Future of Superconducting RF Technology. Sam Posen Americas Workshop on Linear Colliders 29 June 2017

Transcription

1 Future of Superconducting RF Technology Sam Posen Americas Workshop on Linear Colliders 29 June 2017

2 Enabling Accelerator Technology: SRF Cavities High quality EM resonators: Typical Q 0 > Tens of MV/m accelerating gradients with high efficiency, large aperture, and up to 100% duty factor Accelerator technology for production of high current, high energy, high brightness beams Input RF power at 1.3 GHz Slowed down by factor of approximately 4x10 9 Niobium ~1 m Images from linearcollider.org, WIkipedia

3 SRF Cavity Figures of Merit Higher Cryogenic Efficiency Higher energy gain per length 3Quality Factor /29/2017 Sam Posen Accelerating Gradient E acc [MV/m]

4 SRF Accelerators Around the World ISAC CLS LCLS-II FRIB PIP-II/III EIC CESR CEBAF ATLAS MaRIE SNS ESS ALICE SPIRAL2 BESSY ELBE Soleil XFEL LHC FLASH FCC TARLA ALPI HIE-ISOLDE SARAF BEPC-II SC-LINAC ADS C-ADS RAON ANURIB ISNS CepC-SppC TLS ILC LIPAc cerl J-PARC Circular Linear HEP NP Light src USP ANU Oper n Produc n Planning <10 cavities cavities cavities >1000 cavities Sam Posen 4 6/29/2017 Map from Wikipedia. Non-exhaustive facility list.

5 SRF Accelerators Around the World Upcoming ISAC CLS LCLS-II FRIB PIP-II/III EIC CESR CEBAF ATLAS MaRIE SNS ESS ALICE SPIRAL2 BESSY ELBE Soleil XFEL LHC FLASH FCC ALPI HIE-ISOLDE SARAF BEPC-II SC-LINAC ADS C-ADS RAON ANURIB ISNS CepC-SppC TLS ILC LIPAc cerl J-PARC Circular Linear HEP NP Light src USP ANU Oper n Produc n Planning <10 cavities cavities cavities >1000 cavities Sam Posen 5 6/29/2017 Map from Wikipedia. Non-exhaustive facility list.

6 SRF Accelerators Around the World Upcoming ISAC CLS LCLS-II FRIB PIP-II/III EIC CESR CEBAF ATLAS MaRIE SNS ESS ALICE SPIRAL2 BESSY ELBE Soleil XFEL LHC FLASH FCC ALPI HIE-ISOLDE SARAF BEPC-II SC-LINAC ADS C-ADS RAON ANURIB ISNS CepC-SppC TLS ILC LIPAc cerl J-PARC Circular Linear HEP NP Light src USP High DF Low DF ANU Oper n Produc n Planning <10 cavities cavities cavities >1000 cavities Sam Posen 6 6/29/2017 Sam Posen Map from Wikipedia. Non-exhaustive facility list.

7 Q 0 -> Cryogenic Infrastructure, Operating Cost Crucial for high duty factor machines 1500 P AC /P diss ~800 W/W at 2 K T [K] P diss ~ E acc /Q 0 (for fixed E max ) ILC (pulsed, <1% DF) ~0.5 W average per cavity LCLS-II (CW, 100%DF) ~10 W average per cavity 7 6/29/2017 Sam Posen Map from Wikipedia. Non-exhaustive facility list.

8 E acc -> Length for Linear Accelerator In low duty factor machines, high gradient with high Q 0 can shrink length P diss ~ E acc /Q 0 (for fixed E max ) ILC@250 GeV: ~8,000 cavities 8 cavities ~10 m 8 6/29/2017 Sam Posen Map from Wikipedia. Non-exhaustive facility list.

9 Motivation State-of-the-Art SRF Technology Advances in SRF cavity performance improve the feasibility of building new accelerators with unprecedented reach into unexplored scientific frontiers. 9 6/29/2017 Sam Posen Map from Wikipedia. Non-exhaustive facility list.

