If memory serves, the van der graff generator at the Boston Museum of Science was literally used as a particle accelerator at MIT for decades (apparently built by the Van de Graaff). I think the generator itself was the accelerator and just needed to go through an evacuated tube to be used.

> The largest air-insulated Van de Graaff generator in the world, built by Dr. Van de Graaff in the 1930s, is now displayed permanently at Boston's Museum of Science. With two conjoined 4.5 m (15 ft) aluminium spheres standing on columns 22 ft (6.7 m) tall, this generator can often obtain 2 MV (2 million volts).

https://en.wikipedia.org/wiki/Van_de_Graaff_generator https://www.atlasobscura.com/places/worlds-largest-airinsula...

The vacuum tube alone probably qualifies according to most definitions, it's a beam of charged particles accelerated through the control grid and an accelerator voltage. Honestly not sure what else I'd call that.

Nowadays what would be the closest common thing... hand held XPS exists for sure, but that's not super common (photoelectric effect that uses x-rays coming in). Can we go with an arc welder or plasma cutter if we use a definition that just means "charged particles going through an accelerating voltage in free space"?