SUPC
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Student Poster Session: SUPC
19 May 2024, 14:00 -
18:00
Chair: Kiersten Ruisard (Oak Ridge National Laboratory)
SUPC001
Expanding the CERN ion injector chain capabilities: new beam dynamics simulation tools for future ion species
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The present ion physics program in the CERN accelerator complex is mainly based on Pb ion beams. The ALICE3 detector upgrade proposal at the Large Hadron Collider (LHC) requests significantly higher integrated nucleon-nucleon luminosity compared to the present Pb beams, which can potentially be achieved with lighter ion species. These lighter ion species have also been requested by the fixed-target experiment NA61/SHINE in the CERN North Area (NA). To assess the performance capabilities of the CERN Ion Injector chain (consisting of Linac3, LEIR, PS and SPS) for light ions, for which there is little or no operational experience at CERN, beam-brightness and intensity limitations need to be studied. This contribution presents tracking simulation results for the PS and SPS, compared against recent experimental beam data for Pb in the Ion Injectors. These simulations include limiting beam-dynamics effects such as space charge and intra-beam scattering, and their impact on the intensity and emittance evolution is discussed. These simulation models are used to predict the optimal ion species for maximum performance out of the Ion Injector Chain.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-MOPC08
About: Received: 08 May 2024 — Revised: 18 May 2024 — Accepted: 18 May 2024 — Issue date: 01 Jul 2024
SUPC002
Measurements of beam correlations induced via coupled resonance crossing in the CERN PSB
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Beam profile measurements in the LHC and its injector complex show heavy tails in both transverse planes. From standard profile measurements, it is not possible to determine if the underlying phase space distribution is statistically independent. A measurement campaign in the CERN PSB was carried out to introduce cross-plane dependence in bunched beams in controlled conditions, in view of characterizing the LHC operational beam distributions. The results of the measurement campaign demonstrate how heavy tails can be created via coupled resonance excitation of the lattice in the presence of space charge, in accordance with predictions from the fixed line theory. The coupled resonance introduces dependence between the different planes, which persists after the resonance excitation is removed.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-TUPC07
About: Received: 15 May 2024 — Revised: 22 May 2024 — Accepted: 23 May 2024 — Issue date: 01 Jul 2024
SUPC003
Luminosity effects due to dependent heavy-tailed beams
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The luminosity of particle colliders depends, among other parameters, on the transverse profiles of the colliding beams. At the LHC at CERN, heavy-tailed transverse beam distributions are typically observed in routine operation. The luminosity is usually modelled with the assumption that the 𝑥-𝑦 planes are independent (i.e. statistically uncorrelated particle distributions between the planes) in each beam. Analytical calculations show that the solution of inverting 1D heavy-tailed beam profiles to transverse 4D phase-space distributions is not unique. For a given transverse beam profile, the distributions can be dependent (i.e. statistically correlated) or independent in the transverse planes, even in the absence of machine coupling. In this work, the effect of transverse 𝑥-𝑦 dependence of the 4D phase space distribution on the luminosity of a particle collider is evaluated for heavy-tailed beams.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-MOPC09
About: Received: 15 May 2024 — Revised: 21 May 2024 — Accepted: 22 May 2024 — Issue date: 01 Jul 2024
SUPC004
Numerical methods for emittance computation from luminosity
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The beam transverse emittances play a critical role in high-energy colliders. Various measurement techniques are employed to measure them. In particular, the so-called luminosity emittance scans (or Van der Meer scans) are used in order to evaluate the convoluted beam emittances. This method assumes different emittances in the two planes but identical emittances in the two beams. In this paper, we propose an approach to remove this constraint. After having presented the new measurement protocol, we will discuss its potential and limits, including the statistical measurement error of the luminosity value as obtained from numerical studies.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-MOPC19
About: Received: 15 May 2024 — Revised: 17 May 2024 — Accepted: 17 May 2024 — Issue date: 01 Jul 2024
SUPC005
LHC 2023 ion optics commissioning
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In 2023, about 2 months of the LHC operation were devoted to the Heavy Ions physics, after more than 5 years since the last ion run. In this paper, the results of the 2023 Ion optics commissioning are reported. Local corrections in Interaction Point (IP) 1 and 5 were reused from the regular proton commissioning, but the optics measurement showed the need for new local corrections in IP2. We observed that an energy trim of the level of 10e-4 helped to reduce the optics errors at top energy. The dedicated measurements during the energy ramp revealed a larger than expected beta-beat, which is consistent with an energy mismatch. Furthermore, global corrections were performed to reach a β-beating of about 5% for the collision optics.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-MOPC20
About: Received: 13 May 2024 — Revised: 22 May 2024 — Accepted: 23 May 2024 — Issue date: 01 Jul 2024
SUPC006
Energy dependence of PS main unit harmonics
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CERN Proton Synchrotron (PS) is featured with 100 C-shaped combined-function Main Units (MUs) magnets with a complicated pole shape. The operation and the modelling of the PS-MUs has been historically carried out with empirical beam-based studies. However, it would be interesting to understand whether, starting from a proper magnetic model and using the predicted harmonics as input to optics simulations, it is possible to accurately predict the beam dynamics behavior in the PS, and assess the model accuracy with respect to beam-based measurements. To evaluate the magnetic model quality and its predictions, bare-machine configurations at different energies were prepared, where only the Main Coil is powered and the additional circuits are off. In this paper, a comparison of tunes and chromaticity measurements with the predicted optics is reported, showing the saturation of the quadrupolar and sextupolar components at high energy, which affect these quantities.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-TUPC15
About: Received: 13 May 2024 — Revised: 23 May 2024 — Accepted: 24 May 2024 — Issue date: 01 Jul 2024
Preliminary design consideration for CEPC fast luminosity feedback system
With very small beam sizes at IP (several tens of nanometers in the vertical direction) and the presence of strong FFS quadrupoles in the CEPC, the luminosity is very sensitive to the mechanical vibrations, requiring excellent control over the two colliding beams to ensure an optimum geometrical overlap between them and thereby maximize the luminosity. Fast luminosity measurements and an IP orbit feedback system are therefore essential. In this paper, we will show the preliminary design consideration for a fast luminosity feedback system at CEPC.
