25aD53P
Hydrogen transport in liquid metals under steady state plasma bombardment
毕 海林1)、廣岡慶彦1,2)、八木重郎2)
Hailin Bi1), Yoshi Hirooka1,2), Juro Yagi2)
総研大、 2)核融合研
1)
Sokendai, 2)NIFSResults
Hydrogen PDP experiments through liquid lithium
and GaInSn have been conducted respectively in thetemperature range of ~300-500oC. It has been foundthat hydrogen PDP through lithium is recombination
limited. As a result, hydrogen surface recombination
coefficients have been obtained. For GaInSn,
hydrogen PDP breakthrough curve has been obtained,
which is compared with simulation results fordifferent hydrogen diffusivities, shown in Fig.2.
14500

5x10Temperature
14-44x102400-4o

D=2X10 cm /s
2D=1X10 cm /s

143x10300-52

D=5X10 cm /s
14200

2x10Experiment14

1x10001000

2000

Temperature( C)

Experimental
In the present work, an innovative experimental
technique holding liquid metals on a sheet mesh bysurface tension has been put together for theplasma-driven permeation (PDP) experiments. Shownin Fig. 1 is the PDP setup in a laboratory-scale plasma
device, VEHICLE-1. The electron temperature is~
10eV and the plasma density is of the order of 1010
cm-3. The ion bombardment flux is of the order of 1016
cm-2, and the bombarding energy is set at 100 eV byapplying a negative DC bias on the sample tray. A
liquid metal sample is fixed in such a way that theupstream surface is exposed to hydrogen plasma,
while the downstream side is pumped to ultrahighvacuum (10-6-10-5 Pa). A resistive heater is positioned
beneath the mesh to control the sample temperature,
which is measured by a thermocouple. The hydrogen
permeation flux due to PDP is monitored by the partialpressure of H2 measured by a quadrupole mass
spectrometer (QMS).

Fig.1 Schematic diagram of the experimental setup for
PDP through liquid metals

2Introduction
The application of liquid metals for plasma-facing
components (PFC) draws increasing interest as apotential means to resolve the technical issues
associated with exhaust power and particle handling inmagnetic fusion devices. Molten Lithium is one of thecandidates and has been used in fusion devices such as
NSTX [1] and EAST [2]. In these confinement
devices, it is believed that the interaction between
plasma and lithium plays an important role indetermining edge plasma characteristics and hencecore confinement performance. GaInSn, with low
reactivity and toxicity, is a kind of liquid metal atroom temperature. In JxB-force convected liquid
metal experiment, flowing GaInSn has also shown
ability of reducing both hydrogen and helium
recycling when facing to plasma bombardment [3].
Then it is deduced that GaInSn is also promising for
PFC in fusion reactors, though more information isneeded to evaluate the feasibility.
Hydrogen diffusivities in the bulk of materials andsurface recombination coefficients are essential
parameters to study hydrogen retention and hydrogentransport [4]. However, little information is available
in literature for liquid lithium and GaInSn. Due totheir critical importance to the application of liquid
metals in fusion reactors, these technical issues must
be clear addressed.

H permeation flux(H/cm s)

1)

3000

1000
4000

Time(s)Fig.2 A comparison of experimental data andsimulation results on hydrogen PDP breakthroughcurve for GaInSn.

[1] H.W. Kugel et al, Fusion Eng. Des.87 (2012) 1724–1731[2] J.S. Hu et al, Fusion Eng. Des.89 (2014) 2875–2885[3] Y. Hirooka et al. Presented at ISLA-2015, Granada.
[4] B.L. Doyle, J. Nucl. Mater. 111 & 112 (1982) 628–635.