Search Results (448)

Particle accelerators have become indispensable tools in fundamental charged-particle and beam-physics research, medical diagnostics and therapy, security screening, and many other applications. A small number of large, GeV-scale machines, often called “Big Science,” drive scientific discovery, while thousands of small accelerators serve everyday needs, primarily as X-ray sources when an electron beam is used. When an electron beam in the keV–MeV range strikes a high-Z (high-atomic-number) target material, it produces bremsstrahlung photons, whose interaction with matter is governed by the photoelectric effect, Compton scattering, and pair production, each dominant in a distinct energy regime that also depends on the atomic number of the absorbing material. A small accelerator can generate such significant effects if the energy and material parameters are properly matched, and these interactions can be exploited to generate material-specific signatures. Ion beams, on the other hand, deposit energy in materials and are used for gamma and neutron production, microstructure analysis, and many other applications. Here we review the operating principles of several small accelerators and their potential applications, offering a unified perspective on their role in contemporary science and technology. Full article

The commercially available compact electron linear accelerator (LINAC) products used for high-energy imaging of dense and/or thick objects offer accelerated electron beams in an energy range from 1 MeV to 10 MeV with focal spot sizes generally from 1.0 mm to 2.0 mm on a stopping target measured at Full Width at Half Maximum (FWHM) of usually close to a Gaussian distribution profile. Reducing the focal spot used to generate Bremsstrahlung for imaging is very important, as smaller focal spots permit less penumbra for much better resolution in the produced images. Meeting such demand presents several serious challenges. Common methods for such focal spot reduction add extra elements, complexity, deliver insufficient beam power, etc., making them unsuitable for compact commercial machines. An alternative method to obtain a submillimeter electron beam focal spot FWHM of less than 0.5 mm with a “clean” Gaussian distribution using a novel RF structure design and tuning method (patent pending) is presented, used in the first 3, 6, and 9 MeV Accelerator Beam Centerlines (ABC). This invention started a New MicroBeam LINATRON™ (MBL) product line with the first MBL6 prototype LINAC, built and tested by the High Energy Systems (HES) group at Varex Imaging Corporation. Full article

This work presents a covariance-aware extension of the hybrid nonlinear-kicker (NLK) injection framework. While previous baseline studies established centroid action reduction and hardware-aware NLK placement for idealized beams, the present study addresses finite-beam optimization using a realistic, position-dependent eight-wire kick profile. A realistic NLK field not only corrects the injected-beam centroid but also induces an amplitude-dependent shear across the internal phase-space ellipse. Depending on the injected covariance and ellipse orientation, this shear can either reduce or enhance beam filamentation. To exploit this mechanism, the AC-septum angle is treated as a trajectory-control knob for the injected centroid, while transfer-line matching is used to control the injected covariance matrix. We use ID2-downstream as the primary optics-favored case, as its high ${\beta }_N$ simultaneously increases nonlinear-field sampling and reduces the required correction kick. Furthermore, at this location, the injected beam is close to a matched, near-upright covariance condition (${\alpha }_{beam}\approx 0$). We also examine ID1 middle and ID1 downstream as trajectory-controllable alternatives, and formulate a combined optimization over septum angle, transfer-line optics, and NLK current. Operational measurements of AC-septum stability, first-turn trajectory reproducibility, septum response, and injection-bump response validate the available trajectory-control authority required for realistic NLK optimization. The analysis identifies a residual oscillation floor proportional to the square of the remaining centroid offset and inversely proportional to the local beta function, demonstrating that the physically relevant objective is minimization of the final mean action after the realistic NLK kick, rather than percentage action reduction alone. This framework establishes a practical optimization strategy under realistic aperture, stability, and hardware constraints. In a representative covariance-matched ID2D case, the realistic eight-wire NLK reduces both mean horizontal action (from 3.372 μm to 0.382 μm) and finite-beam spread contribution (from 0.475 μm to 0.039 μm). Operationally, first-turn rms trajectory variations remain under 0.4 mm, and the measured trajectory response of 19.4 mm/mrad closely matches the 19.8 mm/mrad model. Full article

