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MgB2 Development for Accelerator and Medical Applications Xuan Peng Matt Rindfleisch Mike Tomsic Jinji Yue CJ Thong David Doll Thank you! Thank you!

Development partners Past and present financial and moral support: State of Ohio U.S. DOE HEP NIH MIT NIST NASA DOD (USN, USAF) Wollongong CNWU NHMFL FSU CERN AML SMI MMP Mike Sumption Ted Collings Milan Majoros Guangze Li Yuan Yang Chris Kovacs Cory Myers Hyun Sung Kim Thank you: ICFA Workshop Organizing Committee

Outline • Hyper Tech: a MgB2 superconductor and coil manufacturer • Wind and React coils • React and Wind coils • Joints • Low AC loss MgB2 conductors • MgB2 cables • Jc improvements (2nd Generation)

Advantages of MgB2 in view of applications

14 years of MgB2 superconductors Ability to customize strand design 5

Standard MgB2 wire products • Up to 5 – 6 km (25 kg billets), the designed piece length is 60-80 km. • C-doped B, Nb, Cu, Monel Customized conductor design 24-NM Lock-in conductor design 36-CM Jc (4K, 4T) = 200,000 A/cm2 Jc (20K, 2T) = 140,000 A/cm2 18-MS 30-NM 6

Outline • Hyper Tech: a MgB2 superconductor and coil manufacturer • Wind and React coils • React and Wind coils • Joints • Low AC loss MgB2 conductors • MgB2 cables • Jc improvements

RHIC e-lens system at BNL • An example of HTS magnets potentially reducing the cost of ownership (capital + operation) while enhancing the performance of certain machines • An e-lens system is part of RHIC luminosity upgrade • Project proposes replacing high power consuming RT Cu solenoids with MgB2 magnets which could significantly increase the field to significantly improve the design and performance of the system while consuming little power. • MgB2 solenoids could operate at ~10-25 K cooled by a cryocooler or return (exhaust) helium gas of the LTS solenoids which are already part of the e-lens system

e-lens MgB2 solenoid coil modeling (1) • MgB2 solenoid modeled for a GS1 coil (17.6 cm bore) producing 1 T • 260,000 A-turns • For a GSB coil (48.5 cm bore) producing 0.45 T • 198,000 A-turns Ramesh Gupta Seetha Lakshmi Lalitha Arup Ghosh Mike Furey

e-lens MgB2 solenoid coil fabrication Actual parameters of MgB2 Wind & React solenoid • B0 = 0.7 T (20 K) • 86 A • Je = 170 A/mm2 (20 K) • IR = 0.0876 m • Length of solenoid = 0.263 m • 2180 turns • 8 layers • 272.5 turns/layer • Conductor length = 1229 m Coil at BNL to carry out extended testing over a large number of power, quench and thermal cycles and perform field quality measurements to confirm that coil performance and reliability is appropriate for this and other future accelerator facilities.

Image Guided Radiation Treatment Medical System Hyper Tech is designing a background magnet for image guided radiation treatment. Magnet uses magnesium diboride superconducting wire and is conduction cooled less than 10K– helium bath free. Project funded by NIH. Coil Set - both sides Magnet structural supports (3) 40 cm DSV Gradient and RF send/receive coils 0.5 T 3 T Gantry supporting 3 Co-60 treatment sources Field Profile – Right Side

Conduction-cooled React and Wind coil • Ic= 152 A (20 K) • Je = 275 A/mm2 (20 K) • Bw = 1.31 T (20 K) • B0 = 0.15 T (20 K) • Coil ID = 0.46 m (18”) • Coil height = 20 mm • 225 turns • 12 layers • 19 turns/layer • Conductor length = 406 m • Conductor Φ = 0.84 mm Measured in cryostat at OSU between 15 and 30 K. • Design of current injection end regions good • No sub-cooling there • Ramp rate independent (0.1 ~ 5 A/sec)

Persistent Joints: Joining Reacted MgB2 Wire

Low AC loss MgB2 conductor development • The development of finer filament MgB2 wire for superconducting stators. The goal is for an all-electric aircraft that uses all cryogenic motors and generators. Original goal was 10 μm filaments for stators in the 5-200 Hz range. • Superconducting fault current limiters • Other physics applications MgB2 rotor coils have been made for NASA 2 MW 15,000 rpm generator