10 How to Push SRF Cavity Performance? 1) Improve understanding via surface science Material science tools are essential to understand the nanometer-scale structural changes that lead to dramatic changes in performance At the present day, we know the baked Nb has a layered structure that consists of A. Romanenko et al., Appl. Phys. Lett. 104, (2014) 1. dirty Nb layer and 2. clean bulk Nb. N"#reconstruc, on# Copper& O"#reconstruc, on# Nb&layer& 10 Presenter Presentation Title Dirty Nb 6/29/2017 Clean Nb 24

11 Performance are determined by nanometer scale structure of inner surface Image from linearcollider.org RF fields Niobium ~3 mm Helium cooling RF fields <0.1% of thickness RF currents ~100 nm 11 6/29/2017

12 How to Push SRF Cavity Performance? 2) R&D Cavity Processing and SRF Experiment Fermilab JLab Vertical Test Stands Horizontal Test Stands Cavity Processing Facilities Cornell KEK 12 Sam Posen 6/29/2017

13 Superconducting RF Technology Recent Advances 13 10/12/16 Sam Posen Nb3Sn SRF Coatings at Fermilab

14 First XFEL Commissioning Results PRELIMINARY RESULTS: Energy reach 14 Mature technology Compare to 250 GV Courtesy N. Walker L1 L2 L3 Design accelerating gradient: 23.5 MV/m Average accelerating gradient: (after module test and waveguide tailoring) 26.0 MV/m After initial commissioning design gradient almost reached On-going measurement campaign to assess limits and reasons Americas Workshop on Linear Colliders - June 28 th SLAC Julien Branlard, DESY

15 2013 R&D Advance: Nitrogen doping treatment for high Q 0 800C UHV, 3 hours 800C N 2 p = 25 mtorr 2 minutes 800C UHV, 6 minutes UHV cooling 5 um EP Y. Trenikhina et Al, Proc. of SRF 2015 N 2 Nb Final RF Surface Nb x N y N N Interstitial 15 Y. Trenikhina et al, Proc. of SRF 2015

16 Improved Q 0 from N-doping Anti-Q-slope N-doped Q Typical EP/120 C bake preparation 10 9 f = 1.3 GHz T= 2K LCLS-II E acc spec E acc (MV/m) >2x Q 0 improvement at 2 K, 16 MV/m Reduced maximum field OK for high duty factor applications 16 A. Grassellino et al, 2013 Supercond. Sci. Technol (Rapid Communication) A. Romanenko and A. Grassellino, Appl. Phys. Lett. 102, (2013)

17 LCLS-II High Repetition Rate X-Ray FEL at SLAC See also talk on Wednesday from Andrew Burrill, SLAC 17 Sam Posen 6/29/2017

18 Magnetic Flux Sensitivity and Expulsion Infusion: low sensitivity to trapped flux New understanding of expulsion Preservation of Q in CM environment Q Magnetic Flux Trapping B ext < 1 m G B ext : 5 m G E acc 2 K, 16 MV/m, 1.3 GHz 900 C furnace treatment Magnetic Flux Expulsion Q 0 B ext < 1 m G B ext : 5 m G E acc M. Martinello et al. Effect of interstitial impurities on the field dependent microwave surface resistance of niobium, Appl. Phys. Lett. 109, (2016) S. Posen et al. Efficient expulsion of magnetic flux in SRF cavities for high Q0 applications, Journal of Applied Physics 119, (2016) 18 Sam Posen 6/29/2017

19 Fermilab Prototype LCLS-II Cryomodule Cavity Usable Gradient* [MV/m] 2K Fast Cool Down TB9AES E+10 TB9AES E+10 TB9AES E+10 TB9AES E+10 TB9AES E+10 TB9AES E+10 TB9AES E+10 TB9AES E+10 Average E+10 Total Voltage MV Spec: 133 MV Spec: 2.7x Sam Posen 6/29/2017

20 LCLS-II Cryomodule Production Underway 20 Sam Posen 6/29/2017

21 Superconducting RF Technology On the Horizon 21 10/12/16 Sam Posen Nb3Sn SRF Coatings at Fermilab

22 Exploring Phase Space of Nitrogen Treatment 2/6 Nitrogen Doping 800C UHV, 3 hours 800C N 2 p = 25 mtorr 2 minutes 800C UHV, 6 minutes UHV cooling 5 um EP 800C UHV, 3 hours 120 C Nitrogen Infusion 120C N 2 p = 25 mtorr 48 hours UHV cooling Can tailor treatment to application (optimize for Q 0 at a given E acc ) A. Grasselllino et al. arxiv: /29/2017 Sam Posen!

