ANL, Argonne, Illinois, USA
Fast fiber-optic (FFO) beam loss monitors (BLMs) installed with the first two superconducting undulators (SCUs) in the Advanced Photon Source storage ring have proven to be a useful diagnostic for measuring deposited charge (energy) during rapid beam loss events. The first set of FFOBLMs were installed outside the cryostat of the short SCU, a 0.33-m long device, above and below the beam centerline. The second set are mounted with the first 1.1-m-long SCU within the cryostat, on the outboard and inboard sides of the vacuum chamber. The next 1.1-m-long SCU is scheduled to replace the short SCU later in 2016 and will be fitted with FFOBLMs in a manner similar to original 1.1-m device. The FFOBLMs were employed to set timing and voltage for the abort kicker (AK) system. The AK helps to prevent quenching of the SCUs during beam dumps* by directing the beam away from the SC magnet windings. The AK is triggered by the Machine Protection System (MPS). In cases when the AK fails to prevent quenching, the FFOBLMs show that losses often begin before detection by the MPS.
K. Harkay et al., these proceedings
ANL, Argonne, Illinois, USA
A MatLab program has been created to investigate off-orbit ray tracing possibilities for the APS-Upgrade stor-age ring vacuum system design. The goals for the pro-gram include calculating worst case thermal loading conditions and finding minimum shielding heights for photon absorbers. The program computes the deviation possibilities of synchrotron radiation rays emitted along bending magnet paths using discretized local phase space ellipses. The sizes of the ellipses are computed based on multi-bend achromat (MBA) lattice parameters and the limiting aperture size within the future storage ring vacuum system. For absorber height calculations, rays are projected from each point in the discretized ellipse to the locations of downstream absorbers. The absorber heights are mini-mized while protecting downstream components from all possible rays. For heat loads, rays are projected until they hit a vacuum chamber wall. The area and linear power densities are calculated based on a ray's distance trav-elled and striking incidence angle. A set of worse case local heat loads is collected revealing a maximum condi-tion that each vacuum component must be designed to withstand.
ANL, Argonne, Illinois, USA
ANL, Argonne, Illinois, USA
A beam abort system has been implemented in the Advanced Photon Source storage ring. The abort system works in tandem with the existing machine protection system (MPS), and its purpose is to control the beam loss location and, thereby, minimize beam loss-induced quenches at the two superconducting undulators (SCUs). The abort system consists of a dedicated horizontal kicker designed to kick out all the bunches in a few turns after being triggered by MPS. The abort system concept was developed on the basis of single- and multi-particle tracking simulations using elegant and bench measurements of the kicker pulse. Performance of the abort system–kick amplitudes and loss distributions of all bunches–was analyzed using beam position monitor (BPM) turn histories, and agrees reasonably well with the model. Beam loss locations indicated by the BPMs are consistent with the fast fiber-optic beam loss diagnostics described elsewhere [1]. Operational experience with the abort system, various issues that were encountered, limitations of the system, and quench statistics are described.
[1] J. Dooling et al., these proceedings.
ANL, Argonne, Illinois, USA
SLAC, Menlo Park, California, USA
Development of superconducting undulator (SCU) technology continues at the Advanced Photon Source (APS). Experience of building and successful operation of the first short-length, 16-mm period length superconducting undulator SCU0 paved a way for the second 1-m long, 18-mm period device, SCU1, which is in operation since May 2015. The APS SCU team has also built and tested a 1.5-m long, 21-mm period undulator as a part of LCLS SCU R&D program aiming at demonstration of SCU technology availability for free electron lasers. This undulator successfully achieved all the requirements including a phase error of 5 degree rms. Our team is currently completing one more 1-m, 18-mm period undulator that will replace the SCU0. We are also working on a helical SCU for the APS. The status of these projects will be presented.
ANL, Argonne, Illinois, USA