  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
appropriate 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 last in a series of four, describes the
vacuum system modifications of the superconducting wigglers to accommodate the
diagnostic instrumentation for the study of electron cloud (EC) behavior within
wigglers. Earlier papers provided an overview of the accelerator physics
program, the general modifications of CESR, 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, EC effects,
intra-beam scattering, fast ion instabilities as well as general improvements
to beam instrumentation. While the initial studies of CesrTA focussed on
questions related to the International Linear Collider damping ring design,
CESR is a very versatile storage ring, capable of studying a wide range of
accelerator physics and instrumentation questions.
