Transport and beam line development

To match the compact size of the laser-driven ion source, we aim to miniaturize the systems for transporting and refocusing the bunches as well. Various possible applications of laser-driven ions demand the delivery of the particles to a remote location from the laser-target interaction. This has the advantage that irradiations can be performed under different conditions, for example on air, and that secondary radiation from the target can be avoided.

In order to achieve high particle fluences at the irradiation site a beamline that actively focuses the ions is required. The particles broad energy spectrum combined with an extremely small emittance make laser accelerated ion bunches a special challenge for conventional ion transport systems. This creates the demand for new and innovative approaches to ion transport that enable to exploit these particular properties. The aim of our development is to specifically manipulate the phase space of the particle bunch in order to adapt it to the required applications.

As a basis, we implement permanent magnet quadrupoles for transverse focusing with the aim to create a sub-millimetre size focus of laser accelerated protons. Therefore careful magnetic field measurements and characterization with high precision are required. We developed both offline and online methods to position the magnets reproducibly with micrometre precision. This enables online energy selection. Further, we investigated protection and damage mitigation methods which are crucial when operating in immediate surroundings of the laser target interaction.

Ion optical simulations and modelling accompany our beamline development. This allows us to develop further understanding and control of the transport of broad particle energy spectra in order to predict fluence and spectral distribution in the ion focus. These calculations in turn enable detailed investigation on the microscopic laser-driven ion source.