ANL, Argonne, Ilinois, USA
The proposed Advanced Photon Source (APS) multi-bend achromat (MBA) lattice includes a passive bunch-lengthening cavity to alleviate lifetime and emittance concerns. Feedback in the main radio-frequency (rf) system affects the overall impedance presented to the beam in this double rf system. To aid beam stability studies, a realistic model of rf feedback has been developed and implemented in elegant and Pelegant.
ANL, Argonne, Ilinois, USA
The Advanced Photon Source (APS) multi-bend achromat (MBA) lattice will require a bunch-lengthening cavity to decrease the effects of Touschek scattering on the beam lifetime and of intrabeam scattering on the beam emittance. Using ELEGANT, we've performed tracking studies of a passive, i.e. beam-driven, fourth-harmonic cavity in the MBA lattice, including the predicted longitudinal impedance of the ring. The studies include an exploration of the required detuning and loaded Q of the main rf cavities and the harmonic cavity in order to stabilize the beam and achieve significant lengthening. We also studied the effects of bunch population variation and missing bunches. The computed bunch profiles are used for computation of the Touschek lifetime, verifying the beneficial effects in detail.
ANL, Argonne, Ilinois, USA
When computing gas-scattering lifetime for storage rings, it is common to use the average pressure, even though it is known that the pressure varies with location in the ring and varies differently for different gas species. In addition, other simplifications are commonly made, such as assuming that the apertures in the horizontal and vertical planes are independent and assuming that the momentum acceptance can be characterized by a single value. In this paper, we describe computation of the elastic- and bremsstrahlung-scattering lifetimes that includes species-specific gas pressure profiles computed with VACCALC and MOLFLOW. In addition, the computations make use of the detailed shape of the dynamic acceptance and the position-dependent momentum acceptance. Comparisons are made to simpler methods for the Advanced Photon Source storage ring and the multi-bend achromat upgrade lattice.
ANL, Argonne, Ilinois, USA
ELEGANT has long had the ability to model collective effects in various ways, including beam-driven cavity modes, short-range wakes, and coherent synchrotron radiation. Recently, we made improvements specifically targeting simulations that require multiple bunches in storage rings. The ability to simulate long-range, non-resonant wakes was added, which can be used for example to study the effect of the resistive wall wake and multibunch instabilities. We also improved the implementation of short-range and resonant wakes to make them more efficient for multibunch simulations. Finally, improvements in the parallel efficiency were made that allow taking advantage of larger parallel resources.
ANL, Argonne, Ilinois, USA
A hybrid seven-bend-achromat lattice has been proposed for the APS upgrade that will feature very strong focusing elements and relatively small vacuum chamber. Achieving design lattice parameters during commissioning will need to be accomplished in a short period of time to minimize dark time for APS users. We describe here start-to-end simulation of the machine commissioning beginning from first-turn trajectory correction, performing orbit and lattice correction, and finally evaluating nonlinear performance of the corrected lattice in terms of dynamic aperture and lifetime.
ANL, Argonne, Ilinois, USA
Both intra-beam scattering (IBS) and the Touschek effect become prominent for multi-bend-achromat- (MBA-) based ultra-low-emittance storage rings. To mitigate the transverse emittance degradation and obtain a reasonably long beam lifetime, a higher harmonic rf cavity (HHC) is often proposed to lengthen the bunch. The use of such a cavity results in a non-gaussian longitudinal distribution. However, common methods for computing IBS and Touschek scattering assume Gaussian distributions. Modifications have been made to several simulation codes that are part of the {\tt elegant} toolkit to allow these computations for arbitrary longitudinal distributions. After describing these modifications, we review the results of detailed simulations for the proposed hybrid seven-bend-achromat (H7BA) upgrade lattice for the Advanced Photon Source.
