Feedback via the Beam-Signal Shielding

A further ingredient of cooling theory known as ‘feedback via the beam’ or ‘signal shielding’ is introduced. Although this refinement will change the previous results by at most a factor of 2, the change of the beam signals when the cooling loop is closed/opened has become an important diagnostics tool. The effect on transverse cooling is explained and then a generalisation is presented to include the longitudinal case.