23 Concentration (Atoms/cm3) Nitrogen Infusion Treatment Furnace treatment of cavity developed at Fermilab in 2016 Designed to diffuse nitrogen interstitial impurities tens of nm deep into surface 1E+22 1E+21 1E+20 N H 1E+19 O 1E+18 C 1E+17 1E+16 1E Depth (µm) N-doping treatment μm-scale N-infusion treatment 10s of nm 23 6/29/2017 Sam Posen

24 gradients with low temperature (120C) nitrogen treatment Results comparison : standard 120C bake vs N infused 120C bake Increase in Q factor of two, increase in gradient ~15% Same cavity, sequentially processed, - Record no EP Q at in between fields > 30 MV/m - Preliminary data indicates potential 15% boost in achievable quench fields - Can be game changer for ILC Achieved: 45.6 MV/m 194 mt With Q ~ 2e10! Q at ~ 35 MV/m ~ 2.3e10 All Q vs E curves shown are for 1.3 GHz single cells, T=2K Alexander Romanenko FCC Week Rome Sam Posen 4/12/16 6/29/2017 A. Grassellino et al. Unprecedented Quality Factors at Accelerating Gradients up to 45 MV/m in Niobium Superconducting Resonators via Low Temperature Nitrogen Infusion, arxiv:

25 Reproducibility: repeatedly highest Q ever measured >2e10 at very high gradients > 40 MV/m! So far three out of 4 cavities processed with this regime have reached 45 MV/m with high Q ILC vertical test specification First attempts of N- infusion on 9-cell cavities are underway All Q vs E curves shown are for 1.3 GHz single cells, T=2K 25 6/29/2017 Sam Posen A. Grassellino et al. Unprecedented Quality Factors at Accelerating Gradients up to 45 MV/m in Niobium Superconducting Resonators via Low Temperature Nitrogen Infusion, arxiv:

26 9-cell cavity results, 120C infusion Same high Q as single cells Highly reproducible CAV0018 limited by FE -> might have gone even higher in gradient 1.3 GHz cavities, tested at 2K 26 6/27/17 S. Aderhold N-Infusion and Cost Reduction Fermilab

27 How Does this Compare to Statistics from XFEL? RI XFEL: Maximum Gradient Yield (2D) 11 RI XFEL cavities accepted for module assembly (includes those cavities which have been retreated) Gmax MV/m N. Walker Q0 XFEL Compared to this table values for XFEL, result would lay in top 1% 27 6/12/16

28 Trick to delay flux penetration - layering TTC@Saclay 24 The vortex is pushed by the S-S boundary to the direction of the material with a larger λ. f vortex T.Kubo, in proceedings of LINAC14, Geneva, Switzerland (2014), p. 1026, THPP A. Grassellino GARD-RF Workshop λ=300nm λ=100nm 2/10/17 G. S. Mkrtchyan, F. R. Shakirzyanova, E. A. Shapoval, and V. V. Shmidt, Zh. Eksp. Theor. Fiz. 63, 667 (1972).

29 Cost (%) Impact in Cost Model for ILC 120 ILC cost vs. gradient and Q GeV Baseline design Q=4.0E+09 Q=6.0E+09 Q=1E+10 Q=2E+10 Q=3E+10 ILC Standard surface 120 processing C bake N N-infusion doping Short term goal: next ~3 years Eacc [MV/m] Medium-term goal 29 Sam Posen 6/29/2017

30 ILC Cost Reduction Collaboration Taking Advantage of New SRF Developments Harness recent SRF R&D advances Harness strengths of different laboratories N-infusion, reduced field emission, minimized flux losses Demonstrate that significant reduction in the cost of the ILC is possible to help make the project realizable Progress will benefit programs also outside of ILC 30

31 Spreading N-Infusion Capability P. Dhakal (JLab) 31 Sam Posen See also talks on Tuesday from F. Furuta (Cornell), M. Wenskat (DESY), and 6/29/2017 E. Kako (KEK)

32 Combine N-Infusion with Other Reduction Methods 32 6/29/2017 Sam Posen See talk on Wednesday from Akira Yamamoto (KEK)

33 Superconducting RF Technology Next Generation R&D 33 10/12/16 Sam Posen Nb3Sn SRF Coatings at Fermilab

34 Beam view, inside the cavity 34 6/29/2017

35 Beam view, inside the cavity 1500 f = 1.3 GHz P AC /P diss ~800 W/W at 2 K ~250 W/W at 4 K T [K] Jefferson Lab Sumitomo 35 6/29/2017

36 Recent Developments in Nb 3 Sn SRF Cavities Q Wuppertal 2000 Cornell 2015 T~4.4 K 1-cell cavity GHz E acc [MV/m] 36 6/29/2017 Sam Posen S. Posen, M. Liepe and D. Hall, Appl. Phys. Lett., 106, (2015). S. Posen and D.L. Hall, Supercond. Sci. Technol., (2017).

