b'(a) -3 -3 -4 -4 -4 dose rate(b)2x10 1x10 5x10 2x10 1x102440.5 in dpa/s 2.52440SAW Speed [m/s] SAW Speed Change [m/s]2439.5 224392438.51.524382437.5 on on on on onbeam 2437 off off off off off 10 50 100 150 200 250 10 -4 10 -3Time [min] Dose Rate [dpa/s](a) Time-dependent record of surface acoustic wave (SAW) velocity in pure nickel subject to impulse irradiations of 31 MeV nickel ions at 500C using in situ time-dependent transient grating spectroscopy. (b) Impulse velocity step-changes resulting from irradiations at different dose rates. Further evolution beyond the initial interstitial-dominated stiffening response is clearly visible in the short beam on periods.PUBLICATIONS:Hirst, C. A. and C. A. Dennett, Toward Quantitative Inferenceof Nanoscale Defects in Irradiated Metals and Alloys, Frontiers in Materials 9 (2022) 888356. 49'