No abstract

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.

No abstract

The development of compact accelerator machines is leading towards the use of plasma-based devices that are able to sustain large acceleration gradients up to several tens of GV m −1 . The main issue, in this regard, is due to the necessity to produce the plasma shot-by-shot starting from neutral gases, since its lifetime is limited to a few tens of microseconds. This puts severe limitations on its resulting uniformity, stability and reproducibility, which in turn strongly affects the quality of accelerated beams by plasmas. In this work, we describe a gas-filled discharge-capillary where the plasma generation, achieved by ionizing Hydrogen gas with a high-voltage electrical discharge, is stabilized by triggering its ignition with an external laser pulse. Results show a noticeable stabilization of the resulting plasma density along the capillary and the discharge pulse. This enables the development of very long capillaries and in turn, acceleration lengths as required, for instance, by next-generation plasma-based facilities delivering beams in the GeV-scale.

We report the experimental activity on the plasma-discharge capillary tubes suitable for plasma-based accelerators (PBAs) carried out at the SPARC LAB (sources for plasma accelerators and compton with laser and beam) test-facility. A high-voltage discharge is produced inside a Hydrogen-filled capillary tube. Through spectroscopic techniques, the density of the plasma thus produced is monitored either spatially or temporally through the line Stark broadening profiles.