27E34P
Deuterium ion driven permeation through palladium coated tungsten
LEE Heun Tae1、大塚裕介1、波多野雄治2, 上田良夫1
Heun Tae LEE, Yusuke OHTSUKA, Yuji HATANO, Yoshio UEDA
阪大院工1、富山大水素研2

Graduate School of Engineering, Osaka University1
Hydrogen Isotope Research Center, Toyama University2

3. Results and Discussion
The steady state permeation flux as function oftemperature is plotted in Figure 1 for Pd-coated andprevious data on uncoated W specimen. 3 At T <800 K, good agreement between the coated anduncoated W was observed. At T > 800 K, large
deviation between the two specimens was observed.
Evidently, the conditions of permeating surface
have a large effect at higher temperatures.
Next, the diffusivity was determined by fitting
the transient rise of the permeation spectra and isplotted in Figure 2. A clear break is observed at AT= 740 K which we interpret as trapping effects. We
further argue that the activation energy for diffusion
at T > 740 K represent volume diffusion. A
corresponding trap energy of 0.63 eV can be

16-2 -1

Permeation Flux (D m s )3.0x10Pd-coated W
Tungsten

16

2.5x1020162.0x10φi = ∼1.5x10-2 -1

Dm s

16

1.5x1016

1.0x1015

5.0x100.0500

600

700

8009001000

1100

Temperature (K)Fig.1. Steady state permeation flux for Pd-coated anduncoated tungsten specimen as function of temperature.
-910T = 740 K-101022. Experimental
A 75 µm thick tungsten specimen was coated on
one side with 250 nm thick layer of Pd. The
specimen was irradiated with Deutrium ion beamusing HiFIT apparatus at Osaka University.1 The
permeation flux was measured in the apparatus
described in Ref. 2. The incident D flux was varied
between 1019-1020 m-2 s-1 and ion energy was 1.0
keV. The temperature was 500 K ≤ T ≤ 1000 K.

calculated using diffusivity measured at T < 740 K.
We compare our results to the presently widelyused hydrogen transport values in the literature andthe implication for fusion.

Diffusivity (m /s)

1. Introduction
Tungsten (W) is the material choice for ITER
divertor and DEMO. Therefore, it is important tounderstand hydrogen interaction with tungsten toestimate recycling, permeation, and in-vessel
tritium inventory. We have performed ion drivenpermeation experiments to study hydrogen
diffusion, recombination, and trapping processes intungsten. However, surface barriers (e.g. thin oxidelayer) can greatly affect permeation experiments.
Often, their role is unknown or simply ignored.
Therefore, we have performed permeation
experiments with Palladium (Pd) coated tungsten
specimen to quantify surface barrier effects. This
presentation compares permeation fluxes between
Pd-coated and uncoated tungsten specimens asfunction of temperature.

3e-9 exp (-0.26 eV/kT)-11104e-5 exp (-0.89 eV/kT)-12106e-3 exp (-1.17 eV/kT)

-13

10

Pd-coated W
Tungsten
-14

10

0.8

1.0

1.2

1.4

1.6

1.8

2.0

-1

1000/T (K )Fig.2. Diffusivity determined by fitting the transient
rise to steady state.

References[1] Y. Ueda, H. Kikuchi, T. Shimada, A. Sagara, B.
Kyoh, and M. Nishikawa: Fusion Engineeringand Design 61 (2002) 255.
[2] H.T. Lee, H. Tanaka, Y. Ohtsuka, Y. Ueda: J.
Nucl. Mater. 415 (2011) S696.
[3] H.T. Lee, E. Markina, Y. Ohtsuka, and Y.
Ueda: Physica Scripta T145 (2011) 014045