SUPC008
Electron cloud studies for DAΦNE collider and FCCee damping ring
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DAΦNE is a a medium energy electron-positron collider operating in the National Laboratory of INFN at Frascati, Italy. The accelerator complex consists of two rings with an approximate circumference of 97 m. High-intensity electron and positron beams circulate and collide with the center of mass energy of around 1.02 GeV. The FCCee is an ongoing lepton collider project and its current injector design includes a damping ring for emittance cooling of positron beams. The electron cloud is one the most important collective effects and can represent a bottleneck for the performances of accelerators storing particles with positive charge. Several undesired effects such as transverse instabilities, beam losses, emittance growth, energy deposition, vacuum degradation may arise due to interaction of the circulating beam with the e-cloud. The aim of this presentation is to provide e-cloud buildup simulations for the DAΦNE positron ring and the Damping Ring of FCCee. This study will also include experimental studies concerning the instabilities induced by the e-cloud exploiting the opportunity offered by the positron beam at DAΦNE.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-WEPR08
About: Received: 15 May 2024 — Revised: 24 May 2024 — Accepted: 24 May 2024 — Issue date: 01 Jul 2024
SUPC009
First FCC-ee lattice design with nested magnets
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The Future Circular Electron-Positron Collider (FCC-ee) represents a cutting-edge particle physics facility designed to further investigate the Z, W± and Higgs boson in addition to the top quark. The implementation of Nested Magnets (NMs) in the FCC-ee arc cells would maintain high luminosity and reduce its energy consumption. The use of these special magnets induces changes in the damping partition numbers. To mitigate this the dipole fields in focusing and defocusing quadrupoles have to be different. This solution gives rise to incompatibility problems for the machine layout between the different energy configurations as the optics is also changed. This problem is tackled by defining different bending and geometric angles for the NMs. The beam dynamics and performance aspects of the new lattice are studied in this paper.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-WEPR10
About: Received: 15 May 2024 — Revised: 20 May 2024 — Accepted: 21 May 2024 — Issue date: 01 Jul 2024
SUPC011
Dynamic aperture of the RCS during bunch merges
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The Rapid Cycling Synchrotron (RCS) of the Electron Ion Collider (EIC) will be used to accelerate polarized electrons from 400 MeV to a top energy of 5, 10, or 18 GeV before injecting into the Electron Storage Ring. At 1 GeV, the RCS will perform a merge of two bunches into one, adding longitudinal dynamics that effects the dynamic aperture, depending on the merge parameters. In this paper, results for different merge models will be compared, as well as finding the relationship between the merge parameters of the RCS and its dynamic aperture.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-TUPC06
About: Received: 15 May 2024 — Revised: 23 May 2024 — Accepted: 23 May 2024 — Issue date: 01 Jul 2024
SUPC012
Application and comparative analysis of the APES_CBI module in BEPC-II experimental results
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In this paper, we delve into the application and comparative analysis of the Accelerator Physics Emulation System Cavity-Beam Interaction (APES_CBI) module within the BEPC-II (Beijing Electron-Positron Collider) experiments. We developed the APES_CBI module as an advanced time-domain solver, specifically designed to analyze RLC circuits driven by beam and generator currents and to simulate the dynamic responses and synchrotron oscillations of charged particles within the cavity. We begin by discussing our method for solving RLC parallel circuits, followed by an explanation of the logical architecture of our program. In the second part, we detailed our simulation results, starting with the BEPC-II electron ring. By comparing these results with experimental data, we validate the reliability of our simulations, showcasing our module's ability. Additionally, we extend our simulations to the CEPC Higgs mode on-axis injection conditions and studied the transient phase response to the sudden change of beam pattern.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-TUPC14
About: Received: 15 May 2024 — Revised: 20 May 2024 — Accepted: 23 May 2024 — Issue date: 01 Jul 2024
SUPC013
A study for emittance growth compensation by space charge effects at the injector of KEK-STF after dry ice cleaning of the RF gun
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The Round to Flat Beam Transformation (RFBT) is one of the emittance exchange techniques that can improve the Luminosity for the future accelerator project International Linear collider (ILC). RFBT experiment can be conducted in the KEK-STF, and the expected performance is 334 in emittance ratio. In December 2023, we performed a pilot experiment at STF to optimize the injector conditions. To improve the RF Gun of STF, we applied dry ice cleaning to reduce the field emission. The field enhancement factor was improved from 233 to 100.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-MOPC33
About: Received: 15 May 2024 — Revised: 16 May 2024 — Accepted: 17 May 2024 — Issue date: 01 Jul 2024
SUPC014
Transfer learning for field emission mitigation in CEBAF SRF cavities
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The Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab operates hundreds of superconducting radio frequency (SRF) cavities in its two linear accelerators (linacs). Field emission (FE) is an ongoing operational challenge in higher gradient SRF cavities. FE generates high levels of neutron and gamma radiation leading to damaged accelerator hardware and a radiation hazard environment. During machine development periods, we performed gradient scans to record data capturing the relationship between cavity gradients and radiation levels measured throughout the linacs. However, the field emission environment at CEBAF varies considerably over time as the configuration of the radio frequency (RF) gradients changes and due to the changing behavior of field emitters. An artificial intelligence/machine learning (AI/ML) approach with transfer learning could be a valuable tool to mitigate FE and lower the radiation levels. In this work, we mainly focus on leveraging the RF trip data gathered during CEBAF operations. We develop a transfer learning-based surrogate model for radiation detector readings given RF cavity gradients to track CEBAF’s changing configuration and environment. Then, we could use the developed model in an optimization process for redistributing the RF gradients within a linac to minimize radiation levels.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-MOPC44
About: Received: 14 May 2024 — Revised: 11 Jun 2024 — Accepted: 11 Jun 2024 — Issue date: 01 Jul 2024
SUPC015
Development of an S-band multi-beam acclearator for stationary CT application
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Stationary CT is a novel CT technology to significantly improve scanning speed, by using distributed multiple ray sources instead of conventional helical rotation with single source. This work presents an S-band multi-beam accelerator as a multiple MV-level X-ray source for industrial stationary CT application. This accelerator consists of 7 parallel-distributed acceleration cavity and 6 coupling cavity, operating in pi/2 standing-wave mode with a centre frequency of 2998MHz. This structure can generate 0.7 MeV electrons with 100 mA peak current at each beamline according to the imaging requirement. The novel multiple high-energy X-ray source will fill in the blank of source requirements in industrial stationary CT application.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-MOPC57
