Wednesday Poster Session: WEPG (2024)

WEPG

-

Wednesday Poster Session: WEPG

22 May 2024, 16:00 - 18:00

Advanced Photon Source Upgrade (APS-U) storage ring, currently in installation and testing, is set for beam commissioning in early 2024. In the APS-U storage ring, there are 560 Beam Position Monitor (BPM) pickups, each equipped with high resolution electronics. This paper presents outcomes from pre-beam testing and beam commissioning of the APS-U BPM system. We discuss tailored features for advanced beam measurements, testing methodologies, challenges, and successful integration into the storage ring. Our findings demonstrate the robustness of the BPM system, emphasizing its crucial role in achieving the first beam and optimizing the APS-U storage ring's performance.

About: Received: 15 May 2024 — Revised: 17 May 2024 — Accepted: 17 May 2024 — Issue date: 24 May 2024

Maintaining beam-accelerating structure RF phasing of a linac is crucial for maintaining optimal beam transport performance. At the Advanced Photon Soure (APS), in 2008 we implemented an analog phase detector system using the Analog Devices AD8302 phase detector chip. The APS phase detectors use as an S-Band RF phase reference an out-coupled signal from the waveguide supplying the accelerating structures with RF and an S-Band filtered RF signal from a bpm for the beam-RF system phase measurement. The phase detectors are used throughout the length of the linac in a control law to automatically maintain the beam on-crest phase condition during operations. We have obtained from Instrumentation Technologies two phase detection systems we evaluated as a possible upgrade path for the legacy APS phase detector system. The systems are the Libera LLRF and Libera cavity BPM products available from Instrumentation Technologies. We compare the performance of each system to induced phase changes using the APS Linac RF thermionic gun electron source.

About: Received: 15 May 2024 — Revised: 21 May 2024 — Accepted: 21 May 2024 — Issue date: 24 May 2024

The BPM feedthroughs were manufactured and tested at the vendor and the APS lab. All feedthroughs were sorted in groups of four according to their capacitance. Four feedthroughs with close capacitance were welded to the housing in an assembly. The assemblies were measured in the APS lab to confirm their electrical performance acceptable and their x/y offsets were calculated according to VNA data. After the BPM assemblies were installed in the SR, they were measured again to verify their connections. The x/y offsets including the cables were compared with the previous data and will be used as the reference in beam commissioning. The testing results at the vendor, APS lab and APS-U SR were analyzed.

About: Received: 15 May 2024 — Revised: 18 May 2024 — Accepted: 19 May 2024 — Issue date: 24 May 2024

Single-pulse, high dynamic range BPM signal detection has been at the top of the Argonne Wakefield Accelerator (AWA) Test Facility's most-wanted list for many years. The AWA beamline's unique capabilities require BPM instrumentation with an unprecedented dynamic range, making it challenging to design and prototype a cost-effective solution. We have prototyped many different approaches over the years. Finally, a recent prototype shows the long-sought solution for AWA's low-cost button BPM signal detection is becoming feasible. This paper shares the design and test results of this prototype.

About: Received: 21 May 2024 — Revised: 23 May 2024 — Accepted: 23 May 2024 — Issue date: 24 May 2024

The Inverse Compton Scattering Interaction Point (ICS-IP) vacuum chamber provides a UHV environment where the electron and IR laser beams are overlapped in space and time to generate hard X-rays between 4 and 20 keV. The chamber has over two dozen motorized stages that position YAG screens with ~10 nm precision utilizing the EPICS framework for instrumentation interface. Using agile programming methods, MATLAB GUIs were created to control all the motors inside the chamber. Each YAG screen has a linear array of holes ranging between 10 microns and 2 mm that are imaged by cameras mounted on top of the chamber. Programmable focus lenses and IR mirrors are positioned to focus the IR laser at the interaction point. An X-ray optic is mounted onto a six degree of freedom nano-positioner enabling capture and collimation of X-rays coming from the IP. The X-ray optic can also be extracted from the beam path to transport the freely diverging X-rays to the experiment hutch for imaging experiments. We present the systems integration of the chamber, diagnostics elements, and control software and comment on its performance during instrument commissioning.

About: Received: 15 May 2024 — Revised: 20 May 2024 — Accepted: 20 May 2024 — Issue date: 24 May 2024

One major factor contributing to electron beam stability in a storage ring is the mechanical vibrations of magnets. At NSLS-II, we employ electromagnetic actuators to induce controlled vibrations in the support girders of the magnets. Beam position monitors distributed around the ring measure the spatial and frequency distribution of beam oscillations. The collected data is used to create and validate a computer model through a simulated commissioning tool, simulating beam motion caused by magnet vibrations. This computational model is useful for establishing mechanical stability specifications for the low-emittance upgrade of NSLS-II.

About: Received: 07 May 2024 — Revised: 17 May 2024 — Accepted: 17 May 2024 — Issue date: 24 May 2024

The Radio Frequency System-on-Chip (RFSoC) FPGA-based high-performance bunch-by-bunch beam position monitor (BxB BPM) was developed and commissioned at NSLS-II. The new BxB BPM features a 14-bit 5 Gsps ADC, directly sampling 2 ns four-button signals, and digital signal processing with a synchronized 500 MHz RF reference clock. The BxB BPM provides 32 K points of ADC raw data, 5 K turns for up to 1320 bunch amplitude and position data, 2.6 million turn-by-turn (TxT) data points, 10 K turns of circular buffer, and 10 Hz streaming data. The potential applications include, but are not limited to measuring injection transient, efficiency, ion instability detection, and single/multi-bunch motion analysis. A ~15 μm single-bunch resolution was confirmed with the beam test. This paper will present the beam test results, hardware FPGA firmware architecture, and control system interface for operation.

About: Received: 17 May 2024 — Revised: 18 May 2024 — Accepted: 18 May 2024 — Issue date: 24 May 2024

A novel soft X-ray BPM (sXBPM) for high-power white beams of synchrotron undulator radiation has been developed through a joint effort of BNL/NSLS-II and Stony Brook University. In our approach, custom-made multi-pixel GaAs detector arrays are placed into the outer portions of the X-ray beam, and the beam position is inferred from the pixel photocurrents. Our goal is to achieve micron-scale positional resolution without interfering with user experiments, especially the most sensitive ones exploiting coherent properties of the beam. An elaborate mechanical system, which provisions for possible intercepts of kW-level beam in abnormal conditions, has been designed, fabricated, and installed in the 23-ID canted undulator beamline first optical enclosure. Separately, GaAs detectors with specially tailored spectral response have been designed, fabricated, and tested in the soft and hard X-ray regions at two NSLS-II beamlines. The paper gives an overview of the sXBPM system, presents the first results from the high-power white X-ray beam, and explains why our approach can be beneficial for XBPMs in future light sources with highly coherent beams.

Designing the cryogenic BPM pick-up for the Hadron Storage Ring (HSR) of the Electron-Ion Collider (EIC) is a challenging task as it needs to provide reliable beam position measurements over a variety of beam species and operating modes with various energies. The existing RHIC BPM stripline pick-up are not compatible with the planned HSR beam parameters as the HSR beam, compared to RHIC, will have a factor of 10 shorter bunch length (to 6 cm rms), a factor of 3 more currents (0.69 Amps, with 290 bunches), and will have a large radial offset (±20 mm) to adjust the path length for different beam energies. The BPM pick-up design takes into consideration the potential elevated heating concerns caused by resistive wall loss due to radial beam offset and heat conduction through cryogenic BPM signal cables. The geometric impedance associated with the button configuration and housing transition to the adjacent HSR beam screen must also be minimized. This paper focuses on the design of the HSR cryogenic BPM pick-up and describes simulation results of the position-related voltage signals, and beam-induced losses on the metallic BPM buttons due to the radial offsets.

About: Received: 15 May 2024 — Revised: 20 May 2024 — Accepted: 21 May 2024 — Issue date: 24 May 2024

We present a demonstration of time-resolved diagnostics within the Coherent Electron Cooling (CeC) Pop Experiment. This technique utilizes a combination of a focusing lattice, transverse deflecting cavity, and YAG screen, along with unique analytical techniques, to precisely measure and analyze the longitudinal profile information of the CeC electron beams. Additionally, our measurement of slice quantities contains slice emittance, slice current, and slice Twiss parameters. Through comprehensive analysis of these key parameters, we acquire essential information that aids in the detailed control of the beam instability of the CeC electron beams. This ultimately enhances our understanding of beam dynamics and contributes to the optimization of performance within the Coherent Electron Cooling system.

