FAQs

What is the maximum pressure I can achieve with the HeliosDAC and a given culet size?

(*) The Pmax values are only indicative. The maximum pressure achievable with a DAC is influenced by many others experimental parameters, like the gasket characteristics (material, thickness and hole size) or the pressure transmitting medium.

What makes the HeliosDAC Unique?

The HeliosDAC stands out due to its capability to handle high temperatures and pressures, making it ideal for geophysicists studying elements like iron in the Earth’s core mantle. Unlike commercially available diamond anvil cells, the HeliosDAC features an internal gasket heater that localizes heat in the center, keeping the exterior relatively cool and protecting sensitive surrounding equipment. It maintains a sample at 1,000°C with the exterior only reaching just over 400°C, and its gas-membrane drive efficiently compensates for pressure changes during heating, ensuring stable high-temperature operations.

Is an additional power supply necessary for the HeliosDAC?

Yes, the HeliosDAC requires an external power supply and a thermocouple reader, which are not included as standard. These can be purchased from Almax easyLab. We recommend the PS03, a programmable power supply that comes with our Labview® based Temperature Manager software. This software allows you to set a target temperature and control the heating rate. The PS03 also includes a thermocouple reader for comprehensive temperature management.

Is the heater in the HeliosDAC a one-time use product?

No, the HeliosDAC’s gasket heater is designed for multiple uses. Its lifespan primarily depends on how frequently it operates at maximum temperatures (800-900°C). Regular use at these high temperatures can lead to wear and eventually require replacement of the heating element. Fortunately, the heater assembly is user-replaceable, allowing for easy maintenance and minimal downtime.

Can the HeliosDAC be operated without its heater?

Yes, the HeliosDAC can function without the heater, but keep in mind that the heater also serves as a gasket holder. It ensures precise placement of the gasket relative to the diamond anvils in terms of centring and height. Without the heater, you would need to position the gasket more basically, such as using modelling clay. However, this method is less common and not the recommended way to use the DAC.

Is the HeliosDAC cell suitable for loading with argon and helium?

The HeliosDAC is not designed for cryogenic loading; therefore, it cannot be used with cooling methods like nitrogen cooling due to its gasket heater made of fragile pyrophyllite and ceramic, which are unsuitable for low temperatures.

Which gases are recommended for use with the HeliosDAC membrane?

Inert gases are recommended for the gas membrane. Helium is unnecessary unless the experiment requires low temperatures. Argon or nitrogen are suitable for high-temperature operations. Be aware that output pressure from the gas regulator should reach at least 150 bar. Always check local regulations to ensure you use the appropriate regulator for your gas cylinder.

Can nitrogen be used in the HeliosDAC’s gas membrane?

Yes, dry nitrogen is suitable for generating pressure in the HeliosDAC. While we typically use a mix of argon and hydrogen for flushing the DAC at high temperatures and in the membranes, nitrogen alone is acceptable if that’s what you have available. However, nitrogen regulators often don’t support pressures as high as argon regulators, which might affect performance and slightly reduce the membrane’s lifespan. In high temperatures, some metals may become brittle in nitrogen, but the robust construction of the HeliosDAC generally mitigates this risk.

What gas mixture is recommended for anvil protection at temperatures above 200/300°C?

For temperatures above 200/300°C, an argon/hydrogen gas mixture (97% argon, 3% hydrogen) should be used to protect the anvil.

Which type of regulator is recommended for the inert gas in the HeliosDAC?

A single-stage regulator that can provide an output pressure of 2.5 bar is sufficient for optimal operation.

What is the typical power requirement to reach maximum temperature with a HeliosDAC?

To reach temperatures above 900°C with a HeliosDAC, a current of approximately 6.5A and a voltage of around 13V are typically sufficient.

How is pressure monitored inside the HeliosDAC Plus during heating?

For XRD Measurements: Utilize a standard material with a well-known pressure-temperature (P-T) phase diagram from the literature, such as gold (Au), platinum (Pt), or tantalum (Ta).

For Optical Measurements: Opt for YAG or Strontium borate (Sm2+:SrB4O7) for more accurate pressure readings. These materials provide clearer pressure indications compared to ruby, which tends to exhibit too broad of a peak at high temperatures.

Can I carry out high temperature resistivity measurements with the HeliosDAC?

Conducting high-temperature resistivity measurements with the HeliosDAC is challenging due to both the DAC design and the nature of high-temperature measurements. The DAC design makes it difficult to practically route wires out of the gasket heater and the cell. Additionally, high temperatures affect the behavior of coatings and contact methods between wires and coated pads on the anvil, complicating the measurements. A potential alternative is using an OmniDAC with a ring heater, which simplifies wire routing, but the feasibility depends on the required maximum temperature. Do you know the specific temperature needed for your measurements?

HeliosDAC Piston Cylinder Fit Issue

If you’re having trouble inserting the piston into the cylinder, despite previous success, start with a thorough cleaning to remove any unwanted particles or objects. The piston/cylinder fit in the HeliosDAC is very tight and precise. For stubborn pistons, you can use Precision Oil Silber K 7132/10.000 as a lubricant. Make sure to wipe out any lubricant thoroughly before the next high-temperature use.

How are the anvils installed to the HeliosDAC – by glue or mechanical force?

In the HeliosDAC, the anvils are mechanically fixed in anvil rings, which are then secured by a holding plate. This method is especially suitable for high-temperature and high-pressure applications, as it provides the necessary mechanical stability, unlike gluing, which is not recommended for these conditions.