Beam Optics Study for a Potential VHEE Beam Delivery System

• Cameron Robertson (University of Oxford)

Abstract: Heavy-ion therapy is currently the favoured modality for the treatment of deep-seated tumours. Facilities for heavy ion therapy are however very large and expensive since cyclotrons are principally used to accelerate the ions up to appropriate energies for cancer treatment. There is evidence that VHEE (Very High Energy Electron) therapy can be superior to conventional radiotherapy for the treatment of deep-seated tumours, whilst not necessarily requiring the space and cost of heavy-ion facilities. Developments in high gradient RF technology have allowed electrons to be accelerated to VHEE energies in a very compact space, meaning that treatment could be possible with a short linac, that could fit in a typical hospital campus. A crucial component of VHEE treatment is the transfer of the beam from accelerator to patient. This is required to magnify the beam for tumour coverage whilst ensuring a flat, uniform distribution. Here, two principle methodologies for the design of a compact transfer line are presented. The first of these is for the design of a quadrupole lattice. A minimisation algorithm is used to enforce certain criteria on the transverse beam distribution at the patient, setting quadrupole strengths and positions in the transfer line through an automated routine. Separately, the utilisation of a dual scattering-foil system for beam magnification is also studied, using a similar minimisation principle to optimise the foil geometry.