About: Received: 13 May 2024 — Revised: 17 May 2024 — Accepted: 17 May 2024 — Issue date: 01 Jul 2024
SUPC016
Studies of space-charge compensation of positive ions by creating time-dependent secondary electrons in low-energy beam transport line
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The space-charge neutralization of an ion beam by created electrons when the beam ionizes the gas is investigated using a three-dimensional electrostatic particle-in-cell code. Different kinds of injected gases are considered, and their space-charge compensation transient times are compared. The created secondary electrons by the beam collision with neutral gas along the beam trajectories are loaded in the simulation by a Monte Carlo generator, and their space charge contribution is added to the primary beam space charge densities. The injection and accumulation of secondaries are time-dependent and this process is continued until total space charge densities reach a steady state. In this study, a 2.4-meter LEBT line with two solenoid magnets is considered. Usually, the proton beam energy is 25 keV and the current level is around 10-15 mA. Additionally, beam extraction studies are conducted, and the extracted beam is used in both IBSIMU and Tracewin codes for LEBT lines to validate the results.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-MOPC61
About: Received: 13 May 2024 — Revised: 17 May 2024 — Accepted: 17 May 2024 — Issue date: 01 Jul 2024
SUPC017
Computational simulations and beamline optimizations for an electron beam degrader at CEBAF
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An electron beam degrader is under development with the objective of measuring the transverse and longitudinal acceptance of the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab. This project is in support of the CE+BAF positron capability. Computational simulations of beam-target interactions and particle tracking were performed integrating the GEANT4 and Elegant toolkits. A solenoid was added to the setup to control the beam's divergence. Parameter optimization of the solenoid field and magnetic quadrupoles gradient was also performed to further reduce particle loss through the rest of the injector beamline.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-MOPC62
About: Received: 15 May 2024 — Revised: 17 May 2024 — Accepted: 17 May 2024 — Issue date: 01 Jul 2024
SUPC018
Energy deposition and radiation level studies for the FCC-ee experimental insertions
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The Future Circular Collider (FCC) study foresees the construction of a 90.6 km underground ring where, as a first stage, a high-luminosity electron-positron collider (FCC-ee) is envisaged, operating at beam energies from 45.6 GeV (Z pole) to 182.5 GeV (ttbar). In the FCC-ee experimental interaction regions, various physical processes give rise to particle showers that can be detrimental to machine components as well as equipment in the tunnel, such as cables and electronics. In this work, we evaluate the impact of the synchrotron radiation emitted in the dipoles and the beamstrahlung radiation from the interaction point (IP). The Monte Carlo code FLUKA is used to quantify the power deposited in key machine elements, such as the beamstrahlung dump and the dipole and quadrupole magnets, as well as the cumulative radiation levels in the tunnel. We also examine the effect of synchrotron radiation absorbers in the vacuum chamber, in combination with additional shielding. The results are presented for the different operation modes, namely Z pole and ttbar.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-TUPC66
About: Received: 13 May 2024 — Revised: 22 May 2024 — Accepted: 23 May 2024 — Issue date: 01 Jul 2024
SUPC019
Simulation of coupled space charge and wakefield effects for a prototype TW-gun at SwissFEL
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In the injector section of electron linacs, both internal space charge forces and wakefield effects influence the beam dynamics. So far, existing simulation approaches can not account for both effects simultaneously. To fill this gap, we have developed a computational method to account for both effects self-consistently*. It couples a space charge solver in the rest frame of the bunch with a wakefield solver by means of a scattered field formulation. The novelty of this approach is that it enables us to simulate the creation of wakefields throughout the emission and acceleration process. In our contribution, we present extensive studies of the coupled wakefield and space charge effects in a traveling wave electron gun under development at the Paul Scherrer Institute. Wakefields created by the multi-cell design and the transition to the beam pipe are accounted for. Hence, the respective influences of these causes for geometric wakefields on particle dynamics are compared, providing detailed insights into the coupling of wakefields on bunches at low energies. Specifically, uncorrelated energy spread and emittance are investigated which are of key interest for FEL operation.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-WEPR71
About: Received: 08 May 2024 — Revised: 19 May 2024 — Accepted: 21 May 2024 — Issue date: 01 Jul 2024
SUPC020
Introducing a semi-Gaussian mixture model for simulating multiple coulomb scattering in RF-Track
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Within the context of a design study of a LINAC for ionization cooling, this paper presents the result of incorporating a scattering model in RF-Track (v2.1) for charged particles heavier than electrons. This inclusion enables simulations for applications like ionization cooling channels for muon colliders. Within RF-Track, a novel semi-Gaussian mixture model has been introduced to describe the deflection of charged particles in material. This innovative model comprises a Gaussian core and a non-Gaussian tail function to account for the effects of single hard scattering. To validate the accuracy of our results, we conducted a benchmarking comparison against other particle tracking codes, with the outcomes demonstrating a high level of agreement.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-WEPR31
About: Received: 14 May 2024 — Revised: 19 May 2024 — Accepted: 19 May 2024 — Issue date: 01 Jul 2024
SUPC021
Searching for the best initial beam parameters for efficient muon ionization cooling
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Ionization cooling stands as the only cooling technique capable of efficiently reducing the phase space of a muon beam within a short time frame. The optimal cooling parameters of a muon collider aim to minimize transverse emittance while simultaneously limiting longitudinal emittance growth, resulting in optimal luminosities within the collider ring. This study shows that achieving efficient cooling performance requires selecting the best initial muon beam parameters. Because for every transvere emittance there exist an optimal beam energy for ionization cooling. We present a technique that enables the determination of these optimal initial parameters through simulations and compare them with an improved analytical scattering model.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-WEPR30
About: Received: 14 May 2024 — Revised: 20 May 2024 — Accepted: 20 May 2024 — Issue date: 01 Jul 2024
SUPC022
Simulating a rectilinear cooling channel using BDSIM for the 6D muon cooling demonstrator
