ISIS, well, the first thing I should say is that it's not a terrorist organisation.
ISIS is a neutron and muon facility that's designed to deliver neutron beams for users.
So they put samples in the beam line to study things like structure of materials, how they
work. All sorts of things from materials science to biology to environmental science.
So ISIS started operating in 1984 producing the first neutrons.
And the way we produce the neutrons is by shooting protons into a heavy metal target
at very high velocity. The heavy metal contains lots of neutrons because it has big atomic
nuclei. And the nuclei are quite unstable. So if you hit them hard, you knock bits off.
Obviously we had to build a particle accelerator to do that. So neutrons are non charged particles,
you can't accelerate those because you need to use a charged particle in an electric field.
So we smash the protons at high energy into a target and then neutrons come out of that target.
So around this so called target we have beam lines for users. It happens 50 times a second.
Four of those pulses go to this target station and one of those five pulses goes to the other
target station.
At it's full capacity we use about 10MW of power. It takes many, many millions of volts
to be able to pull neutrons out of atoms, you have to overcome the strong nuclear force
and that's why we have to smash them so hard with a proton beam and it takes lots and lots
of energy to actually build the power in that proton beam.
My name is Suzie Sheehy and I design particle accelerators for various applications.
We are currently standing in the heart of the ISIS neutron and muon facility in which
there is an 800 mega electron volt proton synchrotron. There's two main systems around
a synchrotron like ISIS that need lots of power. One of them is the accelerating system
which are these big, what we call, radio frequency cavities which there's one just behind us
here. There's a radio frequency cavity. So they use quite a lot of power to accelerate
the particles. The main magnets in this machine repeat ten times around the circumference.
And in each section you'll see one of these big yellow magnets. It's about 4.5 metres
long, weighs about 35 tonnes and it's just there to bend the beam. These green ones here
are called quadrupole magnets. They focus and de-focus the beam to keep it stable and
under control.
Each of those magnets has a field inside it but that field needs to change during the
acceleration cycle. My name is John Thomason. I'm accelerator division head for ISIS and
that means I'm in charge of all the equipment that keeps the accelerators running and all
the people that keep that equipment running.
Because effectively the magnets are bending the particles around in the circle. It's a
particle accelerator so you can guess that the particles are going to go faster while
you're doing that so the field strength needs to increase in the magnet.
The beam goes around about 10,000 times in it's acceleration cycle but that happens 50
times every second. As the beam gains energy, we have to synchronise the increase in the
magnetic field in order to keep that beam travelling around the same circle the whole time.
OK, you're in the main capacitor room for the ISIS synchrotron. Basically this is part
of the system which powers the main magnets in the synchrotron ring. I'm Steve West, I'm
an electrical engineer and I work in the ISIS electrical engineering group.
What we use to power the magnets there's a resonant circuit. We use resonance to make it easier to get
the power into the magnet.
So current oscillates back and forth in the circuit and it allows us to very quickly move
energy in and out of the magnets. We can store that energy efficiently within the circuit
and effectively kind of slosh it around rather than pulling in new energy continuously from
the grid.
You have ten what we call superperiods or groups of magnets around the synchrotron and
you have ten capacitor banks in here, one for each superperiod. They're all part of
this circuit which allows us to swing the energy backwards and forwards.
The resonant circuit has an inductance and capacitance and a resistance. The part of that
that is called the choke is providing the inductance in that circuit. We have ten
main sets of magnets, so in an ideal world we'd have ten separate chokes but it so happens
that when we first built the machine, we inherited a choke which can do ten different actions
all at the same time but it's an integrated choke so it all looks like one big lump of metal.
And it looks a bit like a transformer which some people might be familiar with and it
stores energy in a magnetic field. Basically it's a big lump of iron with a coil of wire
around it.
The square concrete building is the old choke house and this is what you see here. There's
a big steel tank. The choke is inside that. The whole thing is oil cooled.
So if any one part of that goes wrong it's extremely difficult to mend. So we're trying
to move away from it now and have one where we'll have ten separate chokes.
The new system is being split so that instead of it all being built into this one single
block of steel, it's being split into ten separate ones.
We need ten of these chokes. If you count them you'll find there's 12. It'll be very
easy if one of these failed in some way, to switch onto one of the spares and that can
be done in a few hours. That's one of the reasons why we built this system is to add
that extra bit of safety.
It's a bit like the kidneys. You need them, you can't do without them but if you lose one
actually you'll still be alright.
Not just the choke system, it's congruent with a number of other components on ISIS
because a 30 year old accelerator is old enough, many of the components are 50 or even 60 years old.
So it's an ongoing worry that there are going to be single point failures that wouldn't
just take you off, because we get that kind of thing all the time and we have armies of
people that come and mend them, but would take you off for a significant amount of time.
The magnets teams are absolutely vital to what goes on here. So we have scheduled maintenance
periods where we basically pick up all of the problems that have accumulated during
a user run and deal with them. We're generally off for between a week and four weeks depending
on what time of year it is. And this is all scheduled at least a couple of years in advance.
So I'm Aaron, I'm a third year apprentice. Currently I'm working in the ISIS technical
support workshop. I'd say the maintenance teams are probably the most important teams
that are here. Without them it just wouldn't happen. I've always been hands on. I've been
able to fix cars, I've restored classic cars. I've worked on motorbikes. ISIS is definitely
more complicated than a classic car. But I'd say that when you're working on the system
for so long, and you've put so much hard work into it, it's hard to not get a bit attached.
Like us humans, we need care and attention. That's the main part of the job, is to give
it care and attention just to keep it going.
There's a relationship there between the people and the accelerator and generally speaking
it's a very loving one. Possibly a bad analogy but it's a bit like having an ageing parent
or something like that. That you owe it something, it owes you something. It's almost like a
symbiotic relationship if you like.
You know, we have a facility where there's maybe a thousand people. There's users coming
from all over the world. They're trying to understand how we can use particles from inside
the atom that we can't see with our own eyes and then say save babies lives or make better
aeroplanes that don't fall out of the sky. So that's an incredible human story because
we would not be able to do such amazing science without both that technology and the people
behind it.