Energy recovery LINACs (ERLs) are a type of novel accelerator, which recycle energy from old beams to new beams to increase machine energy efficiency. However, this can heighten beam instabilities, which limits the maximum beam current and increases beam losses. An optical fibre beam loss monitor (OBLM) can provide rapid and reliable beam loss monitoring, which is important for mitigating these instabilities. It obtains the beam loss location via time-of-flight analysis of Cherenkov radiation (CR) produced in optical fibres by relativistic particle showers from beam loss events. Operational demonstration of the OBLM system has previously been shown at several non-ERL facilities, but the multi-energy, fast-repeating beams of ERLs present a unique challenge. Successful interpretation of ERL beam loss signals involves distinguishing losses from beams of different energies, which can be investigated through end-to-end Monte Carlo simulations of the radiation environment and its interaction with the OBLM system. This contribution presents Geant4 simulations of the OBLM response to sample sources of beam loss for beam energies of 7-500 MeV and bunch populations of 1-10M electrons.

The slow losses measured by Beam Loss Monitors (BLMs) at synchrotron light source facilities offer useful but indirect insight into the state of the beam. Patterns arise across the set of BLMs depending on the movement of insertion devices, beam current, temperature, humidity, and other contributors. A variety of neural network models were designed and evaluated to model this behaviour under user beam operation to enable anomaly detection and aid fault investigations.

One of the principal roles of CERN’s Beam Loss Monitoring (BLM) system pertains to the protection of LHC’s superconducting magnets against quench-inducing beam losses. Thus, the continuous surveillance of the BLM system’s performance is essential for the high reliability and availability of the LHC. This paper focuses on the architecture of a novel data pipeline with implementations on monitoring the communication status between the 864 acquisition tunnel modules that digitize the analog loss measurements, and the 432 processing surface modules that determine and act upon the criticality of the beam losses. The discussed pipeline replaces an older batch Extraction-Transformation-Loading (ETL) process, which published daily BLM status reports, in favor of a streaming ETL process. The new pipeline expands beyond the daily publication of static status reports by exploiting real-time data analysis and processing enabling the live assessment of the system’s status via online fault detection and web-based dashboards. Future development on the implemented pipeline envisions online machine learning and automated Jira issue generation features permitting fault prognosis and issue tracking.

The Super Proton Synchrotron (SPS) beam loss monitoring (BLM) system at CERN, operational for several decades, currently comprises 286 Ionisation Chambers (ICs) around the SPS ring and approximately 144 additional detectors along various extraction lines (TT20, TT40, TT60, etc.). A complete renovation of the system is planned during Long Shutdown 3 (LS3), encompassing detectors, cabling, and acquisition electronics. The upgraded architecture will adopt a design similar to the current LHC BLM system—featuring front-end and back-end electronics housed in separate crates and connected via optical links—ensuring compatibility with the LHC upgrade scheduled around LS4. This paper presents an overview of the proposed architecture for the SPS ring and transfer lines, detailing the key components and expected improvements in performance, modularity and reliability.

An optical beam loss monitor (oBLM) has recently been installed at the slow extraction region of the Super Proton Synchrotron (SPS) at CERN. The oBLM offers a new method for detecting beam losses at the SPS by utilizing the Cherenkov radiation emitted during beam loss interactions with an optical fibre. This setup should allow to measure losses continuously over a large section of the accelerator, thus minimising the non-linearities caused by the finite coverage of the currently installed ionisation chambers. Due to the high radiation levels and low expected signals at this location, special care was taken during the procurement process to maximise the signal levels while at the same time extending the lifetime of the system as much as possible. The rationale behind the choice of specific components is discussed, highlighting their advantages compared to other options. Furthermore, initial measurements of beam loss during extraction are presented, and the system’s ability to provide real-time diagnostics for beam protection and machine optimization investigated.

The CSNS-II linear accelerator upgrade will adopt superconducting accelerator structures, with the beamline enclosed in low-temperature modules. Detection of beam loss can only be done on the outer surface of the low-temperature modules. The CSNS-II accelerator plans to use a parallel plate multi-electrode ionization chamber as the beam loss monitor (BLM) probe for the superconducting section. The electronic system of the beam loss measurement (BLM) is primarily used for signal conditioning, digitization (ADC), transmission storage as EPICS PV quantities, and providing interlock signals for machine protection based on the output signals from the BLM probes. The main tasks of the development of the beam loss measurement (BLM) electronic system include: signal conditioning of weak current output from the BLM probes in the analog circuit section; and analog-to-digital conversion, digital signal processing, storage, PV quantity publication in the digital circuit section for the front-end analog output signals.

