Residual orbit of BC bump for CSNS/RCS

BackgroundIn a beam cycle, there is a chicane bump (BC bump) in the injection region of the 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 closed-orbit 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.
PurposeThe purpose is to develop a suitable method to judge and correct the residual orbit of BC bump.
MethodsAccording to the physics design, there is no residual orbit of BC bump in theory. However, if the residual orbit of BC bump exists in the actual operation, the circular beam orbit outside the injection region would be affected. By comparing the circular beam orbit outside the BC bump region in theory and that is measured in the actual operation, whether the residual orbit of BC bump exists can be judged. By using the three auxiliary windings of BC magnets, the residual orbit of BC bump can be corrected.
ResultsThe 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 reduced by the three auxiliary windings of BC magnets.
ConclusionThe methods to judge and correct the residual orbit of BC bump worked well and had been applied to the beam commissioning of CSNS/RCS.