In principle both accelerator types can deliver the required proton beam for ADS applications. However, the nature of each — one compact unit for an isochronous cyclotron, a sequential modular structure for the linac — brings both advantages and disadvantages.
Due to its recirculation nature, a cyclotron is compact and cost effective. However, it lacks every form of redundancy which is crucial for fault tolerance. Hence, a cyclotron will not reach the wanted level of availability, and furthermore an upgrade of its beam energy is not a realistic option.
Linacs on the other hand, can be built as a sequence of many independent accelerating structures (RF cavities), which is a highly modular situation. It is this modularity that makes such a linac particularly well suited to tackle the availability issue. In case of failure of a single accelerating module, independently controlling the RF amplitude and phase of the adjacent modules creates the conceptual possibility of recovering the beam within a short time. Furthermore, increasing the final beam energy is obtained by merely adding accelerating modules.
For these reasons MYRRHA favours the linac option.
Linac versus cyclotron
|Large space requirement (few hundred m long) but light
||Compact but heavy|
||Cheaper in construction|
|Less efficient power conversion
||More efficient power conversion |
|Modularity provides redundancy
||No intrinsic redundancy|
|Upgradable in energy
||Difficult to upgrade in energy |
|Straightforward beam extraction
||Difficult extraction and related beam losses|
|Capable of high beam current (100 mA)
||Modest beam current capability (5 mA)|