ANL, Argonne, Illinois, USA
SLAC, Menlo Park, California, USA
MAX IV Laboratory, Lund University, Lund, Sweden
LBNL, Berkeley, California, USA
With the recent success in commissioning of MAX IV, the multi-bend achromat (MBA) lattice has begun to deliver on its promise to usher in a new generation of higher-brightness synchrotron light sources. In this paper, we begin by reviewing the challenges, recent success, and lessons learned of the MAX-IV project. Drawing on these lessons, we then describe the physics challenges in even more ambitious rings and how these can be met. In addition, we touch on engineering issues and choices that are tightly linked with the physics design.
ANL, Argonne, Illinois, USA
ANL, Argonne, Illinois, USA
he Advanced Photon Source (APS) is pursuing an upgrade to the storage ring to a hybrid seven-bend-achromat design*. The nominal design provides a natural emittance of 67 pm. By adding reverse dipole fields to several quadrupoles**, we can reduce the natural emittance to 41 pm while simultaneously providing more optimal beta functions in the insertion devices. The improved emittance results from a combination of increased energy loss per turn and a change in the damping partition. At the same time, the nonlinear dynamics performance is very similar, thanks in part to increased dispersion in the sextupoles. This paper describes the properties, optimization, and performance of the new lattice.
* L. Farvacque et al., IPAC13, 79 (2013).
** J.P. Delahaye \em et al., PAC89, 1611 (1990); A. Streun, NIM A 737, 148 (2014).
ANL, Argonne, Illinois, USA
The proposed upgrade of the Advanced Photon Source (APS) to a multibend achromat lattice relies on the use of swap-out injection to accommodate the small dynamic acceptance, allow use of unusual insertion devices, and minimize collective effects at high single-bunch charge. This, combined with the short beam lifetime, will make injector reliability even more important than it is for top-up operation. We used historical data for the APS injector complex to obtain probability distributions for injector up-time and down-time durations. Using these distributions, we simulated several years of swap-out operation for the upgraded lattice for several operating modes. The results indicate that obtaining very high availability of beam in the storage ring will require improvements to injector reliability.
ANL, Argonne, Illinois, USA
BNL, Upton, Long Island, New York, USA
The Advanced Photon Source has proposed an upgrade to a multi-bend achromat (MBA) with a proposed timing mode calls for 48 bunches of 15 nC each. In this mode of operation we find that phase space mismatch from the booster can drive large wakefields that in turn may limit the current below that of the nominal collective instability threshold. We show that collective effects at injection lead to emittance growth that makes usual off-axis accumulation very challenging. On-axis injection ameliorates many of these issues, but we find that transverse feedback is still required. We explore the role of impedance, feedback, and phase-space mismatch on transverse instabilities at injection.
ANL, Argonne, Illinois, USA
BNL, Upton, Long Island, New York, USA
The Advanced Photon Source (APS) at Argonne National Laboratory (ANL) is considering upgrading the current double-bend, 7-GeV, 3rd generation storage ring to a 6-GeV, 4th generation storage ring with a Multibend Achromat (MBA) lattice. In this study, a novel method is proposed to determine fabrication and assembly tolerances through a combination of magnetic and mechanical tolerance analyses. Mechanical tolerance stackup analyses using Teamcenter Variation Analysis are carried out to determine the part and assembly level fabrication tolerances. Finite element analyses using OPERA are conducted to estimate the effect of fabrication and assembly errors on the magnetic field of a quadrupole magnet and to determine the allowable tolerances to achieve the desired magnetic performance. Finally, results of measurements in R&D quadrupole prototypes are compared with the analysis results.
ANL, Argonne, Illinois, USA
A helical superconducting undulator is planned for installation at the APS. Such an installation would be first of its kind – helical devices were never installed in synchrotron light sources before. Due to its reduced horizontal aperture, a lattice modification is required to accommodate for large horizontal oscillations during injection. We describe the lattice change details and show the new lattice experimental test results. To understand the effect of the undulator on single-particle dynamics, first, its kick maps were computed using different methods. We have found that often-used Elleaume formula* for kick maps gives wrong results for this undulator. We then used the kick maps obtained by other methods to simulate the effect of the undulator on injection and lifetime.