Tech-X, Boulder, Colorado, USA
Sierra Nevada Corporation, Centennial, USA
ANL, Argonne, Illinois, USA
Efficient implementation of general-purpose particle tracking on GPUs can bring significant performance benefits to large-scale tracking simulations and direct (tracking-based) accelerator optimization techniques. This presentation is an update on the current status of our work on accelerating Argonne National Lab’s particle accelerator simulation code ELEGANT [*] using CUDA-enabled GPU. We summarize the performance of beamline elements ported to GPU, and discuss optimization techniques for some important collective effects kernels. We also outline briefly our testing and code validation infrastructure within ELEGANT and present the latest results of scaling studies with realistic lattices of the GPU-accelerated version of the code.
* M. Borland, ‘‘elegant: A Flexible SDDS-compliant Code for Accelerator Simulation", APS LS-287, September 2000
ANL, Argonne, Ilinois, USA
A hybrid seven-bend-achromat lattice has been designed for the APS upgrade. We describe the design goals, constraints, and methodology, including the choice of beam energy. Magnet strength and spacing is compatible with engineering designs for the magnets, diagnostics, and vacuum system. Dynamic acceptance and local momentum acceptance were simulated using realistic errors, then used to assess workable injection methods and predict beam lifetime. Predicted brightness is two to three orders of magnitude higher than the existing APS storage ring. Pointers are provided to other papers in this conference that cover subjects in more detail.
ANL, Argonne, Illinois, USA
Multi-bunch stability simulations were done for the very-low-emittance hybrid seven-bend-achromat (H7BA) lattice proposed for the Advanced Photon Source (APS) upgrade. The simulations, performed using tracking code elegant, were meant to determine whether the long-term wakefields of the higher-order modes (HOMs) of the main 352-MHz cavities will produce an instability. The multi-particle simulations include the important effects of the Higher-Harmonic Cavity (HHC) and the longitudinal impedance of the new vacuum chamber. These realistic simulations show that the HHC provides additional damping in the form of the Landau damping. Still, the HOMs may likely produce a multi-bunch instability which can be cured with more effective HOM damping or a longitudinal feedback system.
ANL, Argonne, Ilinois, USA
A 67-pm hybrid-seven-bend achromat (H7BA) lattice is proposed for a future Advanced Photon Source (APS) multi-bend-achromat (MBA) upgrade. This lattice requires use of a swap-out (on-axis) injection scheme. Alternate lattice design work has also been performed to achieve better beam dynamics performance than the nominal APS MBA lattice, in order to allow beam accumulation. One of such alternate H7BA lattice designs, which still targets a very low emittance of 76 pm, is discussed in this paper. With these lattices, existing APS injector complex can be employed without the requirement of a very high charge operation. Studies show that an emittance below 76 pm can be achieved with the employment of reverse bends in an alternate lattice. We discuss the predicted performance and requirements for these lattices and compare them to the nominal lattice.
ANL, Argonne, Illinois, USA
The APS MBA (multi-bend achromat) upgrade storage ring will employ a “swap out” injection scheme and requires a single-bunch beam with up to 20 nC from the injector. The APS injector, which consists of a 450-MeV linac, a particle accumulator ring (PAR), and a 7-GeV synchrotron (Booster), was originally designed to provide up to 6 nC of beam charge. High charge injector study is part of the APS upgrade R&D that explores the capabilities and limitations of the injector through machine studies and simulations, and identifies necessary upgrades in order to meet the requirements of the MBA upgrade. In the past year we performed PAR and booster high charge studies, implemented new ramp correction of the booster rap supplies, explored non-linear chromatic correction of the booster, etc. This report presents the results and findings.
ANL, Argonne, Ilinois, USA
DLS, Oxfordshire, United Kingdom
CLS, Saskatoon, Saskatchewan, Canada
HZB, Berlin, Germany
SOLEIL, Gif-sur-Yvette, France
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
SLAC, Menlo Park, California, USA
PAL, Pohang, Kyungbuk, Republic of Korea
SINAP, Shanghai, People's Republic of China
The Advanced Photon Source and other existing storage ring light sources are contemplating replacing an existing, operating storage ring with a multi-bend achromat lattice. One issue is that existing light sources have large user communities who are greatly inconvenienced by extended shutdowns. Hence, there will be a premium placed on rapid commissioning of the new lattice. To better understand the possibilities, we undertook a survey of recent commissioning experience at third-generation light sources. We present a summary of that survey here.
