Photoemission from Diamond and Fullerene Films for Advanced Accelerator Applications - Plasma Science, IEEE Transactions on

The photoemission properties of thin diamond and fullerene films were investigated for advanced accelerator applications, using subpicosecond laser pulses at three different wavelengths (650, 325, and 217 nm). The quantum efficiency (QE) obtained at 217 nm with a boron-doped, p-type, (111) polycrystalline diamond film (2.6 lop4) was only five times smaller than the QE obtained with a mirror polished copper sample (1.3 . but more than nine times larger than the QE obtained with a pure diamond film or with natural diamond monocrystals. Similar results were obtained for the two-photon electron yields at 325 nm. The electron yields obtained with pure fullerene films were small and comparable to the ones observed with the pure diamond samples. With 650 nm pulses, the damage threshold of the (110) Type IIa natural diamond monocrystal (9.38 . lo4 pJ cmP2), defined here as the fluence leading to an onset of ion emission, was 25 times larger than the damage threshold for a copper sample (3.75 . lo3 pJ cm-’). The damage threshold of the boron-doped sample at the same wavelength was two times larger than that of copper. Damage thresholds with 325 nm pulses were lower, and with 217 nm pulses ion emission was observed at all fluences probably attributed to ablation of surface hydrocarbon contaminants. Results show that high-quality highboron concentration diamond films could be a good candidate for high-RF electron guns.