J-PARC Linac accelerates the high-intensity beam of 50 mA using an RF system of 324 MHz and 972 MHz. In order to accelerate and transport the high-intensity beam to facilities stably, the current value, centroid, and distribution of the beam must be measured to realize optimum operating conditions. This paper reports on the transformations and improvements of the linac beam diagnostics since 2015. As an example, carbon nanotubes (CNTs) were employed in the WSM at the upstream of the linac. There has never been an unintentional WSM failure after the CNT replacement. Other reports on the status of BSM operations will also be presented. The diagnosis of beam anomalies experienced during beam tuning will also be reported.

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.

Optically active point defects, known as color centers (CCs), are created in the crystal lattice of lithium fluoride (LiF) by irradiation with various types of ionizing radiation. Some of these CCs emit light in the red and green regions of the visible spectrum when optically excited with blue light. When a proton beam irradiates a LiF crystal, a volume distribution of CCs is formed, with defect concentration point-by-point proportional to the absorbed dose for values up to approximately 10^5 Gy. By illuminating the irradiated crystal with blue light in a fluorescence microscope, a luminescent image produced by the CCs can be observed and recorded. A high-resolution diagnostics both for spot imaging and energy in a proton accelerator has been developed based on this technique. Regarding energy, a luminescent replica of the Bragg curve in LiF is extracted and analyzed using a theoretical model of Bragg curve applied to dose deposition, taking into account the crystal dimensions. We report an application of this method to the 71 MeV TOP-IMPLART linac at ENEA Frascati, where it was used to evaluate the beam energy spectrum at both the crystal position and the accelerator exit.

The Compact Linear Accelerator for Research and Applications (CLARA) is STFC Daresbury Laboratory’s flagship accelerator facility. We present the latest data from the commissioning of the CLARA facility at Daresbury Laboratory. This will include initial beam measurements and diagnostic performance for the 250 MeV high brightness, highly compressed electron bunches. An overview of the diagnostic requirements and anticipated challenges for these high impact user experiments will be provided. The future direction of diagnostics at CLARA, including potential system upgrades and plans for virtual diagnostics, is also discussed.

HEPS beam charge measurement includes bunch charge measurement system and average current meas-urement system. The injection scheme of HEPS requires charge monitor with high precision, stability, and a large dynamic range at each phase. This paper introduces the design and commissioning status of HEPS charge meas-urement system Signal reconstruction method applied in bunch charge measurement is also described in the paper.

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.

PIP-II (Proton Improvement Plan-II) is a critical upgrade to the Fermilab accelerator complex. The 800 MeV superconducting linear accelerator will utilize 126 beam position monitors (BPMs) across the Warm Front End (WFE), superconducting linac (SC LINAC), and Beam Transfer Line (BTL). These BPMs provide beam position, phase, timing, and intensity data, meeting stringent physics requirements: 10 µm position resolution, 0.1 mm position accuracy, 1% intensity resolution, 0.3° phase resolution, and 1° phase stability. This paper presents the uTCA4.0-based BPM electronics system. Each AMC with an RTM processes eight signals from two BPMs, with a 12-slot uTCA chassis supporting up to 24 BPMs. The system features 8-channel 250 MSPS ADCs and a Xilinx UltraScale+ SoC FPGA running Linux, facilitating high-speed data transfer via 10 Gigabit Ethernet. Key design aspects include analog signal conditioning, JESD204B routing, clock distribution, and thermal management. FPGA handles BPM signal processing, time tag, digital down-conversion, and phase drift compensation. Performance benchmarks, including position, phase resolution and temperature stability, are validated through dedicated testing.

For the ESS linac commissioning, twelve extremely compact beam destinations were designed in place of bulky and expensive beam dumps, in order to dump [0.075, 250] MeV protons. The beam destinations were either Faraday Cups (FC) for the NCL commissioning or Insertable Beam Stops (IBS) for the SCL commissioning. Both FC and IBS are beam-intercepting devices, operated under vacuum, water cooled and movable by means of a pneumatic actuator. The **manufacturing** of FC and IBS relied on high-precision machining. The limited installation space and vacuum requirements required strict tolerances, complex welding of small components and vacuum brazing of compact cooling pipes. The **installation** of the devices themselves, their radiation shielding and portable cleanrooms were particularly challenging due to the limited space not only outside but also inside the beamline. The main challenge during the **operation** was posed by the beam power density. Radiation transport calculations allowed to minimize residual dose rates. Thermo-mechanical simulations allowed to define the operational limits thus avoiding damage to the beam destinations themselves and linac components nearby.

