Proton laser-plasma-based acceleration has nowadays achieved a substantial maturity allowing to seek for possible practical applications, as for example Particle Induced X-ray Emission with few MeV protons. Here we report about the design, implementation, and characterization of a few MeV laser-plasma-accelerated proton beamline in air using a compact and cost-effective beam transport line based on permanent quadrupole magnets. The magnetic beamline coupled with a laser-plasma source based on a 14-TW laser results in a well-collimated proton beam of about 10 mm in diameter propagating in air over a few cm distance.

Particle-induced x-ray emission (PIXE) is a well-established ion-beam analysis technique, enabling quantitative measurement of the elemental composition of a sample surface under an ambient atmosphere with an external beam, which significantly simplifies the measurements, and is strictly necessary for those samples that cannot sustain a vacuum environment. Few-MeV electrostatic proton accelerators are used today in PIXE systems. We present here an external beam PIXE methodology based on a compact laser-driven proton accelerator. A 10-TW class ultrashort laser is used to generate a few-MeV proton beam, and a compact transport magnetic beamline is used to collect and transport the proton beam and to prevent unwanted fast electrons from reaching the sample. An x-ray CCD camera in single-photon detection mode is used to retrieve the spectrum of radiation emitted by the samples upon proton irradiation in air. Elemental composition analysis is performed and validated against standard energy-dispersive x-ray spectroscopy, demonstrating quantitative and accurate external beam PIXE analysis with compact laser-driven accelerators.

Laser-accelerated electron beams, in the so-called Very High-Energy Electron (VHEE) energy range, are of great interest for biomedical applications. For instance, laser-driven VHEE beams are envisaged to offer suitable compact accelerators for the promising field of FLASH radiotherapy. Radiobiology experiments carried out using laser-driven beams require the real-time knowledge of the dose delivered to the sample. We have developed an online dose monitoring procedure, using an Integrating Current Transformer (ICT) coupled to a suitable collimator, that allows the estimation of the delivered dose on a shot-to-shot basis under suitable assumptions. The cross-calibration of the measured charge with standard offline dosimetry measurements carried out with RadioChromic Films (RCFs) is discussed, demonstrating excellent correlation between the two measurements.