# Thou shalt be judged… Round-robin request.

As some of you will know, we are currently running a SAXS round-robin experiment, with a bit over ten labs participating at the moment. The idea is that we will know what the approximate reproducibility is between instruments for measuring small particles in solution after this experiment. While the experiment is already underway, there is still room for a few more laboratories to participate…

Every participating laboratory is sent two samples of stabilized silver nanoparticles suspended in water (synthesized by my colleagues at BAM). What we are asking is for the laboratories to send us back the data as measured on their instrument, with a water background subtracted, and on absolute scale if possible.

The nanoparticles are somewhat polydisperse, and have a nominal radius of around 3 nm. Since it silver, synchrotrons should take care to limit the amount of exposure they receive (it can survive for about a second at an incident rate of 10^12 photons per second). Measurements of this high-contrast sample should not be too hard, and should not take too long. We are looking for measurements over a $q$-range of $0.1 < q (\mathrm{nm}^{-1}) < 3$. Results will be anonymized before publication by default (though you can ask not to be anonymous); we are particularly interested in the reproducibility.

If you are not yet participating, interested in joining the experiment, and if you can promise a turn-around time of a few weeks, then I would be happy to send you a pair of these vials. Please send an e-mail to me (contact details are in the “about me” tab on this site), or contact me on Twitter (@drheaddamage).

In case of very high demand, I may limit the number of extra participants to about five to ten, in order to keep things manageable on my side. We hope to see some more excellent laboratories joining!