Bunch Length Measurement and the Beam Spectra Observation Through High Power RF Waveguide System
A wide-band pick-up, which is mounted on the wall of waveguide between the klystron and the RF cavity, has been developed for measuring beam spectra in KEKB. The spectrum between 5 GHz and 20GHz is taken to calculate the bunch length. And the synchrotron oscillation is observed as the side band of revolution peak. The bunch length and synchrotron frequency are measured under the different momentum compaction factors {alpha} and different total RF voltages Vc. Measured bunch length is compared with the measurement of streak camera.
MEASUREMENT OF BUNCH LENGTH BASED ON BEAM SPECTRUM IN THE KEKB
An amplitude ratio of two frequency components in the beam spectrum gives the bunch length. It is analytically demonstrated that this technique can detect an rms bunch length under that normalized frequencies are less than 1. Such a bunch length monitor was fabricated for the KEKB. Design, hardware and the performance of a bunch-length monitor are described. The bunch length was measured both in single bunch and multi-bunch modes. The average bunch length in multi-bunch mode with a 4-bucket bunch spacing did not indicate a significant difference from that in single bunch mode.
Time behavior of gas pressure and PD activity in insulation cavities under AC voltage
In the framework of developing defect-based life models (i.e. the life model of partial discharge-induced damage growth from a micro-void in polymer matrix), ageing tests were performed on PE layered specimens with artificial cavities under constant gas pressure and constant gas volume conditions, respectively. Time behavior of the discharge repetition rate and amplitude were recorded and compared under these two conditions. Results show that pressure variation has little influence on PD activities at constant gas volume. Under constant gas pressure, the evolution of gas volume has similar characteristic to the product of discharge amplitude and repetition rate.