  Cornell's electron/positron storage ring (CESR) was modified over a series of
accelerator shutdowns beginning in May 2008, which substantially improves its
capability for research and development for particle accelerators. CESR's
energy span from 1.8 to 5.6 GeV with both electrons and positrons makes it
ideal for the study of a wide spectrum of accelerator physics issues and
instrumentation related to present light sources and future lepton damping
rings. Additionally a number of these are also relevant for the beam physics of
proton accelerators. This paper, the second in a series of four, discusses the
modifications of the vacuum system necessary for the conversion of CESR to the
test accelerator, CesrTA, enhanced to study such subjects as low emittance
tuning methods, electron cloud (EC) effects, intra-beam scattering, fast ion
instabilities as well as general improvements to beam instrumentation. A
separate paper describes the vacuum system modifications of the superconducting
wigglers to accommodate the diagnostic instrumentation for the study of EC
behavior within wigglers. While the initial studies of CesrTA focussed on
questions related to the International Linear Collider (ILC) damping ring
design, CesrTA is a very flexible storage ring, capable of studying a wide
range of accelerator physics and instrumentation questions.
