Ion irradiation for nuclear materials research at University of Wisconsin-Madison

1. Ion irradiation for nuclear materials research at University of Wisconsin-Madison Li He, Gabriel Meric De Bellefon, Kim Kriewaldt, Kumar Sridharan, Adrien Couet, Todd Allen University of Wisconsin – Madison SNEAP 2018 conference Madison, WI September 24th, 2018

2. Overview • Ion Beam Lab and post-irradiation examination facility • Upgrades • Materials study examples • Access IBL

3. Ion Beam Laboratory (IBL) Irradiation Facility • 1.7 MV tandem accelerator from National Electrostatics Corporation (NEC) • Temperature monitored with thermocouples and IR camera • Various samples geometries • Rastered or defocused beam • Toroidal Volume Ion Source (TORVIS) and Source of Negative Ions via Cesium Sputtering (SNICS) ion sources

4. Ion sources • TORVIS • High current hydrogen, deuterium, and helium ion source, from < 1 μA to 100 μA for protons (H+ ions). • Emulate neutron irradiation effect with proton irradiation. • Damage rate ~ 10-6 dpa/s (displacements per atoms/s) • Flat damage/depth profile. • SNICS • Wide range of heavy ions, Fe, Si, C, V, Nd, and more. • Fast to achieve high damage, e.g., 250 dpa peak damage of stainless steels in 9 hours. • Damage rate 10-4-10-2 dpa/s • No radiation-induced radioactivity.

5. CLIM - PIE Equipment • JEOL 6610 SEM with Energy Dispersive Spectroscopy (EDS) and Electron Backscatter Diffraction (EBSD) capabilities • Rad sample certified (outside of CLIM): X-ray Diffraction.

6. CLIM - PIE Sample Preparation Facilities • Parallel polisher • Low speed saw • Electro-polisher • Ion mill • High accuracy balance

7. Non-rad sample PIE Materials Science Center at UW FEI Titan Cs-corrected scanning transmission electron microscope Hysitron TI 950 TriboIndenter FEI Helios G4 UX Plasma FIB/FE SEM

8. Lab upgrade timeline • 2009: Nuclear Science User Facility partner. • 2011: TORVIS ion source (high beam current for H and He). • 2014: CLIM laboratory (consolidation of sample preparation tools and SEM). • 2015: Chamber upgrade (control of irradiation area, pre-loading chamber). • 2016: Sample activity screening (count integration over time, better accuracy). • 2017: Sample stage upgrade (liquid metal contact to ensure proper cooling). • 2018: two-dimensional moving sample stage.

9. Irradiation Chambers * Manufacturer specifications.

10. New Chamber Design • Remote controlled four jaw slits for in-situ control of irradiation area • Sample load-lock (pre-chamber) • Liquid nitrogen cooling • Tantalum wire heating elements on boron nitride mandrel, heating to 900ºC (radiative heating) • Handle both small and high current measurements (>3μA) – isolated (floating) stage • Openings for two low energy (<30 keV) ion guns

11. Indium cooling Stage Courtesy of Zefeng Yu • Provide accurate sample temperature measurements in accordance with ASTM E521 guidelines. • In-situ temperature measurements by IR camera calibrated by thermocouples. • Efficient cooling by liquid indium pool (melting point 156.6 ºC) for proton irradiation. 1 cm Indium pool at the center.

12. 2D-Moving stage Courtesy of Michael Moorehead • Stage is attached to 1D-manipulator both vertically (automated) and horizontally (manual). • A ~ 2” ×3” area can be sequentially irradiated.

