Beam line used in photocathode studies. The beam moves from right to left.
Typical transverse profile of a laser spot incident on the photocathode (a) after a circular aperture and (b) for a Gaussian imaged beam.
(a) Typical beam profile as measured by the wire scanner and the fit. (b) Typical solenoid scan data and emittance fit (GaAs, 860 nm).
Transverse phase space of the beam with thermal emittance. Current signal in nA. (a) GaAs and (b) GaAsP. Calculated emittances as a function of encompassing ellipse area after the noise subtraction for (c) GaAs and (d) GaAsP data, respectively (refer to the text).
Comparison between different emittance measurement techniques for GaAs at 532 nm. Filled squares correspond to a Gaussian laser profile.
Thermal emittance of GaAs as a function of rms laser spot size for various illumination wavelengths.
Thermal emittance of GaAsP as a function of rms laser spot size. (a) and (b) .
Thermal energy of GaAs as a function laser wavelength.
Thermal energy of GaAsP as a function laser wavelength.
Fraction of the electron pulse emitted up to time upon arrival of a delta-function laser pulse for the photoemission response function given by Eq. (11).
Calculated dependence of the transverse beam size of the beam at the location of the wire scanner for different values of parameter . Charge per bunch 100 fC, gun voltage 250 kV, , initial rms laser spot size . (a) Solenoid scan and (b) change of the spot size relative to the case of negligible space charge for unpowered solenoid as a function of parameter .
Fit of the measured solenoid scan when excited by 100 fs laser pulse at 710 nm. (a) 200 kV and (b) 250 kV.
Example of fit to solenoid scan data for GaAs when excited with 300 fs laser pulses at 460 nm. The bunch charge is 97 fC, the initial electron distribution is assumed to be identical to the laser (prompt response). All parameters except for the gun voltage are identical for the two fitted curves.
Results of data fitting for GaAs response time.
Results of data fitting for GaAsP response time.
Article metrics loading...
Full text loading...