V.Rampazzo<br />Superconductivity Laboratory<br />Legnaro National Laboratories<br />National Institute of Nuclear Physics...
Goals<br />Find solution/melt recipe for electropolishing Nb without using F—-ions<br />Put this recipe on application to ...
Electrochemistry and properties of  Nb<br />Nb  -> Nb3+ +3e-   E0 = -1.1 V<br />Nb  -> Nb5+ +5e-   E0 = -0,96 V<br />Perni...
IonicLiquid: Composition<br />A Ionicliquidis a mixtureoftwosalt, thatdissolvesitself at a temperature lowerthan the fusio...
Structural formulas of mixture <br />We have found mixture which can etch Nb without using F--ions and gives good result o...
Investigation samples system<br />Holder<br />Cathode<br />Thermocouple <br />Anode (Sample)<br />Stirrer<br />6<br />Elec...
We were using our automatic method to find correct electrical characteristic of electropolishing<br />EP plateau<br />7<br />
Electropolishing  of samples<br />Front<br />Back<br />8<br />
Surface quality analyze with profilometer<br />9<br />where m – quantity of measurements which where taken to calculation<...
Surface quality as function ofsulfamic acid concentration<br />10<br />
Surface quality as function of sulfamic acid concentration<br />11<br />
Changing quantities of melt compounds we have found  correct recipe<br />Because of high relatively power of process solut...
Ra – f(C(SA))<br />Roughness: classical EP versus Ionic liquid EP<br />13<br />Adding 30g/l Sulfamic acid in 4:1 Choline C...
Surface quality as a function of process time<br />14<br />
Results in different  treatment duration (min)<br />15<br />Front side<br />5<br />60<br />30<br />20<br />10<br />5<br />...
Surface characterization with profilometer<br />Classical EP, 10min<br />Raw<br />IL EP, 60min<br />IL EP, 10min<br />16<b...
17<br />EP samples in process…<br />
EP on 6GHz cavities<br />After the goodresult on samples, we start toapply the EP on real 6GHz cavities<br />Cathodes, flu...
Improvement road<br />Toimprove the EP westudy some possibilities:<br />Alternative tosulfammicacid<br />Differentflux ins...
Vertical EP: holedcathode<br /><ul><li>Vertical EP
 High activity formation of cathode gas brings to saturation of electrolyte with H2
IL comes from flanges and goes out from the cathode.
The cathode makes from tube 8mm in diameter with holes.
During the pumping electrolyte goes through the holes inside the tube</li></ul>20<br />
21<br />Cavity 6 GHz EP system with IL<br />Holed cathode<br />Output flange<br />Input flange<br />Solution collector<br ...
Vertical EP: holedcathode<br />22<br />Dopo<br />Prima<br />1:4 CholineChloride-Urea<br />Sulfammicacid: 30 g/L<br />T: 15...
Q-factorresult<br />23<br />
About electrical field distribution<br />24<br /><ul><li>Tobalance the differentdistancebetweencavity and cathode, thiswer...
Differentflux<br />Brokencathodes: the shapeofcathodeschangedtoget more uniformity on IL flux<br />25<br />
Twopossibilitiesofflux<br />26<br />OUT<br />OUT<br />IN<br />IN<br />Fromcathodestoflanges<br />Fromflangestocathodes<br />
New shapedcathodes<br />27<br />
Sulfamic Acid: fromflangestocathodes<br />28<br />Solution: 1:4 CholineChloride – Urea,<br />Sulfammic Acid :30 g/L<br />T...
Sulfammic Acid:fromcathodestoflanges<br />The oppositeconfigurationbrings a lotofbubbles and the cavityweren’t electropoli...
Alternative tosulfammic acid<br />The best result on sampleswerereachedwithsulfammic acid, butcavityisquitedifferentenviro...
Comparisonbetweenregulator (–NH4)<br />31<br />
AmmoniumPersulfate<br />The addidionofAmmoniumPersulfatedecreases the high initialvoltagenecessarytodisrupt the oxidefilm<...
AmmoniumPersulfate and Sulfammic Acid<br />On samples, agood compromise is the proportion 30 g/L ofSulfammic acid and 2.5 ...
Vertical EP: PA+SA<br />Vertical<br />ChCl:Urea 1:4<br />c(SA) = 30 g/l<br />c(PS) = 1.5 g/l<br />Distancebetweencathodes:...
Vertical EP: PA+SA<br />Vertical<br />ChCl:Urea 1:4<br />c(SA) = 30 g/l<br />c(PS) = 1.5 g/l<br />Some irregularsurface<br...
Upcoming SlideShare
Loading in …5
×

Rampazzo - Electropolishing of niobium 6 GHz cavities in choline chloride – urea melt

1,180 views
907 views

Published on

http://www.surfacetreatments.it/thinfilms

Electropolishing of 6GHz cavities by ionic liquids (Vanessa Rampazzo - 20')
Speaker: Vanessa Rampazzo - Legnaro National Laboratories of INFN | Duration: 20 min.
Abstract
The electropolishing of niobium using RTIL without fluorine shows good surface improvements, and the original recipe based on Urea and Choline Chloride is under study for application on 6 GHz niobium cavities. The goal is to obtain a uniform electrical field on the internal surface, despite of the big differencies in distances from the cathode inserted into the cavity. Morevoer, the electrical power injected into the cavity degrades the ionic liquid, if this isn't efficiently cooled down. All of this pratical problems are partially solved adding various special reagents in IL, that raise the uniformity in electrical field and decrease the working current of electropolishing. Another goal is the use of a continuos flux of liquid, that flows through the cavity.

