ALEXANDER MATTA FERMILAB SIST PROGRAM SUPERVISOR: TENGMING SHEN Developing high-current, mechanically reinforced BSCCO 2212 cable: a survey of compatible materials 1

The Agenda Superconductor Background BSCCO 2212 superconductor and its properties So what’s the problem with making magnets out of 2212 and how do we solve it? My Laboratory Experience  My Division  Project Overview  Tensile Testing  Chemical Compatibility Testing Results Conclusions What else did I learn? Acknowledgements Questions 2

So What Are Superconductors and What Makes Them So Super? Unlike regular conductors, superconductors exhibit zero electrical resistance below a certain critical temperature. Superconductivity is due to electron pairing (Cooper pairs). 2 big limitations  Magnetic Field strength  Current Density 3

Moving Forward With Superconductors Currently NbTi is used for most superconducting magnets  Can be used to create ~ 8.3 Tesla magnets  A relatively strong and cheap superconductor (known as the workhorse superconductor) We want higher fields and warmer magnets  8.3 Tesla is a lot but WE WANT MORE (<30 Tesla for the Muon Collider)  Liquid helium is used to cool current magnets (boiling temp of ~4.5k), in the future liquid nitrogen might be a cheaper option. The Solution: High temperature superconductors  Some have critical Temperatures above the boiling point of liquid nitrogen (~77K)  But we don’t fully understand how or why they superconduct 4

BSCCO 2212 Superconductor and Its Properties BSCCO 2212 (Bi 2 Sr 2 CaCu 2 O 8+x ) is a high temperature superconductor that has a critical temperature of ~95 k. The wire remains superconducting in much stronger magnetic fields (higher Bc) and with a much higher current density (higher Jc) than conventional superconductors can. It is also currently the only High Temp. Superconductor that can be manufactured into thin round wire wire consists of many superconducting fibers encased in silver Unfortunately like many other superconductors 2212 is strain sensitive. 5

So What’s the Problem With Making Magnets Out of 2212 and How Do We Solve It? The big problem is that 2212 is strain sensitive  Lorentz Force  Stronger Fields, means Stronger Forces Cabling with alloy wires could take some load off the 2212  2 Requirements for the alloys  Remain mechanically strong after high temperature heat treatment  Chemically compatible with BSCCO 2212 Wire Alloy Reinforcement Wire BSCCO 2212 Cable Cross-section

TD and What They Do Worked in Technical Division  Responsible for Accelerator Components Design and construction  Magnets  Cryomodules  RF and SRF Cavities  Various Instrumentation 7

My Project My job was to mechanically test several pre-chosen alloys, and to test their chemical compatibility with 2212  Inconel 600 (Ni, Cr, Fe, C, Mn, S, Si, Cu, Co)  Inconel 625 (Ni, Cr, Fe, Mo, Nb, C, Mn, Si, P, S, Al, Ti, Co)  Inconel X750 ( Ni, Cr, Fe, Ti, Al, Nb, Mn, Si, S, Cu, Co )  Nickel Chromium (80% Ni, 20%Cr)  Kanthal A-1 (Fe, Cr, Al, Si, Mn, C) 8

Sample Groups Mechanical Property Testing 2 Sample Groups  Unprocessed wires in their raw form (control)  Heat treated wires (brought to a Temp of ~890 C and kept in almost pure oxygen environment) 9

Specimen Holder Design Mechanical Property Testing The old thin wire holder caused additional stress on the wire samples while they were being tested. So in NX7 I designed a more suitable holder. It was then machined using the drawings I created. Old wire holder New wire holder 10

Using The Tensile Testing Machine Mechanical Property Testing Instron 4400 Series  Is used to perform tensile and compressive tests  Capable of testing to 1000 lbs  Stretches samples at a constant rate 11

Furnace Preparation Chemical Compatibility Testing This part of the experiment required the calibration and set up of a tube furnace before any testing could be done.  Thermo-plug placement and marking  Homogeneity zone identification  Oxygen system setup 12

Heat Treatment Chemical Compatibility Testing Each specimen consisted of one 2212 which was encompassed by 6 alloy wires  3 unaltered 2212 wires per alloy  3 coated 2212 wires per alloy (6 µm layer of Titanium Oxide) A 4 day heat treatment was performed on the specimens All specimens were prepared during the same heat treatment 13

Lets Flash Back to the Tensile Testing The heat treated wires used for mechanical testing underwent the same heat treatment used for the chemical compatibility testing. By coincidence during these tests we saw that Inconel 625 was not a viable candidate. So we did not continue further testing of it. Inconel 625 contained between 8-10% Molybdenum, an element not found in 600 or X

Stress/Strain Graph Example Tensile Testing Results 15

Tensile Testing Results 16 Before Heat TreatmentAfter Heat Treatment Yield Strength (MPa) Tensile Strength (MPa) Young's Modulus (GPa) Yield Strength (MPa) Tensile Strength (MPa) Young's Modulus (GPa) Inconel Inconel X Kanthal A Nickel Chrom

Chemical Compatibility Testing Results Leakage Predictions based on basic observations Kanthal seemed to smallest reaction Inconel X750 and NiCh seemed to moderately react Inconel 600 seemed to have the largest reaction 17 Samples have been sent to National High Magnetic Field Lab for further testing. Bare 2212 WireCoated 2212 Wire Nickel Chromium leakage occurred -2 nd weakest bond between alloy and 2212 wire leakage did not occur -There was slight oxide coating removal Kanthal A leakage occurred -1 st weakest bond between alloy and 2212 wire leakage did not occur -There was slight oxide coating removal Inconel X leakage occurred - 3 rd weakest bond between alloy and 2212 wire leakage did not occur -There was slight oxide coating removal Inconel leakage occurred - 4 th weakest bond between alloy and 2212 wire leakage did not occur -There was large oxide coating removal

Conclusions Inconel X750 Potential Candidate  Strongest Mechanically  Doesn't seem to react when 2212 is coated Kanthal A-1 Potential Candidate  Seems to be the least reactive of tested alloys  Mechanically acceptable Better conclusions can be made when the results are returned 18

What Else I Learned Always double check your experimental set up  Spending a little time beforehand could save you a lot of time later  You don’t want to end up with inaccurate data Sometimes you have to trim down your experiments  Material such as superconductor is expensive and you cant just use it carelessly Get to know other employees  You never know when you might suddenly need there help  Surprise! Things get done much quicker when you know people 19

Acknowledgements Supervisor: Tengming Shen SIST Committee Mentors: Jamieson Olsen, Elliott McCrory Dr. James Davenport Donna Hicks TD Employees 20

Questions? 21

References Tensile Testing, Materials Information Society Tengming Shen