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Muon colliders hold promise for high luminosity multi-TeV collisions, without synchrotron radiation challenges. However, this involves investigation into novel methods of muon production, acceleration, cooling, storage, and detection. Thus, a cooling demonstrator has been proposed to investigate 6D muon ionization cooling. The MICE experiment validated ionization cooling to reduce transverse emittance. The demonstrator will extend this to also cool longitudinal emittance. It would also use bunched beams instead of single particles from a muon source. The 6D cooling lattice comprises successive cells which consist of: solenoids for tight focusing, dipoles to introduce dispersion in the beam, wedge-shaped absorbers for differential beam absorption, and RF cavities for reacceleration. In this paper, the simulation and further optimization of the rectilinear cooling channel is discussed. This analysis extends existing theoretical and numerical work using BDSIM, a Geant4-based accelerator framework built to simulate the transport and interaction of particles. The study also incorporates beams from existing proton drivers, using output from targetry and capture designs for the same.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-TUPC20
About: Received: 15 May 2024 — Revised: 22 May 2024 — Accepted: 24 May 2024 — Issue date: 01 Jul 2024
SUPC023
Beam correction for multi-pass arcs in FFA@CEBAF: status update
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This work examines the multi-pass steering of six electron beams in an FFA arc ranging from approximately 10.5 GeV to 22 GeV. Shown here is an algorithm based on singular value decomposition (SVD) to successfully steer all six beams through the arc given precise knowledge of all beam positions at each of one hundred and one diagnostic locations with one hundred individual corrector magnets: that is successive application of SVD to different 100 × 101 response matrices—one for each beam energy. Further, a machine learning scheme is developed which only requires knowledge of the energy-averaged beam position at each location to provide equivalent steering. Extension of this scheme to other beam optics quantities as well as transverse and longitudinal coupling is explored.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-TUPC23
About: Received: 15 May 2024 — Revised: 17 May 2024 — Accepted: 17 May 2024 — Issue date: 01 Jul 2024
SUPC024
Optimization of nanostructured plasmas for laser wakefield acceleration using a Bayesian algorithm
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Nanostructures are currently attracting attention as a medium for obtaining ultra-high-density plasmas for beam-driven or laser-driven acceleration. This study investigates Bayesian optimization in Laser Wakefield Acceleration (LWFA) to enhance solid-state plasma parameters towards achieving extremely high gradients on the order of TV/m or beyond, specifically focusing on nanostructured plasmas based on arrays of carbon nanotubes. Through Particle-In-Cell (PIC) simulations via EPOCH and custom Python scripts, we conducted a parameter analysis for various configurations of carbon nanotube arrays. Utilizing the open-source machine learning library BoTorch for optimization, our work resulted in a detailed database of simulation results. This enabled us to pinpoint optimal parameters for generating effective wakefields in these specialized plasmas. Ultimately, the results demonstrate that Bayesian optimization is an excellent tool for significantly refining parameter selection for nanostructures like carbon nanotube arrays, thus enabling the design of promising nanostructures for LWFA.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-TUPC29
About: Received: 14 May 2024 — Revised: 17 May 2024 — Accepted: 17 May 2024 — Issue date: 01 Jul 2024
SUPC025
Optimization of cooling distribution of the EIC cooler ERL
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The Electron-Ion Collider (EIC) Hadron Storage Ring (HSR) will use strong hadron cooling to maintain the beam brightness and high luminosity during long collision experiments. An Energy Recovery Linac is used to deliver the high-current high-brightness electron beam for cooling. For the best cooling effect, the electron beam requires low emittance, small energy spread, and uniform longitudinal distribution. In this work, we simulate and optimize the longitudinal laser-beam distribution shaping at the photo-cathode, modeling space charge forces accurately. Machine parameters such as RF cavity phases are optimized in conjunction with the beam distribution using a genetic optimizer. We demonstrate the improvement to the cooling distribution in key parameters.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-TUPC43
About: Received: 15 May 2024 — Revised: 22 May 2024 — Accepted: 23 May 2024 — Issue date: 01 Jul 2024
SUPC026
BAGELS: A general method for minimizing the rate of radiative depolarization in electron storage rings
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We present a novel method for minimizing the effects of radiative depolarization in electron storage rings by use of vertical orbit bumps in the arcs. Electron polarization is directly characterized by the RMS of the so-called spin orbit coupling function in the bends. In the Electron Storage Ring (ESR) of the Electron-Ion Collider (EIC), as was the case in HERA, this function is excited by the spin rotators. Individual vertical orbit bumps in the arcs can have varying impacts on this function globally. In this method, we use a singular value decomposition of the response matrix of the spin-orbit coupling function with each orbit bump to define a minimal number of most effective groups of bumps, motivating the name “Best Adjustment Groups for ELectron Spin” (BAGELS) method. These groups can then be used to minimize the depolarizing effects in an ideal lattice, and to restore the minimization in rings with realistic closed orbit distortions. Furthermore, BAGELS can be used to construct groups for other applications where a minimal impact on polarization is desirable, e.g. global coupling compensation or vertical emittance creation. Application of the BAGELS method has significantly increased the polarization in simulations of the 18 GeV ESR, beyond achievable with conventional methods.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-MOPC81
About: Received: 15 May 2024 — Revised: 22 May 2024 — Accepted: 23 May 2024 — Issue date: 01 Jul 2024
SUPC027
Various methods for computing dominant spin-orbit resonance strengths in storage rings
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The strength of a first-order spin-orbit resonance is defined as the amplitude of the corresponding Fourier component of the spin-precession vector. However, it is possible to obtain the resonance strength without computing the Fourier integral directly. If a resonance is sufficiently strong, then to a good approximation, one can neglect all other depolarizing effects when near the resonance. Such an approximation leads to the single resonance model (SRM), for which many aspects of spin motion are analytically solvable. In this paper, we calculate the strength of first-order resonances using various formulae derived from the SRM, utilizing spin tracking data, the direction of the invariant spin field, and jumps in the amplitude-dependent spin tune. Examples are drawn from the RHIC Blue ring.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-TUPC55
About: Received: 14 May 2024 — Revised: 18 May 2024 — Accepted: 18 May 2024 — Issue date: 01 Jul 2024
SUPC028
Analyzing sudden beam loss in the SuperKEKB/Belle-II experiment with RFSoC technology
