What are c-beams?

While I'm unable to say for certain what Roy in "Blade Runner" was refering to, the C-Beams in use today are heavy ion beams. They are currently used in two forms, 9C and 12C, in Charged Particle Therapy for cancer treatment. The application of β-delayed particle decay beams like 9C ions in a military weapon system would make sense in a science fiction scenario.