Emittance measurement along transport beam line for laser driven protons

Particle emittance quantifies the ability to focus and transport a beam, and is one of the most important parameters for a beamline. The emittance of a proton beam produced by ultraintense laser irradiation of a micron-thick flat solid target has been measured systematically for the first time, using three different methods at different positions along the transport beamline: Pepper-pot method, quadrupole triplet scan technique, and single-shot emittance measurement. Emittance growth is shown both in experiments and in simulations using CST. An over 3-fold emittance growth was found for 5 MeV laser-driven protons with an energy spread of ±2% and divergence of ±20 mrad after being transported 5.9 m in the experiment, due to the energy spread and angular dispersion of the protons.