Perhaps surprisingly, the key innovation in this experimental set up is not the presence of the controllable ionisation source (from the Proton Synchrotron accelerator), but rather the state - of - the - art instrumentation of the chamber that has allowed them to see in unprecedented detail what is going on in
the aerosol nucleation process (this is according to a couple of aerosol people I've spoken about this with).
The team started by looking at the formation of the very small particles — a
process called
aerosol nucleation — by mimicking atmospheric conditions inside an ultraclean steel «cloud chamber», which Kirkby says is the cleanest ever created.