Study of N Doped Samples before and after Electrochemistry Wydglif - - PowerPoint PPT Presentation

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Study of N Doped Samples before and after Electrochemistry Wydglif - - PowerPoint PPT Presentation

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Study of N Doped Samples before and after Electrochemistry Wydglif Dorlus Supervisor: Anna Grassellino GEM Final Report 08/06/18 Outline SRF Cavities Treatments Methods LSCM Results AFM Results Conclusion 2 8/4/18

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SLIDE 1

Wydglif Dorlus Supervisor: Anna Grassellino GEM Final Report 08/06/18

Study of N Doped Samples before and after Electrochemistry

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SLIDE 2
  • SRF Cavities
  • Treatments
  • Methods
  • LSCM Results
  • AFM Results
  • Conclusion

Outline

8/4/18 Wydglif Dorlus | Surface Roughness Study 2

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SLIDE 3
  • Superconducting Radiofrequency
  • Key technology of the particle accelerators
  • Used to accelerate particle beams by storing electromagnetic

energy

  • Energy given to particle beams as they pass through the cavity
  • Low energy loss

What are SRF Cavities?

8/4/18 Wydglif Dorlus | Surface Roughness Study 3

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SLIDE 4
  • Typically made of Nb, 𝑂𝑐#π‘‡π‘œ
  • Can operate at Tc<T
  • Elliptical shape

Β§ Clean and uncontaminated Β§ Smooth Surface

SRF Cavities Properties & Requirements

8/4/18 4 Wydglif Dorlus | Surface Roughness Study

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SLIDE 5
  • Buffer Chemical Polishing (BCP)

– Mixture of Hydrofluoric acid (HF), Nitric acid (𝐼𝑂𝑃#), Phosphoric acid (𝐼#𝑄𝑃))

  • Electropolishing

– Current applied to cathode through electrolyte contain mixture of HF and Sulfuric Acid (𝐼+𝑇𝑃))

  • Cavity High T Vacuum Baking (H degassing)
  • High Pressure Rinsing (HPR)
  • Nitrogen Doping

– Bake 800ΒΊC/3hr in High Temperature Vacuum Bake – Nitrogen Diffusion/2 min – N redistribution/6 min

Treatments

8/4/18 5 Wydglif Dorlus | Surface Roughness Study

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SLIDE 6
  • Discovered by Anna Grassellino
  • Poor performance due to Nitrides
  • After additional treatment (EP) to remove nitrides β†’ 𝑅- β‰ˆ

factor up to 4

  • Hypothesis to test: Accelerating gradient 30% less due to

surface roughness?

N-Doping - Goal

?

Doped 120C bake 8/4/18 5 Wydglif Dorlus | Surface Roughness Study

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SLIDE 7

Study steps

8/4/18 7

Coupon From Nb sheet

HPR Ethanol Rinse

Bulk EP 150 Β΅m N Doping 2/6

HPR Ethanol Rinse

BCP 5 Β΅m EP 5 Β΅m

HPR HPR Ethanol Rinse Ethanol Rinse

Wydglif Dorlus | Surface Roughness Study

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SLIDE 8
  • High resolution optical and electron microscopes used to

capture images and roughness measurement of grain boundaries

  • Laser Scanning Confocal Microscope

– Laser beam pass through light source aperture, focused by

  • bjective lens (50x) into small area on surface

– Image build up pixel by pixel

Method of investigations

8/4/18 8 Wydglif Dorlus | Surface Roughness Study

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SLIDE 9
  • Atomic Force Microscope

– Laser intensity and cantilever height difference – Contact and non-contact mode – Gwyddion software for analysis

8/4/18 9 Wydglif Dorlus | Surface Roughness Study

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SLIDE 10
  • Rp = π’π’ƒπ’šπ’”π’

Highest peak

  • Rv = 𝒏𝒋𝒐𝒔𝒍

Lowest valley

  • Rz = Rp + Rp

Roughness height

  • Ra = 𝟐

π’βˆ‘

𝒔𝒍

𝒐 𝒍8𝟐

Roughness average

  • Rq =

𝟐 π’βˆ‘

π’”πŸ‘π’

𝒐 𝒍8𝟐

Roughness root mean square

  • Rku = 𝟐

π’π‘ΊπŸ“ βˆ‘

π’”πŸ“π’

𝒐 𝒍8𝟐

Kurtosis (spikiness of peaks and valleys)