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In the SuperKEKB/Belle-II experiment, a multitude of elementary particle reactions is initiated through the collision of 4 GeV positrons with 7 GeV electrons, paving the way for the exploration of new physics. The experiment includes plans for the substantial enhancement of luminosity in the future, aiming to achieve an integrated luminosity approximately 100 times the current level. However, the realization of this goal is impeded by a recurrent occurrence of a phenomenon known as "Sudden Beam Loss," which entails the abrupt disappearance of the beam within tens of microseconds. The cause and location of these occurrences have not yet been identified. To provide the tools to diagnose and debug these sudden beam loss events, a new Bunch Oscillation Recorder (BOR) has been developed to analyze this phenomenon, utilizing the Radio Frequency System on Chip (RFSoC) from AMD/Xilinx. The beam position of each individual bunch is measured and recorded by the BOR just prior to the onset of sudden beam loss. We will present how the signal from the button beam position monitor of the beam pipe is processed by RFSoC, along with the results obtained from observing the actual SuperKEKB beam using RFSoC.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-TUBD3
About: Received: 15 May 2024 — Revised: 23 May 2024 — Accepted: 24 May 2024 — Issue date: 01 Jul 2024
SUPC029
Background mitigation concepts for Super-NaNu
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Super-NaNu is a proposed neutrino experiment as part of the SHADOWS proposal for the high intensity facility ECN3 in CERN's North Area. It aims to detect neutrino interactions downstream of a beam-dump that is penetrated with a 400 GeV high intensity proton beam from the SPS. The experiment would run in parallel to the HIKE and SHADOWS experiments, taking data with an emulsion detector. Simulations show that various combinations of muon backgrounds pose the major limiting component for NaNu operation. As muons will leave tracks in the emulsion detector, their flux at the detector location is directly correlated to the frequency of emulation exchange and therefore with the cost of the experiment. Finding ways of mitigating the muon background as much as possible is therefore essential. In this paper, we present a possible mitigation strategy for muon backgrounds.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-TUPC63
About: Received: 15 May 2024 — Revised: 20 May 2024 — Accepted: 20 May 2024 — Issue date: 01 Jul 2024
SUPC030
Optimizations and updates of the FCC-ee collimation system
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The Future Circular electron-positron Collider, FCC-ee, is a design study for a 90 km circumference luminosity-frontier and highest-energy e+e- collider. It foresees four operation modes optimized for producing different particles by colliding high-brightness lepton beams. Operating such a machine presents unique challenges, including stored beam energies up to 17.5 MJ, a value about two orders of magnitude higher than any lepton collider to date. Given the high stored beam energy, unavoidable beam losses pose a serious risk of damage. Thus, an adequate protection system has to be implemented. To address this challenge, a beam collimation system to protect the sensitive equipment of this machine is indispensable. This paper presents the studies that led to a new collimation system baseline and a collimation performance evaluation under selected beam loss scenarios.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-TUPC76
About: Received: 15 May 2024 — Revised: 21 May 2024 — Accepted: 21 May 2024 — Issue date: 01 Jul 2024
SUPC031
Normalized uniformity-based common points layout optimization method for alignment installations
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The alignment installation work of Hefei Advanced Light Facility (HALF) is usually carried out in tunnels. We convert the coordinates of the landmark points to the global coordinate system through coordinate transformation, and accurately adjust them to the corresponding coordinate values for alignment and installation. However, tunnels are often long and narrow, which can easily lead to ill-conditioned normal equations and loss of accuracy when solving coordinate transformation parameters. Therefore, to quickly and accurately obtain the coordinate transformation parameters, this paper proposes a common point selection method based on uniformity division space, which divides the coordinate transformation space according to the uniformity in different directions to select the optimal common points combination, and uses simulation and measured data to verify the method in this article. The results show that the conversion parameters solved by this method are more accurate and more stable, avoiding accuracy loss due to aggregation in a certain direction, and are suitable for narrow and long layout scenarios.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-TUPC78
About: Received: 14 May 2024 — Revised: 22 May 2024 — Accepted: 23 May 2024 — Issue date: 01 Jul 2024
SUPC032
A faster algorithm to compute lowest order longitudinal and transverse resistive wall wake for non-ultrarelativistic case
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With the development of the steady state micro bunching (SSMB) storage ring, its parameters reveal that the ultra relativistic assumption which is wildly used is not valid for the electron beam bunch train, which has length in the 100 nm range, spacing of 1 μm and energy in hundreds MeV range. The strength of the interaction between such bunches and the potential instability may need careful evaluation. At the same time, the effect of the space charge inside a single bunch due to space charge effect also needs to be considered. In this article, we reorganized the lowest-order longitudinal wakefield under non-ultra relativistic conditions, and modified the inconsistent part in the theoretical derivation in some essays of the lowest-order transverse wakefield. We present the modified theoretical results and analysis. Then based on the result we have derived, we give a algorithm which is thousands time faster than direct calculation. It lays foundation in future research.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-MOPG09
About: Received: 14 May 2024 — Revised: 19 May 2024 — Accepted: 19 May 2024 — Issue date: 01 Jul 2024
Single-shot meV-resolution hard X-ray spectrograph for CBXFEL diagnostics
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A cavity-based x-ray free-electron laser (CBXFEL) is a possible future direction in the development of fully coherent hard x-ray sources of high spectral brilliance, a narrow spectral bandwidth of ~1-100 meV, and a high repetition rate of ~1 MHz. A diagnostic tool is required to measure CBXFEL spectra with a meV resolution on the shot-to-shot bases. Here we present test results of a single shot hard x-ray angular-dispersive spectrograph designed for this purpose. Angular-dispersive x-ray spectrographs are composed of a dispersive element — Bragg reflecting crystals arranged in an asymmetric scattering geometry, a focusing element, and a pixel detector [1]. The CBXFEL spectrograph was designed to image 9.8 keV x-rays in a ~200 meV spectral window with a spectral resolution of a few meV. Two Ge asymmetrically cut crystals in the dispersive 220 Bragg reflection geometry were used as the dispersive element. A compound refractive Be lens was used as the focusing element. The spectrograph was built and tested at the Advanced Photon Source beamline 1-BM-B. The spectrograph operates close to design specification featuring a 185 meV (FWHM) spectral window of imaging, a 1.4 μm/meV linear dispersion rate, and a spectral resolution of 15 meV estimated with a 40 meV width of the spectral reference benchmark available in the test measurements.
