When users apply for beamtime at Diamond via the Standard Access route, proposals are submitted in advance, and subject to peer review. It's a process designed to ensure that beamtime is allocated fairly, to the most valuable science. It assumes that one (or possibly two) blocks of beamtime will be needed during the same six-month allocation period.
But what happens when users need urgent access to a beamline, some preliminary data to test out a new idea, or one last piece of a puzzle to finish off a publication? That's where Diamond's Rapid Access comes into play. Many beamlines set aside a small amount of beamtime for these types of experiments, which are assessed and allocated with a much faster turn-around. The impact of the Rapid Access proposals are fed back to the peer review panel.
Principal Beamline Scientist, Philip Chater, explains how Rapid Access works on the I15-1 beamline:
I15-1 is the dedicated X-ray Pair Distribution Function (XPDF) beamline. XPDF gives local structure information for materials, allowing you to see correlations between atoms on length-scales all the way from single bonds up to tens of nanometers. It's very useful data that can give information on a wide range of samples. Very few researchers have access to XPDF in their home labs, but on I15-1 we can run a sample in about 10 minutes. We therefore can give many more people access to this technique by scheduling occasional days for Rapid Access experiments throughout the year. We often work with several user groups on each of those days.
Rapid Access works particularly well for remote access, where users send samples loaded into capillaries to Diamond for the beamline staff to run their experiment. The staff on I15-1 are in the process of installing a robotic sample changer, which will dramatically increase the number of samples they can examine. With the current setup, there's room for 15 samples at a time before they have to be manually changed. The robotic sample changer will hold 440 samples!
We've been working hard to make it quick and easy for users to load their samples for use with the robot. It will greatly increase our capacity for Rapid Access experiments, both at room temperature and under variable temperature conditions.
Rapid Access might be the right choice for users who don't need a full experiment or need quick results. It can also be used to test out ideas and get preliminary data to strengthen a proposal for a full experiment. Most researchers who use the Rapid Access system to access XPDF on I15-1 send around five samples for analysis. Here are two examples of experiments that have benefitted from Rapid Access to I15-1.
RMCProfile is software used for analysis of pair distribution function data. When Dr Wojciech Slawinski wanted to add a new analysis method, he needed sample data to test it. Using Rapid Access allowed him to get the test data he needed, allowing the updated software to benefit the entire XPDF community.
Dr Wojciech Slawinski, said:
While I was working as a post-doc at ISIS neutron and muon source, I was the main developer of the RMCProfile7 program, dedicated to large box Reverse Monte Carlo simulations and refinement of Pair Distribution Function (PDF) data. An update to the program contained several novel capabilities, and we needed some specific datasets to test it.
I applied for a Rapid Access to the Diamond I15-1 beamline, which is state-of-the-art for high-quality PDF data on powder samples. I was granted beamtime within a week, and the experiment was performed remotely by the beamline staff a month later. The beamline staff also helped analyse the data.
The new feature for RMCProfile is the "rigid body" constraint. It should allow quicker refinement for structures such as molecular crystals, where the structure is built of molecules which - by definition - are rigid bodies.”
Professor Candace Chan’s group did proof-of-concept collections via Rapid Access, and used the data to support a full standard proposal. Data from both beamtimes contributed to the paper.
Prof Candace Chan, said:
The overall aim of our research project is to investigate the relationships between the structure and electrochemical properties of clathrate compounds in the context of their use as potential electrode materials in lithium-ion battery applications. These compounds have cage-like structures and there has been little understanding of how the features of the initial structure evolve during lithium insertion reactions, particularly how the cage-structure collapses when the material is stuffed with too much lithium.
Pair distribution analysis has emerged as a powerful tool in the battery community for studying phase transformations that take place in Li-ion battery electrodes, particularly for probing the local structure when amorphisation reactions take place. We used the I15-1 Rapid Access opportunity to obtain PDF data of silicon and germanium-based clathrate electrode materials with different amounts of electrochemically inserted lithium.
The results showed substantial changes in the local structure upon reaction with lithium, which motivated us to submit a proposal for on-site access to investigate more samples and obtain a holistic view of the phase transformations and amorphisation reactions that take place. With the aid of in situ heating of the samples during our on-site beamtime, we were able to assess the stability of the lithiated amorphous phases and their relationship to known crystalline phases. The end result is a better understanding of the lithiation pathway in clathrate materials and the structural origins of the observed electrochemical properties, which can aid the design of novel materials for improved battery performance.
Dopilka A et al. Understanding the Amorphous Lithiation Pathway of the Type I Ba8Ge43 Clathrate with Synchrotron X-ray Characterization. Chemistry of Materials (2020). DOI: 10.1021/acs.chemmater.0c03641.
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