About: Received: 13 May 2024 — Revised: 21 May 2024 — Accepted: 21 May 2024 — Issue date: 24 May 2024

One of the main tasks for advanced experiments in modern accelerators is the generation of low-energy and high-brightness beams. The Advanced Research Electron Accelerator Laboratory (AREAL) is a linear electron accelerator based on a photocathode RF gun. The basic aim of this facility is to generate electron bunches of sub-picosecond duration with an extremely small beam emittance for ultrafast processes in advanced experimental studies in the fields of accelerator technology and dynamics, material and life sciences. In this paper, the current status and plans for further upgrades of the diagnostic system, along with the techniques used for transverse beam emittance measurements, are presented.

About: Received: 14 May 2024 — Revised: 20 May 2024 — Accepted: 23 May 2024 — Issue date: 24 May 2024

Minimising the energy spread within the electron bunch is essential for optimal performance of free electron lasers. Wakefields from corrugated and dielectric structures have been demonstrated to be effective in bunch dechirping. However, the repercussions in beam quality are not yet well understood. Here, a dielectric wakefield structure, manufactured to be included at the CLARA facility, has been studied with simulations. It consists of two planar and orthogonally oriented dielectric waveguides with an adjustable dielectric gap. This structure allows the longitudinal wakefield to compensate the energy spread whilst controlling the undesirable effect of the transverse wakefields on the beam quality. Simulations have been performed at different bunch lengths, bunch energy spreads and dielectric gaps to allow a better understanding of longitudinal and transverse wakefields beam effects within the dechirper.

About: Received: 10 May 2024 — Revised: 20 May 2024 — Accepted: 20 May 2024 — Issue date: 24 May 2024

Passive streaking devices have been proposed and developed at several facilities worldwide, providing a flexible and cost-effective longitudinal bunch profile diagnostic. A passive streaker, using wakefields excited in dielectric lined waveguides, is planned to be installed in the FEBE experimental chamber at CLARA Phase-2. We present experimental tests of bunch reconstruction performed during dielectric wakefield acceleration experiments at Phase-1 of CLARA, with 100 pC, 35 MeV electron beams. These profiles have been compared to simulated beam profiles, produced using S2E simulation codes Elegant and ASTRA. Conclusions have been drawn on the operation of passive streakers, applicable to the design and operation of the future streaker at CLARA.

About: Received: 14 May 2024 — Revised: 21 May 2024 — Accepted: 21 May 2024 — Issue date: 24 May 2024

Development of an optical fiber-based beam loss monitor (OBLM) is in progress at the co*ckcroft Institute (CI), UK. The novel sensor utilizes the Cherenkov radiation (CR) emitted in optical fibers by relativistic particle showers generated in beam loss or breakdown events. Breakdowns are a problem for high-power magnetrons, such as those in medical accelerator facilities, as damage to the magnetron cathode reduces the device efficiency and lifetime. These events can be detected by emitted CR channeled along the fibers to photomultiplier detectors, and a time-of-flight method can be used to calculate the breakdown location from the CR arrival time. This has previously been demonstrated with the OBLM system on RF cavities (at CLARA, Daresbury Laboratory, and CTF3, CERN); and allows for rapid and reliable breakdown detection which is important for damage mitigation. This contribution presents proof-of-concept measurements from OBLM studies into magnetrons at Teledyne e2v, Chelmsford. It also discusses design adjustments made to improve the detector sensitivity and how the performance can be enhanced using the sensor (or similar).

About: Received: 14 May 2024 — Revised: 20 May 2024 — Accepted: 21 May 2024 — Issue date: 24 May 2024

Synchrotron radiation (SR) is a phenomena found in most accelerator facilities. Whilst many look to reduce the amount of SR produced to minimize beam losses, its existence allows for several types of novel non-invasive beam instrumentation. The aim of this study is to use SR in the development of a non-invasive, high resolution, longitudinal bunch length monitor. The monitor will be capable of sub 100 fs bunch measurements, which are becoming more common in novel acceleration and free electron laser facilities. This contribution details the simulation work carried out in Synchrotron Radiation Workshop (SRW), which allows for complex studies into the production and features of coherent synchrotron radiation (CSR). The design of the monitor has also been discussed, alongside simulations of the planned optical setup performed in Zemax OpticStudio (ZOS).

About: Received: 08 May 2024 — Revised: 20 May 2024 — Accepted: 20 May 2024 — Issue date: 24 May 2024

A non-invasive bidirectional beam profile monitor using beam-induced fluorescence upon a thin sheet of gas has been developed at the co*ckcroft Institute in collaboration with CERN and GSI. This device is particularly suited to the Electron Beam Test Stand, and as such, a bespoke gas injection has been optimized for this specific use-case to provide diagnostics unavailable to conventional scintillator screens. The bidirectionality allows for the observation of beam reflections back along the beam path as a result of a beam dump with non-optimized repeller electrode potential. Furthermore, the heating effects of a high current DC beam are negated by the self-replenishing gas sheet. These benefits make this device ideal for use in the Electron Beam Test Stand. This contribution summarizes the optimization study of the gas jet generation performed with a multi-objective genetic algorithm to meet required screen dimensions whilst maintaining acceptable vacuum levels.

About: Received: 14 May 2024 — Revised: 22 May 2024 — Accepted: 22 May 2024 — Issue date: 24 May 2024

A minimally-invasive gas jet in-vivo dosimeter for medical treatment facilities is being developed at the co*ckcroft Institute (UK), to provide full online (real time) monitoring with less frequent calibration. The monitor functions via a thin, low-density, gas jet curtain, intersecting with the beam. Online monitoring is crucial for hadron beams where acceptable dose tolerances are narrow, hence the beam should be perturbed only by the minimum amount necessary to acquire a signal. An experiment to determine the level of invasiveness of supersonic gas jet beam profile monitors was undertaken to quantify how much the gas jet perturbs the beam. This was accomplished using a 10 keV electron gun with a maximum current of ~100 μA, available in the DITAlab of the co*ckcroft Institute. A scintillator screen and Faraday cup were placed in path of the beam to measure the change in beam size and current respectively. In the future, a simulation study using GEANT4 will be completed with the experimental beam parameters to verify the results. This contribution examines the perturbation experienced by a particle beam from a gas jet beam profile monitor, and quantifies the effect the jet has on the beam size and current.

About: Received: 14 May 2024 — Revised: 24 May 2024 — Accepted: 24 May 2024 — Issue date: 24 May 2024

The Cornell Electron Storage Ring (CESR) beam position monitors (BPM) consists of four button-shaped pick-up electrodes, each individually instrumented with readout electronics that allow acquisition of turn-by-turn data. The beam position is reconstructed using the measured signal amplitude from the four electrodes. Systematic effects such as physical differences between the electrodes (displacement, tilt) and gain differences between the readout electronics bias the measured amplitudes, thus the measured beam position. An improved beam-based method to measure the relative gains has been developed and validated using Monte Carlo simulations, and has been successfully deployed at CESR. It relies on solving a system of equations for different beam positions and simultaneously for the relative gains, knowing the response map of the pick-up electrodes as a function of beam position. The typical implementation uses 9 beam positions at one BPM with horizontal and vertical spatial separation greater than 500 microns. The main limitation of the method is time; it takes about 15 minutes to collect data for a single/few BPMs, making it impractical to calibrate all the 100 BPMs. We are planning on using a transverse resonance island buckets (TRIBs) lattice demonstrated at CESR to allow collecting 9 beam positions at all BPMs at once in a matter of minutes. This paper will present the new method, how it performs and its deployment at CESR.

About: Received: 15 May 2024 — Revised: 20 May 2024 — Accepted: 20 May 2024 — Issue date: 24 May 2024

A critical factor in determining the limit of the brightness of an electron beam is the mean transverse energy (MTE) of its source, which describes the spread in transverse momentum of electrons at the moment of emission from the source. To increase beam brightness, there has been much work in growing novel photocathodes with low MTE and high quantum efficiency (QE) near threshold photoemission excitation energies. Therefore, it is important to have a testing platform for accurately measuring the MTE of a cathode over a range of cryogenic temperatures and photoexcitation energies, with self-consistent results across multiple measurement techniques. Here, we will discuss the characterization and operation of the Cornell Cryo-MTE-Meter beamline which aims to fulfill these criteria for a robust photocathode testing platform.

About: Received: 17 May 2024 — Revised: 18 May 2024 — Accepted: 23 May 2024 — Issue date: 24 May 2024

Due to improvements of the performance of FELs, the measurements of the beam’s slice energy spread is becoming increasingly important for optimization of the brightness. Of particular interest are measurements of the uncorrelated energy spread near the gun as this determines the lower limit of the energy spread for the rest of the machine. At the Photo Injector Test facility at DESY in Zeuthen (PITZ), the uncorrelated energy spread is measured of an electron beam generated from an L-band electron gun and accelerated to 20 MeV with a booster cavity. The energy spread of the central time slice is measured using a transverse deflecting structure (TDS) and a dispersive arm to image the longitudinal phase space. Scans of the TDS voltage and quadrupole strengths are used to remove the contributions from the TDS, transverse emittance, and imaging resolution. Presented is an overview of the measurement procedure, resolution, and results of measurements tests.

