Resonant Slow Extraction in Synchrotrons by Using Anti-symmetric Sextupole Fields

Abstract

This paper proposes a novel method for resonant slow extraction in synchrotrons by using special antisymmetric sextupole field, which can be produced by a special magnet structure and was proposed earlier [1]. The method has the potential in applications asking for very stable slow extraction from synchrotrons. Our studies show that the slow extraction at the half-integer resonance by using anti-symmetric sextupole field has some advantages compared to the normal sextupole field which is used in the usual third-order resonant extraction method. One of them is that it can work at a more distant tune from the resonance, so that it can weaken significantly the problem of the intensity variation of the extracted beam mainly caused by the ripples of magnet power supplies. The studies by both Hamiltonian theory and numerical simulations show that the stable region at the proximity of the half-integer resonance by antisymmetric sextupole field is much smaller and flatter than the one by standard sextupole field at the third-order resonance, and the particles outside the region will be driven out in two possible directions in quite short transit time but with spiral steps similar as in the third-order resonance extraction. By gradually increasing the field strength, the beam can be extracted in a more homogeneous intensity than the usual third-order resonant method, in the means of both smaller intensity variation and spike in the beginning spill.