SCU Development at LBNL Soren Prestemon Lawrence Berkeley National Laboratory Superconducting Undulator R&D Review Jan. 31, 2014 Outline Background Areas of contribution to the proposal Status of technology in each area and proposed R&D – – – – Test cryostat for tuning development Tuning concepts Nb3Sn SCU prototyping SCU testing Cost estimate: LBNL contribution Project schedule: LBNL contribution Infrastructure and resource availability Conclusions SCU R&D Review, Jan. 31, 2014 Background Long history in undulator development at LBNL – ~1985: Halbach initiated development of PM technology – ~1991-: Development, fabrication, and implementation of large number of plane-polarizing and elliptically-polarizing undulators for the ALS – ~1995-1996: Studies of NbTi helical SCU’s for SLAC FEL – 2002-: Development of Nb3Sn SCU’s • • • • • • *First LDRD, ALS-motivated: 2003 – Prototype 1 *Continuation LDRD, ALS-motivated: 2004 – Prototype 2 *WFO funding from ANL: 2006 – Prototype 3 LDRD, Variable-polarizing undulator, NGLS-motivated: 2011 *NGLS R&D funds: 2011-2012 *Continued funding via LDRD:mid-2013, 2014 – 2012-: Responsible for the LCLS-II hybrid PM baseline undulators SCU R&D Review, Jan. 31, 2014 Areas of contribution Tuning system scale-up – Scale-up existing tuning concept and test off-line Tuning test cryostat – “Simple” extension of existing cryogen free cryostat: 1m => 1.5m – Primary purpose: will allow testing of tuning system in parallel with main cryostat fabrication ⇒avoid risk of commissioning tuning system late in project Nb3Sn 1.5m prototype – 18.5mm period, end corrections – Potential for significant performance enhancement or significantly increased performance margin (e.g. temperature) vs NbTi Testing – Participate in testing and tuning of SCU prototype in the ANL Test Cryostat SCU R&D Review, Jan. 31, 2014 Tuning concepts Guidelines: – Want method that provides sufficient degree-of-freedom correction – Want to minimize cool-down => warm-up cycles – Want minimal complexity Approach: – Single active electrical circuit drives multiple correctors in series – Initially large selection of possible corrector locations • At each location +Icor,0,-Icor are allowed – Optimize distribution of active correctors to minimize trajectory and phase-shake errors. SCU R&D Review, Jan. 31, 2014 Tuning concept scale-up General approach to field-errors: – Minimize errors via tight machining tolerances, assembly – Eliminate “global” steering and displacement via end correction coils – But… also provide a mechanism for local field error correction Use detailed error analysis to develop algorithm for tuning concept scale-up – Many poles (N) can have correction loop carrying current ±Icor – Icor can be varied with main coil current I0 – N varies from undulator to undulator • selected based on measurements SCU R&D Review, Jan. 31, 2014 Tuning concept: basics SCU R&D Review, Jan. 31, 2014 Tuning concept - improvements SCU R&D Review, Jan. 31, 2014 Tuning concept scale-up: proposed R&D Scale up tuning concept for application to 1.5m undulators Demonstrate concept off-line (no undulator) in advance of NbTi and Nb3Sn undulator readiness Develop algorithms to optimize corrections based on measured field and/or first and second integrals SCU R&D Review, Jan. 31, 2014 Existing Test Cryostat: features A cryogen-free test cryostat has been fabricated – – – – – – Currently compatible with 1m prototypes Uses 2 pulsed-tube cryocoolers 500A HTS leads for main coil 250A HTS leads for end correctors 250A HTS leads for tuning system Large number of possible diagnostics (thermal, voltage,…) SCU R&D Review, Jan. 31, 2014 Test cryostat: details SCU R&D Review, Jan. 31, 2014 Test cryostat modifications for tuning development: proposed R&D Extend existing cryostat ends to