Radiation transport simulations allow the design and operation of entire facilities such as the European Spallation Source (ESS) in Lund, Sweden. This paper summarizes three of the first applications of Attila4MC simulations to the high-power proton accelerator of ESS and its beam instrumentation. Entire linac sections and beam-interceptive instrumentation were modelled by implementing existing CAD models, relying on unstructured tetrahedral meshes and zeroing out the time spent in manually crafting MCNP6 models. As a result, it was possible to accurately quantify the beam power density within beam-interceptive devices and in turn their operational limits. Activation and 3D dose maps were computed and swiftly visualized in 3D, on top of the actual linac model. This work paves the way for e.g. advanced instrumentation design, linac operation, safe maintenance, categorization of radiation waste and future dismantling.

The Canadian Light Source (CLS) linear accelerator (linac) serves as the injector for the 2.9 GeV synchrotron. The original linac, which was installed in the 1960's, was replaced in 2024. The new 3000.24 MHz linac was designed and built by RI Research Instruments GmbH. The linac makes use of a 90 kV thermionic source, three 5m long accelerating S-band structures and a SLED pulse compressor system to accelerate electrons to 250 MeV. The initial beam instrumentation included a faraday cup, yag screens, beam position monitors and fast current transformers. During the course of commissioning directional couplers and microphones were added to provide insight into the location of RF breakdowns. This paper will provide an overview of the new linear accelerator and our experience commissioning the new equipment.

The Beam Test Facility (BTF) at the National Laboratories of Frascati provides highly configurable positron/electron beams for different type of experiments. Extracted from the DAΦNE LINAC, the beam delivers up to 49 bunches/s, with 1 to $10^{10}$ particles/bunch. Secondary beams span 25-780 MeV (electrons) and up to 550 MeV (positrons). BTF includes two experimental halls: BTFEH1, suited for high-intensity and long-term experiments, and BTFEH2, optimized for lower intensities (up to 10⁶ particles/s). Both halls feature remote-controlled movable tables, beam diagnostics, and essential services like laser alignment, networking, high-voltage support, and gas pipelines, ensuring comprehensive experimental capabilities and 24/7 user support. A notable strength of BTF lies in the user-friendly approach: beam is easily manipulated to meet users' specific needs, even during ongoing data collection. In this talk the upgrades concerning the development of a new control system based on Epik8s (EPICS on Kubernates) will be reported as well as the new improvement in beam dimension and energy loss concerning the substitution of the 500 $\mu$m BeO exit window with 120 $\mu$m Anticorodal one.

The KEK e⁺/e⁻ Linac supplies electron beams to SuperKEKB HER, PF, and PF-AR, and positron beams to SuperKEKB LER. We utilize machine learning for both online beam tuning and offline data analysis. Machine learning based on Bayesian optimization has been employed to improve and maintain beam quality, contributing to the enhancement and stabilization of beam injection efficiency into SuperKEKB HER and LER. In this report, we present monitors and beam tuning methods that incorporate machine learning. Identifying parameters that affect beam quality and stability is important, but finding them among the vast number of parameters is not easy. In machine learning-based beam tuning, selecting the appropriate parameters for tuning is crucial, and another important issue is identifying factors that lead to beam instability. To address this, we have applied explainable AI techniques to analyze archived data and attempted to extract parameters that have a significant impact on the beam. This report also covers our data archiving system and analysis efforts using explainable AI.

China Spallation Neutron Source (CSNS) accelerator complex will employ a new superconducting accelerating section to achieve high beam power. To protect the superconducting cavity from contamination, the second phase of the CSNS superconducting linac section will adopt laser stripping technology for transverse distribution measurements of the negative hydrogen beam at nine stations. In 2024, a laser wire(LW) prototype was installed to measure the profile of the 80MeV H- beam. This paper describes the commissioning results of this LW prototype, including the optimization before scanning, and data analysis.

During the pre-research phase of China Spallation Neutron Source (CSNS) upgrade project (CSNS-II), in order to conduct beam commissioning of the Radio Frequency Quadrupole (RFQ) under high-intensity beam conditions, The structure of the last-stage wire scanner of the Medium Energy Beam Transport (MEBT) was innovatively modified. This modification not only added a Beam Stop but also significantly enhanced the efficiency of wire scanner. This paper presents the architecture and operational programming of a novel multifunctional device designed for accelerator beam diagnostics and beam termination: beam profile measurement via advanced sensing mechanisms and Beam Stop using a braided carbon fiber plate as the primary beam stop.

A laser wire monitor has bean developed at the China Spallation Neutron Source (CSNS).The monitor utilizes a 1064 nm laser source to measure the horizontal and vertical profiles of a negative hydrogen ion (H-) beam with an energy of 80 MeV in the injection zone. This paper describes the design of the laser optical path layout and the characterization of the transport performance. The experiment focuses on the laser system's quality factor M2 of the laser after more than 60 meters of transmission as well as the beam pointing stability. In this experiment, the laser quality factor M2 after transmission is better than 4, and the beam pointing stability after focusing is less than ± 2.5 um, which is able to satisfy the required specifications for the first laser wire monitor of the CSNS.

