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Accueil du site > Activités scientifiques et techniques > Physique & technologie des accelérateurs > R&D générique > Cavités supraconductrices > Surface polishing

Polissage de surface

Mechanical polishing techniques have been now used for decades for e.g. optical devices, achieving unsurpassed surface quality with surface roughness in the nano-metric scale. The aim of this R&D activity is to study and build an innovative set-up to improve, quality-wise and safety-wise, the process for surface polishing of SRF cavities.

Indeed the standard current surface treatments typically used in the community are either a Buffered Chemical polishing (BCP) or an Electro-Polishing (EP) in a concentrated acid mixture containing highly concentrated hydrofluoric acid, extremely delicate (hazard) to handle and to recycle. Combining and transferring the mechanical process technology, know-how and adapting the techniques for SRF cavities would be a major step. More precisely, the reduction of the roughness of the RF surface of the resonator will results in improvement of the RF performances of the cavity, increased efficiency, reliability and yield rate of SRF cavities surface preparation and treatment process prior to cold test in LHe. Moreover, safety would also be significantly improved. Finally, mastering of this process, jointly with advanced surface studies and RF testing will help in understanding the effect of surface state on the behaviour of superconducting material subjected to high electromagnetic RF surface fields. All studies done so far by other laboratories were done on elliptical structures. No real studies, as far as we know, have been performed on other type of cavities like QWR, HWR or Spoke cavities. Elliptical cavities, thanks to their simple 2D geometry can be mechanically polished with standard barrel polishing machines. Other structures, like QWR, HWR or Spoke cavities show way more complex geometries and tend to be more fragile. Polishing such structures would need more complex polishing device to achieve a homogeneous polishing all over the structure.


Photo d’un échantillon de Niobium poli au microscope électronique à balayage (IPNO/CSNSM)

Contact : David LONGUEVERGNE

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Institut de Physique Nucléaire Orsay - 15 rue Georges CLEMENCEAU - 91406 ORSAY (FRANCE)
UMR 8608 - CNRS/IN2P3

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