A Cherenkov fiber-based shut-off system is being developed for TRIUMF’s ARIEL e-Linac to provide a scalable, cost-effective solution for monitoring beam losses in high-radiation environments. The system uses a single 100m long thin silica fiber with photomultiplier tubes at both ends, allowing sensitive electronics to be located outside the radiation area. This design is favorable over bulky ionization chambers and more expensive scintillation-based detectors, as it improves and simplifies deployment in complex environments, particularly the ARIEL beamline tunnel. The prototype demonstrates sub-10 µs response times and position-sensitive detection via the time delay between upstream and downstream signals. Ongoing work focuses on the achievable spatial resolution, the integration into ARIEL’s operations control environment and the systematic evaluation of reliability and sensitivity.

CERN’s Beam Instrumentation Group is developing a mini-crate to host the future Beam Loss Monitor (BLM) and Beam Positioning Monitor (BPM) systems acquisition electronics at HL-LHC and SPS accelerators. For this purpose, a new power supply has been designed to meet the low noise requirements, high reliability, and availability standards for these harsh radioactive environments. This design makes use of CERN-developed ASICs and radiation-tolerant qualified COTS and follows a modular architecture for quick interventions and safe handling. The paper presents the design, prototype characterisation results, identified issues, and mitigation methods to achieve the required radiation tolerance.

CERN’s Beam Loss Monitoring (BLM) system is essential for the protection of machine elements against energy deposition due to beam losses. The protection function relies on approximately 5000 ionisation chamber type detectors installed along all of CERN's accelerators. Some of the areas where the detectors are installed have a high background dose (above 2mSv/h). Installation and maintenance times must be minimised to ensure person-nel safety. For this reason, a new solution was designed that allows the manipulation of detectors and their sup-ports by robotic action. Every aspect of the solution has been designed to reduce intervention time, using a rapid locking mechanism and the possibility of transporting the material by robot. The paper presents the design, prototype characterisation results, identified issues, and mitigation methods developed for the automated manipulation of these detectors.

Several systems protect the superconducting magnets of the Large Hadron Collider (LHC), which operate at -271.3C. The Beam Loss Monitoring (BLM) system is critical for detecting lost particles around the machine and reacting on their quantity and associated energy. It protects the machine from quenching and irreversible damage. To measure these losses, various detectors are used, primarily ionisation chambers (IC), but also other types of monitors depending on loss intensity. In injection and extraction areas, additional fast polycrystalline Chemical Vapor Deposition (pCVD) diamond detectors measure time structured losses. To increase sensitivity, a new detector, the cryogenic Beam Loss Monitor (CryoBLM), based on pCVD, was developed. It is mounted inside the cryostat between two superconducting magnets in the vicinity of the beam pipes and operates at cryogenic temperatures. Two CryoBLM locations in the LHC target different loss scenarios: betatron halo cleaning and luminosity losses from the CMS physics debris. This contribution presents the CryoBLM performance and comparisons with other detectors.

The Hefei Light Source is a synchrotron radiation facility operating in the vacuum ultraviolet and soft X-ray regions. If the evolution of beam parameters and beam loss during the injection transient process can be observed synchronously, analyzing their correlation can provide more quantitative guidance for further optimizing the injection process. To achieve this goal, a monitoring system capable of synchronously capturing the 3D position of each bunch and rapid beam loss has been established at the Hefei Light Source. Experiments investigated both TOP-UP injection and empty-ring injection processes. Thanks to the unique multi-parameter synchronous diagnosis capability of this system, some previously unnoticed special phenomena have been captured, and a deeper analysis of the correlation between bunch parameters can be conducted. TOP-UP mode exhibited maximum beam loss in the injected bunch, with secondary losses at the 14th subsequent bunch. Peak beam loss occurred immediately after injection in both modes, followed by rapid attenuation within several turns. Loss resurgence appeared after ~85 turns (TOP-UP) or 180 turns (empty ring), followed by oscillatory decay.

