1 / 14

Cavity Treatment (BCP, Heat Treatment & HPR)

Cavity Treatment (BCP, Heat Treatment & HPR). Sergio Calatroni with many contributions from: Rama Calaga, Leonel Ferreira, Antonio Mongelluzzo. Outline. Caveat: several personal remarks What do we want to do, and why Cortical layer, defects etc.. H2 degassing Cleanliness

gigi
Télécharger la présentation

Cavity Treatment (BCP, Heat Treatment & HPR)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Cavity Treatment(BCP, Heat Treatment& HPR) Sergio Calatroni with many contributions from: Rama Calaga, Leonel Ferreira, Antonio Mongelluzzo Sergio Calatroni

  2. Outline • Caveat: several personal remarks • What do we want to do, and why • Cortical layer, defects etc.. • H2 degassing • Cleanliness • How we are going to do it • Surface treatments • Vacuum furnace • HPWR • CERN hardware Sergio Calatroni

  3. Surface treatment goals • Removal of defects • Due to welding (irregularities, beads, etc) • Due to machining (EDM oxidation & cracks, machining chips, etc) • Removal of “cortical layer” • Rule of thumb: 5% sheet thickness either side • Obtaining a smooth surface • Allows highest RF performance (suppression of B-field enhancement at steps, etc.) Sergio Calatroni

  4. Options • Buffered Chemical Polishing, Electropolishing, Centrifugal Barrel Polishing • Need to specialize material removal & finishing treatment? No • Efficient and economical treatment is more important than ultimate performance • My conclusion: BCP Sergio Calatroni

  5. Is it feasible? 4 rods RF dipole ¼ wave All three designs have features which allow correct acid flow and evacuation Sergio Calatroni

  6. BCP Niowave CERN BCP 1:1:2 done 8/2012! 150 µm removed All hardware ready for BCP (but we need to invest for “production”) Sergio Calatroni

  7. Degassing goal • Removal of hydrogen in solid solution • Prevent “hydrogen disease” B. Bonin SRF1991 (DESY) http://accelconf.web.cern.ch/AccelConf/SRF91/papers/srf91d01.pdf M Hakovirta SRF2001 (Tsukuba) http://accelconf.web.cern.ch/accelconf/srf01/papers/pr023.pdf (S. Isagawa J. Appl. Phys. 51 (1980), 4460) Sergio Calatroni

  8. H2 degassing • Done at >600 °C for >24h • H2 partial pressure / furnace total pressure have a peak then have to decrease • Final equilibrium is reached (Sievert’s law for exothermic material) • for 1 ppm H:< 10-7 mbar @ 600 °C< 10-6 mbar @ 800 °C • Note: 30000 ppm@ RT @ 10-8 mbar !!!(but slow kineticsfor uptake) Sergio Calatroni

  9. CERN furnace P=3.5x10-7 mbar @ 650 °C P=1x10-7mbar @ RT Venting with Air Sergio Calatroni

  10. Oxygen contamination • It is well known that Nbacts as a GETTER • When “activated”, ie surface oxide is dissolved in the bulk (> 380 °C), its surface is extremely reactive, and impurities steadily diffuse in the bulk • Surface layer gets contaminated • Diffusion progresses in the bulk with time and temperature • Solution: “light” (chemical) polishing, typically around 20 µm • More material removal may increase H2 uptake from the acid bath Sergio Calatroni

  11. Cleanliness • Removal of dust particles • Prevent electron field emission • (Improves Q) Peak of E-field: 4 rods RF dipole ¼ wave (**) (****) (****) Sergio Calatroni

  12. HPWR CERN • Removal of dust particles • HPWR • Line-of-sight access to all high E-field regions Bulk Nb 1.3 GHz cavity, Ep + HPWR @ CERN, circa year 2000 Recently refurbished with new ultrapure H2O production plant & filters, new controls Sergio Calatroni

  13. New HPWR and clean room From Janic Chambrillon Sergio Calatroni

  14. Conclusions • BCP favoured • Minimal sequence: • Heavy BCP • H2 degassing • Light BCP • HPWR • All crab designs compatible with surface treatments • 4-rods seems not optimal for HPWR • At CERN • HPWR and H2 degassing OK • BCP OK, dedicated cabinet needed for series “production” Sergio Calatroni

More Related