A non-invasive photon-detection beam profile monitor using a gas sheet, named the gas sheet monitor, has been developed. Our gas sheet is formed based on rarefied gas dynamics. To obtain a beam profile quantitatively, we have also devised a beam reconstruction method with a response function measurement method. These methods gave a 2-D beam profile of a high-intensity 3 MeV beam at the J-PARC RFQ test stand, which well agreed with a simulated 2-D profile by a particle-in-cell code and 1-D profiles measured by a wire-scanner monitor. As the next step, measurement of a 400 MeV hydrogen negative ion beam at the end section of the J-PARC Linac was challenged. Since a high-energy beam rarely interacts with a gas due to the small cross-section and induces an intense radiation noise, the captured image had a very low signal-to-noise ratio though the beam-induced signal was detected. Through some measurements, it was found that the primary noise was a radiation directly acting on a built-in multi-channel plate of an image intensifier. We will reports the details of these recent efforts on the gas sheet monitor.

The Synchrotron Light Research Institute (SLRI) in Thailand aims to operate a 6 MeV electron linear accelerator for irradiation, supporting various agricultural and industrial applications. This study presents a method for measuring electron beam energy using the existing dipole magnet in the beamline, originally designed for scanning X-rays on samples through a scan horn. An aluminum sheet coated with terbium-doped gadolinium oxysulfide (Gd₂O₂S) was used as a scintillation screen for X-ray illumination and placed downstream of the scan horn. X-ray scintillator images were captured with a CCD camera. By analyzing shifts in the X-ray image centroid as the dipole magnet current varied, we were able to determine the electron beam energy. The experimental setup, simulations, and measurement results are presented and discussed.

The Synchrotron Light Research Institute (SLRI) operates the SPS-I facility located in Nakhon Ratchasima, Thailand, which provides synchrotron light for various scientific and industrial applications. The linac injector, serving as the primary injector, is responsible for electron beam bunching and acceleration to 40 MeV, after which the beam is transported to the booster ring via the Low-Energy Beam Transport line (LBT). To ensure optimal beam quality and efficient transport, various beam instrumentation devices are installed along the linac injector and LBT for diagnostics and monitoring. This contribution presents an overview of the beam instrumentation used to measure beam current, transverse profiles, and energy profiles, serving as a fundamental reference for future beam optimization and performance improvements of the SPS-I linac injector system.

The Siam Photon Source (SPS) is a 1.2-GeV synchrotron facility in Thailand, operated by the Synchrotron Light Research Institute (SLRI), providing synchrotron radiation for various applications to the user community. The SPS injector linac generates 40-MeV electron bunches, which are then transported to the booster synchrotron via the Low-Energy Beam Transport line (LBT). To ensure effective beam monitoring along the injector linac and LBT, key beam diagnostics—including beam current, transverse profile, and energy profile monitoring—have been installed in the injector linac. In order to maintain full diagnostic performance, the screen monitor system is planned to be upgraded to enhance transverse beam profile monitoring, improve radiation resistance, and support injector linac optimization for higher machine performance. This paper presents the current status of the screen monitor system for the SPS injector linac and discusses the design and implementation plan for its upgrade.

As part of the new Proton Improvement Plan (PIP-II), Fermilab is undertaking the development of a new 800 MeV, 2 mA H- superconducting RF linac to replace its present normal conducting 400 MeV linac. The PIP-II linac consists of a series of superconducting RF cryomodules from 2.1 MeV to 800 MeV. To limit the potential damage to the superconducting RF cavities, PIP-II will utilize non-invasive laser-based monitors (laserwires) to obtain beam profiles via photoionization. This paper will present the design of this PIP-II laserwire system including the picosecond pulsed laser, optical transport line, 13 individual laserwire stations, laser feedback and timing controls. The paper also describes the signal detection system and operation of the profile measurements.

A Feschenko-style Bunch Shape Monitor (BSM) was used to measure the longitudinal profile of H- bunches at the Los Alamos Neutron Science Center (LANSCE) accelerator. The measurements were taken in the 201.25-MHz drift tube linac (DTL), where the design beam energy is 72.72 MeV. The results of the measurements are presented, and several unexpected features of the measurements are discussed.

EuPRAXIA@SPARC_LAB is a FEL user-facility currently under construction at INFN-LNF in the framework of the EuPRAXIA collaboration. The electron beam will be accelerated to 1 GeV by an X-band RF linac followed by a plasma wakefield acceleration stage. This high-brightness linac requires diagnostic tools able to measure the beam parameters with high accuracy and resolution. To monitor the beam energy and its spread, magnetic dipoles and quadrupoles will be installed along the linac, together with viewing screens and CCD cameras. Macroparticle beam dynamics simulations were performed to determine the optimal energy measurement setup in terms of accuracy and resolution. Similar diagnostics evaluations were carried out for the spectrometer installed at the 100 MeV RF linac of the beam facility SSRIP (IFIN-HH, Romania), whose commissioning planned for 2026 will be performed by INFN-LNF in collaboration with IFIN-HH. Optics measurements were performed to characterize the resolution and magnification of the optical system foreseen to be used at EuPRAXIA@SPARC_LAB and SSRIP for beam energy monitoring.

