Simulations and measurements of the TTF phase-1 injector gun

The TTF phase-1 injector will use a conventional thermionic triode gun as its electron source. The temporal structure of the injector will be obtained by the application of fast (<1 ns) pulses to the gun cathode. As it is necessary to operate the injector at a fixed average macropulse current of 8 mA, while having the ability to vary the repetition frequency of the micropulses, the gun has to function at peak currents varying from 100 mA to 400 mA. We report on both measurements and simulations (using EGUN) of the current-voltage characteristics of the TTF gun. In addition we report on measurements of the emittance of the gun over a limited range of current and voltage. The emittance is seen to be dependent upon the operating perveance and is smallest for perveances closest to the space-charge limited value