A Concept For Cancelling The Leakage Field Inside The Stored Beam Chamber Of A Septum Magnet

TL;DR

This paper presents a novel septum magnet design for the APS-U upgrade that effectively cancels leakage fields inside the stored beam chamber, reducing beam deflection and minimizing unwanted magnetic effects.

Contribution

A new concept for leakage field cancellation inside the stored beam chamber of a septum magnet is introduced, improving beam stability and injection efficiency in the APS-U upgrade.

Findings

Leakage field inside the chamber was reduced to below 1 micro-rad.

The septum magnet deflects the injected beam by 89 mrad at 6 GeV.

The design minimizes skew quadrupole and sextupole fields inside the chamber.

Abstract

The Advanced Photon Source is in the process of up-grading its storage ring from a double-bend to a multi-bend lattice as part of the APS Upgrade Project (APS-U). A swap-out injection scheme is planned for the APS-U to keep a constant beam current and to enable a small dynamic aperture. A novel concept that cancels out the effect of leakage field inside the stored beam chamber was introduced in the design of the septum magnet. As a result, the horizontal deflecting angle of the stored beam was reduced to below 1 micro-rad with a 2 mm septum thick-ness and 1.06T normal injection field. The concept helped to minimize the integrated skew quadrupole field and normal sextupole fields inside stored beam chamber as well. The designed septum magnet deflects the injected electron beam by 89 mrad with a ring energy of 6 GeV. The stored beam chamber has an 8 mm x 6 mm super-ellipsoidal aperture. The magnet is straight; however, it is tilted in yaw, roll, and pitch from the stored beam cham-ber to meet the on axis swap out injection requirements for the APS-U lattice.