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a b s t r a c tNew linear plasma devices are currently being constructed or planned in the Trilateral Euregio Cluster (TEC) to meet the challenges with respect to plasma surface interactions in DEMO and ITER: i) MAGNUM-PSI (FOM), a high particle and power flux device with super-conducting magnetic field coils which will reach ITER-like divertor conditions at high magnetic field, ii) the newly proposed linear plasma device JULE-PSI (FZJ), which will allow to expose toxic and neutron activated target samples to ITER-like fluences and ion energies including in vacuo analysis of neutron activated samples, and iii) the plasmatron VISION I, a compact plasma device which will be operated inside the tritium lab at SCK-CEN Mol, capable to investigate tritium plasmas and moderately activated wall materials. This contribution shows the capabilities of the new devices and their forerunner experiments (Pilot-PSI at FOM and PSI-2 Jülich at FZJ) in view of the main objectives of the new TEC program on plasma surface interactions.

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This contribution reports on isotope exchange studies with both Ion Cyclotron Wall Conditioning (ICWC) and Glow Discharge Conditioning (GDC) in TEXTOR and TORE SUPRA. The discharges have been carried out in H 2, D 2 (ICWC and GDC) and He/H 2 mixtures (ICWC). The higher reionization probability in ICWC compared to GDC, following from the 3 to 4 orders of magnitude higher electron density, leads to a lower pumping efficiency of wall desorbed species. GDC has in this analysis (5-10) times higher removal rates of wall desorbed species than ICWC, although the wall release rate is 10 times higher in ICWC. Also the measured high retention during ICWC can be understood as an effect of the high reionization probability. The use of short RF pulses (~1s) followed by a larger pumping time significantly improves the ratio of implanted over recovered particles, without severely lowering the total amount of removed particles.

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A new in situ wall conditioning method by reactive gas fuelling has been investigated in TEXTOR; this method is applicable during plasma discharges of the operating machine. For these experiments, trimethylboron, B(CH3)3, was fed into the torus instead of hydrogen. While the hydrogen of the trimethylboron molecules fuels the plasma to sustain the discharge, boron and carbon are screened at the plasma edge and redeposited at the wall. The impurity concentration in the plasma is negligible, as it is after the usual boronization by radiofrequency assisted glow discharge. The plasma performance was improved shot by shot. This new technique may open a way to direct local control of erosion and redeposition processes at wall elements subject to high heat loads

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