Single bunch intensity monitoring system using an improved wall current monitor

The length and intensity of individual beam bunches are important parameters in collider operations. A system for automatically measuring these parameters has been developed using a wall current monitor signal digitized by a 1 GHz sampling oscilloscope under microprocessor control. Bunch length and intensity are computed by the microprocessor and presented to the host computer. To verify the accuracy required, attention was given to the system's calibration and frequency response. The system has been successfully used to monitor colliding beam operations at Fermilab. The current 5% accuracy in measuring single-bunch intensity demonstrates the excellent fidelity and bandwidth of the system. The design of a resistive wall monitor with 3 kHz to 6 GHz bandwidth and less than 1 dB amplitude variation is presented. Using a microwave absorber inside the vacuum chamber to reduce noise is discussed. >