Applications of Microwaves to Antiproton Control

A major achievement in particle accelerator physics has been the invention of stochastic cooling, a method which increases the density of beams of rare particles, like antiprotons, by several orders of magnitude. The beam circulates in a storage ring where it is sampled by electromagnetic devices which detect and correct the statistical fluctuations in position and energy. The efficiency is related to the sampling resolution which is itself associated with the system frequency bandwidth, a few gigahertz in practice. The coupling structures are made of electrode arrays connected by combiner or splitter networks. The dynamic range may exceed 150 dB yet fulfilling stringent linear characteristics. At the detection stage, the thermal noise is reduced using cryo-electronic techniques. At the other end of the amplification chain, solid state amplifiers delivering up to 100 watts CW power have been preferred to travelling wave tubes for reasons of phase linearity, lifetime and economy. The performances and technological aspects of the microwave systems are discussed by the example of the CERN antiproton project, ACOL.