About: Received: 16 May 2024 — Revised: 20 May 2024 — Accepted: 21 May 2024 — Issue date: 24 May 2024

Efficient operation of the Large Hadron Collider (LHC) relies on accurate longitudinal beam measurements to diagnose beam instabilities and verify the correctness of bunch-shaping techniques. To achieve this goal, a diagnostic system was developed to perform high-resolution measurements of longitudinal bunch profiles. High-performance oscilloscopes, synchronized to precise accelerator events, are employed to carry out the measurements, acquiring data from wideband wall-current monitors installed in the machine. This paper provides details on the implementation of the system, highlighting its current and future applications that will play a key role in increasing beam intensity in the LHC.

About: Received: 02 May 2024 — Revised: 20 May 2024 — Accepted: 22 May 2024 — Issue date: 24 May 2024

A new design of fast wire scanner was installed in the CERN injector complex as part of the upgrades linked to the High-Luminosity LHC Project. Initial operations with these beams were good, but during the planned intensity ramp-up one early 2023, all four SPS scanners failed at the same time. An urgent program was put in place to understand and address this failure with experts from across the accelerator fields. Many measurements and simulations were performed and solutions implemented. This paper gives an overview of the issues seen, understanding and mitigations put in place to allow the instrument to perform at the maximum planned operational intensities.

About: Received: 13 May 2024 — Revised: 21 May 2024 — Accepted: 21 May 2024 — Issue date: 24 May 2024

A low-latency, real-time diagnostic system for the analysis of longitudinal Schottky signals in CERN’s antiproton chain has been developed. The system, installed in CERN’s Antiproton Decelerator (AD), processes the combined output of two low-noise, wideband AC beam transformers. It uses a GPU and the NVIDIA CUDA Toolkit, exploiting the directly sampled data and hardware features provided by the low-level radio-frequency (LLRF) VMEBus Switched Serial (VXS) system and its companion ObsBox server, to implement the FFT-based multi-harmonic spectral analysis needed to set up and monitor the stochastic and electron cooling processes. Longitudinal beam properties, such as mean momentum and momentum spread, are also derived to evaluate and log the machine performance. This paper describes the implementation of the system and its integration within the CERN control system, achieved using the Front-End Software Architecture (FESA) framework and a graphics co-processor directly installed in the Front-End computer (FEC), running a real-time operating system environment. Preliminary results of its usage in the Extra Low ENergy Antiproton (ELENA) ring and next steps to process bunched beam spectra are also presented.

About: Received: 02 May 2024 — Revised: 18 May 2024 — Accepted: 18 May 2024 — Issue date: 24 May 2024

A comprehensive model accurately depicts and tracks emittance and luminosity evolution in the Large Hadron Collider (LHC), considering known effects like IBS, synchrotron radiation damping, coupling and incorporating data-driven factors on emittance growth and intensity losses. Used extensively in LHC Run 2, the model is updated for compatibility with new optics and operational schemes in Run 3, featuring luminosity leveling. This paper discusses the analysis of 2022 and 2023 LHC data, exploring emittance evolution and identifying extra blow-up at injection and collision energies compared to model predictions. Examining the model's agreement with collision data provides insights into the impact of degradation mechanisms, configuration options, filling schemes, and beam types on delivered luminosity. These studies offer valuable insights into potential gains in integrated luminosity for subsequent Run 3 years.

About: Received: 15 May 2024 — Revised: 21 May 2024 — Accepted: 21 May 2024 — Issue date: 24 May 2024

All wires of the four CERN SPS rotational wirescanners broke when increasing the beam intensity towards the target for the LHC Injector Upgrade in 2023. Impedance and thermal studies were immediately launched, with simulations and measurements indicating that beam induced heating from resonant modes on the thin wire could be sufficient to cause these breakages. Mitigation measures to displace electromagnetic losses away from the wire were proposed and implemented. This allowed a much higher beam intensity to be reached, close to the LIU target. Simulations now predict that the modified wirescanners can sustain the LIU beam parameters.

About: Received: 13 May 2024 — Revised: 21 May 2024 — Accepted: 21 May 2024 — Issue date: 24 May 2024

Observation of Schottky signals provides information on important beam and machine parameters, such as transverse emittance, betatron tune, and first-order chromaticity. However, the so-far developed theory of Schottky spectra does not include the impact of the higher-order chromaticity, known to be non-negligible in the case of the Large Hadron Collider (LHC). In this contribution, we expand the theory of Schottky spectra to also take into account second-order chromaticity. Analytical results are compared with macro-particle simulations and the errors resulting from neglecting second-order chromaticity are assessed for the case of the LHC.

About: Received: 10 May 2024 — Revised: 22 May 2024 — Accepted: 22 May 2024 — Issue date: 24 May 2024

Schottky monitors are valuable non-invasive tools used for beam diagnostics, providing insights into crucial bunch characteristics such as tune, chromaticity, bunch profile, or synchrotron frequency distribution. This study investigates Schottky spectra at the Large Hadron Collider (LHC) through a combination of simulations and measurements. Experimental data from lead ion bunches are compared with simulated spectra derived from time-domain, macro-particle simulations. In particular, amplitude detuning due to the octupole magnets, known to influence the Schottky spectra, is incorporated into the simulations. These simulations are performed for various octupoles currents with the goal of better understanding the interplay between octupoles and the Schottky spectrum. Finally, measured spectra are compared to simulations performed using the best available knowledge of the parameters impacting the spectra.

About: Received: 14 May 2024 — Revised: 17 May 2024 — Accepted: 17 May 2024 — Issue date: 24 May 2024

Schottky monitors serve as non-invasive tools for beam diagnostics, providing insights into crucial bunch characteristics such as tune, chromaticity, bunch profile, or synchrotron frequency distribution. However, octupole magnets commonly used in circular storage rings to mitigate instabilities through the Landau damping mechanism, can significantly affect the Schottky spectrum. Due to the amplitude-dependent incoherent tune shift of individual particles, the satellites of the Schottky spectrum are smeared out as the octupolar field increases. This study investigates the impact of octupoles and their incorporation into theory, with the goal of improving beam and machine parameter evaluation from measured spectra. Theoretical findings are validated through macro-particle simulations conducted across a range of octupole strengths, encompassing typical operational conditions at the Large Hadron Collider.

About: Received: 14 May 2024 — Revised: 20 May 2024 — Accepted: 24 May 2024 — Issue date: 24 May 2024

The WS superconducting systems are based on scintillator detectors and wavelength shifting fibers are mounted on the beam pipe. The detectors are coupled to long haul optical fibers, which carry the signals to custom front end electronics sitting in controls racks at the surface. The acquisition chain have been characterized at IHEP (Protvino), CERN PSB, COSY Juelich and SNS before installation in the ESS tunnel. The beam test results of this system design, differing from the standard approach where photomultipliers are coupled to the scintillator will be presented.

About: Received: 08 May 2024 — Revised: 20 May 2024 — Accepted: 21 May 2024 — Issue date: 24 May 2024

BPM signal processing uses digital or analog down-conversion to report phase and magnitude at a single frequency, however the digitized BPM signal may contain many more harmonics and a larger bandwidth of information which may be useful. An FPGA implementation is described which captures the full bandwidth BPM signal with minimal processing and resources. This approach can be scaled to captures as many beam harmonics as needed, limited only by the bandwidth of the ADC used. The periodic nature of the BPM signal is utilized to use time-interleaved sampling to effectively multiply the sampling rate of the ADC.

About: Received: 16 May 2024 — Revised: 21 May 2024 — Accepted: 21 May 2024 — Issue date: 24 May 2024

We report updates on design work* and ongoing development of a fluorescence-based molecular gas curtain which will be used to observe the 2D transverse profile of multi-charge state heavy ion beams at the Facility for Rare Isotope Beams (FRIB). The device will produce an ultra-thin, rarefied nitrogen gas sheet and requires that the gas curtain be uniform and thin to prevent distortion of the collected signal in operation. To determine the characteristics of the generated curtain, we evaluate the design using a combination of bench-testing with a Bayard-Alpert gauge and molecular dynamics simulations using MolFlow+. This paper details the design and bench testing of the sheet generator, gas removal system, and interaction chamber of the device, as well as expected photon generation from these parameters.

