The Taiwan Photon Source (TPS) is a third-generation synchrotron light source located in Taiwan. Currently, it operates with two RF stations, each capable of delivering 300 kW of RF power. As the number of beamlines at TPS increases, more insertion devices will be installed, necessitating additional RF power. Presently, each RF station provides approximately 250 kW of power. To maintain operational margin, increasing the RF power available per station is a critical task. To address this, we have implemented a heterogeneous power combination method, where the power from solid-state power amplifiers is combined to raise the available RF power per station to 375 kW. This report describes the power combination methodology employed at one of the RF stations, high-power testing results, and the outcomes of long-term operation under combined power conditions. Future plans for power combination are also discussed in this paper.

After more than 40 years of services the 2856~MHz linac injector of The Canadian Light Source (CLS) has been retired to leave space for a new 3000.24~MHz linac injector, the frequency of which is a multiple of the 500.04~MHz CESR-B type superconductive radio frequency cavity. The new CLS linac injector has been designed and built by RI Research Instruments GmbH. The design is based on their robust S-band technology RF structures that already serve other laboratories in the USA, Australia, Taiwan, Switzerland and Sweden. In order to save money and space the CLS has replaced its six long Accelerating RF structures (3.4~m long) delivering 250~MeV electron beam by three 5~m long accelerating structures that will deliver the same beam energy. In order to do so, one RF structure is powered by one modulator-klystron and the last two RF structures received their RF power from a second modulator-klystron that passes through a SLED system. The SLED system multiplies the power by a factor 5 to 6 and is then equally split to power each structure. We are reporting on the progress of the commissioning of this new injector.

The Variable Energy Gamma (VEGA) system is under implementation in Bucharest-Magurele (Romania) as one of the major components in the project of Extreme Light Infrastructure Nuclear Physics (ELI-NP). Photon beams will be resulting from the Inverse Compton Scattering of laser photons off relativistic electrons. VEGA is dedicated for photonuclear research both in applied and fundamental physics and will be open for worldwide users. The RF and synch system has to ensure stable, synchronized and coherent operation of all RF pulsed devices. It plays a crucial role in the overall performance of the particle accelerator and ultimately the beam quality. This paper presents the LLRF and synch system for the VEGA electron linac. It is based on commercial S-band Libera products from Instrumentation Technologies (Slovenia). Experience with its operation, tests results of key performance parameters and the current operational status together with plans for future upgrade are presented. Likewise the HLRF system for the RF photocathode gun and the TW cavities, based on klystrons followed by SLEDs and hybrid power dividers, is described here. Also the phase tuning of the RF cavities is discussed.

As part of the MYRRHA project, which is being implemented in Mol, Belgium, two of the planned 17 normal-conducting CH cavities have been built and tested at several kilowatts of RF power. Since the cooling concept for the stems was revised after their construction, concerns arose that the two existing cavities might have suffered a degradation in performance during high-power testing due to the outdated cooling system. Consequently, it was decided to subject cavity CH02 to renewed LLRF measurements at IAP Frankfurt to ensure that its performance has not deteriorated. The cavity is then scheduled for high-power testing at the newly established high-power station at IAP. This will not only serve to commission the test stand but also recondition the cavity This paper summarizes the recent LLRF measurements performed on CH02 and reports on the current status of preparations for the upcoming conditioning.

ALBA is a 3rd generation synchrotron light source located in Barcelona, Spain. The circumference is 268.8 meters and electrons are stored at 3 GeV. In the framework of the upgrade towards the 4th generation light source ALBA II, an active 3rd harmonic RF system at 1.5 GHz is foreseen to increase the Touschek lifetime component. The system will be installed and available for operation in the current machine, which will allow to gather experience before the upgrade. Four normal conducting HOM damped harmonic cavities will be placed in the storage ring, each of it including a complete WR650 waveguide system with circulator and load, a 20 kW high power SSPA amplifier and a Low Level RF control system. We are presenting in this contribution the complete design of the active harmonic RF system for ALBA and the expected performance during operation.

