190, Toyama 930, Japan

Abstract

    To apply mass spectrometers and ionization gauges to thermonuclear fusion devices such as pressure gauges, we measured the relative sensitivities (normalized to H₂) of Bayard-Alpert(B-A) gauges (UGD-1S and UGS-1A, ANELVA Co.) and a quadrupole mass spectrometer (MSQ-150A, ULVAC Co.) for hydrogen isotopes. In the case of the B-A gauges, the relative sensitivities were determined as R^HD_B = 1.07, R^D2_B = 0.99, R^HT_B = 0.97, and R^T3_B = 0.95. In the case of the quadrupole mass spectrometer, they were R^HD_M = 1.09, R^D2_M = 0.99, R^HT_M = 1.06, R^DT_M = 0.96, and R^T3_M = 0.88. These values agreed quite well with those observed by Dibeler et al. for the mass spectrometer of the magnetic deflection type. It was revealed that the relative sensitivities of the quadrupole mass spectrometer were essentially the same as those for the B-A gauges except T₂.

Isao Kanesaka^a, Hiroyuki Nishimura^a, Kan Kanamori^a, Kiyoyasu Kawai^a, Kenji Ichimura^b, Kuniaki Watababe

^a Faculty of Science, Toyama University, Gofuku, Toyama 930, Japan

^b Tritium Research Center, Toyama University, Gofuku, Toyama 930, Japan

Abstract

    The infra-red spectrum of [Co(en)₃]Cl₃･3T₂O has been observed over a period of 5 months. The spectrum changes considerably even in 2 days after preparation of the hydrate, revealing quite different features from the parent. Initially some bands due to the NH₂ group disappear, while new bands appear. These are explained in terms of a change in bonding character or as an interaction between the complex ion and the chloride anion in the crystal. Subsequently, the bands due to ethylenediamine decrease in intensity and almost vanish, while additional new bands appear. The new bands are explained in terms of ammine complexes. It is proposed that a decomposition reaction of en → 2NH₃ + HCCH takes place through intermediates such as vinylamine and so on. After one month the spectrum still changes slowly with further new bands due to a H-T exchange reaction.