About: Received: 15 May 2024 — Revised: 18 May 2024 — Accepted: 18 May 2024 — Issue date: 24 May 2024

As the Facility for Rare Isotope Beams (FRIB) ramps up to 400 kW, a thermal imaging system (TIS) is essential to monitor the beam spot on the production target. The TIS is an array of mirrors and a telescope in the target vacuum chamber; this relays the image through a window to the optics module outside the chamber. The design presented many challenges from alignment, to remote installation of the TIS and integrated shielding, and repeatable re-installation of the mirror array and optics module. The target TIS has been in operation since 2021 and supports FRIB operations for secondary beam production, with incident power up to 10 kW. The temperatures seen validate the expected temperatures from analysis. The mechanical design of the FRIB target TIS is presented here as well as initial performance.

About: Received: 14 May 2024 — Revised: 18 May 2024 — Accepted: 23 May 2024 — Issue date: 24 May 2024

Beam tomography is a method to reconstruct the higher dimensional beam from its lower dimensional projections. Previous methods to reconstruct the beam required large computer memory for high resolution; others needed differential simulations, and others did not consider beam elements' coupling. This work develops a direct 4D reconstruction algorithm using Markov Chain Monte Carlo.

About: Received: 15 May 2024 — Revised: 19 May 2024 — Accepted: 19 May 2024 — Issue date: 24 May 2024

The Proton Improvement Plan-II (PIP-II) accelerator upgrade at Fermilab represents a groundbreaking leap forward in high-energy physics research. This ambitious initiative involves enhancing Fermilab's accelerator complex by replacing the current linear accelerator with a warm front end (WFE) capable of accelerating H- beams up to 2.1 MeV. Subsequently, a superconducting linac further accelerates these beams up to 800 MeV. To pre-cisely measure the transverse beam profile, a combination of traditional wire scanners at the WFE section and Laser wire scanners along the superconducting linac are planned for implementation. This investigation centers on refining the Faraday cup design for the PIP-II Laser wire scanners by utilizing GEANT4, a Monte Carlo simulation toolkit. Leveraging this method enables a comprehensive analysis of particle trajectories, energy deposition, secondary electron emission, backscattering, etc., facilitating optimization through adjustments to cup geometries, materials, and placement to maximize its efficacy in beam diagnostics.

About: Received: 17 May 2024 — Revised: 22 May 2024 — Accepted: 22 May 2024 — Issue date: 24 May 2024

We present the design details and outline the construction progress of the Ionization Profile Monitors (IPMs). Two IPMs, designed for transverse beam size measurements of 70 MeV/c protons, are slated for installation—one horizontal and one vertical—in the IOTA ring. These IPMs are fast (1.8 microsecond, one turn), accurate (to better than 10%) and non-destructive diagnostics. They will play a pivotal role in facilitating comprehensive beam studies, particularly in investigating the dynamics of space-charge dominated proton beams in IOTA.

About: Received: 11 May 2024 — Revised: 20 May 2024 — Accepted: 23 May 2024 — Issue date: 24 May 2024

The Fermilab Side-Coupled Linac contains seven 805 MHz modules accelerating H- beam from 116 MeV to 400 MeV. Each module contains at least one wire scanner, yielding beam intensity at positions along a transverse direction. These wire scanners each contain three wires, mounted at different angles: "X", "Y", and 45° between "X" and "Y" to analyze coupling. Recently, a significant amount of transverse X-Y coupling was identified within wire scanner data from the Side-Coupled Linac, which has been present in data from the past decade. This realization has prompted an investigation into the wire scanner's utility as a diagnostic tool in the Fermilab Linac. This work presents efforts to better characterize the wire scanners' limitations and the phenomenon occurring in the Side-Coupled Linac.

About: Received: 15 May 2024 — Revised: 22 May 2024 — Accepted: 22 May 2024 — Issue date: 24 May 2024

The measurement of beam emittances by extracting the quadrupole mode signal from a 4 plate BPM was published at least 40 years ago. Unfortunately, in practice, this method suffers from poor signal to noise ratio and requires a lot of tuning to extract out the emittances. In this paper, an improved method where multiple BPMs are used together with better mathematical analysis is described. The BPM derived emittances are then compared with those measured by the Ion Profile Monitor (IPM). Surprisingly, the BPM measured emittances behave very well and are more realistic than those measured by the IPM.

About: Received: 13 May 2024 — Revised: 21 May 2024 — Accepted: 23 May 2024 — Issue date: 24 May 2024

Cryogenic Current Comparators (CCC) are ultrasensitive DC-Beam Transformers based on superconducting SQUID technology. With the aim to provide a robust and high resolution intensity measurement for application at FAIR and CERN machines, numerous steps of optimization were carried out over the last years by a collaboration of institutes specialized on the various subtopics. Different types of CCCs with respect to pickup, magnetic shielding, SQUID types and SQUID coupling have been developed and were tested in the laboratory as well as under beamline conditions. In parallel, the cryogenic system has steadily been optimized, to fulfill the requirement of a standalone liquid helium cryostat, which is nonmagnetic, fit for UHV application, vibration damped, compact and accessible for maintenance and repair. We will present the particular development steps and describe the final version of the CCC for FAIR as their outcome. The latest beamtime results are shown as well as recent tests with the cryogenic system. The CCC for FAIR will be a so called Dual-Core CCC (DCCC), which runs two pickups in parallel with independent electronics for better noise reduction and redundancy. The magnetic shielding will have an axial meander geometry, which provides superior attenuation of external magnetic noise.

About: Received: 14 May 2024 — Revised: 21 May 2024 — Accepted: 21 May 2024 — Issue date: 24 May 2024

Bunch length is an important parameter for free-electron laser (FEL). The deflecting RF cavity was used in the beam length diagnostic instrument. In this paper, we present the design of a 3-cell rectangular deflecting RF cavity for a compact terahertz (THz) free-electron laser (FEL) facility. The 3-cell deflecting cavity has a residual orbit offset of zero as compared to single-cell deflecting cavity. Rectangular deflecting cavity does not need to lock the dipole polarisation direction as compared to cylindrical cavity. The time resolution of the measurement system can reach 500 fs. In this paper, the cavity design is carried out using CST and the results of cavity analysis are presented. Particle tracking is performed with the Astra code and the space charge effect is taken into account.

About: Received: 14 May 2024 — Revised: 18 May 2024 — Accepted: 23 May 2024 — Issue date: 24 May 2024

Accurate beam emittance and transverse phase space measurement are crucial for obtaining high-quality sample information in Ultrafast Electron Diffraction (UED). Traditional methods rely on general initial assumptions about the electron beam's phase space and lack specific distributions. The transverse phase space reconstruction technique based on the Computed Tomography (CT) algorithm eliminates the need for prior assumptions, resulting in more precise measurements. In this paper, we utilize an Algebraic Reconstruction Technique (ART) algorithm for HUST-UED, enabling the reconstruction of the beam transverse phase space distribution at the sample location and further facilitating system optimization.

About: Received: 06 May 2024 — Revised: 16 May 2024 — Accepted: 18 May 2024 — Issue date: 24 May 2024

To realize very precise measurement of the muon spin precession frequency in the level of sub-ppm, a muon beam is injected into a precisely adjusted storage magnet of sub-ppm uniformity via “Three-dimensional spiral beam injection scheme [1]” at J-PARC muon g-2/EDM experiment. This injection scheme requires a strongly X-Y coupled beam which is applied by eight rotating quadrupoles on the 10m of beam transport line [2]. Currently we have two scenarios of set of rotation angles (1) 45 or 60 degrees fixed, (2) any angles. In this presentation, strategy to precise control of the X-Y coupling at the beam transport line is discussed: how to control/monitor X-Y coupled phase space with eight rotatable quadrupole magnets including its alignment requirements for the case of (1) and (2). Results of alignment of the newly developed mount system for the rotating quad is also introduced. A pair of dedicated magnets called active shield multipole magnet (ASXM) will be set at the entrance and the exit of the beam channel of the storage magnet yoke. These devices will guarantee how well the beam phase space is matched with requirements at the reference point inside the storage magnet [3].

About: Received: 15 May 2024 — Revised: 22 May 2024 — Accepted: 22 May 2024 — Issue date: 24 May 2024

A beam position monitor based on Cherenkov diffraction radiation (ChDR) is being investigated as a way to disentangle the signals generated by the electromagnetic fields of a short-pulse electron bunch from a long proton bunch co-propagating in the AWAKE plasma acceleration experiment at CERN. These ChDR BPMs have undergone renewed testing under a variety of beam conditions with proton and electron bunches in the AWAKE common beamline, at 3 different frequency ranges between 20-110 GHz to quantify the effectiveness of discriminating the electron beam position with and without proton bunches present. These results indicate an increased sensitivity to the electron beam position in the highest frequency bands. Furthermore, high frequency studies investigating the proton bunch spectrum show that a much higher frequency regime is needed to exclude the proton signal than previously expected.

