It's a component of the SPARC_LAB (LNF-INFN) particle accelerator; in particular, it is a capillary tube that is used to accelerate the particles using plasma
I designed this model in Autodesk Fusion following a specification sheet available to the public and printed it with overture transparent PETG. I suggest looking at the .gcode for an example of print settings.
The author marked this model as their own original creation.