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The Advanced Photon Source (APS) particle accumulator ring (PAR) was designed to accumulate linac pulses into a single bunch using a fundamental radio frequency (rf) system, and longitudinally compress the beam using a harmonic rf system prior to injection into the booster. The APS Upgrade injectors will need to supply full-current bunch replacement with high single-bunch charge for swap-out injection in the new storage ring. Significant bunch lengthening is observed in the PAR at high charge, which negatively affects beam capture in the booster. Predictions showed that the bunch length could be compressed to better match the booster acceptance using a combination of higher beam energy and higher harmonic gap voltage. A new 10-kW harmonic rf solid-state amplifier (SSA) was installed in 2021 to raise the gap voltage and improve bunch compression. The SSA has been operating reliably. Initial results show that the charge-dependent bunch lengthening in PAR with higher gap voltage agrees qualitatively with predictions. A tool was written to automate bunch length data acquisition. Future plans to increase the beam energy, which makes the SSA more effective, will also be summarized., Proceedings of the 5th North American Particle Accelerator Conference, NAPAC2022, Albuquerque, NM, USA

It is well known that the efficiency of an advanced control algorithm like machine learning is as good as its data quality. Much recent progress in technology enables the massive data acquisition from a control system of modern particle accelerator, and the wide use of embedded controllers, like field-programmable gate arrays (FPGA), provides an opportunity to collect fast data from technical subsystems for monitoring, statistics, diagnostics or fault recording. To improve the data quality, at the APS Upgrade project, a general-purpose data acquisition (DAQ) system is under active development. The APS-U DAQ system collects high-quality fast data from underneath embedded controllers, especially the FPGAs, with the manner of time-correlation and synchronously sampling, which could be used for commissioning, performance monitoring, troubleshooting, and early fault detection, etc. This paper presents the design and latest progress of APS-U high-performance DAQ infrastructure, as well as its preparation to enable the use of machine learning technology for APS-U, and its use cases at APS., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

The APS-Upgrade presents several challenging demands to the booster synchrotron. Swap-out injection requires the booster to capture a high charge bunch (up to 17 nC), accelerate it to 6 GeV, and maintain a low emittance at extraction for injection into the storage ring. To accommodate these conflicting demands, the RF frequency will be ramped between injection and extraction. However, the RF cavity tuners will remain static, which means the couplers will need to withstand a high reflected power at extraction. This paper presents a plan for a system that will meet the requirements for injection efficiency, extracted emittance, and equivalent power at the coupler. Results from tracking simulations and beam studies with a frequency ramp will also be shown., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

The modern and state-of-the-art technology provides great potential to acquire accelerator high speed data, and the possibility to fine tune the particle beam. The widely use of embedded controllers, like field-programmable gate arrays (FPGA, enriches the opportunity to collect fast data from accelerator technical subsystem, for example diagnostics and low-level radiofrequency (LLRF) for monitoring, statistics, diagnostics or fault recording of like. A modern embedded controller may contain several gigabytes of memory for such purposes. This presents a number of challenges related to data acquisition and data management to collect, transfer, manage, and utilize a large amount of data from numerous controllers. Currently at APS Upgrade project, a general purpose DAQ system is under active development, which interfaces with a number of technical subsystems to provide time-correlated and synchronously sampled data acquisition for commissioning, performance monitoring, troubleshooting and early fault detection. This paper will present the status and progress of APS-U general purpose DAQ system, and its use cases at APS-U project., Proceedings of the 9th International Beam Instrumentation Conference, IBIC2020, Santos, Brazil

APS Upgrade multi-bend achromat accelerator (MBA) uses state-of-the-art embedded controllers coupled to various technical subsystems. These controllers have the capability to collect large amounts of fast data for statistics, diagnostics, or fault recording. At times, continuous real-time acquisition of this data is preferred, which presents a number of challenges that must be considered early on in the design; such as network architecture, data management and storage, real-time processing, and impact on normal operations. The design goal is selectable acquisition of turn-by-turn BPM data, together with additional fast diagnostics data. In this paper we discuss engineering specifications and the design of the MBA Data Acquisition System (DAQ). This system will interface with several technical subsystems to provide time-correlated and synchronously sampled data acquisition for commissioning, troubleshooting, performance monitoring and fault detection. Since most of these subsystems will be new designs for the MBA, defining the functionality and interfaces to the DAQ early in the development will ensure the necessary components are included in a consistent and systematic way., Proceedings of the 17th International Conference on Accelerator and Large Experimental Physics Control Systems, ICALEPCS2019, New York, NY, USA

Next-generation, high-performance storage ring light sources based on multibend achromat optics will require on-axis injection because of the extremely small dynamic aperture. Injectors will need to supply full-current bunch replacement in the ring with high single-bunch charge for swap-out. For upgrades of existing light sources, such as the Advanced Photon Source Upgrade (APS-U), it is economical to retain the existing injector infrastructure and make appropriate improvements. The challenges to these improvements include achieving high single-bunch charge in the presence of instabilities, beam loading, charge stability and reliability. In this paper, we discuss the rationale for the injector upgrades chosen for APS-U, as well as backup and potential alternate schemes. To date, we have achieved single-bunch charge from the injectors that doubles the original design value, and have a goal to achieve about three times the original design value., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

