Laser-photofield emission from needle cathodes for low-emittance electron beams |
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Authors: | Ganter R Bakker R Gough C Leemann S C Paraliev M Pedrozzi M Le Pimpec F Schlott V Rivkin L Wrulich A |
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Institution: | Paul Scherrer Institute, 5232 Villigen, Switzerland. |
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Abstract: | Illumination of a ZrC needle with short laser pulses (16 ps, 266 nm) while high voltage pulses (-60 kV, 2 ns, 30 Hz) are applied, produces photo-field emitted electron bunches. The electric field is high and varies rapidly over the needle surface so that quantum efficiency (QE) near the apex can be much higher than for a flat photocathode due to the Schottky effect. Up to 150 pC (2.9 A peak current) have been extracted by photo-field emission from a ZrC needle. The effective emitting area has an estimated radius below 50 microm leading to a theoretical intrinsic emittance below 0.05 mm mrad. |
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