13. Rastering or defocused beam irradiation • Rastering beam achieves large irradiation area. However, beam lands on sample intermittently. • It has been reported that rastering beam may enhance interstitial/vacancy recombination, hinder void or other defect formation [1,2]. Aperture confining irradiation area Zero flux High flux >> average flux Constant flux Defocused beam Rastering beam [1] Gigax et. al., Journal of Nuclear Materials465 (2015) 343-348 [2] Getto et. al. Journal of Nuclear Materials465 (2015) 116-126

14. Defocused beam irradiation result • 3.5 MeV Fe2+ defocused beam, 50 dpa, 500 ºC • Annealed 316 stainless steel • Void swelling ~ 6 %. [3] Gabriel Meric de Bellefon 2018 Ph.D. thesis, University of Wisconsin-Madison

15. IBL Usage in 2017-2018 • 22% UW-Madison committed non-NSUF projects • 50% NSUF, Nuclear Energy Enabling Technologies (NEET), Nuclear Energy University Program (NEUP) projects • Oak Ridge National Laboratory “Mechanical Properties and Radiation Resistance of Nanoprecipitates-Strengthened Advanced Ferritic Alloys” NEET 2015 • University of Wisconsin-Madison “Radiation Damage in High Entropy Alloys” NSUF RTE 2018 • 28% others • Naval Nuclear Laboratory “Proton Irradiation and TEM Analysis of Zr-4” • Total 350 hours/year • Still able to accommodate considerably more hours.

16. NEUP funded project - 709 steel: ion irradiation damage • 100 dpa peak damage, 350 ºC. • Frank loop size 10-16 nm, increasing with damage level. • Frank loop density – (5-9)×1021 m-3. [4] He L, Mo R, Tyburska-Pueschel B, Xu H, Chen T, Tan L, Sridharan K 2017 Materials Research Society Spring Meeting

17. Comparison of Fe2+-irradiated 709 and 316H 709 316H 316H 54 dpa TEM sample thickness:95 nm 42 dpa, 56 nm thick 63 dpa, 69 nm thick Counted only dislocation loops visible to g=[002]. [4] He L, Mo R, Tyburska-Pueschel B, Xu H, Chen T, Tan L, Sridharan K MRS Spring 2017

18. Irradiation induced volume density change in 316H Ion Concentration (at. %) • 100 dpa peak damage, 350 ºC. • Electron volume density inversely correlates with ion implantation profile. Swelling (%) 316H: Average swelling=0.15±0.05 % [5] He L, Xu H, Tan L, Voyles P, Sridharan K 2017 Microscopy & Microanalysis Meeting

19. NEET project – Nanoprecipitates-strengthened advanced ferritic alloys NiAl • Fe-12Cr-3W-3Ni-3Al-1Nb • 4 MeV Fe2+,170 dpa, 475 ºC • B2-structure NiAl particles fully coherent with matrix NiAl 5 nm Li He, Lizhen Tan, Kumar Sridharan

20. DOE funded project – redeposition layers in DIII-D fusion facility Courtesy of C. Wetteland and D. Donovan, University of Tennessee-Knoxville • Particle Induced X-Ray Emission (PIXE) • 2 MeV proton beam, 6 mm2 spot size, ~10 μC of charge. • PIXE can offer higher resolution/sensitivity scans than x-ray fluorescence (XRF) with a better calibrated depth into the surface (~20 microns). • PIXE’s background significantly reduced as compared to using electrons (EDS).

21. Access UW-IBL • UW-IBL is continually improved to meet the research needs involving ion irradiation. • Access IBL through NSUF proposal: • DOE Consolidated Innovative Nuclear Research (CINR), annual submission. • Rapid Turnaround Experiments, three calls a year. • https://nsuf.inl.gov/

22. Contact • Details, rates, and application forms: • http://ibl.ep.wisc.edu • https://nsuf.inl.gov/ • Contacts: • Li He - (li.he@wisc.edu) – NSUF POC • Kumar Sridharan (kumar.sridharan@wisc.edu) • Adrien Couet (couet@wisc.edu) • Todd Allen (todd.allen@wisc.edu) • Kim Kriewaldt – lab manager, technical questions only (kriewald@engr.wisc.edu)

23. Acknowledgements • Iron irradiation of 709 and G92 • US Department of Energy Nuclear Engineering University Program (NEUP) under project Number 14-6346 • Iron irradiation of ferritic alloys • Nuclear Energy Enabling Technologies (NEET): Reactor Materials FY 2015 Award • Analysis of redeposition layers in DIII-D • US Department of Energy under DE-AC05-00OR22725(ORNL), DE-FG02-07ER54917(UCSD), and DE-FC02-04ER54698(General Atomics).