Ultrasonic Lamb waves are promising for the nondestructive evaluation of silicon wafers; however, their dispersive, multimode, and orientation-dependent propagation complicates multidirectional measurements in anisotropic media. This study presents a measurement system for wedge-free, multidirectional, A0-dominant Lamb-wave interrogation in a silicon wafer. The distinctive feature of the system is the integration of a fixed normal-incidence PZT source with non-contact scanning laser Doppler vibrometry, enabling wavefield acquisition along arbitrary in-plane directions without repeated wedge coupling or directional source reconfiguration. Frequency–wavenumber analysis demonstrates an A0-dominant wavefield, with the S0-associated power virtually indistinguishable from the baseline spectrum. A noise-adaptive Hilbert-envelope time-of-flight method and locally weighted scatterplot smoothing (LOWESS) reconstruct the orientation-dependent A0 group-velocity profile. The reconstruction shows a root-mean-square percentage deviation of 1.39% relative to the theoretical group velocities obtained from numerical simulations. This capability is practically important for wafer inspection as it reduces setup complexity, thereby improving measurement consistency. Full article

A remote automation controller NA64-DTC was developed, constructed, and integrated for the so-called “DESY Table” motorized platform, widely used in CERN East-Area and North-Area experimental installations. The device interfaces with the table manual control panel through a signal duplication connector, enabling remote operation without modifications to the original hardware. Button commands are emulated using opto-isolated switches, allowing seamless coexistence with the standard manual control system. The controller is based on an ESP32-C3 System-on-Module and hosts an HTTP server that provides a simple and flexible interface for experiment-specific integration and automation. The system was successfully commissioned at CERN using the PS-T9 and SPS-H4 beamline facilities. A positioning accuracy of approximately $0.2$ mm and $0.3$ mm was achieved over the full movement range of the vertical and horizontal table axes, respectively, with the residual positioning error dominated by the finite inertia of the platform. The device was operated continuously for more than two months without any observed failures or communication errors. Although originally developed for the NA64 experiment, the proposed solution is applicable to any CERN installation employing the DESY Table platform. This work describes in detail the device technical design and operation, as well as the performances obtained during the commissioning. Full article

Optical fibre beam loss monitors (oBLMs) are in use at several accelerator facilities worldwide as an online, low-cost, and reliable beam loss monitoring solution. They measure beam loss locations through time-of-flight analysis of Cherenkov radiation produced in optical fibres by relativistic particle showers from beam loss events. They offer continuous accelerator coverage and can attain a beam loss location precision of 1 m or better. The recirculating multi-energy particle beams of energy recovery LINACs present difficulties in tracking losses from beam bunches throughout their journey in the machine. A potential solution is offered through estimation of the beam loss energy from the measured intensity of the oBLM signal, which could be used to determine the beam bunches associated with each loss signal. Monte Carlo simulations of beam loss interaction with the oBLM were performed in Geant4 to qualitatively investigate the feasibility of this method. The most feasible scenario occurs when the percentage change in the number of lost particles (loss intensity) from two beam losses is less than half of their corresponding percentage energy change. Otherwise, a complementary means of determining loss intensity is recommended for this method. Additionally, the relationship between beam energy and oBLM signal intensity was found to vary strongly with beam loss position relative to the fibre. Measurements were collected from the oBLM system installed at CLEAR, CERN; qualitative agreement was observed with the simulations, although quantitative analysis was not possible. Simulations were therefore identified as a critical component of oBLM energy estimation—to determine the expected behaviours of the oBLM signal on an accelerator and guide the analysis and interpretation of the intensity measurements. Full article

Electro-optical bunch arrival time measurement is a method to monitor the timing of bunches in predominantly linear electron accelerators to below femtosecond precision. Despite the method being well established, a stable and fully available measurement was reported only recently. DESY’s free-electron lasers FLASH and EuXFEL feature Bunch Arrival Time (BAM) diagnostics that serve as a standard operation data source for the facility’s longitudinal fast and slow stabilization, as well as an instrument available to the users for pump laser alignment and offline analysis. A comprehensive upgrade and R&D effort targeting the performance of DESY’s BAM was carried out in recent years. The complexity of the device poses challenges to its control layer, calibration, drift control, and operation setup. Solving these proved to be essential in reaching operational stability and high availability. We report on the updates to the BAM controls and the development of automation of numerous tasks that contributed a great deal to achieving long-term stability and full run availability. Full article

