Preparation and evaluation of thin diamond-like carbon foils for heavy-ion tandem accelerators and time-of-flight spectrometers

Thin diamond-like carbon (DLC) foils in the thickness range of 0.6–15 μg/cm2 were produced and evaluated as heavy-ion strippers for tandem accelerators and as secondary-electron emitters for time-of-flight (TOF) spectrometers. The foils were produced by DC glow discharge sputter deposition of pure carbon with condensation of DLC films onto glass slides coated with a release agent. Irradiation lifetimes of 3 μg/cm2 DLC foils made by this technique were compared with lifetimes of standard vapor deposited carbon foils when bombarded with 14 MeV 197Au− ions at the terminal of the BNL MP7 Tandem Accelerator. Preliminary measurements have indicated that DLC strippers outlast the standard foils by a factor of at least three. The high tensile strength of DLC foils allowed reducing of the minimal thickness of start foil, for TOF spectrometer down to ≈ 0.6 μg/cm2, resulting in considerably improved energy resolution, due to lower ion energy straggling in the foil. Along with initially used special DC sputter deposition system, a commercially available diode RF sputtering technique was investigated as candidate method for large-scale production of DLC foils.