Production of carbon stripper foils for high-power cyclotrons

TRIUMF, Canadaʹs National Laboratory for Particle and Nuclear Physics operates three industrial negative ion cyclotrons for commercial radioisotope production. Two of these cyclotrons (TR30 and TR30-2) can deliver 30 MeV protons at beam currents in excess of 1000 μA and are designed for optional dual beam extraction and continuous operation. ower negative ion accelerators use stripper foils as thick as 500 μg/cm2. It has been found that very smooth films with nanocrystalline microstructure perform the best in high-current applications. However, high-quality thick foils with good uniformity are difficult to manufacture. To meet our specific requirements, we have developed a carbon arc deposition system capable of producing durable, homogeneous carbon stripper foils. In this paper, we report on the fabrication of carbon foils with a thickness of 100–200 μg/cm2. The manufacturing equipment capable of producing ∼600 cm2 of foil in a single run and the process details are described. Properties of these foils and their performance in the cyclotron are discussed.