Some experiments at the ATF require higher energies than what is available from the photoinjector. We use two traveling wave linac structures, known as 'SLAC sections' (from the famous 2-mile SLAC linac). Each section provides an acceleration given by:
Energy gain (in MeV) = 10.8*SQRT(Power in MW)-39.5*Current(in amps)
The current to be used is an equivalent steady state current. The microwave drive power, at a frequency of 2856 MHz, is provided by a single XK5 klystron tube (the old SLAC klystron). This tube can provide up to 25 MW. The ATF modulator can provide the XK5 klystron with high voltage for about 3 microseconds. This 3 microsecond pulse is called the macropulse. The repetition rate for the macropulses is from 1 to 6 per second. Within each of these macrobunches we accelerate from 1 to about 200 electron bunches (depending on the photoinjector's laser setting). These current bunches are called micropulses. The micropulse repetition rate is up to 81 MHz.