First mirror test in JET for ITER: Complete overview after three ILW campaigns

Abstract

The First Mirror Test for ITER has been carried out in JET with mirrors exposed during (1) the third IIW campaign (11.W-3, 2015-2016, 23.33 h plasma) and (ii) all three campaigns, Le LW1 to ILW-3: 20112016 63,52 h in total. All mirrors from main chamber wall show no significant changes of the total reflectivity from the initial value and the diffuse reflectivity does not exceed 3% in the spectral range above 500 nm. The modified Layer on surface has very small amount of impurities such as D, B, C N O and Ni. All mirrors from the divertor (inner, outer, base under the bulk ile) lost reflectivity by 20-80% due to the beryllium-rich deposition also containing D, CN, O, Ni and W. In the inner divertor N reaches 5 x 107 cm2 W is up to 4.3 x 10 cm while the content of Ni is the greatest in the outer divertor 3.8 x 10 cm Oxygen-18 used as the tracer in experiments at the end of ILW-3 has been detected at the level of 1.1 x 10 cm . The thickness of deposited Layer is in the range or 90 nm to 900 nm. The layer growth rate in the base (2.7 pms !) and inner divertor is proportional to the exposure time when a single campaign and all three are compared. In a few cases, on mirrots located at the cassette mouth, flaking of deposits and crosion occurred.