ANL, Argonne, Illinois, USA
For next-generation storage ring light sources, such as the Advanced Photon Source (APS) Multi-Bend Achromat (MBA) upgrade, the strong nonlinearities introduced by the strong chromaticity sextupoles plus the small physical apertures make it challenging to achieve large dynamic acceptance (DA) and long Touschek lifetime, even when using the on-axis swap-out injection scheme. Several different methods have been explored for nonlinear dynamics optimization. The optimization objectives variously include the chromaticities up to third order, resonance driving and detuning terms, on- and off-momentum dynamic acceptance, chromatic and geometric tune footprint, local momentum acceptance (LMA), variation of betatron oscillation invariant, Touschek lifetime, etc. In addition, optimization can be performed without errors, with selected random errors, and with sets of errors that reflect post-commissioning conditions. In this paper, these different optimization methods are compared for the nonlinear beam dynamics performance of the Advanced Photon Source upgrade (APS-U) lattice, in terms of the dynamic acceptance, local momentum acceptance, and other performance measures. The impact from different error sources is also studied.
ANL, Argonne, Illinois, USA
On-axis swap-out injection was chosen for the Advanced Photon Source Upgrade (APS-U) to allow pushing the beam emittance to an extremely low value. The injection section configuration was optimized within a multi-dimensional parameter space and made consistent with up-to-date technical developments. The booster-to-storage ring (BTS) transport line was designed to bring the electron beam from the existing Booster to the new storage ring (SR). Due to various limitations, this new BTS line is twisted both horizontally and vertically when approaching the injection point, which introduces challenges in both geometrical and optical matching. This paper presents our simple solution to these issues. The coupling effect caused by the twisted BTS line is also discussed.
ANL, Argonne, Illinois, USA
The Advanced Photon Source (APS) is pursuing an upgrade of the storage ring to a hybrid seven-bend-achromat* design, which will operate in swap-out mode. The ultra-low emittance (about 30 pm in both planes) combined with the desire to provide high charge (15 nC) in individual bunches, entails very high energy density in the beam. Simple estimates, confirmed by simulation, indicate that interaction of such a bunch with the dump material will result in localized melting. Over time, it is possible that the beam would drill through the dump and vent the ring vacuum. This would seem to prevent extraction and dumping of bunches as part of swap out, and also suggests that transferring of bunches out of the ring carries significant risk. We devised an idea for using a pre-kicker to cause decoherence of the target bunch emittances, making it safe to extract. Simulations show that the concept works very well.
*L. Farvacque et al., IPAC13, 79 (2013).
ANL, Argonne, Illinois, USA
A fast beam interlock system for the Advanced Photon Source (APS) Particle Accumulator Ring (PAR) based on the detection of Cerenkov light is proposed for high-charge operations associated with the APS Upgrade (APS-U). Light is generated from lost electrons passing through high-purity, fused-silica fiber optic cable. The cable acts as both radiator and light pipe to a Pb-shielded photomultiplier tube. Results from a prototype installation along the PAR south wall have shown excellent sensitivity, linearity, and reproducibility after 10,000 hours of operation to date with little change in the optical transmission of the fiber. High sensitivity allows more accurate measurement of low-level loss than possible with current monitors. The radiator and detector provide a much faster response than the installed gamma or neutron detectors. A faster, more accurate response to electron loss will be important as we run with higher charge and consider operating at increased energy for APS-U. Initial calibration measurements of the prototype system with radiation monitors for various loss scenarios are discussed. Comparison of the scenarios with simulations are presented.
ANL, Argonne, Illinois, USA
BNL, Upton, Long Island, New York, USA
