Dependence of loss rate of electrons due to elastic gas scattering on the shape of the vacuum chamber

• Shape factors which depends on shape and size of vacuum chamber are discussed.
• Shape factor derived as function of longitudinal position for electron storage ring.
• Estimated loss rate of electrons in Indus-2 with measured vacuum pressure and shape factor.
• Derived shape factor required when large variation in vacuum pressure along beam path.

The loss rate of electrons of stored electron beam due to elastic scattering with the nuclei of residual gas atoms in an electron storage ring depends upon the shape factor which is governed by the shape and size of vacuum chamber. As the vacuum pressure along the circumference of storage ring is normally not uniform so the shape factor as a function of longitudinal position is required to be known. In this paper, expressions for the shape factor for a rectangular and an elliptical vacuum chamber as a function of longitudinal position along the circumference in a storage ring are derived and applied for the estimation of shape factor in Indus-2 storage ring. Using measured vacuum pressure and shape factor along the longitudinal position, the beam loss rate in Indus-2 due to elastic gas scattering with residual gas atoms considering rectangular and elliptical shape of vacuum chamber are also reported.