Cryogenic SIMS Preserving Elemental Distributions Formed Under Extreme Conditions: Hydrogen Distribution Measurement in Iron

We established a cryogenic secondary ion mass spectrometry (Cryo‐SIMS) system, in which all procedures—sample recovery, transport, and analysis—are performed under cryogenic temperatures. Using this system, we determined hydrogen concentrations in Fe–H alloys, which form only under high pressure and lose hydrogen upon decompression at ambient temperature. The hydrogen contents obtained were in good agreement with the X‐ray diffraction (XRD) measurements conducted under high pressure. The present cryogenic SIMS techniques can be applied to the determination of hydrogen isotopic composition of iron alloys, which is not possible with XRD analysis, but is important for understanding the origin of water on Earth.