Accelerator neutron sources meeting epithermal beam requirements
In plain words
Hospitals need compact accelerators that produce intense beams of medium-speed neutrons without too many fast neutrons or gamma rays. The targets that make the neutrons wear out quickly.
Precise statement
Design an accelerator-driven source giving epithermal neutron flux above $10^9\,\mathrm{per}\,\mathrm{cm}^2\,\mathrm{per}\,\mathrm{s}$ at the beam port with fast-neutron and photon dose per epithermal neutron below the IAEA-recommended limits (of order 2 x 10^-11 rad cm^2 each), using $\mathrm{Li}-7(p,n)$, $\mathrm{Be}-9(p,n)$ or $(d,n)$ reactions, with target lifetime of at least hundreds of treatment hours under proton-induced blistering and heat loads of order $10^{11}\,\mathrm{erg}/\mathrm{s}$. An answer is a source with measured spectrum, flux and target lifetime meeting all criteria.
What would settle it
Measured beam-port spectra and dose components plus target endurance tests on an operating clinical source.
Status in the literature
An accelerator-based neutron capture system was approved in Japan in 2020 for head and neck cancer, while target lifetime and beam quality at lithium targets remain under development.