Dose enhancement and localisation by combining reduced mass targets and a pulsed solenoid for radiobiological effectiveness studies of laser accelerated protons

Proton beams by means of the well-confined dose deposition in matter are a promising tool for improving radiotherapy of cancer. Wider clinical use, however, is limited by the complexity and expense of current proton accelerators. Compact laser-driven proton therapy accelerators are a potential alternative, yet require substantial development in reliable beam generation, transport and dosimetric monitoring as well as validation in radiobiological studies.

In vitro cell irradiations with laser-accelerated protons show radiobiological effectiveness similar to conventionally accelerated protons. In vivo animal irradiations – the next step in the translational research chain towards laser-driven proton therapy of cancer – are currently restricted by the low proton yield and energy at the irradiation site.

We report on systematic investigations of the ultrashort pulse laser-driven acceleration of protons from thin targets of narrow lateral dimension, so-called reduced mass targets (RMTs). A robust maximum energy enhancement (almost doubled) was found when compared to reference irradiations of plain foils of same thickness and material. Combining RMTs with a pulsed high-field solenoid for particle capturing, as developed at Helmholtz-Zentrum Dresden-Rossendorf, gives the potential to enhance and localise the dose per pulse applied to the tumour, thus making further radiobiological studies on volumetric tumours feasible in the future.