The Advanced Light Source maintains a gas loading apparatus for inert gas pressure medium loadings of Diamond Anvil Cells in support of ALS experimenters. Gas loadings are performed for users by trained ALS staff. There are a few considerations for those interested in utilizing this service to maximize chances for a successful loading. Please read the below for guidance, and pay special attention to the section on the details of how to prepare your DAC while loading your sample such that it is compatible with our system.
Who may request gas loadings for DACs?
The ALS high pressure support staff and equipment are funded by the US Department of Energy for the express purpose of supporting scientific research performed at the Advanced Light Source. We do not have the personnel or resources to gas-load DACs for experimental work outside of the ALS framework.
How do I request a gas loading?
Please indicate your needs during your standard communication with beamline scientists coordinating your beamtime at the ALS and the relevant details will be worked out. If you are reading this document, you probably were pointed here through those communications. If you found this document through other means, please contact BL 12.2.2 staff directly for coordination.
What types of DACs are compatible with the ALS gas loader?
We can gas load symmetric DACs with english screws and BX-90 DACs with metric screws. We can accomodate DACs with all right handed (or all left handed) screws or DACs with two right handed and two left handed screws.
It is possible to load other types of DACs if appropriate adaptors are manufactured. Please be aware that to manufacture such an adaptor would be a collaborative endeavour that would need to be planned months in advance of execution. Contact BL 12.2.2 staff if you are interested in helping us expand our capabilities in support of your experiments.
What gases can the ALS load?
Our system is qualified for inert gasses only. Our most common pressure medium is Neon, and we have performed gas loadings with Helium, Nitrogen, Argon, and CO2. Contact BL staff about your interest in other gas mediums.
Are there special considerations for how to load my DAC?
Yes! To be able to work in our gas loader, utilize its in-situ ruby fluorescence capability, as well as take optimal diffraction data, there are a few important things to keep in mind when you are preparing your DAC.
We have the ability to monitor the sample well pressure as a means of determining when we have sealed the DAC. However, due to the geometry of our system, we only have the ability to measure a ruby fluorescence signal if the ruby is visible form a very specific side of the DAC. See illustration for correct ruby placement. The rubies need to be visible from the side opposite the screw heads.
The mechanism we use to turn the screws of the DACs have a limited length in how far they can “reach” to engage with the screws of DACs. It is vitally important that the tops of the screws, when your DAC is finger tight, are nominally flush with the surface of the DAC. A few mm’s below the surface is OK, but any more than that will not work for our system. You should utilize longer screws and add an appropriate amount more washers to your washer stack. It is also a problem if your screw tips protrude from wither side of the DAC, so pick a length that can close your cell without exiting the back side more than a small amount or protruding on the screw-head side above the DAC surface by more than 1 - 2 mm. The latter can cause the DAC to close when loading it into the gearbox for the gas loader.
- If your DAC has both cBN and WC seats, the cBN seat has to be on the opposite side of where the rubies are placed, i.e. the cBN needs to be on the side of the screwheads. This is because the online ruby system on the beamline is opposite the diffraction detector, and the cBN (the side with the larger opening angle) needs to be on the diffraction side of the DAC.
If in doubt ask the beamline scientists
