Producing neutron beams by the spallation method involves a complex engineering infrastructure to accelerate particles to high energies. Each section of the ISIS machine is looked after by a highly skilled and experienced team.
The process starts with an ion source to produce negative hydrogen ions (two electrons bound to a proton, H-) which are extracted and injected into a chain of linear accelerators. Then stripped of the electrons by a thin piece of aluminium oxide foil, the bare protons enter a circular accelerator 50 metres across called a synchrotron, around which are placed devices and magnets to accelerate, steer and focus the protons. They are gradually crammed into two equally-spaced bunches, circulating 10,000 times before being kicked out of the accelerator towards the targets where neutrons and muons are produced.The whole process is repeated 50 times a second. Muons are made in a carbon target, whereas the neutrons are generated from a target composed of tungsten clad in tantalum to prevent corrosion and cooled with water.
