JRA1 Meeting CEA Saclay Electropolishing in Saclay Status 2005

JRA1 Meeting CEA Saclay AGING OF THE BATH

JRA1 Meeting CEA Saclay Aging of the Bath Advantage: can be carried out on samples (9 cm 2). Two settings: with « fixed » electrodes or with « rotating » electrodes

JRA1 Meeting CEA Saclay Measurements Intensity Niobium removal rate Gloss (20° and 60° Brightnesses) Surface State F - and SO 4 2- concentrations (ionic chromatography) Roughness Sulfur Generation

JRA1 Meeting CEA Saclay Results Decrease in intensity with time Deterioration of surface states Fading in oscillations Decrease in F - concentration (Consumption+Evaporation) Surface deteriorates for Nb concentration between 5 and 7g/L for 1vol HF – 9 vol H 2 SO 4 mixture

JRA1 Meeting CEA Saclay Decrease in intensity: 1 vol HF – 9 Vol H 2 SO 4 mixture 8 Volts

JRA1 Meeting CEA Saclay Surface Evolution: 1 vol HF – 9 Vol H 2 SO 4 mixture 14 Volts 14 V 4mm

JRA1 Meeting CEA Saclay F - and Gloss Evolution 1 vol HF – 9 vol H 2 SO 4 8 Volts

JRA1 Meeting CEA Saclay NEW MIXTURES

JRA1 Meeting CEA Saclay Tested Mixtures (HF – H 2 SO 4 – H 2 O) 0.5 Vol – 9 Vol 2 Vol – 9 Vol 3 Vol – 6.72 Vol – 0.28 Vol 1 Vol – 9 Vol – 1 Vol

JRA1 Meeting CEA Saclay Possible compositions

JRA1 Meeting CEA Saclay Effect of Water Fast deterioration of the surface Low brightness Lower removal rate

JRA1 Meeting CEA Saclay Sample surface after 1170 min EP mixture 14 Volts 4 mm

JRA1 Meeting CEA Saclay Effect of HF Higher removal rates Low sulfur generation Surface is improved for very high Nb concentrations (>20g/L for 3vol – 6.72 vol – 0.28 vol) « The plateau » is shortened But Al Cathode corrosion Safety issues Temperature control problem

JRA1 Meeting CEA Saclay Niobium removal rates comparison ExperimentInitial removal rate µm/min 1vol-9vol 8 Volts0,945 1vol-9vol 14 Volts1,485 1vol-9vol-1vol 14 Volts 0,744 0,5vol-9vol 16,5Volts0,902 2vol-9vol 6 Volts1,817

JRA1 Meeting CEA Saclay More details concerning sulfur generation Sulfur is more likely to be generated after long sequences (probably due to HF losses) Generation is favored during electrolysis (SO 4 2- reduction at the cathode): SO e H + S + 4 H 2 O

JRA1 Meeting CEA Saclay I(V) curves for different concentrations 1vol – 9vol mixture 23°C

JRA1 Meeting CEA Saclay 2vol – 9vol mixture 14°C

JRA1 Meeting CEA Saclay 4 vol – 9 vol 16°C

JRA1 Meeting CEA Saclay New monitoring system I (V) Curves plots Intensity monitoring Temperature monitoring

JRA1 Meeting CEA Saclay Oscillations plots 3.5 Volts 1 vol – 9 vol Mixture

JRA1 Meeting CEA Saclay EP monocell device

JRA1 Meeting CEA Saclay

Security The Saclay Security Committee gathered on October the 13 th We are allowed to start tests to check leaks with water and then with acids.

JRA1 Meeting CEA Saclay Problem of HF concentration If %mass HF > 7% Mixture is toxic + Maximum storage capacity for safety reasons 250 kg.