Plasma acceleration is paving the way for new compact accelerators aiming at reducing the scale of the facilities needed by free electron laser (FEL) or high energy physics by employing accelerating gradients much larger than conventional RF structures. The EuPRAXIA Design Study is dedicated to realizing a distributed FEL facility powered by plasma acceleration in the European framework (it is...
The Relativistic Heavy Ion Collider (RHIC) is a high energy collider currently in operation at Brookhaven National Lab that collides both proton beams and heavy ion beams at energies of up to 250 GeV. The use of a low phase noise RF system is important to the operation of the collider, as phase noise will cause beam emittance growth as beam is circulated and collisions occur. In an effort to...
Coherent Electron Cooling Proof-of-Principle (CeC PoP) is an experimental accelerator system currently commissioned at Brookhaven National Laboratory (BNL). The purpose is to demonstrate cooling of a single hadron bunch circulating in the relativistic heavy ion collider (RHIC) with co-propagating electron beam. To support CeC operation, FPGA based LLRF Controllers provide system controls,...
The CLARA Accelerator at Daresbury Laboratory requires timing information to be distributed to locations up to 100m apart with femtosecond accuracy. This information is delivered as laser pulses via 6 stabilized fibre optic links. Each link uses 3 main subsystems which condition and modify the laser pulses: a piezoelectric fibre stretcher provides closed loop length stabilization to compensate...
We present a phase-locked loop (PLL) system integrating a balanced optical microwave phase detector (BOMPD) and a voltage-controlled phase shifter (VPS) for precise phase synchronization. The BOMPD is employed to extract the phase error between a 1.3 GHz microwave signal and 216 MHz laser pulse sequence. The error signal originating from the BOMPD is fed into the VPS through a PI servo....
Abstract
Since June 2024, LCLS-II has been providing users with an X-ray laser that features a higher repetition rate and more intensity compared to LCLS-I. This advancement offers users a broader range of X-ray free electron laser (FEL) options and significantly reduces data collection time. Existing photon instruments and beam diagnostic systems for LCLS-I must be able to detect the X-rays...
The China initiative Accelerator Driven System (CiADS) requires a stable phase reference distribution system (PRDS) to provide low-drift reference signals for over 300 radio-frequency (RF) clients on its superconducting linac and beam transport lines. PRDS is realized using a coaxial cable that transmits 162.5 MHz reference signals, and the phase averaging technique will be employed to...
The timing system is a crucial component in scientific facilities like particle accelerators and laser ignition installations. It ensures that all subsystems within these facilities share a common time reference, enabling coherent operation and accurate tracking of events throughout the machine's operation. Additionally, the timing system generates discrete triggering events and periodic...
The PIP-II timing system is planned to be a two part system consisting of a global timing system (referred to as ACLK) that provides high level, event based timing for the whole Fermilab accelerator complex while the second part is a RF synchronized clock system unique to the PIP-II Linac itself (referred to as LCLK). The ACLK System will make use of an external 10 MHz GPS based signal source...
The redesigned RF reference generation and distribution system at FLASH was installed in 2022. The upgrade is based on a European-XFEL-based Main Oscillator (FL-MO1300), Frequency Conversion (FL-FCM), and RF Distribution (FL-DISM) modules. The main 1.3 GHz RF reference signal is synthesized in FL-MO1300, and the remaining signal frequencies are synthesized in FL-FCM and synchronized to the...
We present recent advancements in the development of the real-time redundancy subsystem for the Master Oscillator of the European XFEL. This system improves upon the usual method of manually switching to a hot-spare in the event of a failure in the main source. Its primary objective is to maintain uninterrupted operation of the facility by minimizing the impact of potential Master Oscillator...
The heavy-ion accelerator of the Institute for Rare Isotope Science (IRIS) has been developed and beam commissioning for the low energy superconducting linear accelerator has been performed. There are three types of SRF cavity, which are 81.25 MHz quarterwave resonator (QWR), 162.5 MHz half-wave resonator (HWR), 325 MHz single-spoke resonator (SSR). There are 22 QWRs and 102 HWRs in the...
The CEBAF accelerator at Jefferson Lab relies on precise frequency references distributed throughout the site. CEBAF’s infrastructure has aged from decades of successful operation, and grounding issues have made the system susceptible to electromagnetic interference. This weakness is particularly noticeable during lightning storms. To address this, the Master Oscillator (MO) system was...
The Einstein Telescope (ET) project is the research infrastructure to host the future European gravitational wave detector and Italy is a candidate to host it in Sardinia. It is a large underground facility for a third-generation gravitational wave detector, which will be able to observe a volume of the universe about one thousand times larger than current instruments. It is considered a...