The European Spallation Source (ESS) superconducting linear accelerator (linac) represents a key component in delivering high-intensity proton beams for cutting-edge neutron science research. This paper details the first cold technical commissioning of the superconducting linac in 2MW configuration, focusing on the performance validation of cryomodules, superconducting radio-frequency (SRF) cavities and associated systems.

For years, Instrumentation Technologies and ScandiNova have developed advanced products to optimize RF performances in LINAC applications. In 2024, the companies began integrating the Libera LLRF system into ScandiNova modulators during assembly. This innovation enables the modulators to offer enhanced operational flexibility and improved performances. This paper will focus on mechanical integration and performance results. The integrated system enables real-time monitoring of critical signals such as drive power to the RF amplifier and klystron, as well as forward and reflected klystron power. Performance metrics include amplitude stability <0.01% RMS and phase stability <0.01° RMS. Experimental results are presented using a ScandiNova modulator with an Sband klystron and a standard Sband Libera LLRF. Pulse-to-pulse stability measurements demonstrate consistency between conventional electrical methods and RF-based methods, achieving stability in the 10 ppm range. Electromagnetic compatibility tests confirm that the modulators do not interfere with the LLRF system. Additionally, new tools are introduced to identify components with the greatest impact on phase stability.

We are developing a low-level RF (LLRF) controller based on RF System on Chip (RFSoC) for an electron linac. The AMD Zynq RFSoC was employed for this controller, which has a large-scale high-speed FPGA together with high-speed ADCs and DACs (8 channels each). The RFSoC also has an application CPU for Linux and a real-time CPU for time-critical tasks, capable of a 1 kHz repetition rate. A general-purpose pizza-box module with an RFSoC was designed and manufactured, and firmware for LLRF control was developed. This LLRF module will be first utilized for an X-band (11.424 GHz) transverse deflector system* for SACLA. A pulsed X-band RF signal is generated by upconverting a 476 MHz IF signal from the DAC and RF signals from the X-band high-power components are converted to 476 MHz IF signals and digitized by ADCs. The IF signal is converted to a baseband IQ signal and the phase and amplitude are obtained. Since the latency of ADC, DAC, and FPGA is as short as several 100 ns, the intra-pulse feedback control is anticipated to stabilize the phase and amplitude of the acceleration RF field. This presentation will give the design and basic performance of the LLRF controller.

EuPRAXIA, the "European Plasma Research Accelerator with eXcellence In Applications," represents the next generation of free-electron lasers (FEL). It aims to develop a compact, cost-efficient particle accelerator using innovative wake-field accelerator technology. High-energy physics often demands higher acceleration voltages, and X-band technology offers high gradients in compact structures. The EuPRAXIA@SPARC_LAB LINAC injector, featuring an S-band RF gun, four S-band structures, and sixteen X-band structures, achieves a maximum beam energy of 1 GeV. For femtosecond-level synchronization and stability, Low-Level Radio Frequency (LLRF) systems are essential. However, commercial X-band LLRF solutions are unavailable. This project, in context of the EuPRAXIA - Doctoral Network, develops an X-band LLRF prototype tailored to meet the EuPRAXIA@SPARC_LAB LINAC's stringent requirements. After validation on a testbench, the prototype will enable industrial production and commercialization. This paper presents the Front-End, Back-End analysis, and further evaluation of the prototype.

The installation phase of the European Spallation Source (ESS) linear accelerator is nearly complete. As with other superconducting linacs operating in pulse mode, LLRF systems play a crucial role in controlling accelerating beam parameters. Modern LLRF systems go beyond providing fast and reliable feedback for RF signal regulation; they also ensure precise, dynamic cavity tuning. Additionally, they enhance machine availability by monitoring various signals to identify potential issues and implementing fast and slow algorithms to optimize cavity performance within safety limits, tailored to specific accelerator conditions. Preparation for these tasks begins during cryomodule and cavity testing, prior to tunnel installation. Key parameters such as Lorentz force detuning coefficients, piezotuner range and polarity, main mechanical cavity modes, Pi-mode frequencies, slow tuner sensitivity, and backlash must be accurately determined to enable peak LLRF performance. This paper outlines the development, implementation, and application of software tools designed to determine these parameters for cavities tested at ESS Test Stand 2 (TS2) and those installed in the accelerator tunnel.

