Characterization of plasma sources for plasma-based accelerators

This work is concerned with both theoretical studies and the experimental developments of a plasma device to be used in plasma-based accelerators. In the field of the particle accelerators is growing the interest in the development of compact accelerator machines that also have to be able to exceed the current limits of the conventional accelerator structures. This research activity is leading towards plasma-based devices able to produce accelerating gradients in the GV/m scale. The activity of the SPARC_LAB test-facility concerns the development of this kind of plasma devices, as the gas-filled capillary plasma sources. In these devices, to create the plasma, one or more gas inlets feed the channel with a neutral gas (hydrogen, argon, nitrogen, etc.), which will be ionized by using a high-voltage discharge. The plasma plumes produced at the ends of such a capillary can affect the beam, due to the stability and uniformity of the electron density in which in these areas decrease strongly and, consequently, the beam emittance can degrade. A study on the plasma plumes formation presented here, where also a possible solution based on the capillary shape modifications proposed to optimize the density profile at the ends.