Published in: Technology
0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total views
1,180
On SlideShare
0
From Embeds
0
Number of Embeds
2
Actions
Shares
0
Downloads
16
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide

Rampazzo - Electropolishing of niobium 6 GHz cavities in choline chloride – urea melt

  1. 1. V.Rampazzo<br />Superconductivity Laboratory<br />Legnaro National Laboratories<br />National Institute of Nuclear Physics, Italy<br />Electropolishing of Niobium 6GHz cavities inCholine chloride – Urea melt<br />2010<br />
  2. 2. Goals<br />Find solution/melt recipe for electropolishing Nb without using F—-ions<br />Put this recipe on application to 6GHz cavities <br />2<br />
  3. 3. Electrochemistry and properties of Nb<br />Nb  -> Nb3+ +3e- E0 = -1.1 V<br />Nb  -> Nb5+ +5e- E0 = -0,96 V<br />Perniobates<br />2Nb + 5Cl2 -> 2NbCl5<br />NbCl5 + 4Н2О -> 5HCl + Н3NbO4<br />Niobium acid<br />A(+):<br />Niobate<br />K(-):<br />3<br />
  4. 4. IonicLiquid: Composition<br />A Ionicliquidis a mixtureoftwosalt, thatdissolvesitself at a temperature lowerthan the fusionpointof single salt<br />Heating the salts, those dissociate itselfintoions and assume the liquid state<br />After the formationof IL, thisremainliquidwhencooled down<br />4<br />
  5. 5. Structural formulas of mixture <br />We have found mixture which can etch Nb without using F--ions and gives good result on application to cavities<br />5<br />Urea<br />CholineChloride<br />Sulfamic acid<br />
  6. 6. Investigation samples system<br />Holder<br />Cathode<br />Thermocouple <br />Anode (Sample)<br />Stirrer<br />6<br />Electrolyses time – 5 min<br />
  7. 7. We were using our automatic method to find correct electrical characteristic of electropolishing<br />EP plateau<br />7<br />
  8. 8. Electropolishing of samples<br />Front<br />Back<br />8<br />
  9. 9. Surface quality analyze with profilometer<br />9<br />where m – quantity of measurements which where taken to calculation<br />Scan 1<br />Scan 6<br />Scan 2<br />Scan 5<br />Scan 3<br />Scan 4<br />
  10. 10. Surface quality as function ofsulfamic acid concentration<br />10<br />
  11. 11. Surface quality as function of sulfamic acid concentration<br />11<br />
  12. 12. Changing quantities of melt compounds we have found correct recipe<br />Because of high relatively power of process solution gets big heat.<br />12<br />
  13. 13. Ra – f(C(SA))<br />Roughness: classical EP versus Ionic liquid EP<br />13<br />Adding 30g/l Sulfamic acid in 4:1 Choline Chloride Urea melt gives possibility to obtain brightness surface, without spots and pitting on sides of the sample <br />The best result of IL is comparable with the result of classical EP<br />The back roughness is the same of the front : good current distribution around the sample<br />
  14. 14. Surface quality as a function of process time<br />14<br />
  15. 15. Results in different treatment duration (min)<br />15<br />Front side<br />5<br />60<br />30<br />20<br />10<br />5<br />60<br />30<br />20<br />10<br />Back side<br />
  16. 16. Surface characterization with profilometer<br />Classical EP, 10min<br />Raw<br />IL EP, 60min<br />IL EP, 10min<br />16<br />
  17. 17. 17<br />EP samples in process…<br />
  18. 18. EP on 6GHz cavities<br />After the goodresult on samples, we start toapply the EP on real 6GHz cavities<br />Cathodes, flux system, concentration, newadditionwerestudiedtofind the best EP<br />We are stillworking…<br />18<br />
  19. 19. Improvement road<br />Toimprove the EP westudy some possibilities:<br />Alternative tosulfammicacid<br />Differentflux inside cavity<br />Differentorientationofcavity<br />19<br />
  20. 20. Vertical EP: holedcathode<br /><ul><li>Vertical EP
  21. 21. High activity formation of cathode gas brings to saturation of electrolyte with H2
  22. 22. IL comes from flanges and goes out from the cathode.
  23. 23. The cathode makes from tube 8mm in diameter with holes.
  24. 24. During the pumping electrolyte goes through the holes inside the tube</li></ul>20<br />
  25. 25. 21<br />Cavity 6 GHz EP system with IL<br />Holed cathode<br />Output flange<br />Input flange<br />Solution collector<br />Pump<br />
