Pressure bump in cooling section

The pressure bump phenomenon, the beam induced pressure rise, was considered for the 10m long cooling section. For a proton storage ring, this effect is caused by residual gas ions being accelerated into the vacuum chamber wall by the electrostatic potential of the stored beam. This liberates molecules from the chamber wall and causes a runaway local pressure rise which destroys the beam. Calculations of the critical storage ring current are shown. The implication is that to operate the cooling region with 26A of electrons, the desorption coefficient (the number of molecules released/incident charged particle created by ionization and striking the chamber surface) has to be less than one, and preferrable less than zero. Further study of desorption coefficient of accelerator materials is recommended