  In a beam cycle, there is a chicane bump (BC bump) in the injection region of
China Spallation Neutron Source (CSNS). It is a core part of the injection
system and the important guarantee that the Linac beam injecting into the rapid
cycling synchrotron (RCS). During the beam commissioning, the residual orbit of
BC bump, i.e. the closedorbit distortion (COD) due to the imperfect BC bump,
was an important problem which can affect the orbit correction and beam loss
control of the RCS. In this paper, a method to measure the residual orbit of BC
bump was studied and given. By using the three auxiliary powers of BC magnets,
a method to correct the residual orbit of BC bump was developed. The numerical
simulation results showed that the measurement and correction methods had
worked well and they can be applied to the beam commissioning of CSNS/RCS. The
measurement results in the machine study showed that the residual orbit of BC
bump is not large and can be corrected by the three auxiliary powers of BC
magnets.

Accelerator Physics