The new APS storage ring has about 40 cm smaller circumference than the ring it replaced. Consequently, the 6-GeV Booster synchrotron is no longer able to operate at the same rf frequency as the storage ring. Rather than rebuilding the Booster, a novel synchronization system (IETS) was developed that dynamically modifies the Booster rf frequency using a cosine-like frequency program, thus...
The relative timing between different subsystems of SwissFEL is critical for a fast recovery of operation after a machine shutdown or a restart of any subsystem. For the LLRF system, deterministic phase measurements and stable macro-pulse timing w.r.t the trigger are critical for stable beam acceleration with pulsed RF stations. The phase and macro-pulse timing uncertainties are introduced...
Accurate phase and amplitude noise measurements are substantial for the advancement of, and academic exchange on low-level RF, (laser) timing synchronization and timing diagnostic systems. However, the notion of phase, timing and amplitude noise, and their various representations can be quite overwhelming for scientists and newcomers to the field without a deep background in electrical...
Precise measurements of the cavity-loaded quality factor (QL) is crucial for monitoring the performance of superconducting radio-frequency (SRF) cavities. The conventional "field decay method" cannot be used to measure QL accurately when the impedance is mismatched. This can lead to nonzero forward signals (Vf), which significantly affect the measurement accuracy. To address this limitation,...
The linear accelerator of European XFEL exhibits an outstanding phase and amplitude stability using state-of-the-art low-Level RF (LLRF) controls in combination with an optical synchroniation system. The achieved RF field regulation precision is well within design criteria, chosen to reach an electron bunch arrival time stability on the 10fs rms level. However, the high complexitiy of the...
The traditional method for determining the synchronous phase (SP) of beam typically relies on “phase scan method”. Despite its high precision and reliability, this method requires a significant amount of runtime. Processes such as phase drift caused by environmental disturbances or rapid recovery after cavity faults (such as Quench) necessitate repeated execution of the phase scan procedure....
In this contribution, we describe the advantages of the pilot tone compensation technique that we have implemented in a new BPM system for Elettra 2.0. The injection of a fixed reference tone upstream of the cables allows for a continuous calibration of the system, compensating for the different behaviour of each channel due to thermal drifts, variations in cable characteristics, mismatches...
In recent years, we witnessed an increasing interest in the search of light Dark Matter (DM), addressing in particular axions. Axion existence would untie the long-standing DM problem. Its cosmological evolution and astrophysical constraints indicate a favorable mass range between 1 μeV < ma < 10 meV.
The axion observation technique is based upon its inverse Primakoff conversion into one...
The new Advanced Photon Source Upgrade (APS-U) storage ring is now operating and x-ray beamlines are coming back online. Targeted suppression of 60-Hz-harmonic-related rf amplitude and phase noise from megawatt-class klystrons has played a role in achieving orbit stability at the micron level and reducing beam energy fluctuations. Measurements of beam stability are made from an analysis of...
Accurate knowledge of the voltage and phase in an RF cavity gap is essential to preserve beam quality and to achieve efficient, precise real-time correction with LLRF feedback. Voltage calibration using longitudinal phase-space tomography is a well-established beam-based technique that has demonstrated remarkable precision in determining the RF voltage experienced by a particle bunch. In a...
The PIP-II Accelerator is an 800 MeV superconducting Linac in the injection chain of the Fermilab accelerator complex. The LLRF systems are a based on two different hardware platforms controlling a variety of cavity types and resonance control systems including temperature, pneumatic and piezzo tuners. The various calibrations required prior to beam operation include, signal power, gradient,...
Precisely calibrating RF superconducting radio-frequency linear accelerators is crucial for accurately assessing cavity bandwidth and detuning, which provides valuable insights into cavity performance, facilitates optimal accelerator operation, and enables effective fault detection and diagnosis. In practice, however, calibration of RF signals can present several challenges, with calibration...
The Low-Level Radio Frequency (LLRF) system is a vital subsystem in particle accelerator facilities, tasked with generating and maintaining a stable electric field within accelerator cavities by precisely controlling both amplitude and phase. As facilities transition from legacy analogue LLRF systems to modern digital counterparts, the enhanced computational power of current Field-Programmable...
High performance synchrotron light sources like Soleil2 or Lunex5 require LLRF systems with high IQ accuracy: typically 0.01° RMS in phase and 1e-4 relative error in amplitude. This accuracy may be ultimately limited by the phase noise of the reference signal. In most LLRF systems, frequency downconversion to an IF signal of10 MHz is used before the digital IQ-demodulation. It can be shown...
The Electron-Ion Collider (EIC), a decade-long project at Brookhaven National Laboratory (BNL) funded by the Department of Energy (DOE), aims to design and build a facility for colliding polarized high-energy electron beams with polarized proton and heavy ion beams. The EIC will operate at center-of-mass energies between 20 GeV and 140 GeV and achieve luminosities up to 1034 cm-2s-1. This...