Roughness Parameters

8/4/18 10 Wydglif Dorlus | Surface Roughness Study

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SLIDE 11

8/5/18 11

Coupon From Nb sheet

HPR Ethanol Rinse

Bulk EP 150 Β΅m N Doping 2/6

HPR Ethanol Rinse

BCP 5 Β΅m EP 5 Β΅m

HPR HPR Ethanol Rinse Ethanol Rinse

Wydglif Dorlus | Surface Roughness Study

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SLIDE 12

Nb before electrochemistry

8/4/18 12

20 40 60 80 100 120 140 160 180 Rp Rv Rz Ra Rq Rku Β΅m Roughness parameters

Nb before Treatments

Rough surface and spiky pits and bumps, due to machining of the surface

Laser intensity image from LSCM

Wydglif Dorlus | Surface Roughness Study

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SLIDE 13

8/5/18 13

Coupon From Nb sheet

HPR Ethanol Rinse

Bulk EP 150 Β΅m N Doping 2/6

HPR Ethanol Rinse

BCP 5 Β΅m EP 5 Β΅m

HPR HPR Ethanol Rinse Ethanol Rinse

Wydglif Dorlus | Surface Roughness Study

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SLIDE 14

Pure Nb β†’Bulk EP 150 um removal

8/4/18 14

2 4 6 8 10 12 Rp Rv Rz Ra Rq Rku

Β΅m Roughness parameters

Bulk EP

Roughness height decreased by a factor of up to 30, smooth surface due to electropolishing

Laser intensity image from LSCM

Wydglif Dorlus | Surface Roughness Study

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SLIDE 15

8/5/18 15

Coupon From Nb sheet

HPR Ethanol Rinse

Bulk EP 150 Β΅m N Doping 2/6

HPR Ethanol Rinse

BCP 5 Β΅m EP 5 Β΅m

HPR HPR Ethanol Rinse Ethanol Rinse

Wydglif Dorlus | Surface Roughness Study

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SLIDE 16

Bulk EP β†’ Nitrided surface

8/4/18 16

1 2 3 4 5 6 Rp Rv Rz Ra Rq Rku

Β΅m Roughness parameters

N-Doped

Roughness decreased by a factor of 2 Nitrides added on surface

Wydglif Dorlus | Surface Roughness Study Laser intensity image from LSCM

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SLIDE 17

8/5/18 17

Coupon From Nb sheet

HPR Ethanol Rinse

Bulk EP 150 Β΅m N Doping 2/6

HPR Ethanol Rinse

BCP 5 Β΅m EP 5 Β΅m

HPR HPR Ethanol Rinse Ethanol Rinse

Wydglif Dorlus | Surface Roughness Study

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SLIDE 18

Nitrided surface + 5um EP Γ  N doped surface

8/4/18 18

0.5 1 1.5 2 2.5 3 3.5 4 4.5 Rp Rv Rz Ra Rq Rku

Β΅m Roughness parameters

EP Post N-Doping

Roughness is roughly the same Nitrides removed off surface

Laser intensity image from LSCM Wydglif Dorlus | Surface Roughness Study

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SLIDE 19

8/5/18 19

Coupon From Nb sheet

HPR Ethanol Rinse

Bulk EP 150 Β΅m N Doping 2/6

HPR Ethanol Rinse

BCP 5 Β΅m EP 5 Β΅m

HPR HPR Ethanol Rinse Ethanol Rinse

Wydglif Dorlus | Surface Roughness Study

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SLIDE 20

Nitrided surface + 5um BCP

8/4/18 20

2 4 6 8 10 12 14 16 Rp Rv Rz Ra Rq Rku

Β΅m Roughness parameters

BCP Post N-Doped

Roughness drastically increased; correlates with performance; doping + BCP gives very poor quench field

Wydglif Dorlus | Surface Roughness Study Laser intensity image from LSCM

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SLIDE 21

Single Grains analysis

8/4/18 21

Treatments do not affect grains significantly, but grain boundaries

Wydglif Dorlus | Surface Roughness Study

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SLIDE 22

AFM contact mode image of nitrided surface

8/4/18 22

Nitrides are 54 nm tall

Length Height

Wydglif Dorlus | Surface Roughness Study

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SLIDE 23

EDS using SEM

8/4/18 23

Atoms get excited by electrons which release x- rays that get picked up by an EDS detector

Wydglif Dorlus | Surface Roughness Study

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SLIDE 24

N doped surface (nitrides + 5 um EP)

8/4/18 24

Surface got smoother, and nitrides disappeared

EP AFM Image

Wydglif Dorlus | Surface Roughness Study

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SLIDE 25

Nitrides plus BCP

8/4/18 25

Rz = 680nm β‰  13Β΅m Not sure why…(maybe small secondary nitrides phases?)

BCP AFM image

Wydglif Dorlus | Surface Roughness Study

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SLIDE 26
  • Found opposite: Surface does NOT get rougher in N doping

(EP) but seems to be actually smoother compared to Bulk EP

  • Surface gets rougher for BCP treatment Γ  correlates with

performance

  • Surface roughness (EP doped) is not a factor why Eacc is

30% less than 120C bake

  • BCP is not a good additional treatment option for doped

cavities

8/4/18 26

Conclusion

Wydglif Dorlus | Surface Roughness Study

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SLIDE 27

I would like to thank the GEM Committee, my supervisor Anna Grassellino for advising me, and my mentors.

8/5/18 27

Acknowledgements

Wydglif Dorlus | Surface Roughness Study