Space gravitational wave detection missions demand ultra-stable calibration of inertial sensor capacitive sensing. Conventional dynamic methods suffer from mechanical vibration noise and bias separation difficulties, while large-displacement operation introduces pronounced nonlinearity. This work proposes a static calibration method using an image-based displacement measurement system to establish a vibration-free benchmark. A subpixel edge detection algorithm locates the Test Mass and Electrode Housing edges with a repeatability of approximately 0.05 pixels, and the Test Mass geometry is independently calibrated by a Coordinate Measuring Machine (CMM, ±2 µm, $k=2$) to provide SI traceability. A nonlinear calibration model incorporating higher-order Taylor terms is developed, combined with a forward/reverse connection technique for composite bias modeling. Experimental validation at $x_0=665$ µm ($x_0/d_0\approx 0.665$) demonstrated a gain coefficient repeatability of 0.01658% RMSPER and a combined expanded uncertainty of $U\approx 2.18\times {10}^{-5}$ $1/\mathsf{\mu }\mathrm{m}$ ($k=2$). Intended as a complementary ground-based technique to dynamic calibration, this method avoids dynamic excitation-induced noise while establishing complete SI traceability, offering a reliable solution for ground validation and long-term monitoring of space inertial sensors. Full article

The bias-dependent capacitance of varactors can introduce harmonic distortion into the circuits where they are utilized. A gate capacitance model valid through inversion–depletion has been presented for GaN HEMT varactors in the drive for their utilization in monolithic GaN ASICs. This work focuses on the circuit and the methodology employed to accurately measure on wafer the harmonic distortion caused by one such device. The circuit is presented and its design considerations and operation trade-offs are discussed, followed by a presentation of the measurements resulting from its use. Second- and third-order harmonic distortion is recorded and presented, with Verilog-A model simulations used to fit the measured data. The model consists of a charge-based expression of the HEMT varactor capacitance, with a minimal number of parameters. The good fit of the model is demonstrated, proving both the suitability of the circuit used for the measurements and the validity of the capacitance model for real-world applications. Full article

The development of FLASH particle therapy, especially proton therapy, characterized by ultra-high dose rates (>40 Gy/s), presents significant challenges for dosimetry and beam monitoring. For example, ionization chambers (ICs) exhibit charge recombination effects leading to saturation, and other passive detectors cannot be used for real-time monitoring. This paper presents the idea, simulations and the preliminary prototype of a scintillating-fibers SiPM-based dosimeter for both high-flux and conventional dose-rate proton beam therapy. The prototype is based on 1 mm diameter plastic scintillating fibers, coupled to Silicon Photomultipliers (SiPMs). We estimated the interactions and the produced light signal within the fibers by the protons and towards the photodetectors using a semi-analytical model combining SRIM and analytical calculations. We estimated a light signal reaching the SiPMs in the range of 10⁷–10¹¹ photons (in a 50 ms beam pulse), for proton energies in the range 70–228 MeV, between the minimum and maximum beam current levels for conventional and FLASH conditions. Results highlight the very large dynamic range needed to be compatible with conventional and FLASH regimes. We also evaluated the linearity limits of the SiPMs and of the scintillating fibers. Finally, we preliminarily validated a reduced prototype version with a proton beam, demonstrating a good linearity of the system. Full article

In proton beam therapy, ideally, beam monitoring should be non-invasive to provide online real-time feedback, such that the total dose delivered to the patient is not significantly affected. The invasiveness of the Supersonic Gas-Curtain-Based Ionization Profile Monitor (SGC-IPM) system was quantified by perturbation in beam current and transverse beam profile parameters induced by the supersonic gas-curtain for a 4.9–5.3 keV electron beam, representing a worst-case scenario where perturbations can be more easily observable. The experimentally measured gas-curtain effects on transverse beam parameters (≤2%), intensity (≤−1%) and beam current (≤−1%) were small in magnitude and largely below resolution limits. To confirm these effects, order-of-magnitude beam–gas interaction approximations were calculated for the experimental energy range, demonstrating negligible energy loss with minor scattering, broadly consistent with the experimental results. Clinical proton beam gas-curtain predictions (70–250 MeV) indicate a further reduction of ∼${10}^4$ compared to the experimental observations. Even under the conservative electron beam conditions used in this study, the observed perturbations were minor or unresolvable and measured effects were significantly smaller than spatial and dosimetry scales relevant to proton radiotherapy. Overall, the experimental measurements and supporting order-of-magnitude estimates demonstrate that the SGC-IPM introduces negligible perturbations to beam parameters and is predicted to provide non-invasive beam profile monitoring for clinical proton beam diagnostics. Full article