About: Received: 14 May 2024 — Revised: 22 May 2024 — Accepted: 23 May 2024 — Issue date: 24 May 2024

A laserwire diagnostic capable of measuring 5D phase space is to be installed on the Front End Test Stand (FETS) at the Rutherford Appleton Laboratory. The FETS beamline is a hydrogen ion source and the laserwire operates on the principle of photodetachment. A conventional tranverse laserwire is capable of 4D transverse profiling and emittance reconstruction. The FETS laserwire has a pulse duration shorter than the bunch temporal length enabling longitudinal profiling. A detector capable of measuring the laserwire signal is under development. One scheme being considered is a modular detector system. The initial section of the detector would consist of a scintillator to absorb the incoming beam, emitting photons. Following this an optical system will direct the signal to a CCD. Simulations for the photon production for a range of scintillators are compared. A configuration to remove the CCD from the direct line of the accelerator using an optical transport system is considered along with the impact on potential measurements. The expected signal to the CCD and reconstruction of beam size, temporal distribution, and transverse emittance are presented.

About: Received: 15 May 2024 — Revised: 23 May 2024 — Accepted: 23 May 2024 — Issue date: 24 May 2024

The Karlsruhe research accelerator KARA offers a setup to measure the beam energy with resonant spin depolarization. The depolarization is excited by the stripline kickers of the bunch-by-bunch feedback system and the resonant frequency is measured via change in Touschek lifetime. Energy measurements with resonant spin depolarization are implemented as a standard routine in the control system and are used regularly to measure both the beam energy and the momentum compaction factor for different energies and optics regimes. Long-time experience with the setup, short polarization time, and variation options of beam energy in combination with much available beam time qualify KARA as a test facility for systematic studies. Such studies are of particular interest for future colliders designed for precision studies like FCC-ee, as resonant spin depolarization is known for its high accuracy. This contribution presents the resonant spin depolarization setup at KARA and selected results of recent measurement campaigns.

About: Received: 15 May 2024 — Revised: 19 May 2024 — Accepted: 19 May 2024 — Issue date: 24 May 2024

A Compact Transverse Deflecting System (Compact-TDS) designed for longitudinal electron bunch diagnostics in the femtosecond regime is presently undergoing commissioning at the Karlsruhe Institute of Technology (KIT). This technique, based on THz streaking using a resonator structure, demands a high level of electron beam controllability and stability at the micrometer scale. To meet these requirements, the linear accelerator FLUTE (Ferninfrarot Linac- Und Test-Experiment) has undergone major upgrades in 2023, incorporating a new RF system equipped with a klystron, RF photoinjector and solenoid magnet. In this contribution, we present first experiments conducted with the Compact-TDS at FLUTE, utilizing the upgraded RF setup.

About: Received: 14 May 2024 — Revised: 20 May 2024 — Accepted: 23 May 2024 — Issue date: 24 May 2024

Various design options have been studied and simulated using CST MICROWAVE STUDIO for a compact transverse-deflecting system proposed for diagnostics of extremely short electron bunches. The idea of the method is to use terahertz radiation, produced from optical rectification of the facility’s electron gun laser pulse. The proposed system is to be checked experimentally at the test facility FLUTE (Ferninfrarot Linac- und Test-Experiment) at Karlsruhe Institute of Technology (KIT). The present paper is focused on the simulations of the resonator providing interaction between the electron bunch and the terahertz pulse. Two types of resonators and their arrays have been studied for this purpose: inverse split-ring resonator and tilted slit resonator. Different types of terahertz pulse structure have been studied, including plane wave and transversely focused (Gaussian) beam. Useful analytical models have been proposed to systematize the results of the simulations.

About: Received: 13 May 2024 — Revised: 20 May 2024 — Accepted: 23 May 2024 — Issue date: 24 May 2024

A far-field electro-optical (EO) setup based on a balanced detection scheme has been set up to measure the coherent synchrotron radiation (CSR) at the Karlsruhe Research Accelerator (KARA). To enable the readout with a spectrally decoded scheme (EOSD), a KALYPSO based line array camera sensitive to NIR operating at a readout rate of 2.7 MHz has been included in the set-up. In this contribution, measurement results with the KALYPSO based spectrometer in combination with a commercial THz emitter are presented.

About: Received: 15 May 2024 — Revised: 20 May 2024 — Accepted: 20 May 2024 — Issue date: 24 May 2024

Understanding the evolution of complex systems with numerous interacting particles requires advanced analytical tools capable of capturing the intricate dynamics of the phase space. This study introduces a novel approach to longitudinal phase space density tomography in an electron storage ring, leveraging constraints imposed by the Vlasov-Fokker-Planck equation. The Vlasov-Fokker-Planck equation provides a comprehensive description of the evolution of density functions in phase space, accounting for both deterministic and stochastic processes. Measurements of the turn-by-turn bunch profile offer a time-dependent projection of the phase space. Observing the bunch profile evolution of charged particles in regimes characterized by a rich phase space dynamics presents a challenging inverse problem for reconstructing the phase space densities. In this work, we present a tomographic framework for reconstructing the longitudinal phase space density of an electron bunch at the Karlsruhe Research Accelerator (KARA). This framework utilizes simulated data and applies the Vlasov-Fokker-Planck equation to drive the reconstruction process.

About: Received: 13 May 2024 — Revised: 18 May 2024 — Accepted: 18 May 2024 — Issue date: 24 May 2024

The Karlsruhe Research Accelerator (KARA) is an electron storage ring for accelerator research and the synchrotron of the KIT light source at the Karlsruhe Institute of Technology (KIT). KARA features an electro-optical (EO) in-vacuum bunch profile monitor to measure the longitudinal bunch profile in single shot on a turn-by-turn basis using electro-optical spectral decoding (EOSD). A simulation procedure has been set up to evaluate its suitability as a beam instrumentation for the operation of the future electron-position collider FCC-ee. In order to assess the simulations, this contribution focuses on a comparison to EO sampling (EOS) measurements at KARA and a study on the heat load of the EO crystal due to the expected high bunch repetition rate envisioned for FCC-ee.

About: Received: 15 May 2024 — Revised: 18 May 2024 — Accepted: 22 May 2024 — Issue date: 24 May 2024

At the Karlsruhe Research Accelerator (KARA) facility, an electron beam is generated by a thermionic electron gun, pre-accelerated to 53 MeV by a microtron and then ramped up to 500 MeV in a booster synchrotron before being injected into the storage ring, where a final electron energy of 2.5 GeV is reached. Compared to a 2D camera, when using 1D photodetectors either directly at the synchrotron light port or after a fiber optics segment, the optic design goal is to maximize the optical intensity at the photo detector, rather than to keep spacial coherence. In this field of non-imaging optics the emitter, optical setup and sink can be modeled in the optical phase space, with the etendue being the conserved quantity and position and angle the independent variables. In this contribution we describe the synchrotron radiation emitted at a dipole in the KARA booster synchrotron and the imaging setup into an optical multimode fiber with this formalism and compare the results with measurements at the synchrotron light port of the booster synchrotron.

About: Received: 15 May 2024 — Revised: 19 May 2024 — Accepted: 19 May 2024 — Issue date: 24 May 2024

In the upcoming compact STorage ring for Accelerator Research and Technology (cSTART), LPA-like electron bunches are only stored for about 100 ms, in which the equilibrium emittance will not be reached. Therefore, to measure parameters such as bunch profiles, arrival times and bunch current losses, bunch-resolved diagnostics are needed. The booster synchrotron of the KARA accelerator accepts pre-accelerated bunches from a racetrack microtron and accelerates them further over a 500 ms long energy ramp. As the KARA booster synchrotron has a similar circumference and injection energy as the cSTART storage ring, new bunch-by-bunch diagnostics developed there can be transferred to the cSTART project with minimal effort. Currently the diagnostic system of the booster is not designed for bunch-by-bunch diagnostics, thus after using the booster as a testbed for cSTART, such a system could be used permanently. At the booster synchrotron we use the picosecond sampling system KAPTURE-II to read-out a button beam position monitor and an avalanche photo diode at the synchrotron light port and compare the results with a commercial bunch-by-bunch system.

