scu development at lbnl

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SCU Development at LBNL Soren Prestemon Lawrence Berkeley National Laboratory Superconducting Undulator R&D Review Jan. 31, 2014

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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 - PowerPoint PPT Presentation

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Page 1: SCU Development at LBNL

SCU Development at LBNL

Soren PrestemonLawrence Berkeley National Laboratory

Superconducting Undulator R&D ReviewJan. 31, 2014

Page 2: SCU Development at LBNL

SCU R&D Review, Jan. 31, 2014

Outline

BackgroundAreas of contribution to the proposalStatus of technology in each area and proposed R&D– Test cryostat for tuning development– Tuning concepts– Nb3Sn SCU prototyping– SCU testing

Cost estimate: LBNL contributionProject schedule: LBNL contributionInfrastructure and resource availabilityConclusions

Page 3: SCU Development at LBNL

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

Page 4: SCU Development at LBNL

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

Page 5: SCU Development at LBNL

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.

Page 6: SCU Development at LBNL

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

Page 7: SCU Development at LBNL

SCU R&D Review, Jan. 31, 2014

Tuning concept: basics

Page 8: SCU Development at LBNL

SCU R&D Review, Jan. 31, 2014

Tuning concept - improvements

Page 9: SCU Development at LBNL

SCU R&D Review, Jan. 31, 2014

Tuning concept scale-up: proposed R&D

Scale up tuning concept for application to 1.5m undulatorsDemonstrate concept off-line (no undulator) in advance of NbTi and Nb3Sn undulator readinessDevelop algorithms to optimize corrections based on measured field and/or first and second integrals

Page 10: SCU Development at LBNL

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,…)

Page 11: SCU Development at LBNL

SCU R&D Review, Jan. 31, 2014

Test cryostat: details

Page 12: SCU Development at LBNL

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 lengthCommission modifications via demonstration of cryogenic performanceUse test cryostat to demonstrate scale-up of tuning concept in advance of undulator prototype readiness

⇒ minimize schedule risk

Page 13: SCU Development at LBNL

SCU R&D Review, Jan. 31, 2014

Nb3Sn SCU development at LBNL: background

Motivated by performance potential

Page 14: SCU Development at LBNL

SCU R&D Review, Jan. 31, 2014

Nb3Sn superconductor options

Page 15: SCU Development at LBNL

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

Page 16: SCU Development at LBNL

SCU R&D Review, Jan. 31, 2014

Nb3Sn prototyping: history (2)

Prototype 2 (2004):– Demonstrated that simple current loop on a pole can

provide adequate field perturbation to serve as tuning mechanism

-0.0025

0.0025

0.0075

0.0125

0.0175

0.0225

0 25 50 75 100 125 150 175 200Position [mm]

B [T

]

Page 17: SCU Development at LBNL

SCU R&D Review, Jan. 31, 2014

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

Page 18: SCU Development at LBNL

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

Page 19: SCU Development at LBNL

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 tolerancesDetailed tolerance and tuning analysis

Page 20: SCU Development at LBNL

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

Page 21: SCU Development at LBNL

SCU R&D Review, Jan. 31, 2014

End design (2)Odd number of polesIdeal 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)

Page 22: SCU Development at LBNL

SCU R&D Review, Jan. 31, 2014

Nb3Sn prototyping: ongoing - fabrication

Page 23: SCU Development at LBNL

SCU R&D Review, Jan. 31, 2014

Status

Page 24: SCU Development at LBNL

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 choicesDocument all fabrication tolerancesIdentify issues associated with future scale-up to industrial fabrication level

Page 25: SCU Development at LBNL

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

Page 26: SCU Development at LBNL

SCU R&D Review, Jan. 31, 2014

SCU testing: proposed R&D

Implement pulsed-wire in tuning cryostat for tuning scale-up testingImplement pulsed-wire system in ANL test cryostatDemonstrate tuning on NbTi undulator in ANL test cryostatDemonstrate tuning on Nb3Sn undulator in ANL test cryostat

Page 27: SCU Development at LBNL

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

Page 28: SCU Development at LBNL

SCU R&D Review, Jan. 31, 2014

Schedule and Cost for LBNL effort

NOTE: This estimate does not include contingency

Page 29: SCU Development at LBNL

SCU R&D Review, Jan. 31, 2014

Infrastructure

Page 30: SCU Development at LBNL

SCU R&D Review, Jan. 31, 2014

ResourcesEngineering 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&DWork will not be limited by resource availability

Page 31: SCU Development at LBNL

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