Electron beam timing monitor system and feedback for KEKB e-/e+ linac injector

In order to increase positrons, the KEKB e-/e+ Linac is accelerating high-intensity electron beams of 10 nC, which require high stability of each equipment. In the efforts to stabilize the beams, we started to monitor pulse timings concerning beams such as gun-grid pulses of 1 ns pulse width and electron beam pulses of 1 ns/10 ps widths. The grid pulses are measured by means of a digital oscilloscope and the pulse timing is now being controlled within 50 ps by a feedback system. The beam pulses form a wall current monitor at buncher exit gives us bunched beam information, which is measured by a sampling oscilloscope. We are also monitoring RF phases of sub harmonic bunchers with respect to a reference RF wave of 2856 MHz. The time fluctuations of these values can be seen on Web browsers. (author)