Publication: Metrology for femtosecond pulsed x-ray heating in diamond anvil cell experiments at the European XFEL: Revisiting the iron phase diagram up to 150 GPa

Hélène Ginestet just released a new publication ! The work was published in the Journal of Applied Physics on January 23, 2026. In this work, we use the European XFEL in Hamburg to explore the phase diagram of pure iron, up to pressures of 150 GPa.

The experiments were led by S. Merkel and G. Morard for the 3063 proposal at the HED instrument of the European XFEL. The instrument can be tuned to send intense X-ray pulses of less that 50 fs (50 x 10^-12 s) duration, repeated every 220 ns (220 x x 10^-9 s) on samples placed inside diamond anvil cells. The method allows reaching temperatures of several thousands of kelvins within microseconds! Experimental challenges, however, arise from temperature gradients within the sample, changes in temperature at the 100 ns timescale, the difficulty of direct temperature estimates, the effect of thermal pressure, and the presence of metastable crystallites due to rapid cycles of heating and cooling.

In this work, Hélène Ginestet and co-authors develop the metrology for such experiments, how to process data, evaluate pressure and temperature, and validate her technique based on previous publications for iron under pressure.

Full reference for the work: H. Ginestet, R. J. Husband, N. Jaisle, E. Edmund, Z. Konôpková, C. Strohm, M. S. Anae, D. Antonangeli, K. Appel, O. B. Ball, M. Baron, S. Boccato, K. Buakor, J. Chantel, H. Cynn, A. P. Dwivedi, H. Graafsma, E. Koemets, T. Laurus, H. Marquardt, B. Massani, J. D. McHardy, M. I. McMahon, V. Prakapenka, J. Sztuk-Dambietz, M. Tang, T. Xie, Z. Younes, U. Zastrau, A. F. Goncharov, C. Prescher, A. Dewaele, R. S. McWilliams, G. Morard & S. Merkel, Metrology for femtosecond pulsed x-ray heating in diamond anvil cell experiments at the European XFEL: Revisiting the iron phase diagram up to 150 GPa, Journal of Applied Physics, 139, 045901 (2026) [doi: 10.1063/5.0303953]