Role of the gasket in a DAC experiment
The gasket is a thin metal foil (typically 200–300 µm thick, pre-indented to 30–50 µm) that sits between the two diamond anvils and defines the sample chamber. It serves three critical functions: (1) it confines the pressure-transmitting medium and sample, preventing extrusion; (2) it provides lateral support to the diamond culets, reducing the risk of fracture at ultra-high pressures; and (3) it determines the maximum pressure attainable, since the gasket material must withstand deviatoric stresses at the anvil tip without failing. The choice of gasket material is therefore one of the most important experimental decisions in high-pressure research.

Gasket materials — how to choose
· Stainless steel 316L (work-hardened) — BETSA standard. Excellent combination of yield strength (HV 380) and machinability. Suitable to ~80 GPa with standard anvils.
· Rhenium (work-hardened) — the material of choice above 100 GPa. Extremely high yield strength (HV 450+), low fluorescence background, compatible with most PTMs including helium. BETSA supplies pre-indented Re gaskets for megabar experiments.
· CuBe (aged) — non-magnetic alternative to steel. Essential for experiments in magnetic fields or with SQUID detection. HV ~380 after ageing treatment.
· MP35N (aged) — highest strength among non-magnetic alloys (HV 560), used for extreme P in non-magnetic setups.
· Inconel 718 (aged) — excellent at high temperature and pressure simultaneously (HV 450).
· WC / ZrO₂ — rigid seats for sintered diamond or moissanite anvils, not conventional gaskets.

Hardness and its role
Gasket hardness must be carefully matched to the anvil culet size and target pressure. Too soft → extrusion and chamber collapse. Too hard → risk of anvil fracture due to stress concentration. The Vickers hardness (HV) is the standard metric; the converter below handles HV ⇄ HRC ⇄ MPa using the ASTM E140 standard (1 HV = 9.807 MPa).

Boehler R. (2006) Rev. Sci. Instrum. 77:115103 — Diamond anvil cell design and gasket materials
Léger J.M. et al. (1995) Phys. Rev. B 52:13247 — Rhenium gaskets for megabar experiments
ASTM E140-12b — Standard Hardness Conversion Tables for Metals (HV ↔ HRC ↔ MPa)