Armborst, F.; Goslawski, P.; Jankowiak, A.: Tune and Chromaticity Optimization at Bessy II for the Transverse Resonant Island Bucket Optics. In: Mark Boland ... [Ed.] : IPAC 2019, Proceedings of the 10th International Particle Accelerator Conference: Melbourne, Australia, 19-24 May 2019. Geneva, Switzerland: JACoW Publishing, 2019. - ISBN 978-3-95450-208-0, p. TUPGW013/1411-1414
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Transverse Resonant Island Buckets (TRIBs *) correspond to a second stable orbit, longitudinally winding around the core orbit in the transverse x-x^{?}-phasespace. The exploitation possibilities for stable TRIBs are under investigation at the third generation light source BESSY II in Berlin. The applicability for bunch separation is a main subject of these studies. Stable operation of TRIBs optics with a single or few bunches on the second orbit and a multibunch train on the main orbit has been shown **. Photons emitted on the second orbit are well separated from those of the main orbit at all beamlines. This provides the possibility of bunch separation by beamline adjustment for the timing community without significant impact on the average brightness for other users. Simulations based on linear optics from closed orbits (LOCO) and on nonlinear optics derived from the measured chromaticity and tune shift with action (TSWA) predict this separation well. Friendly user experiments in 2018 confirmed these results. The scheduled upgrade BESSY VSR *** features simultaneously stored long and short bunches. Then TRIBs optics would in principle enable the separation of the different bunches at every beamline offering unique possibilities to our users. Simulations and measurements aiming to investigate further possible optimization of the TRIBs optics are presented.