SUPC034
Simulation of CXFEL with MITHRA code
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The CXFEL project at ASU will produce coherent soft x-ray radiation at a university-scale facility. Unlike conventional XFELs, the CXFEL will use an optical undulator in addition to nanobunching the electron beam instead of a static magnetic undulator. This reduces the undulator period from cm-scale to micron scale and lowers the requirements on the electron beam energy. CXFEL’s overtaking geometry design reduces the effective undulator period to 7.86 μm to produce 1 keV photons. This is accomplished by crossing the laser and electron beam at a 30 degree overtaking angle, and using a tilted laser pulse front to maintain temporal overlap between the electron beam and laser pulse. The inverse Compton scattering interaction between a microbunched electron beam and an optical undulator falls out of the range of most accelerator codes. We employ MITHRA, a FEL full-wave FDTD solver software package which includes inverse Compton scattering to simulate the FEL lasing process. We have adapted the code to the CXFEL instrument design to simulate the radiation/electron beam interactions and report results of studies including scaling of key parameters.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-MOPG13
About: Received: 15 May 2024 — Revised: 19 May 2024 — Accepted: 19 May 2024 — Issue date: 01 Jul 2024
Pulsed Compton Gamma-ray beam generation using pulsed FEL beam
For certain photonuclear experiments utilizing Compton gamma-ray beams, beam-uncorrelated background poses a significant challenge. At the High Intensity Gamma-ray Source (HIGS), we have developed methods to generate pulsed free-electron laser (FEL) beams by transversely or longitudinally modulating the storage ring FEL. Both methods enable periods of FEL interaction: one by transversely manipulating the electron beam orbit, the other by de-synchronizing the electron and FEL beams. The recently-developed longitudinal method has proven superior: it avoids beam loss and is applicable across a wide range of electron beam energies. In this work, we describe the operational principle of pulsed FEL beam generation using longitudinal modulation, and we present measurements of the macro- and micro-temporal structure of the FEL beam. Furthermore, we present experimental results demonstrating the effectiveness of using a pulsed gamma-ray beam to reduce beam background.
SUPC036
Characterization of FEL mirrors with long ROCs
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FEL oscillators typically employ a two-mirror cavity with spherical mirrors. For storage ring FELs, a long, nearly concentric FEL cavity is utilized to achieve a reasonably small Rayleigh range, optimizing the FEL gain. A challenge for the Duke storage ring, with a 53.73 m long cavity, is the characterization of FEL mirrors with a long radius of curvature (ROC). The Duke FEL serves as the laser drive for the High Intensity Gamma-ray Source (HIGS). As we extend the energy coverage of the gamma-ray beam from 1 to 120 MeV, the FEL operation wavelength has expanded from infrared to VUV (1 micron to 170 nm). To optimize Compton gamma-ray production, the optimal value for the mirror's ROC needs to vary from 27.5 m to about 28.5 m. Measuring long mirror ROCs (> 10 m) with tight tolerances remains a challenge. We have developed two different techniques, one based on light diffraction and the other on geometric imaging, to measure the long ROCs. In this work, we present both techniques and compare their strengths and weaknesses when applied to measure mirror substrates with low reflectivity and FEL mirrors with high reflectivity.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-MOPG23
About: Received: 16 May 2024 — Revised: 21 May 2024 — Accepted: 22 May 2024 — Issue date: 01 Jul 2024
Commissioning of spectral diagnostics and future concepts for the PAX experiment at FACET-II
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The ongoing Plasma-driven Attosecond X-ray source experiment (PAX) at FACET-II aims to produce coherent soft X-ray pulses of attosecond duration using a Plasma Wakefield Accelerator [1]. These kinds of X-ray pulses can be used to study chemical processes where attosecond-scale electron motion is important. For this first stage of the experiment, PAX plans to demonstrate that <100 nm bunch length electron beams can be generated using the 10 GeV beam accelerated in the FACET-II linac and using the plasma cell to give it a percent-per-micron chirp. The strongly chirped beam is then compressed in a weak chicane to sub-100 nm length, producing CSR in the final chicane magnet at wavelengths as low as 10s of nm. In this contribution we describe the commissioning of the spectral diagnostics as well as the results expected of this experiment. Additionally, we describe a future iteration of the experiment in which short undulators are used to drive coherent harmonic generation to produce attosecond gigawatt X-ray pulses at 2 and 0.4 nm, with lengths comparable to the shortest attosecond pulses ever measured at 2 nm using HHG.
High-energy and narrow-bandwidth X-ray regenerative amplifier FEL design for LCLS-II-HE
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LCLS-II-HE is an energy upgrade of the LCLS-II linac from 4 GeV to 8 GeV. The X-ray FEL photon energy (Self-Amplified Spontaneous Emission mode) will extend towards 12 keV (from the present 5 keV) based on the current beam emittance. To reach higher photon energy range towards 20 keV, a new injector with a much brighter electron beam will be required. Here we study an X-ray regenerative amplifier FEL (XRAFEL) configuration that enables reaching 20 keV photon energy with the current LCLS-II injector parameters, by reamplifying the cavity-returned X-rays in the LCLS-II undulator over multiple passes. At 20 keV, the Bragg mirrors have very narrow angular and wavelength acceptances. In this paper, we discuss how to layout the cavity optics in combination with the electron-beam based Q-switching method to generate fully coherent bright high-energy X-rays with 20 meV spectral bandwidth.
Generating tunable X-ray optical frequency combs using a free-electron laser
As an important experimental tool, the Optical Frequency Combs (OFCs) has had a profound impact on research in various fields, whereas, generating high power high repetition frequency OFCs at tunable frequencies is still a limitation for most of the existing methods. In this study, free-electron laser (FEL) is proposed to generate coherent X-ray OFC with a tunable repetition frequency and high pulse energy. The approach involves using a proper seed laser with frequency modulation, followed by amplification in the Echo-Enabled Harmonic Generation (EEHG) mode to generate X-ray OFCs. Numerical simulations using the realistic beam parameters of the Shanghai soft X-ray free-electron laser facility have demonstrated the feasibility of generating X-ray OFCs. These OFCs have a peak power of about 1.5 GW and repetition frequencies ranging from 6 THz to 12 THz at Centre energies carbon K edge (~284 eV). The proposed technique presents new possibilities for resonant inelastic x-ray scattering (RIXS) spectroscopy and Terabit-level coherent optical communication, etc.
An experimental proposal for the strong-filed Terahertz generation at SXFEL facility
Strong field Terahertz (THz) light source has been in-creasingly important for many scientific frontiers, while it is still a challenge to obtain THz radiation with high pulse energy at wide-tunable frequency. In this paper, we introduce an accelerator-based strong filed THz light source to obtain coherent THz radiation with high pulse energy and tunable frequency and X-ray pulse at the same time, which adopts a frequency beating laser pulse modulated electron beam. Here, we present the experimental preparation for the strong filed THz radiation at shanghai soft X-ray free-electron laser (SXFEL) facility and show its simulated radiation performance.