Stable operation of a modern high current storage rings requires attention to the sources of coupling impedance. Methods ranging from EM modeling to bench and beam measurements are routinely used to characterize accelerator components. The beam-based method presented here complements existing approaches, and allows precise measurements and identification of narrowband resonances in structures such as RF cavities or in-vacuum undulators. We combine the well-established approach of characterizing eigenvalues of coupled-bunch instabilities with modern high-throughput data acquisition tools and automatic analysis methods. By sequentially exciting low-amplitude oscillation of individual modes below the instability threshold and observing open-loop damping, we automatically map the eigenvalues of all even-fill eigenmodes. Repeating the measurements while changing operating conditions, such as cavity temperatures or undulator gaps, provides a detailed mapping of the impedance source. These measurements are used to extract impedance parameters as well as to optimize accelerator settings. Experimental results from the Advanced Photon Source and other accelerators illustrate the technique., Proceedings of the 6th Int. Beam Instrumentation Conf., IBIC2017, Grand Rapids, MI, USA

After decades of successful operation as a 7-GeV synchrotron radiation source, the Advanced Photon Source is pursing a major upgrade that involves replacement of the storage ring with an ultra-low emittance multi-bend achromat design. Using a seven-bend hybrid multi-bend achromat with reverse bending magnets gives a natural emittance of 42 pm operated at 6 GeV. The x-ray brightness is predicted to increase by more than two orders of magnitude. Challenges are many, but appear manageable based on thorough simulation and in light of the experience gained from world-wide operation of 3^{\}text{rd}-generation light sources. The upgraded ring will operate in swap-out mode, which has allowed pushing the performance beyond the limits imposed by conventional operation., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

The APS-U 6-GeV MBA storage ring will have 42 pm beam emittance and relatively tight acceptance. This requires limiting the beam emittance out of the Booster synchrotron which is achieved by operating the Booster off-momentum, thus manipulating the damping partitions. However, the much higher charge for the APS-U strongly favors injecting on momentum into the Booster for maximum acceptance. An rf-frequency ramping scheme is proposed to allow injecting on momentum and then moving the beam off momentum. The ramp is adjusted from cycle to cycle to vary the total time taken by the beam from injection to extraction, thus aligning the Booster bunch with any chosen MBA storage ring bucket. The two rf systems will not be locked at any time of the cycle. The proposed scheme is compatible with the existing synchronization of the APS injector cycle to the 60-Hz line voltage which induces a variation in the start time of the acceleration cycle. The scheme removes the need to realign the Booster ring for total path length while optimizing its operation for high charge acceleration. A ferrite tuner is being considered for dynamic tuning of the rf cavities., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

The booster synchrotron for the APS-U is being upgraded to accommodate high-charge bunches, up to 20 nC, for extraction into the MBA lattice. The booster is required to operate at 85% efficiency in order to achieve bunch swap-out into the storage ring. In order to compensate for significant beam-loading effects as well as support a frequency ramp to achieve higher efficiency, a ferrite tuner is being considered to dynamically adjust the cavity frequency. A tuner design will be presented that spans 60 kHz and utilizes a low-loss YIG garnet similar to that used in the Recycler Ring at Fermilab., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

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., Proceedings of the North American Particle Accelerator Conf., NAPAC2016, Chicago, IL, USA

Next-generation storage ring light sources promise dramatically lower emittance due to the use of multi-bend achromat (MBA) lattices. The strong magnets required for such lattices entail small magnet and vacuum bores, which increases concerns about collective instabilities. In this paper, we describe detailed simulations undertaken for the APS MBA lattice using the parallel version of ELEGANT. The simulations include short- and long-range geometric and resistive wakes, a beam-loaded main rf system including feedback, a passive harmonic bunch-lengthening cavity, higher-order cavity modes, and bunch-by-bunch feedback. Applications include insight into transients during filling, effects of missing bunches, evaluation of non-uniform fill patterns, and determination of feedback system requirements., Proceedings of the 12th Int. Computational Accelerator Physics Conf., ICAP2015, Shanghai, China

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., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, 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., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA

A higher-harmonic cavity is planned for the proposed Advanced Photon Source (APS) multi-bend achromat (MBA) lattice to increase the bunch length, improve the Touschek lifetime and increase the single-bunch current limit. We have investigated a range of options including 3rd, 4th, and 5th harmonics of the main radio frequency (RF) system, as well as configurations with and without external RF power couplers. The current baseline is a single 4th harmonic superconducting cavity with adjustable RF couplers and a slow tuner which provide the flexibility to operate over a wide range of beam currents. The cavity is designed to provide 0.84 MV at 1408 MHz for the nominal 6 GeV, 200 mA electron beam, and 4.1 MV main RF voltage. In this paper, we discuss the harmonic cavity parameters based on analytical calculations of the equilibrium bunch distribution and make comparisons to other options., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, 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., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA