OCTOPOD: single bunch tomography for angular-spectral characterization of laser-driven protons

Laser-plasma accelerated (LPA) proton bunches are now prepared and provided for research fields ranging from ultra-high dose rate radiobiology to material science and probing of extreme states of matter. Yet, the capabilities to fully characterize the spectrally and angularly broad LPA bunches lag behind the rapidly evolving applications. The Optical Cone beam TOmograph for Proton Online Dosimetry - short OCTOPOD - translates the angularly resolved spectral characterization of LPA proton bunches into the spatially resolved detection of the volumetric dose distribution deposited in a liquid scintillator. Up to 24 multi-pinhole arrays record projections of the volumetric scintillation light distribution and allow for tomographic reconstruction of the volumetric dose deposition pattern, from which proton spectra may be retrieved in arbitrary directions by spectral deconvolution.
Applying the OCTOPOD at a cyclotron, we show the reliable retrieval of various spatial dose deposition patterns and detector sensitivity over a broad dose range from less than 1 Gy to more than 100 Gy, as required for LPA proton bunch characterization. With a dedicated vacuum housing, the OCTOPOD was installed at a LPA proton source, providing real-time data on proton acceleration performance for various laser-target interaction parameters and attesting the system optimal performance in the harsh laser plasma environment.