*P. Elleaume, EPAC 1992
ANL, Argonne, Illinois, USA
ANL, Argonne, Illinois, USA
ANL, Argonne, Illinois, USA
The proposed multi-bend achromat lattice for the Advanced Photon Source upgrade (APS-U) has a design emittance of less than 70 pm. The Touschek loss rate is high: compared with the current APS ring, which has an average beam lifetime ∼ 10 h, the simulated beam lifetime for APS-U is only ~2 h when operated in the high flux mode (I=200 mA in 48 bunches). An additional consequence of the short lifetime is that injection must be more frequent, which provides another potential source of particle loss. In order to provide information for the radiation shielding system evaluation and to avoid particle loss in sensitive locations around the ring (for example, insertion device straight sections), simulations of the detailed beam loss distribution have been performed. Several possible collimation configurations have been simulated and compared.
RadiaBeam, Santa Monica, California, USA
ANL, Argonne, Illinois, USA
WBFB, Berlin, Germany
Pulsar Physics, Eindhoven, The Netherlands
Design features and experimental results are presented for a sub-mm wave source [1] based on APS RF thermionic electron gun. The setup includes compact alpha-magnet, quadrupoles, sub-mm-wave radiators, and THz optics. The sub-THz radiator is a planar, oversized structure with gratings. Source upgrade for generation frequencies above 1 THz is discussed. The THz radiator will use a short-period undulator having 1 T field amplitude, ~20 cm length, and integrated with a low-loss oversized waveguide. Both radiators are integrated with a miniature horn antenna and a small ~90°-degree in-vacuum bending magnet. The electron beamline is designed to operate different modes including conversion to a flat beam interacting efficiently with the radiator. The source can be used for cancer diagnostics, surface defectoscopy, and non-destructive testing. Sub-THz experiment demonstrated a good potential of a robust, table-top system for generation of a narrow bandwidth THz radiation. This setup can be considered as a prototype of a compact, laser-free, flexible source capable of generation of long trains of Sub-THz and THz pulses with repetition rates not available with laser-driven sources.
[1] A. V. Smirnov, R. Agustsson, W. J. Berg et al., Phys. Rev. ST Accel. Beams 18, 090703(2015)
ANL, Argonne, Illinois, USA
The proposed upgrade of the Advanced Photon Source (APS) to a multibend-achromat lattice requires shorter and much stronger quadrupole magnets than are present in the existing ring. This results in longitudinal gradient profiles that differ significantly from a hard-edge model. Additionally, the lattice assumes the use of five-segment longitudinal gradient dipoles. Under these circumstances, the effects of fringe fields and detailed field distributions are of interest. We evaluated the effect of soft-edge fringe fields on the linear optics and chromaticity, finding that compensation for these effects is readily accomplished. In addition, we evaluated the reliability of standard methods of simulating hard-edge nonlinear fringe effects in quadrupoles.
ANL, Argonne, Illinois, USA
The Advanced Photon Source is in the process of developing an upgrade (APS-U) of the storage ring from a double-bend to a multi-bend lattice. A swap-out injection is planned for the APS-U lattice to keep a constant beam current and accommodate small, dynamic aperture. A septum magnet that has a minimum thickness of 2 mm with an injection field of 1.06 T has been designed. The stored beam chamber has an 8 mm x 6 mm super-ellipsoidal aperture. The required total deflecting angle is 89 mrad with a ring energy of 6 GeV. The magnet is straight, but is tilted in yaw, roll, and pitch from the stored beam chamber in order to meet the swap out injection requirements for the APS-U lattice. In order to minimize the leakage field inside the stored beam chamber, four different techniques were utilized in the design. As a result, the horizontal deflecting angle of the stored beam was held to only 5 μrad, and the integrated skew quadrupole inside the stored beam chamber was held to 0.09 T. The detailed techniques that were applied to the design, the field multipoles, and the resulting trajectories of the injected and stored beams are reported.
Private Address, Westmont, USA