Nonlinear kickers (NLKs) enable off-axis injection in ultralow-emittance storage rings by providing a strong kick to the injected beam while remaining nearly transparent to the stored beam. In hybrid schemes, a conventional four-kicker bump defines the injected trajectory, and the NLK reduces the first-turn action under constrained beam offset and optics conditions. Effective operation additionally requires stable and reproducible first-turn injection trajectories. We develop a compact action–angle framework that expresses NLK dynamics in terms of Courant–Snyder invariants and yields an analytical bound on achievable action reduction. This formulation provides direct design rules for NLK placement, phase advance, injected-beam offset, and kicker field profile. Within this framework, we identify the 8-wire NLK as a practical baseline and extend its design by relaxing the square-geometry constraint, enabling inward shifting of the off-axis field peak while preserving on-axis field and gradient cancellation. Application to the NSLS-II lattice shows how aperture, pulsed-power, and mechanical constraints combine to determine a coupled design solution. Multi-turn tracking confirms that candidate NLK locations maintain sufficient stay-clear (aperture-clearance) margin, while the optimized wire geometry reduces the required current and Lorentz force load. The results establish a unified approach for NLK-assisted injection design and provide a practical pathway for upgrades in diffraction-limited storage rings. Full article

Machine Learning (ML) techniques are increasingly being adopted in particle accelerator operations to enable efficient control of complex systems. At INFN–LNL, we investigated both offline and real-time ML-driven approaches to enhance beam quality, reduce setup time, and improve reliability across different accelerator facilities. As part of this effort, we developed Adaptive Region Bayesian Optimization (ARBO), a custom Bayesian Optimization algorithm that dynamically expands its search domain when the predicted optimum approaches a boundary. Offline studies applied ARBO to the design optimization of the medium-energy beam transport line of the ANTHEM BNCT facility. Real-time online tests demonstrated the effectiveness of ARBO. At PIAVE–ALPI, the combined transmission improved from 44.2% to 52.6%, corresponding to an ALPI-only increase from approximately 69% to 82%, approaching the theoretical maximum of 93%. At the ESS normal-conducting linac, ARBO enabled the simultaneous tuning of more than 50 control elements while improving transmission and maintaining stable trajectory correction. These results indicate that adaptive optimization strategies can substantially improve accelerator performance and support future advances in ML-assisted accelerator operations. Full article

To address the high demand for precise low-current measurements at the Sirius’ beamlines, a quad-channel high-resolution Ethernet picoammeter has been designed. The instrument can measure currents ranging from femtoampere to milliampere across eight selectable ranges, featuring integrated analog-to-digital converters (ADCs), enabling sampling rates of up to 2 ksps and synchronization capabilities. This work describes the hardware design, the hardware handling procedures to achieve sub-picoampere resolution, and the characterization results of the instrument, considering the experimental results from Sirius beamlines. The designed device provides noise performance and gain accuracy that is comparable to high-end commercial solutions, proving its suitability for critical applications like on-the-fly scanning experiments. Special attention will be given to evaluating trigger latency, synchronization outcomes, as well as the device’s installation and commissioning at beamlines. Furthermore, we will deeply explore the interplay between the trigger period, digital filter bandwidth, and front-end analog bandwidth to optimize the signal-to-noise ratio in specific applications. The hardware project is publicly available in CERN’s open hardware repository. Full article

Cosmic-Ray Neutron Sensing (CRNS) has become a standard method for non-invasive soil moisture monitoring at the field scale. With most CRNS sensors being derivatives from scientific nuclear equipment, the development of instruments based on alternative neutron detection technologies is a major development goal for CRNS. We present a modular instrument family based on boron-10-lined proportional counters, specifically designed for long-term autonomous field operation. The system is controlled by a data logger supporting various telemetry options and external SDI-12 environmental sensors, while the frontend electronics use pulse-height and pulse-length information to suppress non-neutron background and electronic noise. Our results show high energy efficiency, with the latest generation close to 50 mW, allowing solar-powered operation even in challenging environments. The performance of the instruments is validated within long-term field deployments in different settings, showing that boron-10-based systems provide a scalable, low-power and cost-efficient alternative for the next generation of CRNS monitoring networks. Full article