SOLARIS storage ring has been equipped with a set of twelve Beam Loss Detectors, controlled by Libera Beam Loss Monitors. This system enhances the ability to monitor and analyze beam losses and operational efficiency. Detectors were strategically placed around storage ring and transfer line, providing ability to optimize injection losses and enable precise localization of beam loss events. Real-time monitoring enables faster identification and mitigation of abnormal loss patterns, improving machine protection, stability and reliability. Data collected by the system will support beam lifetime studies and provide valuable insights for future performance.

The Low Energy RHIC Electron Cooler (LEReC), the world’s first electron cooler utilizing an RF electron accelerator, was designed to operate with 1.6-2.6 MeV electron beams of up to 140 kW beam power. The LEReC successfully worked through RHIC Runs 2019-2021, substantially increasing RHIC luminosity, and has been routinely used for various studies since then. A dedicated, highly configurable Machine Protection System (MPS) is a critical part of the LEReC. This paper summarizes our experience with operating the LEReC MPS.

The Future Circular $ \mathrm{e}^+ \mathrm{e}^- $ Collider (FCC-ee) at CERN will provide collisions at four interaction points along a 91 km long ring, with beam energies ranging from 45.6 GeV (Z pole) to 182.5 GeV ($\text{t}\bar{\text{t}}$ threshold). The radiation environment along the accelerator varies significantly, with different dominant sources depending on location and operational mode. Accurate characterization of this environment is essential for the design and placement of machine equipment, particularly electronic systems and beam instrumentation. In this study, the Monte Carlo code FLUKA is used to characterize tunnel radiation levels from the main sources, including radiative Bhabha scattering, synchrotron radiation, and beam-gas interactions. The results at the Z pole and $\text{t}\bar{\text{t}}$ threshold for both the interaction regions and arcs are presented to guide early-stage design considerations and to quantify exposure risks for electronics at potential installation locations.

The beam loss monitor (BLM) is a diagnostic system designed to protect accelerator components from unexpected high-energy radiation. We have developed a cost-effective BLM system for the next-generation synchrotron light source, Korea-4GSR. The system uses plastic scintillators, optical fibers, and a CMOS camera to localize beam losses with 10 ms time resolution. Scintillators placed along the beam-line emit blue light proportional to the ionization energy deposited by beam losses. The light is transmitted through optical fibers, bundled into a 2D array, and imaged by a CMOS sensor at 100 Hz. The BLM’s sensitivity and calibration were verified using a 2 MBq Co-60 gamma-ray source. The preliminary result shows ~45 counts/GeV. Energy deposition was estimated using Geant4 simulations, and photon-to-count conversion was characterized with a calibrated LED source. The DAQ includes a built-in LED pulser for in-situ calibration of the CMOS detector and cable integrity check. This presentation outlines the system design, calibration methods, and performance results.

The Advanced Photon Source Upgrade (APS-U) storage-ring (SR) is equipped with five horizontal collimators used to intercept 6-GeV electrons during fast whole-beam aborts and protect the rest of the SR. The collimators are located in sectors 37, 38, 39, 40, and 1. A fan-out kicker (FOK) system has been installed to reduce damage to the collimators during whole-beam loss events. Since APS-U began commissioning in April 2024, dozen of these events have taken place; in most, but not all cases, the FOK system has worked properly. Turn-by-turn beam position monitors provide beam centroid dynamics data during the loss events; however, limited diagnostics prevent in situ evaluation of the collimator beam-facing jaw surfaces. During maintenance periods in August 2024 as well as January and May 2025, some of the collimators were extracted from the vacuum chamber and examined. Faint beam strike damage was observed on the S01 collimator jaw, but more significant effects were seen on the S38 jaw. Measurements of beam motion during fast aborts is presented as well as microscopy images of the S38 damage. Coupled simulations results are compared with observations.