allow 1.5m testing – Need additional spools with flanges – Need appropriate cryogenic shielding Modify existing pulsed wire system to accommodate new length Commission modifications via demonstration of cryogenic performance Use test cryostat to demonstrate scale-up of tuning concept in advance of undulator prototype readiness ⇒ minimize schedule risk SCU R&D Review, Jan. 31, 2014 Nb3Sn SCU development at LBNL: background Motivated by performance potential SCU R&D Review, Jan. 31, 2014 Nb3Sn superconductor options SCU R&D Review, Jan. 31, 2014 Nb3Sn prototyping: history (1) Prototype 1 (2003): – Demonstrated that superconducting undulators operating at very high current densities (JE>1500A/mm2, resulting in Jcu>6000 A/mm2 during a quench) can be passively protected without damage PRESTEMON et al.: DESIGN, FABRICATION, AND TEST RESULTS OF UNDULATORS besides requiring that the temperatures stay below the melting point of Sn, the wires cannot be rolled into tape (e.g. made rectangular) without a reduction in critical current [9]. This is most likely due to the nonuniform tin distribution that results from rolling a twisted wire. Recent progress in powder-in-tube (PIT) manufacturing, which has the potential to allow for very small filament diameters and wire rolling, is particularly appealing for future SCU devices. Such wires were successfully used in recent high-field dipole prototypes [10]. The danger of flux-jump limitations with state of the art can be partially alleviated by providing dynamic stability [11], i.e. providing high RRR copper in the conductor matrix. Experience at LBNL shows that appropriate tailoring of the heat treatment cycle can provide significant increases in RRR with nominal decrease in critical current [8]. 1237 Fig. 1. • MAGNET DESIGN ANDJan. FABRICATION SCU III. R&D Review, 31, 2014 Cross-section of the first prototype coilpack, on the beam side. does not require splices, and minimizes fabrication complexity. Design of a (scalable) protection system capable of protecting the conductor during a quench, despite copper current densities approaching 4–5 . Nb3Sn prototyping: history (2) Prototype 2 (2004): 1238 – Demonstrated that simple current loop on a pole can provide adequate field perturbation to serve as tuning mechanism IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, VOL. 15, NO. 2, JUNE 2005 0.0225 B [T] 0.0175 0.0125 0.0075 0.0025 -0.0025 0 25 50 75 100 125 150 175 200 Position [mm] Fig. 2. Beam side of one of the undulator halves, showing the five trim coils installed in the prototype. SCU R&D Review, Jan. 31, 2014 IV. MAGNET PERFORMANCE Fig. 3. Low-field instability measurements. Field sweeps at the specified Nb3Sn prototyping: history (3) Prototype 3 (ANL funded; 2006) one- yoke only Demonstrated field performance consistent with predicted B(λ,gm) curves, as used by Paul Emma SCU R&D Review, Jan. 31, 2014 SCU development for FEL’s - ongoing Systematic R&D undertaken to address key technological issues with high-performance superconducting undulators – Development of an SCU short model to => demonstrate field performance – Development of a magnet measurement system to => evaluate field quality – Development of a shimming concept to => correct trajectory and phase-shake errors SCU R&D Review, Jan. 31, 2014 Nb3Sn prototyping: ongoing… Nb3Sn prototype for FEL applications: – λ=20mm, gm=7.5mm, 50cm device – Optimized end design – Tight fabrication tolerances Detailed tolerance and tuning analysis SCU R&D Review, Jan. 31, 2014 End design (1) Odd number of poles chosen for prototype – Non-ideal effects due to finite permeability and differential saturation of end poles – End kick is dependent on the undulator field – Dipole field is generated by unbalanced yoke field As field is ramped: Pole 2 saturates before 