37 Recent Developments in Nb 3 Sn SRF Cavities W 3 W 5 W 10 W Q W 50 W 10 9 Wuppertal 2000 Cornell 2015 T~4.4 K 1-cell cavity GHz E acc [MV/m] 37 6/29/2017 Sam Posen S. Posen, M. Liepe and D. Hall, Appl. Phys. Lett., 106, (2015). S. Posen and D.L. Hall, Supercond. Sci. Technol., (2017).

38 Maximum Field [mt] High H sh with Nb 3 Sn Nb 3 Sn is predicted to have 2x the fundamental metastable limit of niobium Potential Now Nb Nb3Sn Twice the energy gain per cavity? Not there yet additional R&D required 38 6/29/2017

39 Nb 3 Sn Samples via Vapor Diffusion at Fermilab Nb Nb 3 Sn 39 6/29/2017 Sam Posen Sample measurements by Yulia Trenikhina (FNAL), Jae-Yel Lee (Northwestern), and Zuhawn Sung (FNAL)

40 Nb 3 Sn Coating Chambers Existing vacuum furnace Hot zone Heat shields Sn source Nb coating chamber Sn source Fermilab JLab Cornell 40 6/29/2017 Sam Posen

41 Nb 3 Sn Coating System at Fermilab New door and heat shields New Nb chamber, 20 diam, 82 long Existing vacuum furnace 1.3 GHz 1-cell (current state of Nb 3 Sn R&D) 650 MHz 5-cell (future) 41 2/2/2017

42 Linac Cost (% of nominal) Linac Cost (% of nominal) 4.5 K ILC Upgrade? 4.5 K system helps reduce cryogenic costs (analysis by Tom Peterson). Analysis is specific to ILC, but representative of significant cost savings for machines large and small that would benefit from high gradients ILC SRF Linac Cost vs. Gradient and Q0 Q=4.0E+09 Q=6.0E+09 Q=8.0E+09 Q=1.6E+10 Q=3.2E ILC SRF Linac cost vs. Gradient and Q0 Q=4.0E+09 Q=6.0E+09 Q=8.0E+09 Q=1.6E+10 Q=3.2E Gradient MV/m Gradient MV/m 2.0 K 4.5 K (In ILC staged approach, Nb 3 Sn not ready for 250 GeV first step, but could be developed for high energy upgrade.) 42 6/29/2017 Sam Posen

43 Superconductor-Superconductor (Dirty Layer) Structure High κ film: analytical from London eqs. T. Kubo, Supercond. Sci. Technol. 30, (2017) RF Up to 120 MV/m (thin Nb3Sn-Nb) High k film SC bulk Diffused κ profile: numerical from Ginzburg-Landau eqs. M. Checchin et al., IPAC 2016 & LINAC 2016 RF Up to 70 MV/m (Nb-Nb) k profile SC bulk 43 Mattia Checchin SRF-GARD Workshop 2017

44 44 6/29/2017 Sam Posen

45 High Q frontier roadmap Physics of RF Surface Resistance Doping Understand the field dependence of BCS surface resistance and effect of different impurities Understand origin of residual resistance and its field dependence Understand trapped magnetic flux losses and flux trapping Continue exploration with nitrogen in Nb at different temperatures Probing the ultimate limits of Nb RF surface resistance by doping with different impurities Study Nb doping at different frequencies and temperatures Apply gained knowledge and develop new understanding for alternative materials Doping for new materials Potential of Nb material: Q (2 K) ~ 1x GHz Nb 3 Sn or other new materials Pursue current promising path forward for material in bulk form (Nb 3 Sn) explore and optimize coating techniques and treatments for single cell / multi-cell cavities Evaluate alternative materials, bulk or film (NbN, NbTiN, MgB 2 ) first on samples, then on cavities Nb 3 Sn studies for cryomodule operation Explore SIS for Nb 3 Sn Potential of Nb 3 Sn material: Q (4 K) ~ 1x GHz Magnetic Flux Losses Drastically reduce sensitivity to magnetic flux for Nb and new materials In situ removal of trapped magnetic field (in cryomodule) Develop Materials Specs to ensure maximum flux detrapping Impact: Retain 1x10 11 Sustain very high gradients Goals Q > 4x10 10 at 2 K, 1.3 GHz and E acc > 35 MV/m Nb 3 Sn: E acc > 20 MV/m with Q 0 > 1x10 10 at 1.3 GHz, 4.2 K Residual resistance < 1 nω in cryomodule Nb 3 Sn cryomodule ready technology 45 5/30/2017 S. Belomestnykh FCC Week 2017 US decadal roadmap on SRF for HEP

