Treating cancer and generating nuclear power are two possible applications of a new kind of particle accelerator tested for the first time last week.
EMMA (Electron Machine with Many Applications), a joint project between several UK research institutes and industrial partners, uses prototype technology that promises to pave the way for cheaper and more compact particle accelerators.
The 5m-diameter machine is the first step towards new hospital-based equipment for hadron therapy, which uses protons to destroy cancerous tumours with greater accuracy than the X-rays currently used, reducing damage to healthy tissue.
The UK’s sole existing medical accelerator at the Clatterbridge Centre for Oncology can only treat eye cancer, said EMMA’s project manager, Neil Bliss, who is based at the Science and Technology Facilities Council’s (STFC) Daresbury Laboratory.
‘Protons can also be used to cure cancer in the body but you need much higher energy to go through other tissue,’ he told The Engineer. ‘What you want to do is get the energy into the tumour and not into the good living tissue.’
EMMA combines features from two types of accelerator currently used, cyclotrons and synchrotrons, allowing beams of charged particles to be extracted at different energy levels but without the greater expense associated with synchrotrons.
Known as a non-scaling fixed-field alternating gradient accelerator (ns-FFAG), it uses a ring of magnets to steer and focus a beam of electrons around the machine. On its first use on 31 March, it accelerated a beam to 18 million electron volts (MeV).
The strength of the magnets limits the displacement of the beam as it accelerates and spirals around the ring, and this greater level of control means the ring can be much smaller than existing equivalent accelerators.
Data from EMMA will be used to scale up the technology for use with heavier protons and create a machine known as PAMELA (Particle Accelerator for Medical Applications), which will be two or three times larger but still suitable for a hospital.
This will use superconducting magnets cooled to 4 kelvin (-269°C) with liquid helium in order to produce the near-zero electrical resistance needed to generate sufficiently high currents and fields.
‘With EMMA, we made it easier for ourselves by using electrons because they are lighter and easier to accelerate,’ said Bliss.
‘Protons are heavier so you need more power and so more strength in the magnets and going to superconductors makes everything more compact.’
Protons are more accurate than X-rays in treating cancer because they release most of their energy at a certain point as they travel through matter, allowing doctors to target them at tumours while they pass through bodily tissue without damaging it.
PAMELA will also be designed to work with carbon ions, which are even more effective for cancer treatment, in the hope of making it the first cyclotron able to accelerate them with the necessary properties to target tumours.
The final stage of the project will involve looking at further applications, such as using ns-FFGA accelerators with thorium reactors to generate nuclear power in a way that consumes much less fuel and creates less waste than existing methods.
There are also hopes that ns-FFGA accelerators will play a part in creating muon and neutrino particles for fundamental physics research.
EMMA cost £7m over four years to build and is part of the CONFORM (Construction of a Non-scaling FFAG for Oncology, Research and Medicine) project, run by BASROC (the British Accelerator Science and Radiation Oncology Consortium).
This includes researchers from Manchester, Oxford, Surrey, Imperial, Brunel and Huddersfield universities, as well as the Cockcroft and John Adams institutes and STFC, and a number of industrial and international partners.