As part of the CSNS-II upgrade, an improved injection scheme will be implemented to mitigate the space charge effect. To precisely measure the transverse beam position during injection, painting, and storage in the Rapid Cycling Synchrotron (RCS), a large-aperture (260 mm × 180 mm) Beam Position Monitor (BPM) is essential. The rectangular cut-plane BPM was selected for its excellent linearity over a large area and high signal-to-noise ratio (SNR). Due to limited space in the injection section, the BPMs must be integrated into the AC steering magnet. To prevent thermal heating from eddy current flow, a rib structure has been incorporated into the BPM's outer body. The BPM was designed using numerical simulation codes and subsequently manufactured. This paper details the simulation, design, and calibration results of the diagonal cut-plane BPM.

Our heavy ion beams are slow, short, and thick. For such beams, spiral beam position monitors(BPMs) are expected to provide good linearity and multiple information readouts despite their small size. At the RIKEN Nishina Center, various ion beams are accelerated using linacs and cyclotrons. However, the beams handled are slow enough compared to relativistic speeds, the bunch length is only about the same as the electrode size, and the beam diameter may be close to the electrode spacing. Conventional “diagonal cut” or “cosine two-theta cut” (for quadratic moments) BPMs produce deviations in wave height*. To solve this problem, it is expected that the wave height deviation can be eliminated by cutting the electrode in a spiral shape. Furthermore, by cutting in a spiral shape, multiple cuts can be placed in one BPM, and it is expected that beam intensity, horizontal position, vertical position, and second moment can be read out at a single location. The performance shown by simulations of the spiral BPM and the development of a prototype will be presented.

Modern BPM processors utilize digital processing of the beam induced signals. The information on the signal amplitudes is used for the delta over sum calculation of the beam position, while the readily available phase information is usually discarded. We have experimentally tested measurement of the individual positions of two beams propagating in the common beampipe utilizing both phase and amplitude data. The proposed method can be used for the energy recovery linacs and colliders.

We have developed a Stripline BPM readout device based on an AMD/Xilinx RFSoC chip which integrates multiple ADCs, DACs, a large scale FPGA, and an ARM processor in a single package. The developed device is intended for use at the beam transfer line connecting the KEK injector Linac to the SuperKEKB collider rings. SuperKEKB will operate at unprecedented luminosities requiring very high beam currents. To reach and maintain such currents, high injection efficiency is essential which in turn requires precise tuning of the injection process. The RFSoC based BPM will provide a highly flexible platform for beam orbit measurements near the injection point required for the tuning. One objective is to enable the separate resolution of the orbit of both bunches in the two-bunch injection mode, where two bunches are accelerated and injected with 96 ns spacing. Additionally, we plan to utilize resulting measurements as inputs for real-time automated injection tuning and feedback to the upstream steering in the beam transport line. Here, we present the status of the development including results from prototype tests conducted at the KEK injector Linac.

PERLE is an Energy-Recovery Linac (ERL) to be constructed at IJCLab in Orsay. It will be the First multi-turn ERL with superconducting RF (SRF) with the ambition to reach 10MW beam operation (20mA beam current and 500MeV beam energy) Diagnostics are a key element for PERLE operation and among diagnostics, the salient feature for Beam position monitors (BPMs) is the presence of multiple beams which need to be individually diagnosed and controlled. This document describes the design and the operation of PERLE BPMs with particular attention given to how these BPMs will handle multiple beams during commissioning and under normal operation of PERLE

The SPIRAL2 accelerator, designed for high intensity beams (up to 5 mA), needs to evolve for low intensities in order to reach the requirements of the S3 experimental room. This means increasing the operating range of diagnostic monitors including the Beam Position Monitors (BPM). Twenty BPM are installed in the warm sections of the linac to measure positions, ellipticities and phases. The digital processing of the BPM acquisition has been modified to operate at low intensity. This was done by improving the signal-to-noise ratio with an increase of the averaging resolution, an improvement of the channel equalisation system and with a deduction of parasitic signals induced by the surrounding equipment. The process was also modified to operate with chopper frequencies between 1 Hz and 1 kHz. A new BPM interface, with tables and graphical displays in order to control beam phases and energies in the linac, is now available. These new developments and measurement results in laboratory and with SPIRAL2 beams are presented, which show good results with a low intensity down to 1 µA.