1 SCU R&D Review, Jan. 31, 2014 End design (2) Odd number of poles Ideal end design is used for the main coil (1/8, 1/2, 7/8) Kick corrector + field clamps placed at each end (only generates a kick) Dipole corrector is co-wound with the main coil in the first pocket (generates both kick and dipole) Strength of both correctors is varied as a function of the undulator field (look-up table) SCU R&D Review, Jan. 31, 2014 Nb3Sn prototyping: ongoing - fabrication SCU R&D Review, Jan. 31, 2014 Status SCU R&D Review, Jan. 31, 2014 Nb3Sn prototype: proposed R&D Design and fabricate a Nb3Sn prototype – λ=18.5mm, gm=7.5mm, 1.5m Document all design choices Document all fabrication tolerances Identify issues associated with future scale-up to industrial fabrication level SCU R&D Review, Jan. 31, 2014 SCU testing: capabilities Pulsed wire development – Demonstrated accuracy on SLAC ECHO undulator – Will be incorporated in tuning test cryostat for use during tuning scale-up testing at LBNL – Will be incorporated into ANL test cryostat for SCU testing and tuning SCU R&D Review, Jan. 31, 2014 SCU testing: proposed R&D Implement pulsed-wire in tuning cryostat for tuning scale-up testing Implement pulsed-wire system in ANL test cryostat Demonstrate tuning on NbTi undulator in ANL test cryostat Demonstrate tuning on Nb3Sn undulator in ANL test cryostat SCU R&D Review, Jan. 31, 2014 Summary: proposed LBNL contributions Modifications of an existing cryocooler-based, cryogen-free test cryostat to allow development of a tuning system commensurate with the 1.5m SCU prototypes Development of a 1.5m scale tuning system, based on concepts already tested and proven in previous work at LBNL. Nb3Sn SCU design and fabrication. The Nb3Sn SCU prototype will have a period λ=18.5mm. Contribute to prototype testing in the ANL test cryostat SCU R&D Review, Jan. 31, 2014 Schedule and Cost for LBNL effort Sept Octo Nov Dece Janu Febr Marc April May June July 09 10 11 12 01 02 03 04 05 06 07 Aug Sept Octo Nov Dece Janu Febr Marc April May June July Aug Sept Octo Nov 08 08 09 10 11 12 01 02 03 04 05 06 07 09 10 11 LCLS- II- proposal- LBNL- v2 LBNL- contributions Test Cryostat mods Design 1m ? D.; S.M.; D.2.; H.P. Design review procure components 1.5m Assembly Commissioning Tuner scale- up 3w R.O.; H.P. 1.5m H.P.; T.K. 8.05 months T.K.; R.O.; D.A.; D.2.; H.P. Nb3Sn 1.5m prototype Design 3.55 months D.D.; S.M.; D.A.; D. NOTE: This estimate does not include contingency Integrated design review Final documentation Fabrication 1m D.A. 9.9 months R.O.; B.C.; S.M.; D.D.; T.2.; R.A. Testing Testing I 2.35 months Testing II H.P.; D.A.; R.O.; B.C.; S.P.; R.A.; T.2. 1.6m Summarize results H.P.; D.A.; R.A.; B.C.; S.P.; R.O.; T.2. 1.5m Final review SCU R&D Review, Jan. 31, 2014 D.A. Infrastructure SCU R&D Review, Jan. 31, 2014 Resources Engineering Division: – Magnetic Systems group Accelerator and Fusion Research Division: – Superconducting Magnet Group Together we have a strong team with expertise in: – – – – Magnetics and magnetic systems Undulators: design, fabrication, and implementation Superconducting magnets Cryogenics Ample resources are available to perform the proposed R&D Work will not be limited by resource availability SCU R&D Review, Jan. 31, 2014 Summary We have designed, fabricated and tested multiple prototypes that provide credibility to the proposed design point, and have invested in significant analysis to support the tuning concept. We have infrastructure and resources available to perform the proposed work. The proposed LBNL contributions: tuning system development and 1.5m Nb3Sn design and fabrication, complement the ANL part of the proposal and are critical to minimize risk for the project so as to achieve LCLS-II undulator specifications SCU R&D Review, Jan. 31, 2014