A fiber-optic (FO) beam loss montior (BLM) system, installed along the booster to storage ring (BTS) trasnport line has been useful in identifying loss locations employing time-of-flight (TOF) analysis. The BTS BLM TOF system is comprised of a pair of rad-hard, fused-silica FO cables running along either side of the BTS line at beam elevation. In the initial configuration, we measured losses at both the upstream (US) and downstream (DS) ends of the FO cable pair. However, losses further DS along the septum and injection kicker set are also of interest. We therefore added a 20-m-length, multi-strand fused-silica FO cable bundle, replacing the DS outer FO radiator input. Thus, three of the detectors are configured at the US end of their respective FO radiators. The US detector location provides lower signal but improved spatial resolution over the DS. Loss location identification has been accomplished by inserting YAG screen flags at different positions along the BTS. We present results from studies and operations.

In Fermilab's PIP-II machine protection system, beam loss signals from various detectors are digitized at 125 MS/s. Noise from both high-frequency sources and low-frequency 60 Hz AC power equipment can contaminate the data. To suppress noise across these ranges—especially 60 Hz and its harmonics, which overlap with beam loss signal frequencies—advanced digital processing beyond standard filtering is required. Several real-time functional blocks were simulated and tested on an FPGA: (1) a dual time-constant discharging integrator filter, (2) a de-ripple baseline extraction and storage block, and (3) a fast-recovery discharging integrator. The nonlinear IIR integrator filter removes high-frequency noise and feeds into the baseline extractor. Upon detecting abrupt beam loss, it switches to a longer time constant to prevent baseline distortion. The de-ripple block calculates a valid baseline by averaging over multiple 60 Hz periods, storing results in a 4096-word FPGA RAM. This baseline is subtracted from raw data before integration by the fast-recovery block, which resets quickly after use. All blocks achieved expected performance and were successfully implemented on a low-cost FPGA.

In 2024, the Large Hadron Collider (LHC) delivered Pb-Pb ion collisions at a beam energy of 6.8 Z TeV with a stored beam energy of more than 20 MJ. In order to clean beam halo particles and avoid quenching the LHC superconducting magnets, the novel crystal collimation method employing 4 mm-long crystals was introduced for ion operation in the LHC Run 3. The LHC Beam Loss Monitoring (BLM) system triggers the beam dump in case the measured losses are above certain predetermined thresholds. Important adjustments were needed in order to optimize these thresholds in accordance with the peculiar loss pattern produced by crystal collimation. This contribution explains the newly observed beam loss patterns during Pb ion operation with crystal collimation in place, as well as the study that was carried out to update the BLM thresholds for Pb ion operation in the LHC Run 3.

The superconducting upgrade to the LCLS x-ray free-electron laser at SLAC is now in commissioning, as we gradually raise the repetition rate of the 4-GeV beam toward 1 MHz and the beam power toward 120 kW. A further upgrade next year will double the energy and power. Machine protection at this extremely high power required a novel system of fast beam-loss monitors (BLMs). Points of concern, such as collimators or kickers, are covered by diamond detectors (PBLMs). Long optical fibres (LBLMs) of up to 200 m span the entire 4-km facility, generating and capturing Cherenkov emission from beam-loss showers. Previous papers have reported on the design and early commissioning of this safety system, and on plans to use the loss signals for wire scanners and loss localisation. Subsequent experience in commissioning and operating the full system has demonstrated that the concept is sound and sensitive, but several aspects of the implementation have proven troublesome. Extensive testing and debugging uncovered issues with both hardware and firmware. We will detail these problems, their remedies, and the improvements in performance.

At the SuperKEKB electron-positron collider, which aims to achieve the world's highest luminosity, "Sudden Beam Loss events (SBL)" have prevented its stable operation, in which several tens of percent of the beam current is lost and aborted within several turns (20-50 µs). Elucidating SBLs, which can cause extensive damage to accelerator components and the Belle II experiment detectors, is a pressing issue for SuperKEKB. To measure the beam size and position variation, key information for disentangling SBLs, over dozens of turns just before the SBL-induced beam aborts, we have developed new turn-by-turn beam size monitors in two different wavelength regions, X-ray and visible light, and bunch-by-bunch beam position monitors where one has utilized a novel architecture AMD/Xilinx RFSoC. Simultaneous measurements of turn-by-turn beam size and bunch-by-bunch beam position enable elucidation of the cause and time evolution mechanism of the SBL events. In this presentation, we will first introduce recently developed fast beam size and beam position monitors, then show their simultaneous measurements of SBL events. Finally, we will discuss the possible causes and time evolution mechanisms of the SBL events.