Accelerator technology has been developed over several decades and there is some confidence developed in the technology. There are several approaches. The attributes of the different systems are summarised in Table 13.3.

Linear accelerators or Linacs are thought to be achievable up to relatively high power (200 mA, 1.6 GeV). They have been demonstrated as reliable and efficient research tools, and can be made available at a reasonable cost. The most efficient operating conditions for a linear accelerator at the present time would be around 100 mA.

Cyclotron, i. e. circular proton accelerators’ technology has also advanced enabling a 10-15 mA proton beam to be achievable via a segmented cyclotron or synchrotron concept. The most efficient operating current for these is around 10 mA. They have some benefits compared with a Linac but also some disadvantages. The cyclotron

Table 13.3. Accelerator driven systems

occupies a smaller physical area and is cheaper than the Linac, but the space limitation limits the proton current, in the present day to about 10-20 mA. Linacs do not suffer this limitation.

On a larger commercial scale, one option might be to use one linear accelerator to a number of sub-critical reactors by splitting the beam. However, there may be drawbacks in the event of failure of the beam dividers, in which case the full beam might be directed against one target, or failure of the full beam would shut down all the sub-critical reactors.

This problem could be overcome by using one or more smaller cyclotrons, running several smaller reactors, but at increased cost. Regarding the status of cyclotron technology, cyclotrons of 1.1 MW beam power for a 600 MeV proton accelerator have been developed at the Paul Scherrer Institute (PSI). A number of alternative options are under consideration, e. g. a ‘multi-stage-parallel’ cyclotron arrangement in which several lower energy, low current cyclotrons input into a high-energy cyclotron. This approach would also give some cost benefits in terms of energy scaling, compared with a linear accelerator.