About: Received: 15 May 2024 — Revised: 19 May 2024 — Accepted: 19 May 2024 — Issue date: 24 May 2024

In Korea Multi-purpose Accelerator Complex (KOMAC) of Korea Atomic Energy Research Institute (KAERI), a 100 MeV proton LINAC is in operation and provides the proton beam for various applications since 2013. A radioisotope (RI) production beam line has developed in 2015 and the commissioning started in 2016. Recently, a beam diagnostics system for high proton beam currents of 100 μA was designed to produce the Cu-67 radioisotope, which is considered the next generation of radiopharmaceuticals. The beam diagnostic system includes a multi-wire scanner and Faraday cup to measure the position and current of the proton beam. It also utilizes an AC current transformer and 4-sector collimators for real-time position and current monitoring, respectively. Considering the long beam irradiation time for RI production, the system was designed to be moved up and down using cylinders so that it can only be used for beam QA. The control system was designed to be integrated with the EPICS IOC operating in other target rooms. In this paper, we would like to present the details of the beam diagnostic system and preliminary experimental results of real-time monitoring for 100 MeV RI production.

About: Received: 15 May 2024 — Revised: 18 May 2024 — Accepted: 18 May 2024 — Issue date: 24 May 2024

The ALS Upgrade Project (ALS-U) consists in the replacement of the existing ALS storage ring and the addition of a new accumulator ring in order to decrease the horizontal beam emittance to about 70 pm·rad, resulting in an increase of two orders of magnitude in the soft X-Ray brightness. The vacuum chambers of two new rings, and of the transfer lines connecting them, will include 327 new beam position monitors (BPM). The design of these BPM is now largely completed and relies on the procurement of about 1,500 BPM buttons (including spares and prototypes) from commercial suppliers and their installation on the BPM chamber enclosures. Our design includes more than a dozen different BPM designs and almost as many different buttons. All the buttons, as well as the assembled BPM, have to undergo vacuum and RF testing to characterize them and detect defective units before their installation. In this paper, we describe our electromagnetic testing plan and report on the results covering the entire button production for the accumulator ring and the prototypes for the storage ring, as well as the electromagnetic measurement for the assembled ALS-U Accumulator Ring (AR) BPMs.

About: Received: 16 May 2024 — Revised: 20 May 2024 — Accepted: 20 May 2024 — Issue date: 24 May 2024

This study focuses on the beam source for the LCLS-II-HE Low Emittance Injector (LEI) design: a state-of-the-art superconducting radiofrequency (SRF) gun. The LEI is intended to enable extending the LCLS-II-HE’s useful photon energy to 20 keV without additional cryomodules. We consider a robust two-slit emittance measurement optimized for the LEI SRF gun, compatible with the current LEI gun-to-linac beamline design, and extensible to measuring photocathode mean transverse energy (MTE) with the cathode at or below 4 K. In-situ measurement of photocathode MTE, and evolution thereof, could help optimize the overall performance of the LEI. A two-slit method enables determination of the detailed phase-space distribution of the electron bunch, beyond the normal Twiss parameters and emittance provided by methods such as solenoid scans. Additionally, we investigate the RF emittance by recessing the cathode. This allows us to study the influence of the RF field on the bunch phase space. In summary, our work introduces a cutting-edge two-slit emittance measurement methodology that combines different emittance-dampening techniques to isolate intrinsic emittance from the photocathode. Detailed results will be presented at the workshop to highlight established trends, dependencies, and a summary/concept of the future photocathode characterization beamline implementation.

The cathode test stand at LANL is utilized to test velvet emitters over pulse durations of up to 2.5 µs. Diode voltages range from 120 kV to 275 kV and extracted currents exceed 25 A and depend on cathode size and pulse duration. Current density measurements taken with scintillators or Cherenkov emitters produce inconsistent patterns that disagree with the anticipated beam profile. Several factors contribute to the measured beam distribution, such as electron scatter, X-ray scatter, and Snell’s law. Here, we present a range of experiments designed to evaluate both electron scatter and Cherenkov emission limits in efforts to optimize current density measurements. For electron ranging studies, metal foils of different densities and thicknesses are coupled with a scintillator, which is then imaged with an ICCD. Similarly, Cherenkov emission and Snell’s law are investigated through imaging materials with differing indices of refraction over a range of beam energies. MCNP6® modeling is utilized to further guide and evaluate these experimental measurements.

About: Received: 15 May 2024 — Revised: 23 May 2024 — Accepted: 24 May 2024 — Issue date: 24 May 2024

Single-bunch instability is studied at the Taiwan Photon Source both with and without bunch-by-bunch feedback (BBF). The instability thresholds are investigated at various chromaticities by increasing the bunch current until the instability occurs. BBF and chromaticity can increase the maximum stored bunch current and allow the tune to cross the unstable region. As the bunch current increase, the tune around the betatron frequency decreases and the tune around the synchrotron sideband increases. High radiation doses are detected by beam loss monitors when the bunch current exceeds 2 mA, near the unstable region, originating from synchrotron light scattered by the photon absorber. As the single bunch becomes unstable, electron beam loss occurs after the first band magnet of the straight section with the smallest vertical aperture.

About: Received: 13 May 2024 — Revised: 16 May 2024 — Accepted: 17 May 2024 — Issue date: 24 May 2024

Generative models can be trained to reproduce low-dimensional projections of high-dimensional phase space distributions. Normalizing flows are generative models that parameterize invertible transformations, allowing exact probability density evaluation and sampling. Consequently, flows are unbiased entropy estimators and could be used to solve the high-dimensional maximum-entropy tomography (MENT) problem. In this work, we evaluate a flow-based MENT solver (MENT-Flow) against exact maximum-entropy solutions and Minerbo's iterative MENT algorithm in two dimensions.

About: Received: 15 May 2024 — Revised: 17 May 2024 — Accepted: 17 May 2024 — Issue date: 24 May 2024

A harp system, which is a multi-wire beam profile monitoring (MWPM) system, is planned upstream of the spallation target to make in situ calibration of beam current density configuration on the target along with beam imaging from luminescent coating on the beam entrance window at the Second Target Station (STS) of the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL). This beam interception-based beam diagnostics system on the target will be used to ensure that the maximum beam loads on the target are within the design range during neutron production. Current design of the harp consists of three layers of measurement wires each of which is sandwiched between voltage biasing wire planes. The signal obtained from each measurement wire layer is disturbed by secondary electrons (SE) and delta rays produced by beam-matter interactions in neighboring wires and ionization of residual gases in accelerator vacuum. While the backgrounds from SE can be suppressed by voltage biasing, the delta-ray electrons with kinetic energies above keV ranges overcome the electric potential bias. In this paper, we study the effects of delta-rays on the measurement uncertainties of MWPM using the particle transport simulation code FLUKA. Furthermore, the cases where the harp system is installed in the proximity of a large delta ray sources such as proton beam window or in the core vessel filled with sub-atmospheric gas have been studied.

About: Received: 15 May 2024 — Revised: 19 May 2024 — Accepted: 22 May 2024 — Issue date: 24 May 2024

A pair spectrometer, designed to capture single-shot gamma spectra over a range extending from 10 MeV through 10 GeV, is being developed at UCLA for installation at SLAC’s FACET-II facility. Gammas are converted to electrons and positions via pair production in a beryllium target and are then subsequently magnetically analyzed. These charged particles are then recorded in an array of quartz Cherenkov cells attached to silicon photomultipliers (SiPMs). As the background environment is challenging, both in terms of ionizing radiation and electromagnetic pulse radiation, extensive beamline testing is warranted. To this end, we present Geant4 Monte Carlo studies, assembly of the SiPMs, and future testing plans.

About: Received: 16 May 2024 — Revised: 20 May 2024 — Accepted: 20 May 2024 — Issue date: 24 May 2024

SwissFEL is a normal conducting linear accelerator driving two separate free-electron laser (FEL) lines – one for soft and one for hard x-rays. We report jitter and correlation measurements of two electro-optical Bunch Arrival-Time Monitors (BAMs), which use directly the pulses from a mode-locked laser oscillator. The arrival-time is encoded in the amplitude of one single reference laser pulse in a fiber coupled Mach-Zehnder modulator driven by a fast RF-transient from a button pick-up. Using the modulation slope and the laser amplitude jitter, we demonstrate &LT1 femtosecond resolution at 200 pC bunch charges for the BAM with a 16 mm pick-up beam pipe diameter and &LT10 fs at 10 pC for the BAM with 8 mm pick-up beam pipe diameter. We also report a jitter correlation measurement of two independent BAMs over 1 min at 100 Hz machine repetition rate as well as a similar correlation measurement of one single BAM station with 8 mm pick-up beam pipe diameter and having two identical high resolution channels. The measured correlations are as low as 1.3 fs rms resulting in sub-femtosecond resolution of the optical detection scheme.

