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A novel modulator has been designed, built and tested for the TESLA test facility.This e+ eaccelerator concept uses superconducting RF cavities and requires 2 ms of RF power at 10 pps. As the final accelerator will require several hundred modulators, a cost effective, space saving and high efficiency design IS desired. This modulator uses a modest size switched capacitor bank that droops approximately 20% during the pulse. This large droop is compcns;~ted for by the use of a resonant LC circuit. The capacitor bank is connected to the high side of a pulse transformer primary using a series CT0 switch. The resonant circuit is connected to the low side of the pulse transformer primary. The output pulse is flat to within I% for 1.9 ms during a 2.3 ms base pulse width. Measured efficiency, from breaker to klystron and including energy lost in the rise time, is approximately 85%.

A bunch-by-bunch beam damper has been developed for the Fermilab Tevatron. The system reduces betatron oscillation amplitudes and incorporates some useful machine diagnostics. The device ls programmable via look-up tables so the output is an arbitrary function, on a bunch-by-bunch basis, of the beam displacement. We are presently using this feature to measure the betatron tune throughout the acceleration cycle.

Important parameters in collider operations are the length and intensity of individual beam bunches. A system to automatically measure 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 required accuracy, attention has been paid to the calibration and frequency response of the system. Design and performance of a new wall current monitor with improved bandwidth is presented.

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