Shenzhen Superconducting Soft X-ray Free-electron Laser (S3FEL) is a high repetition-rate X-ray FEL facility whose linear accelerator mainly includes electron gun, beam buncher and superconducting acceleration module. We have developed a digital low-level RF（LLRF）system for the S3FEL buncher to achieve the amplitude and phase control of the microwave. In the prototype design, the architecture,...
For advanced high-Q SRF linacs like LCLS-II, achieving precise control of cavity resonance is crucial to ensuring stable operations. Inadequate control can lead to a substantial increase in RF power demands, thereby escalating both operational and capital expenses due to the need for additional RF power sources. To tackle this challenge, we have developed an innovative cavity resonance...
The Low-Level Radio Frequency (LLRF) system is a critical component in the control infrastructure of any synchrotron, responsible for generating and maintaining a stable electric field within the accelerator cavities by precisely controlling both amplitude and phase.
Safran Electronic & Defense Spain S.L.U. is currently engaged in the development of a new digital LLRF system to upgrade...
Distribution systems are used to provide reference frequencies from a common source to all phase-critical clients at an accelerator. To precisely synchronize remote RF and optical oscillators to the common clock, a combination of phase-stabilized links and phase-locked loops with optimized bandwidth and locking parameters are implemented. A pre-requisite to reach the required phase-stability,...
To explore the implementation of laser-RF synchronization with femtosecond-level precision and stability, we proposed and demonstrated a Sagnac loop-based all-fiber optical-microwave phase detector (AFOM-PD). The repetition rate of the reference laser is 29.134 MHz, and its RIN has been suppressed by 40 dB at 1 Hz offset frequency. A 1.311010 GHz (2.855132 GHz) RF signal was synchronized with...
The Compact Linear Accelerator for Research and Applications (CLARA) is a 250 MeV ultrabright beam test facility at STFC Daresbury Laboratory. Originally conceived as a free electron laser test facility, timing is based on an actively stabilised optical timing architecture, incorporating optoelectronic systems for beam arrival diagnostics and laser/RF client synchronisation. The facility is...
The Phase Reference Line (PRL) of the European Spallation Source (ESS) is a passive system based on a single 1-5/8” coaxial rigid line installed at the tunnel ceiling above the beamline. It is supported by temperature and gas pressure control systems with active electronics installed in the ESS Klystron Gallery Hall. The length of the PRL is around 580 meters. The system is temperature...
The PIP-II Accelerator is an 800 MeV superconducting Linac in the injection chain of the Fermilab accelerator complex. The LLRF systems for the 125 cavities which include a few normal conducting cavities in the warm front-end section, use a variety of LLRF hardware components and sub-systems that are part of the timing and synchronization system. This includes a master oscillator and phase...
In 2023, LINAC Coherent Light Source II achieved first light, spanning over 5 km from injector to the experiment hall. The goal of achieving 10fs relative jitter between the experiment laser and the x-ray led to the development of new systems. We will present the timing system design, architecture, key commission results and challenges along the way.
The challenge of reference distribution in...
New experiments and particle accelerator R&D programs at LNF are pushing the requests on beam stability and reliability towards the limit of the present technology. This drives the study on timing (event management and trigger distribution, down to ps scale) and synchronization (high frequency reference signal generation and distribution, down to fs scale). This presentation will give an...
Recent advances of plasma-based accelerators showed the feasibility to generate multi GV/m gradients for ultra-short electron bunches to be used for user-oriented applications. The shot-to-shot stability of the plasma-accelerated beam is of fundamental importance and represents the last gap to fill to fully compete with state-of-the-art radio-frequency accelerators. In this context we discuss...
Free electron laser has the characteristics of extremely high peak brightness, ultra-short pulse and high coherence, providing unprecedented research opportunity for physics, chemistry, biomedicine, materials science and energy science.
Large-scale free electron laser and its time-resolved pump-probe experiment requires femtosecond-level synchronization. Optical and RF synchronization...
State of the art Free Electron Lasers have rigorous electron beam stability requirements. To fulfill these requirements the low-level RF systems rely on a phase stable RF reference. Classical coaxial RF distribution systems have low complexity and thus offer excellent reliability and also a good short-term performance. However, their long-term stability does not meet today's requirements of...
HEPS is a new built 6GeV 4th-gen synchrotron radiation light source and under beam commissioning right now. The phase distribution system includes master oscillator system and phase reference line system. The DDS-based MO generates 499.8MHz and 166.6MHz, then distributes to Linac, booster RF and storage ring RF, beam station, as well as BI electronics clock around the facility. The 499.8MHz...
This contribution, planned as a sort of short summary/tutorial, will cover the basics of RF synchronization, starting with theoretical definitions and an attempt to put together and organize concepts and names frequently confused by various people. Items such as the definition of synchronization systems and their accuracy measures will be discussed, followed by sources of instabilities and...