About: Received: 15 May 2024 — Revised: 17 May 2024 — Accepted: 17 May 2024 — Issue date: 24 May 2024

The Korean 4GSR project is currently under construction in Ochang, South Korea, with the aim of first beam commissioning in 2027. Designed to achieve an emittance approximately 100 times smaller than that of third-generation synchrotron radiation storage rings, the project requires the development of several high-precision beam diagnostic devices. In particular, the beam position monitor is designed to reduce longitudinal wake impedance, thereby suppressing heating and beam instability. The electronics component has also been developed using RFSOC to enable Turn by Turn data acquisition and Bunch by Bunch beam position monitoring. Additionally, a Beam Loss Monitor utilizing 100 Hz operating-rate scintillating optical fibers has been developed, and an enhanced beam profile monitor utilizing GAGG has also been created. Furthermore, the development progress of a multi-bunch energy measurement beam position monitor system for linear accelerator energy feedback will be introduced. This presentation aims to provide an overview of the current status of beam diagnostic devices developed for the 4GSR project, including details on the overall system configuration.

About: Received: 21 May 2024 — Revised: 23 May 2024 — Accepted: 23 May 2024 — Issue date: 24 May 2024

Ultrafast high repetition-rate laser systems are essential to modern scientific and industrial applications. Variations in critical figures of merit, such as focal position, can significantly impact efficacy for applications involving laser plasma interactions, such as electron beam acceleration and radiation generation. We present a diagnostic and correction scheme for controlling and determining laser focal position by utilizing fast wavefront sensor measurements from multiple positions to train a focal position predictor. We present the deployment and testing of this scheme at the BELLA Center at Lawrence Berkeley National Laboratory. Online optical adjustments are made to a telescopic lens to provide the desired correction on millisecond timescales. A framework for generating a low-level hardware description of ML-based correction algorithms on FPGA hardware is coupled directly to the beamline using the AMD Xilinx Vitis AI toolchain in conjunction with deployment scripts.

About: Received: 16 May 2024 — Revised: 22 May 2024 — Accepted: 22 May 2024 — Issue date: 24 May 2024

The direction of particle accelerator development is ever increasing beam quality, currents, and repetition rates. Advanced control techniques using machine learning are required for the optimization and operation of such accelerators. These techniques greatly benefit from having single-shot beam measurements. However, high intensity beams poses a challenge for traditional interceptive diagnostics due to the mutual destruction of both the beam and the diagnostic. An alternative approach is to infer beam parameters non-invasively from the synchrotron radiation emitted in bending magnets. In this talk, we will discuss the development of such a diagnostic at FACET-II. Inferring the beam distribution from a measured radiation pattern is a complex and computationally expensive task. To address these challenges we use differential simulations and computer vision techniques. This enables both fast inference and uncertainty quantification of the beam parameters.

ISIS-II is the UK's proposed next-generation pulsed, spallation neutron source, and is expected to be driven by a MW-class proton accelerator. A Fixed Field Alternating gradient (FFA) machine is one accelerator configuration being considered. A demonstrator machine, called FETS-FFA, is now being actively developed. Beam Loss Monitors (BLMs) for this demonstrator are presented with the unique challenge of low-energy (3-12 MeV) and low intensity (1e+11 ppp) beams, and should provide turn-by-turn measurements during commissioning as well as form a vital component of the Machine Protection System (MPS). The final BLM systems will operate in stray magnetic fields from the main magnets, and need to fit in the limited available space. This paper presents a feasibility study of using a combination of Ionisation Chambers (IC) and Scintillation Detectors (SD). The ideal geometry of both BLM types will be discussed, and comparisons made between Monte Carlo simulations and beam tests on the FETS linac at the Rutherford Appleton Laboratory.

About: Received: 15 May 2024 — Revised: 17 May 2024 — Accepted: 17 May 2024 — Issue date: 24 May 2024

CLARA is a 250 MeV electron facility at Daresbury Laboratory, which will provide short bunches between 1 and 250 pC for a variety of experiments, including novel acceleration experiments. As part of the Phase 2 upgrade new charge measurement systems have been installed. This paper presents the charge measurement systems that will be used on CLARA, as well as commissioning results without beam for some of those systems. CLARA will include a Wall Current Monitor (WCM), 3 Integrating Current Transformers (ICTs) and five Faraday cups. The ICTs are commercial systems by Bergoz, while a custom front-end has been designed for the WCM and Faraday cups, which includes calibration circuitry and switchable gain. Calibration results, including measurements of resolution, are presented for the in-house front-end design.

About: Received: 15 May 2024 — Revised: 20 May 2024 — Accepted: 20 May 2024 — Issue date: 24 May 2024

After current upgrades are completed, the Compact Linear Accelerator for Research Applications (CLARA) at Daresbury Laboratory (UK) will be capable of producing femtosecond-scale electron bunches, which will be used in the full energy beam exploitation (FEBE) experimental area. CLARA will employ multiple techniques to manipulate the longitudinal beam profile, including a variable bunch compressor (VBC). Optimisation procedures for the CLARA modules must be devised, which will require longitudinal diagnostics. Previous longitudinal diagnostics used on CLARA were multi-shot, but for user experiments a single-shot diagnostic operating at the machine repetition rate of 100 Hz is needed. Here, we present a single-shot, four-channel spectrometer to measure THz coherent transition radiation (CTR) produced by electron bunches, which will be used to deduce information about the bunch profile. In the device, a set of frequency-selective elements designed at STFC RAL Space (UK) distribute specific bandwidths onto single-shot pyroelectric detectors based on earlier wideband THz diagnostics on CLARA. The frequency-selective elements have been characterised using both simulations and THz time-domain spectroscopy. A start-to-end computer model of the spectrometer was created, and simulations were performed showing that the spectrometer can be used for both sextupole tuning on the FEBE arc and optimisation of the compression of the CLARA VBC. The instrument is currently being assembled and tested, and commissioning with beam is planned for the summer of 2024.

About: Received: 15 May 2024 — Revised: 20 May 2024 — Accepted: 23 May 2024 — Issue date: 24 May 2024

The Munich Compact Light Source (MuCLS)* is a compact synchrotron source based on inverse Compton X-ray scattering. This effect produces brilliant quasi-monochromatic hard X-ray radiation with rather low electron energy (tens of MeV) by colliding these electrons head-on with a laser beam. Such sources are sufficiently compact to fit into a laboratory or industrial environment enabling a more widespread use of synchrotron techniques**. Many of these techniques are affected detrimentally by a larger (projected) source size, e.g. X-ray phase contrast imaging. The more precisely the exact shape of the source is determined, the better can its effects be corrected for in the recorded data. We experimentally evaluate a novel approach to obtain an accurate 2D X-ray source profile***. A hole in a strongly absorbing structure is used to record the edge-spread function azimuthally resolved in a single shot. The 2D source spot is retrieved from this data by taking the derivative of the edge-spread function and applying the filtered-backprojection algorithm of computed tomography. We discuss results obtained for the source shape and relate them to general performance parameters of the MuCLS.

Ultra-low-charge operation of free-electron lasers down to 1 pC or even lower, requires adequate diagnostics for both, the users and the operators. For the electro-optical bunch-arrival time monitor (BAM) a fundamental design update is necessary to yield single-digit fs precision with such low charges. In 2023 a vacuum sealed demonstrator for a novel pickup structure with integrated combination network on a printed circuit board (PCB) was built for operation at the free-electron laser ELBE at HZDR. Together with a new low-pi-voltage ultra-wideband traveling wave electro-optical modulator, this concept reaches an estimated theoretical jitter charge product of 9 fs pC. Proof-of-concept measurements with the pickup demonstrator were carried out at ELBE.

About: Received: 15 May 2024 — Revised: 20 May 2024 — Accepted: 21 May 2024 — Issue date: 24 May 2024

The r-process fission cycle terminates the synthesis of heavy elements in binary neutron-star mergers. Fission processes of transuranium nuclides will be studied in electrofission reactions at the thrice-recirculating electron accelerator S-DALINAC*. Due to the minuscule fissile target, the experimental setup requires an active beam-stabilization system with high accuracy and a beam position resolution in the sub-millimeter range. Requirements and concepts for this system regarding beam diagnostics elements, feedback control and readout electronics will be presented. The usage of a cavity beam position monitor and optical transition radiation screens to monitor the required beam parameters will be discussed in detail. Additionally, various measurements including a study of beam stability performed in the injector section of the S-DALINAC to assess requirements and limits for the beam-stabilization system will be presented. Finally, the application of advanced machine learning methods, such as neural networks and agent-based reinforcement learning, will be discussed.

