• Check that the anvils are properly fixed in their supports;
• Verify that all screws are correctly tightened;
• Ensure both anvils are clean and free of debris (dust, metal particles, old gasket material).

• Bring the upper anvil close to the lower one, but do not put them in contact;
• Observe both culets under the microscope;
• Use the cell lateral screws to adjust the lower side anvil so the culets appear concentric;
• The goal is to see two culets that overlap perfectly when viewed from above.

The video on the right shows an example on how to adjust the lateral alignment on a HeliosDAC diamond anvil cell.

• Carefully bring the anvils in contact and observe the interference fringe pattern;
• Note the point where the fringes are densest => one needs to adjust the anvil position in this area.
• Note the DAC orientation, so as not to worsen the alignment with the adjustment (both X and Y directions are reversed under the metallurgical microscope);
• Increase the distance between the anvils;
• Use the DAC’s tilt screws to adjust the anvil position:
  • Tighten the screw (or screws) in the area where the fringes are densest. Tightening a screw pulls the anvil support up, thus increasing the diamonds separation. To be able to tighten the screw, one needs first to loosen the two opposite screws;
• Repeat the above steps until only 3-4 large colored fringes are obtained.

Watch the video on the right for more tips on how to fine-tune the tilt alignment.

• Perfect overlap of culets;
• No more than 3-4 wide colored fringes;
• Uniform pre-indentation mark on both sides of the gasket;
• Sample hole centered on both side of the gasket.

• Crescent shadows on one side;
• Multitude of colored narrow fringes;
• Off-center hole on one side of the gasket and centered on the other side;
• Early anvils failure or gasket failure.