Selecting the right gasket parameters for high-pressure experiment using a diamond anvil cell can be challenging. The users often face questions such as:

• Which material should I choose?
• What is the optimal gasket thickness and sample hole diameter?
• How can I recognize early signs of gasket failure?

This page provides practical considerations and recommendations to help you start high-pressure experiments with confidence.

Gasket material selection depends on the pressure range and experimental conditions. Common options include:

• Stainless Steel – A relatively soft material, easy to work with, suitable for low to moderate pressures (up to ~20–30 GPa).
• BeCu (Beryllium Copper) – Preferred for low-temperature applications and experiments requiring minimal magnetic interference.
• Inconel – Recommended for moderate pressure ranges and also for high-temperature environments due to its thermal stability.
• Rhenium (Re) – The premium choice for pressures above 50 GPa, offering exceptional strength and reliable support for diamond anvils.

Almax easyLab offers a wide range of gasket blanks tailored for diamond anvil cells and high-pressure experiments.

Gasket thickness is a critical factor influencing the maximum pressure achievable for a given culet diameter and gasket material.

Pre-indentation is the standard method for achieving the correct thickness. Start with a relatively thick gasket blank (e.g., 0.25 mm) and compress it between the diamond anvils to the desired thickness.

A common guideline is to pre-indent the gasket to 10–15% of the culet diameter or to the maximum load expected during the experiment. If the same load is applied in pre-indentation as will be applied in the experiment, the gasket will be approximately the correct thickness to remain stable during the pressure increase. The gasket should always be thin enough that the sample hole contracts as the pressure is raised [Spain, I.L., and Dunstan, D.J. (1989) The technology of diamond anvil high pressure cells: II. Operation and use, J. Phys. E: Sci. Instrum. 22, 923–933].

With experience, these guidelines should be refined based on observations:

• If the sample hole enlarges during the run, use a thinner gasket next time.
• If the sample hole has shrunk significantly during the experimental run, the gasket should be made a little thicker the next time.

Continuous monitoring and adjustment are key to optimizing gasket performance.

You can use either the diamond anvil cell (DAC) itself or a dedicated gasket indenter for pre-indentation. Always apply the load in small incremental steps, reducing it to zero between each step to minimize stress on the diamonds.

Important Considerations
For the same applied load, the final gasket thickness will vary depending on the gasket material, culet size, and even the DAC design. Diamonds are more prone to breakage during pre-indentation than during high-pressure runs because the metal extrudes outward, creating maximum tensile stress at the diamond tip.

It is strongly recommended to calibrate the relationship between applied force and resulting gasket thickness for each material and culet size. The gasket can be removed for thickness measurement and then replaced for further thinning. Use a micrometer with small rounded tips to accurately measure the pre-indented thickness.

A hole smaller than the culet diameter is drilled through the pre-indented gasket to form the sample chamber. As a rule of thumb, the hole diameter (d) should be between 33% and 50% of the culet diameter (D).

Sample holes can be drilled using two main techniques:

• Electro-discharge machining (EDM), also known as spark erosion – works with any electrically conductive metal and produces clean, burr-free, and well-centered holes. Advanced automated EDM systems, such as those offered by Almax easyLab, can achieve precision holes as small as 0.05 mm in diameter.
• Laser drilling – allows the drilling of holes smaller than 0.05 mm. It can be used for both conductive materials and non-conductive materials, like amorphous boron, silicon carbide gaskets, diamond, oxide ceramics, salts.

• The hole must be perfectly centered on the pre-indented mark and completely free of burrs.
• Cleaning the gasket in an ultrasonic bath after drilling is highly recommended.
• If the hole is too close to the edge of the pre-indented area, it may migrate during the experiment, causing leaks and potential gasket failure. In severe cases, this can lead to diamond anvil failure.

A gasket can typically be used for multiple pressure points within the same pressure campaign—a series of measurements under pressure during which the diamond anvil cell (DAC) remains closed. Pressure cycling (increasing and decreasing pressure) is possible during the same campaign, provided you carefully monitor the shape and position of the sample hole.

However, once a gasket has been used for a pressure run, it is not recommended to reuse it for a new loading. After the experiement, the gasket is usually very thin, plastically deformed, and the sample hole is likely distorted. Reusing such a gasket increases the risk of leaks and instability during subsequent experiments.

1.Hole Becomes Smaller

• Cause: No pressure-transmitting medium; the hole collapses under load.
• Action: Pressure will not increase effectively. You must open the cell and reload with a new gasket.

2. Hole Becomes Larger 

• Cause: Initial gasket thickness was slightly too high, and the gasket is still flowing.
• Action: If the hole remains centered and far enough from the culet edge, you can continue increasing pressure—but proceed carefully.

3. Hole Enlarges and Deforms in One Direction

• Cause: The diamond anvils are misaligned causing the hole to shift and/or the initial gasket thickness was slightly too high.
• Action:  You must open the cell and reload with a new gasket.