ISIS - The UK's Biggest Microscope
Patrick Kennedy-Hunt | 27 March 2017

“Awesome”, an English teacher once told me, is an overused word: it originated as a way to describe God, and very little in our world, he assured me, deserved that title. Two years on, and I truly believe that there is something not two hours’ drive from Berkhamsted School which can justifiably be described as awesome.


It is pretty hard, after all, to describe a microscope large enough to dwarf a warehouse, which relies on an understanding of relativity and quantum mechanics to function, as anything other than awe inspiring. Yet there is one thing, that above all else epitomises what truly makes this microscope amazing: to study matter the radiation used is not light nor sound nor anything so mundane. The radiation used is nothing less than one of the larger subatomic particles: the neutron. ISIS, as this contraption is colloquially known, is a resource made available to researchers in the UK and Europe; funded by the Science and technology facilities council, it offers a resource unique in the United Kingdom: a particle accelerator which acts as a microscope.


In 1937 two men, Clinton Joseph Davison and George Paget Thomson, were awarded the most prestigious scientific prize on the planet for their work on particle diffraction (somewhat ironically, providing a contrast to the latter’s father, JJ Thompson, who won the same prize some 21 years earlier for showing that electrons were particles and by implication could not diffract). Particle diffraction, in the case of ISIS neutron (and muon) diffraction, rapidly became important in a range of fields throughout science.


One of the issues which one often hears professionals and teachers complain of is the failure of students to grasp the connected nature of subjects; no more clearly are the modern interconnections in science displayed than in the case of the duality of particles and waves (physics) being applied to crystal systems (chemistry) of biological molecules (which is, believe it or not, biology). Yet this is just what particle diffraction does.


The particle accelerator is, in itself, a remarkable feat of engineering; especially since the football pitch size behemoth still relies on parts made in the 1950s. Particles are accelerated through copper pipes consisting of electromagnets. These electromagnets induce a Lorentz force on charged particles and so move a beam of protons in a circle at increasing speeds. Strong magnets shepherd the beam of protons (which according to quantum theory is a lot like a wave) down the pipe as they are accelerated. When these protons reach sufficient speed the centripetal force of the magnets is insufficient to hold them in a loop and so they head off down a pipe to where they are used: two such pipes exist for two different speeds each leading to a target station; up until this point the strength of the magnets is varied in order to ensure that the particles maintain their circular path.


By this point any reader who didn’t tune out at the first mention of electromagnets and Lorentz is probably wondering why on earth anyone would want to go to all this hassle, not to mention astronomical expense, to make some small and irrelevant stuff move quickly. Of course, this was not the whimsical project of a mad scientist or politician, but is rather an invaluable resource. As alluded to above, neutrons moving at these speeds behave rather like waves and the way these neutrons diffract can be used to understand the electrical properties and structure of substances. These neutrons have significant advantages over electrons or X-rays as neutrons only interact with the nuclei of atoms (not the electron clouds) and will do so in part based on spin (a property, which in all honesty nobody really understands but which makes neutrons behave a bit like magnets).


A recent application has been the understanding of catalysts (things which speed up chemical processes); Lindlar catalysts are used to manufacture vitamins. ISIS enabled researchers to understand the mechanism, potentially allowing superior catalyst development and uses.


In truth, what is truly “awesome”, however, is not the fact that we can use this to examine crystals, or to revolutionise computing, or even the remarkable feat of engineering which this project represents. Far more importantly, the historical development of the ideas and principles of operation have revealed to us a world far stranger (and, dare I say it, beautiful) than anything to be found in science fiction. Moving forward into the future, a future where science on the smallest scales is going to become a remarkably big deal, ISIS will ensure that Britain remains a centre for technological and scientific development.

James Routledge 2016