Background

2

The dynamic field integral means the integrated magnetic field along the electron's trajectory in undulator

which will cause the tune shift

dynamic aperture reduction and beam lifetime shortening

etc.

The effect is inversely proportional to the square of the electron energy and the filed transverse roll-off. The field of the APPLE-Ⅱ type Elliptical Polarization Undulator (EPU) has a very fast

intrinsic

transverse roll-off

especially for the vertical polarization mode

creating significant dynamic field integral effect to the beam motion. The research on the dynamic field integral effect of APPLE-Ⅱ type EPU and the corresponding magnetic field shimming method is the hotspot in the field of international particle accelerator.

Purpose

2

The principle of "L-Shimming" method to reduce dynamic field integral effect for APPLE-Ⅱ type EPU is stated in this paper. Methods: The optimization design of "L-Shimming" for EPU148 dynamic field integral effect has been done with "RADIA Code".

Results

2

The measurement results of flipping coil indicate that the magnetic field strength measured is coincident with the simulation result

and the error is less than 10% of the maximum shimming quantity. After shimming

the dynamic field integral effect of EPU148 will reduce an order of magnitude. The machine study has been done after EPU148 is installed in SSRF storage ring with the tune shift less than 0.001

and the beam injection efficiency has almost not been influenced with EPU148 in all operation polarization modes and all operation gaps.

Conclusion

2

It is proved that the shimming to reduce EPU148 dynamic field integral effect is successful.