Speaker
Description
A new discharge capillary plasma source is being developed for the FACET‑II National User Facility at SLAC National Accelerator Laboratory. The FACET accelerator delivers 10 GeV electron beams with nanocoulomb charge and peak currents of 30-100 kA for advanced accelerator
research.
The capillary discharge plasma source provides operational advantages over existing plasma sources at FACET-II. The device is easily operable and highly tunable, which enables more beam time for experiments. Specific experimental goals include emittance preservation in a plasma wakefield accelerator, high transformer ratio acceleration, ionization injection, and photon acceleration.
A laboratory setup replicating the planned FACET‑II installation is currently under construction. This configuration allows offline plasma characterization (without the electron beam) to map key plasma parameters and study their dependence on controllable inputs.
Plasma generation is achieved using a capacitive discharge circuit capable of delivering up to 35 kV and 500 A to a capillary typically 50 mm in length, with the option to adjust the length for specific experimental needs. Helium gas is supplied through a continuous flow regulated by two
mass‑flow controllers. An alternative gas supply configurations and species are also under consideration.
Plasma density profiles and their temporal evolution are measured both along and across the capillary using Stark broadening of helium emission lines in the visible range (587.56 nm, 501.57 nm, and 447.15 nm). Plasma temperature estimates are obtained from intensity ratios of nearby emission lines or from line‑to‑continuum ratios. An auxiliary interferometric system is planned to validate the spectroscopy measurements.
This report provides an overview of the project, describes the diagnostic methods and instrumentation, outlines design considerations, and presents initial experimental results.
| Working group | WG3 |
|---|