ALBA Low-Level RF (LLRF) system has provided over a decade of reliable operation and has been adopted by other synchrotron facilities. To meet the evolving requirements of ALBA and ALBA-II, a new LLRF system has been developed. This system features FPGA and ADC/DAC MTCA boards designed by SAFRAN, enabling direct 500 MHz signal sampling without down/up-conversion. These enhancements reduce system complexity, minimize noise, and simplify maintenance. SAFRAN also supplies peripheral modules and the Tango device server generator, while ALBA implemented it and developed a new GUI. Upgraded GPIO and RF signal patch panels complement the new hardware. The legacy VHDL code has been updated to improve readability and functionality, incorporating advanced features such as octant selection and a harmonic direct feedback selection method. The latter, based on IIR filtering, isolates positive and negative revolution harmonics in the I/Q domain, feeding them back to amplifiers to effectively mitigate transient beam loading caused by the storage ring bunch train gaps. This upgraded LLRF system delivers enhanced performance and greater flexibility to address the future needs of ALBA and ALBA-II.

Superconducting radio frequency (SRF) cavities in particle accelerators rely on accurately calibrated RF signals to assess cavity bandwidth and detuning, ensuring optimal performance. In practice, however, calibration drift due to humidity and temperature fluctuations over time poses a significant challenge, potentially resulting in suboptimal operation and reduced efficiency. This study explores how environmental variables such as humidity and temperature affect this phenomenon. Relative humidity, in particular, is difficult to control and has been shown to impact calibration drift strongly. Building on these insights, we introduce machine learning-based approaches to forecast both relative humidity and calibration drift in SRF cavities. By leveraging advanced algorithms and historical data on cavity operation and performance, we develop predictive models that identify patterns and trends indicative of relative humidity and calibration drift. Two approaches are presented in this work, including a polynomial NARMAX model and an attention-based deep neural network. These models enable real-time compensation and automated recalibration, improving system stability and efficiency.

In various of particle accelerator designs, amplitude and phase modulation methods are commonly applied to shape the RF pulses for implementing pulse compressors or compensating for the fluctuations introduced by the high-power RF components and beam loading effects. The phase modulations are typically implemented with additional phase shifters that requires drive or control electronics. With our recent next generation LLRF (NG-LLRF) platform developed based on the direct RF sampling technology of RF system-on-chip (RFSoC) devices, the RF pulse shaping can be realized without the analogue phase shifters, which can significantly simplify the system architecture. We performed a range of high-power experiments in C-band for evaluating the RF pulse shaping capabilities of the NG-LLRF system at different stages of the RF circuits. In this paper, the high-power characterization results with the Cool Copper Collider structure driven by RF pulses with different modulation schemes will be described. With the pulse modulation and demodulation completely implemented in digital domain, the RF pulse shaping schemes can be rapidly adapted for X-band structures just by adding analogue mixers.

The low-level RF (LLRF) systems for S-band linear accelerating structures are typically implemented with heterodyne base architectures. We have developed and characterized the next generation LLRF (NG-LLRF) based on the RF system-on-chip (RFSoC) for C-band accelerating structures and the platform delivered the pulse-to-pulse fluctuation levels considerably better than the requirement of the targeted applications. The NG-LLRF system uses the direct RF sampling technique of the RFSoC, which significantly simplified the architecture compared with the conventional LLRF. We have extended the frequency range of the NG-LLRF to S-band and experimented with different RFSoC devices and system designs to meet the more stringent requirement for S-band LLRF applications. In this paper, the characterization results of the platform with different system architectures will be summarized and the high-power test results of the NG-LLRF with the S-band accelerating structure in the Next Linear Collider Test Accelerator (NLCTA) test facility at SLAC National Accelerator Laboratory will be presented and analyzed.