  26. 26. Vertical EP: holedcathode<br />22<br />Dopo<br />Prima<br />1:4 CholineChloride-Urea<br />Sulfammicacid: 30 g/L<br />T: 150°C<br />0,3 -0,4 A/cm2<br />
  27. 27. Q-factorresult<br />23<br />
  28. 28. About electrical field distribution<br />24<br /><ul><li>Tobalance the differentdistancebetweencavity and cathode, thiswereshaped in variousmodes</li></ul>Holedcathode<br />Two part cathode<br />
  29. 29. Differentflux<br />Brokencathodes: the shapeofcathodeschangedtoget more uniformity on IL flux<br />25<br />
  30. 30. Twopossibilitiesofflux<br />26<br />OUT<br />OUT<br />IN<br />IN<br />Fromcathodestoflanges<br />Fromflangestocathodes<br />
  31. 31. New shapedcathodes<br />27<br />
  32. 32. Sulfamic Acid: fromflangestocathodes<br />28<br />Solution: 1:4 CholineChloride – Urea,<br />Sulfammic Acid :30 g/L<br />T:120-160°C<br />The best surface quality appeared on bottom cutoff part.<br />
  33. 33. Sulfammic Acid:fromcathodestoflanges<br />The oppositeconfigurationbrings a lotofbubbles and the cavityweren’t electropolished<br />29<br />
  34. 34. Alternative tosulfammic acid<br />The best result on sampleswerereachedwithsulfammic acid, butcavityisquitedifferentenvironment<br />Wechecked the performancesofvariousregulatorcontaining the group (–NHx) on samples<br />30<br />
  35. 35. Comparisonbetweenregulator (–NH4)<br />31<br />
  36. 36. AmmoniumPersulfate<br />The addidionofAmmoniumPersulfatedecreases the high initialvoltagenecessarytodisrupt the oxidefilm<br />Butthiscompoundincreases the roughness and pitting<br />Possibility: can Sulfammic acid and AmmoniumPersulfate work together?<br />32<br />
  37. 37. AmmoniumPersulfate and Sulfammic Acid<br />On samples, agood compromise is the proportion 30 g/L ofSulfammic acid and 2.5 g/L ofAmmoniumPersulfate<br />On cavity, the best concentrationwerefound mixing 1.5 g/L ofAmmoniumPersulfate and 30 g/L ofSulfammic Acid<br />33<br />
  38. 38. Vertical EP: PA+SA<br />Vertical<br />ChCl:Urea 1:4<br />c(SA) = 30 g/l<br />c(PS) = 1.5 g/l<br />Distancebetweencathodes: 10 mm<br />Bright, withfluxline<br />34<br />
  39. 39. Vertical EP: PA+SA<br />Vertical<br />ChCl:Urea 1:4<br />c(SA) = 30 g/l<br />c(PS) = 1.5 g/l<br />Some irregularsurface<br />Distance: 5 mm<br />35<br />
  40. 40. Horizontal EP: PA+SA<br />Horizontal<br />ChCl:Urea 1:4<br />c(SA) = 30 g/l<br />c(PS) = 1.5 g/l<br />Distance from cathodes: 4 mm<br />Some passivation zone<br />36<br />
  41. 41. In future<br />Set up offluxsistemof EP<br />CalculationofQ-factorofILsEpcavities<br />Test toget the result on 1.5 /1.3 GHz<br />37<br />
  42. 42. Advantages and disadvantages<br />38<br />
  43. 43. Thankstoattention!<br />39<br />
  44. 44. Surface quality as function of current density<br />40<br />
  45. 45. Surface quality as function of current density<br />41<br />
  46. 46. Best results obtained in current density 0,33 A/cm2. <br />This current density provides temperature equilibrium in range 150C, and stable yellow viscose film around the anode and “protect” from oxidizing. <br />Distribution of current is similar on both sides which may give good surface quality inside cell and cutoff parts of the cell.<br />42<br />Ra – f(i)<br />
  47. 47. Surface quality as a function of quantity Nb-ions in the melt<br />43<br />
  48. 48. Surface quality as a function of quantity Nb-ions in the melt<br />44<br />
  49. 49. Previous slide illustrates necessity of dissolved Nb ions inside the electrolyte.<br />45<br />Ra–f(C(NbDissolved))<br />
  50. 50. From samples to Cavities…<br />We tried to work in two geometrical performances: horizontal and vertical<br />Horizontal EP didn’t give content results because of very fast temperature rising, after 1 minute temperature inside the cavity was more 190C which brought to degradation of electrolyte and to formation white viscous mass. In that places was done note a polishing but oxidizing. <br />Cutoff part of cavity has enough good view.<br />46<br />
  51. 51. Cavity after EP in IL: horizontal type<br />47<br />Cutoff part<br />Cell part<br />Cell part<br />
  52. 52. Dissolving speed 6,2 um/min<br />(in our laboratory on cavities in classical EP we have 0,5 um/min)<br />48<br />
  53. 53. Conventions<br />49<br />

×