Linking edge-ML X-ray diagnostics and adaptable photoinjector laser shaping for leveraging the capabilities of LCLS-II
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SLAC's LCLS-II is rapidly advancing towards MHz repetition rate attosecond X-ray pulses, opening new opportunities to leverage the abundance of data in combination with advances in machine learning (ML) to better align the x-ray source with specific experimental goals. We approach the challenge from both ends of the facility. Starting at the X-ray output, we showcase our low latency, high throughput ML algorithms implemented at-the-edge for X-ray detection and reconstruction in the Multi-Resolution 'Cookiebox' (MRCO) angle resolved electron spectrometer with its 16 electron time-of-flight detectors. MRCO performs spectro-temporal characterization of X-ray profiles with a resolution that allows single shot identification of well-seeded shots versus SASE background at MHz rate. MRCO enables fast feedback, so we also tackle the problem as a control issue, focusing on programmable photoinjector laser shaping to adjust the initial electron bunch. Towards this end of using advances in ML to explore the parameter space for optimizing X-ray production, we present our progress towards a digital twin linking the photoinjector laser all the way through MRCO in the endstation diagnostics.
SUPC042
Compact high average power THz source driven by thermionic RF gun
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This work presents the design of a compact high-efficiency terahertz source, a collaborative effort between UCLA and RadiaBeam Technologies. The system, driven by a thermionic RF gun, features prebunching elements including alpha-magnet and electromagnetic chicane to effectively compress the long beam generated from the gun. By sending such beam into tapering enhanced waveguide oscillator, we can achieve high efficiency energy extraction in different regimes. This work focuses on the beam dynamics in the beamline prior injection into the undulator. A brief mention of the simulation results for radiation generation is also presented.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-MOPG67
About: Received: 15 May 2024 — Revised: 20 May 2024 — Accepted: 20 May 2024 — Issue date: 01 Jul 2024
SUPC043
Beam dynamics study for a high-repetition-rate infrared terahertz FEL facility
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The paper introduces design and optimization of a high-repetition-rate infrared terahertz free-electron laser (IR-THz FEL) facility, which leverages optical resonator-based FEL technology to achieve a higher mean power output by increasing pulse frequency. Electron beam of the facility will be generated from a photocathode RF gun injector and further accelerated with a superconducting linear accelerator. Taking into account the collective effects, such as space charge, coherent synchrotron radiation (CSR), and longitudinal cavity wake field impacts, beam dynamics simulation for the injector, the accelerator, as well as the bunch compressor, has been done with codes of ASTRA and CSRTrack. With optimized microwave parameters of the linac, current profile with good symmetry has been obtained and the peak current can reach 100 A.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-MOPG71
About: Received: 15 May 2024 — Revised: 19 May 2024 — Accepted: 20 May 2024 — Issue date: 01 Jul 2024
SUPC044
Study on high energy coupling efficiency of laser-electron interaction via vortex beam
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Manipulation electron beam phase space technology by laser-electron interaction has been widely used in accelerator-based light sources. The energy of the electron beam can be modulated effectively under resonant conditions by using an intense external laser beam incident into the undulator together with the electron beam. Enhancing the modulation efficiency is crucial for the performance of high repetition rate seeded free electron lasers (FELs) and other related devices. In this paper, we propose a new scheme to augment the efficiency of laser-electron interaction by employing the interaction between a vortex beam and an electron beam within a helical undulator. Three-dimensional time-dependent simulation results indicate that the modulation repetition rate of laser-electron interaction using a vortex beam can be improved by one order of magnitude over the conventional Gaussian beam at the same input power.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-MOPG72
About: Received: 09 May 2024 — Revised: 17 May 2024 — Accepted: 18 May 2024 — Issue date: 01 Jul 2024
SUPC045
The design of a 2.3-cell X-band photocathode RF electron gun
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Recent advancements in electron beam compression methods have enabled the production of ultrashort electron beams at the sub-femtosecond scale, significantly expanding their applications. However, the temporal resolution of these beams is primarily limited by the flight time jitter, especially during their generation in photocathode RF electron guns. In this paper, to mitigate the impact of microwave phase jitter on the flight time jitter inside the electron gun, we designed a 2.3-cell X-band electron gun, which enables the electron beams to acquire maximum output energy and minimum in-gun flight time at the same injection phase. Moreover, the tolerance of the cavity's machining errors is assessed and the RF input coupler of this cavity has been designed. Our simulation results indicate that this design provides a solid foundation for further improving the temporal resolution of the electron beam.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-WEPC79
About: Received: 13 May 2024 — Revised: 19 May 2024 — Accepted: 23 May 2024 — Issue date: 01 Jul 2024
SUPC046
Study of the radiation field from multiple out-coupling holes in an infrared free electron laser oscillator
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A new infrared Free-Electron Laser (FEL) facility FELiChEM has been established as an experimental facility at the University of Science and Technology of China. It consists of two free electron laser oscillators which produce mid-infrared and far-infrared lasers covering the spectral range of 2-200 μm at the present stage. The output power is a crucial parameter for users, and it is usually achieved by an out-coupling hole located in the center of a cavity mirror. Nevertheless, the spectral gap phenomenon has been observed in FEL oscillators with partial waveguides as the output power is highly dependent on the mode configuration before the out-coupling mirror. Such power gaps have an adverse effect on experimental results since numerous experiments require continuous spectral scanning. In this paper, we propose the utilization of multiple out-coupling holes on the cavity mirror, instead of relying solely on a central out-coupling hole, to reduce the adverse impact of the spectral gap phenomenon.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-MOPG73
About: Received: 15 May 2024 — Revised: 19 May 2024 — Accepted: 19 May 2024 — Issue date: 01 Jul 2024
SUPC047
Experimental characterization of the timing-jitter effects on a beam-driven plasma wakefield accelerator
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Plasma wakefield acceleration is nowadays very attractive in terms of accelerating gradient, able to overcome conventional accelerators by orders of magnitude. However, this poses very demanding requirements on the accelerator stability to avoid large instabilities on the final beam energy. In this study we analyze the correlation between the driver-witness distance jitter (due to the RF timing jitter) and the witness energy gain in a plasma wakefield accelerator stage. Experimental measurements are reported by using an electro-optical sampling diagnostics with which we correlate the distance between the driver and witness beams prior to the plasma accelerator stage. The results show a clear correlation due to such a distance jitter highlighting the contribution coming from the RF compression.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-MOPR43
