Laser-photofield emission from needle cathodes for low-emittance electron beams.
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.
Ganter
R
R
Paul Scherrer Institute, 5232 Villigen, Switzerland.
Bakker
R
R
Gough
C
C
Leemann
S C
SC
Paraliev
M
M
Pedrozzi
M
M
Le Pimpec
F
F
Schlott
V
V
Rivkin
L
L
Wrulich
A
A