Imperfection and vertical intrinsic depolarizing resonances have been overcome by the two partial Siberian snakes in the Alternative Gradient Synchrotron(AGS). The relatively weak but numerous horizontal resonances are the main source of polarization loss in the AGS. A pair of horizontal tune jump quads have been used to overcome these weak resonances. The locations of the two quads have to be chosen such that the disturbance to the beam optics is minimum. The emittance growth has to be mitigated for this method to work. In addition, this technique needs very accurate jump timing. Using two partial Siberian snakes, with vertical tune inside the spin tune gap and 80% polarization at AGS injection, polarized proton beam had reached [Formula: see text] proton per bunch with 65% polarization. With the tune jump timing optimized and emittance preserved, more than 70% polarization with 2[Formula: see text] protons per bunch has been achieved.
Optimal beam optics in the TTF-FEL bunch compression sections: minimizing the emittance growth
