Depth-profiling and thermal desorption of hydrogen isotopes for plasma facing carbon tiles in JT-60U (Long term hydrogen retention) T. Tanabe, Kyushu University ☆ Depth profiles in redeposited layers and eroded area Depth profiles of T in divertor tiles of JET and JT-60U Depth profiles and TDS of hydrogen isotopes (H, D and T) Importance of Isotopic exchange and tile temperature ☆ Deep penetration into the bulk Penetration thorough open pores of CFC and graphite Thermal diffusion Absorption at and/or permeation to the backside of tiles. 9th ITPA meeting on SOL/divertor physics, Garching, May 7-10, 2007

Gas Graphite(Solid) Liquid Determined by ○ : IR ● : NMR ▲ :EELS A:C-H film ever produced Hydrogen solubility (very small) T. Tanabe et al., Journal of Nuclear Materials 313–316 (2003) 478–490 RT Hydrogen solubility Hydrocarbons are unstable above 800K

Keeping nearly the same level Above ~800K Isotope exchange becomes easier H 2 and H 0 Hydrogen retention and depth profile under H + and H 2 exposure All grains are under the same static pressure Below ~700K No diffusion into bulk or particles

Tritium activity is mostly on the plasma facing surface JET tile : Cross section of cored hole in divertor base tile :BN4 Surface Probably due to temperature difference

Backs side of BN7 Stripes corresponding the woven structure of 2-D CFC PSL intensity [PSL/mm 2 ] Absroption of low energy (gaseous) tritium Cf. No stripes were observed on the front surface T. Tanabe et al., Journal of Nuclear Materials 313–316 (2003) 478–490

PSL intensity [PSL/mm 2 ] PSL intensity [PSL/mm 2 ] inside Outside Tritium depth profile : observed by cross-sectional view of dome top tile in JT-60U divertor

SIMS H retention within <2.1  m ～ 4.3 x (/cm 2 ) H/C at surface ~3.5 % 0 0 （ H+D)/ 12 C H/ 12 C D/ 12 C Thin deposits on outer dome wing NRA: D retention within 2.1  m ～ 8.0 x (/cm 2 ) D/C ~ 2%(max) Y. Oya, Y. Hirohata, et al., J. Nucl. Mater (2003) 209 NRA + SIMS (H+D)/C (<2.1  m) ～ 1.2 x (/cm 2 ) (H+D)/C (<0.5  m) (H+D)/C ～ 2.5% depth1.7  m T. Hayashi et al. J. Nucl. Mater

Redeposits on ID3 1000K Eroded area OD1 1400K Redeposits on DM9 800K Temperature/K TDS measurements Desorption rate / molecules ･ m -2 ･ s -1 Total retention / atoms ･ m - 2 Sample position Bulk retention Temperature reduces D/H

D/H << 5.1 (ratio of discharges numbers of DD/HH) → Replacement of D by H D retention D/H ～ 1.6 DM 800K D/H ～ 0.47 ID 1000K H retention Redeposited layers on ID… Deposited at higher temp(1000K). Low D/H DM…Deposited at lower temp.(800K) High D/H (Less exchange) Homogeneous distribution with (H+D)/C = Indicating Isotope exchange even in deep region owing to high temp. On the Inner Divertor 1000K

Keeping nearly the same level Above ~800K Isotope exchange becomes easier Bulk retention given by H 2 and H 0 H 2 and H 0 Below ~700K No diffusion into bulk or particles

Redeposited process with hydrogen incorporation Substrate Starting DD discharge Temperature Low High Low Formation of redeposited layers Higher heat load Lower heat load Addition of HH discharges After DD dischyarge HD mixing in the layers HD mixing near boundary only

Hydrogen retention at eroded area Starting DD discharges Temperature High Eroded area with high heat load (OD) Addition of HH discharges Termination of DD discharges Substrate No deposition High energy implantation

Hydrogen retention and depth profile under exposure of energetic H + and H 2 neutrals All grains are under the same static pressure

773K 973K 623K 623~673K Base temp. 573K Inner divertor Outer divertor Baffle plates Dome Surface temperature increase DD discharges >> HH discharges Because NBI power of HH discharges ~ ½ of that of DD discharge Depth profiles of JT-60U divertor tiles Tile temperature monitored by TCs installed in the tiles Maximum Surface temperatures estimated by a finite element modeling K.Masaki, et.al., J.Nucl.Mater., (2003) 514 Inner divertor tile, ~1000 K Dome unit tile ~800 K Outer divertor tile ~1400 K