46 High Gradient frontier roadmap Fundamental Limits Probing the fields above H sh on samples Probing the limits of accelerating field on sub-nanosecond time scales Evaluate feasibility of > DC H sh fields for up to ~GV/m scale gradients Niobium Nb 3 Sn Other superconductors Produce dirty surface layer on clean bulk to enhance superheating field Probing and altering by doping the ultimate limiting cavity field Pursue current promising paths forward for material in bulk form Evaluate superconductor-superconductor structure to delay flux entry Evaluate superconductor-insulator-superconductor structure to delay flux entry Use theoretical and experimental expertise to evaluate promising options for SRF materials (bulk and films), develop sample coating and test tools Potential of Nb material: H sh limit: 70 MV/m Above DC H sh : >70 MV/m Potential of Nb 3 Sn material: H sh limit: 90 MV/m Above DC H sh : >120 MV/m For materials that show B pk >50 mt with R s <300 nω, develop cavity coating tools Goals Development of techniques to prevent and mitigate field emission H pk >H sh of bulk niobium E acc =70 MV/m Measure and outpace time scales of vortex dissipation E acc >> 120 MV/m 46 5/30/2017 S. Belomestnykh FCC Week 2017 US decadal roadmap on SRF for HEP

47 Alignment of SRF R&D and future machines Main R&D Doping and Flux Expulsion: E acc up to 70 MV/m with Q (2 K) > 3x10 10 Layered structures and advanced concepts on fundamental field limits: E acc > 100 MV/m Nb 3 Sn: E acc up to 90 MV/m with Q (4 K) > 3x10 10 Companion R&D Field emission mitigation, Novel cavity shapes, RF sources, Ancillaries, Microphonics SRF R&D Progress HEP Accelerators PIP-II ILC 1 st Stage 250 GeV PIP-III ILC 2 nd Stage FCC-ee, CEPC Multi-TeV e+e- Collider Synergies: FELs, ADS, Quantum Computing, Compact Accelerators, etc. 47 5/30/2017 S. Belomestnykh FCC Week 2017 US decadal roadmap on SRF for HEP

48 Superconducting RF Technology Conclusion: Continuing Evolution 48 10/12/16 Sam Posen Nb3Sn SRF Coatings at Fermilab

49 SRF Performance Evolution Courtesy A. Grassellino Q E acc (MV/m)

50 SRF Performance Evolution Courtesy A. Grassellino Q E acc (MV/m)

51 SRF Performance Evolution Courtesy A. Grassellino Q E acc (MV/m)

52 SRF Performance Evolution Courtesy A. Grassellino Q E acc (MV/m)

53 SRF Performance Evolution Courtesy A. Grassellino Q EXFEL E acc (MV/m)

54 SRF Performance Evolution Courtesy A. Grassellino Q LCLS-II E acc (MV/m)

55 SRF Performance Evolution ILC cost reduction?? Courtesy A. Grassellino Q E acc (MV/m)

56 SRF Performance Evolution Courtesy A. Grassellino Q Enabling future efficient High Energy Machines E acc (MV/m)?

57 Thanks for your attention!

58 A.Grassellino -GARD SRF Roadmap

59 Barrier Increased Metastable Limit in Nb 3 Sn Superconductors can remain fluxfree even above H c1 Can reach DC superheating field H sh H sh of Nb: ~200 mt (~50 MV/m) Predicted H sh of Nb 3 Sn: ~400 mt Achieving H sh would have huge impact on high energy colliders M. Transtrum, G. Catelani, and J.P. Sethna, Phys. Rev. B, 83, (2011). B applied x λ > x ILC: 16,000 cavities in 31 km linac Energy cost from core (x) first; Energy gain from field (λ) later 59 6/29/2017 Sam Posen Nb3Sn SRF Cavities Slide adapted from J. P. Sethna

60 New video on SRF cavities: /29/2017 Sam Posen