Low AC loss MgB2 conductor development • Machine parameters: • Operating temperature = 20 K • Frequency = 200 Hz • Bm = 0.6 T • Jc = 5280 A/mm2 • Conductor specifications: • Filament diameter deff= 10 m • Twist pitch Lp = 10 mm • Matrix resistivity eff= 100 cm • Non-magnetic sheath materials • Loss contributions • Hysteretic losses = 1.08 W/cm3 • Coupling losses = 0.72 W/cm3 • Transport current losses = 0.34 W/cm3 • Total losses = 2.1 W/cm3 342 filaments 78 filaments Push towards 10 μm filaments

Low AC loss MgB2 conductor development Jc measured with 10 μm filaments at 0.29 mm. Work progressing to get obtain 10 μm filaments with larger wire diameters. Jc maintained with twist pitches as low as 10 mm. Challenge: sheath material that has high resistivity + is non-magnetic + has good mechanical properties at same time

Multi-strand MgB2 Cable Demonstration Great advocate for MgB2: CERN and their high amperage cable links projects Hyper Tech mock-up

Multi-strand MgB2 Cable Demonstration A MgB2 cable was successfully fabricated with MgB2 multifilament conductor. The cable consisted of three reacted strands, each sized to 0.83 mm. The cable had a twist pitch of 100 mm. The highest measured current and temperature were Ic > 1350 A at ~23.5K, respectively. (Ic limited by test equipment). Strain data on strands Cable made using reacted strands

Jc improvement efforts – AIMI route If an across-the-board increase in Jc(B) is desired, there is no substitute for increased connectivity / reduced porosity. In order to design an MgB2 strand with a high engineering Je it is necessary to combine a high layer Jc with a high layer volume-fraction. Need to consider: the choice of processing route, the choice of B powder (density, particle size) and the type and concentration of possible dopants; the powder fill factor; strand architecture; heat treatment conditions. Best strand: 18.8% fill factor (area of MgB2) 90 μm layer thickness As a result, improved both layer Jc and engineering Je.

Multifilamentary AIMI (2nd gen MgB2) Engineering Current Density, Je, 5 T, 4.2 K: CTFF-1 (best of class 36 filament) ……………… 26,000 A/cm2 CTFF-2 (18 filament) ……………………………… 58,000 A/cm22.2x increase CTFF-2 (monofilament, extrapolated) ……… 122,000 A/cm2 4.7x increase

AIMI (2nd generation) MgB2 motivation In comparison with other superconductors: Best layer Jc (C-doped monofilament): 1.57 x 105 A/cm2 at 10 T, 4.2 K

Dy2O3-doped AIMI (2nd gen MgB2) • Present challenges with AIMI: • Maximize MgB2 layer formation: does C-doping suppress? • Lower Jc in multifilaments 4 K, 5 T: Je = ~87,000 A/cm2 2.6 x improvement over 1 Gen • Dy2O3 doping: • Reported to enhance pinning and in-field Jc • Increases Mg diffusivity (?) • Acts like a catalyst (?) • Improves n-value significantly 4 K, 10 T: Jc = 135,000 A/cm2 6.5 x improvement

AIMI (2nd gen MgB2) Jc, Je, Birr at 4 K From Chapter on AIMI in upcoming book on MgB2 (Collings)

Increasing Bc2 at 20 - 30 K • Comparing PIT (1st Gen) to AIMI (2nd Gen) • C-doping increases Bc2 at 4 K • Dy2O3 does at 20-30 K

Summary • Wire configuration established for marketing but can be modified for continued improvements and R&D. • NP SBIR Phase II: W & R at BNL for cyclic testing. Next step is to build large bore coil in 2015. • Successful React & Wind demonstration coil for IGRT unit / project. • Continue to fabricate joints and next step is persistent loop tests. • Successful in modifying strand design for lowering AC losses. • CERN in purchasing MgB2 for cable links projects. • Improved Jc, Je and consistency in Dy2O3-doped AIMI (2nd generation) conductors.

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