About: Received: 15 May 2024 — Revised: 20 May 2024 — Accepted: 20 May 2024 — Issue date: 24 May 2024

Energy-recovery linacs provide high beam currents with lower RF power requirements compared to conventional machines while maintaining the high beam quality of a linac. The S-DALINAC is a thrice-recirculating accelerator operating at a frequency of 3 GHz that is capable of being operated as a multi-turn superconducting energy-recovery linac. Its efficiency is currently limited by the bunch length, which by now is measured using the RF zero-crossing method. In order to improve both accuracy and measurement time a new setup using a streak camera is developed. Optical transition radiation from electron bunches passing an aluminum-coated Kapton screen is used to produce light pulses that can be measured with the streak camera. An imaging system consisting of multiple mirrors is used to maintain a high temporal resolution for the measurement and to support in shielding the streak camera from harmful radiation. The device will be used at two different measurement setups downstream of the injector. The design and current status of the measurement setup will be presented.

About: Received: 15 May 2024 — Revised: 19 May 2024 — Accepted: 19 May 2024 — Issue date: 24 May 2024

Achieving non-invasive in-vivo dosimetry is a critical objective in the field of ion beam therapy. The comprehensive real-time characterization of the ion beam is highly desirable to ensure the safety of patients, treatment precision, and the efficiency of the treatment facility. However, current methods have limitations in terms of the information they provide and can be invasive to the beam. This contribution focuses on the development of a non-invasive, gas jet-based in-vivo dosimeter for use in treatment facilities. This technique relies on a non-disruptive interaction of a low-density supersonic gas jet curtain with the primary treatment beam. An existing gas jet monitor-based ionization profile monitor was modified and coupled with the accelerator beamline at the Dalton Cumbrian Facility (DCF), UK (United Kingdom). The aim of the test was to conduct proof-of-concept measurements for the profile and dosimetry of beams having characteristics similar to the medical treatment facilities. Measurements were carried out for proton and carbon beams of varied sizes, energies, and currents. The results obtained from these measurements demonstrated the feasibility of such a dosimeter and are instrumental for its improvement. This contribution introduces the design of the adapted gas jet dosimeter, discusses the findings from the measurements, highlights the dosimetry challenges addressed and outlines the scope of improvement for an online non-invasive gas jet in-vivo dosimeter.

About: Received: 09 May 2024 — Revised: 17 May 2024 — Accepted: 18 May 2024 — Issue date: 24 May 2024

In-vivo dosimetry is essential to deliver precise doses to patients in ion beam therapy. Real-time dose monitoring without disturbing the beam improves patient safety and treatment efficiency. It is critical for emerging treatment modalities like FLASH therapy due to the narrow dose tolerance. Existing real-time dosimetry devices are invasive to beam, necessitating a non-invasive dosimetry solution. The gas-jet based beam profile monitor developed at the co*ckcroft Institute (CI) is being studied for application in medical accelerator facilities. Recent measurements at the Dalton Cumbrian Facility, UK yielded promising results for beam monitoring at energies equivalent to medical beam. These studies have indicated the need to improve the gas-jet based Ionization Profile Monitor (IPM) to monitor dose in real time. A new IPM detector system is under development at CI to reduce the monitor size and complexity, and increase its sensitivity, resulting in fast acquisition, paving the way for real-time in-vivo dose monitoring. This contribution presents the design of the optimized IPM and its working principle based on electrostatic field and particle trajectory simulations.

About: Received: 09 May 2024 — Revised: 19 May 2024 — Accepted: 23 May 2024 — Issue date: 24 May 2024

To develop a high-power, high-efficiency electron irradiation accelerator system with an adjustable electron beam, a novel constant-gradient backward-travelling-wave (BTW) accelerating structure has been designed. This accelerator tube implements a backward-travelling-wave design, which offers the advantages of short filling time and low power reflection, which are characteristic of traveling-wave acceleration structures, and can incorporate a nosecone design to achieve high shunt impedance. The constant-gradient concept is adopted to further enhance the electron beam power and beam efficiency. This paper presents the design of the BTW accelerating structure, encompassing parameter estimation and comprehensive three-dimensional simulations to validate the concept.

About: Received: 14 May 2024 — Revised: 23 May 2024 — Accepted: 23 May 2024 — Issue date: 24 May 2024

First proof-of-principle steady-state microbunching (SSMB) experiment proved that SSMB has the potential to produce high average power short wavelength light. Tsinghua University has proposed a conceptual design for the future SSMB accelerator light source. A bunch train with an average current of 1 A is required in the electron injector for the future SSMB light source with a bunch spacing of 350 ps. It is essential for diagnosis to measure each bunch in the bunch train. A method of using a fast kicker to measure different bunches simultaneously is proposed in this paper. By using a fast-rising edge power supply, the kicker can give different electron bunches different kick angles, allowing different bunches to be detected on the screen simultaneously. This paper presents measurement methods for the transverse distribution, energy spread, longitudinal phase space, and emittance, along with corresponding simulation results.

About: Received: 15 May 2024 — Revised: 22 May 2024 — Accepted: 23 May 2024 — Issue date: 24 May 2024

Cherenkov threshold detectors (XCET) are used for identifying particles in the experimental areas at CERN. These detectors observe Cherenkov light emitted by charged particles travelling inside a pressurized gas vessel. A key component of the XCET detector is the 45-degree flat mirror reflecting the Cherenkov light towards the photomultiplier (PMT). A thorough analysis and optimization was conducted on the design and materials of this mirror, along with the surface coatings and coating techniques. A suitable manufacturing process was selected, and the first mirror prototype was produced, installed, and tested in the East Area at CERN. Experimental data obtained during beam tests is presented to assess the efficiency of the new coating and materials used.

About: Received: 15 May 2024 — Revised: 21 May 2024 — Accepted: 21 May 2024 — Issue date: 24 May 2024

LhARA, the Laser-hybrid Accelerator for Radiobiological Applications, is a proposed facility for the study of radiation biology. The accelerator will deliver ions at ultra-high dose rates and requires real-time measurement of the dose distribution. We have developed an ion-acoustic dose mapping system that exploits the acoustic waves generated by the beam’s energy deposition. A proposed proof-of-principle experiment is presented. A water-based phantom features a beam entry window sealed with Kapton. Three ports located on three orthogonal sides mount transducer arrays for detecting the acoustic waves. To calibrate their acoustic response, a liquid scintillator will be added to the water and its luminescence arising from the energy deposited by the beam is imaged by two cameras, positioned perpendicularly to each other. The acoustic wave generation and detection have been simulated in Geant4 and k-Wave, and the optical system in OpticStudio. The simulation shows precise reconstruction of the 3D deposited energy distribution using the acoustic and optical systems should be obtained in the proposed design. Combining these will yield a real-time calibrated dose map in the experiment.

About: Received: 15 May 2024 — Revised: 18 May 2024 — Accepted: 20 May 2024 — Issue date: 24 May 2024

The gas sheet ionization based diagnostic is a minimally invasive profile monitor for electron beams. In the ionization based monitor, the electron beam ionizes a neutral gas that is spatially tailored. The newly ionized particles form a footprint of the electron beam, and are imaged using an array of electrostatic lenses. The gas sheet diagnostic was conceptually tested using a 7 MeV electron beam and has shown strong correlations for use as a transverse profile. The concept is extendible, and proposed, for use with electron beams with energy greater than 10 GeV. Although different ionization mechanisms are dominant for each regime, the gas sheet diagnostic imaging scheme is viable when novel algorithms are employed to reconstruct the beam profile.

Coherent synchrotron radiation (CSR) in linear accelerators (linacs) is detrimental to applications that require highly compressed beams, such as FELs and wakefield accelerators. However, traditional measurement techniques lack the precision to fully comprehend the intricate multi-dimensional aspects of CSR, particularly the varying rotation of transverse phase space slices along the longitudinal coordinate of the bunch. This study explores the effectiveness of our generative-model-based high-dimensional phase space reconstruction method in characterizing CSR effects at the Argonne Wakefield Accelerator Facility (AWA). We demonstrate that the reconstruction algorithm can successfully reconstruct beams that are affected by CSR.

About: Received: 15 May 2024 — Revised: 22 May 2024 — Accepted: 23 May 2024 — Issue date: 24 May 2024

Transverse deflection structures (TDS) have been widely used as diagnostic devices to characterize longitudinal properties of electron bunches in a linear accelerator. However, the conventional TDS can only measure either the horizontal or the vertical slice envelopes of electron bunches. In order to give full control of the angles of the transverse streaking field inside of the TDS to characterize the projections of the beam distribution on different transverse axes, we numerically investigate an X-band TDS with variable polarization in this paper. Through variable streaking direction, the orientation of the streaking field of the TDS is adjusted to an arbitrary azimuthal angle. This helps facilitate the development of next-generation TDS for the characterization of electron bunches, such as slice emittance measurement on different planes.

About: Received: 14 May 2024 — Revised: 22 May 2024 — Accepted: 22 May 2024 — Issue date: 24 May 2024