About: Received: 14 May 2024 — Revised: 20 May 2024 — Accepted: 23 May 2024 — Issue date: 01 Jul 2024
SUPC048
Characterisation and optimisation of a C-band photo-injector for compact light sources
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We performed an optimisation study of a C-band photoinjector for high-charge electron beams. Such a device is capable of producing high brightness electron beams, with low energy spread and small transverse emittance, which are properties required by Inverse Compton Scattering radiation sources and compact light sources in general. This work aimed to carry out, via numerical simulations, optimisation and benchmark results of the beam generated by such photoinjector, in the pursuit of its real application in the context of current projects, namely EuPRAXIA@SPARC_LAB, and proposals such as BoCXS at the University of Bologna.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-WEPC06
About: Received: 14 May 2024 — Revised: 19 May 2024 — Accepted: 23 May 2024 — Issue date: 01 Jul 2024
SUPC049
A new rf design of the two-mode transevers deflecting structure
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SSRF (Shanghai Synchrotron Radiation Facili-ty)/SXFEL (Shanghai Soft X-ray FEL) Facility has de-veloped an advanced variable polarization transverse deflecting structure TTDS (two-mode transverse deflect-ing structure) to perform variable polarization based on the design of a dual-mode RF structure. The 15-cell prototype of the TTDS was fabricated at SSRF/SXFEL. Because the two modes operate in the same structure, any geometric change will affect both modes. A new RF design of the regular cell is proposed to improve rf per-formance. The two modes are coupled independently in two pairs of side coupling holes. The work presented in this paper is focused on the new design and the rf param-eters compared with the initial design.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-WEPC14
About: Received: 15 May 2024 — Revised: 24 May 2024 — Accepted: 24 May 2024 — Issue date: 01 Jul 2024
SUPC050
Optimization of bunch charge distribution for space charge emittance growth compensation in the PERLE injector
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Low energy electron bunches experience emittance growth due to space charge. This effect can lead to large emittances which are unacceptable for a facility like PERLE at IJCLab. PERLE will be an ERL test facility circulating a high current electron beam. The traditional method to reduce emittance due to this effect is already planned for the PERLE injector, this has a limit of how small the emittance can be reduced to. This limit is defined by the quality of the bunch as it is upon production at the cathode. The transverse and longitudinal properties of the laser pulse incident on the cathode defines some characteristics of the bunch, to which the space charge effect is related. In addition, the complex evolution of the bunch along the injector could result in optimal laser parameters which are different from the simple flattop distribution currently simulated. Presented here are simulation-based studies of the bunch charge distribution at the cathode and its subsequent evolution along the injector. An optimization of the laser parameters which create the bunch is also performed. We find that there is an optimal bunch charge shape which corresponds to minimal emittance growth.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-WEPC24
About: Received: 15 May 2024 — Revised: 22 May 2024 — Accepted: 22 May 2024 — Issue date: 01 Jul 2024
Optimization of ELSA electron beam transport for its inverse Compton scattering X-ray source
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ELSA LINCS (ELSA Linac INverse Compton Source) at CEA DAM DIF is an Inverse Compton Scattering X-ray source in the 5-40 keV range, through interaction between 10-30 MeV electrons with a Nd:YAG laser. The source was upgraded to increase the X-ray flux produced in the 5-40 keV range. The new experimental setup and imaging systems have been modified for compatibility with fundamental emission at 1064 nm and for better mechanical stability. The upgrade also includes installation of a new RF linearizing cavity before magnetic compression, to improve bunch compression. Experimental optimization of the beam transport has been achieved, relying on recent detailed simulation work. Results taking advantage of this optimization are presented: achieved bunch duration, emittance, dimension at interaction point, for several electron energies and several bunch charges between 50 pC up to 1 nC. Comparisons with simulations provide an insight about major contributions to emittance growth. Achievable X-ray flux through Inverse Compton Scattering and applications are discussed.
Beam dynamics and injection condition in a ring-type dipole of a laser-accelerated electron beam for compact light sources
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We are developing a compact synchrotron light source using laser electron acceleration, focusing on creating a tabletop accelerator-based radiation system. Our approach involves a small ring-type dipole with block-shaped permanent magnets, prioritizing cost and weight reduction. Simple beam dynamic calculations revealed that a smaller electron beam divergence angle results in a more stable orbit and the field modulation of peak magnetic strength improves the stability without the additional quadrupoles. CST simulations shows that the magnetic field of the ring-type dipole includes the field modulation of peak magnetic strength along the orbit due to shape changes. The injection to the ring-type dipole is the one of the issues to be solved for a compact light source. In this paper, we present the studies on designing and optimizing the ring-type dipole including the injection of electron beam and the extraction of dipole radiation.
SUPC053
Picometer scale emittance from plasmonic spiral photocathode for particle accelerator applications
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In this work we demonstrate the generation of a record low root mean square normalized transverse electron emittance of less than 30 pm-rad from a flat metal photocathode – more than an order of magnitude lower than the best the emittance that has been achieved from a flat photocathode. This was achieved by using plasmonic focusing of light to a sub-diffraction regime using plasmonic Archimedean spiral structures resulting in a ~40 nm root mean square electron emission spot. Such nanostructured electron sources exhibiting simultaneous spatio-temporal confinement to nanometer and femtosecond level along with a low mean transverse energy can be used for developing advanced electron sources to generate unprecedented electron beam brightness for various accelerator applications.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-WEPC39
About: Received: 15 May 2024 — Revised: 18 May 2024 — Accepted: 18 May 2024 — Issue date: 01 Jul 2024
SUPC054
Simulation of electrom beams from the ELBE superconducting RF gun for ultrafast electron diffraction experiments
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Moving towards beam energies around 2-6 MeV in ultrafast electron diffraction (UED) experiments allows achievement of larger coherence length for better *k*-space resolution, while the temporal resolution is improved when shorter electron bunches are generated and the velocity mismatch between the optical pump and UED probe is reduced. At Helmholtz-Zentrum Dresden-Rossendorf (HZDR), a series of superconducting cw RF (SRF) guns has been designed, build, and tested, with the latest version currently in routine operation as one of the electron sources for the ELBE Center for High Power Radiation. This SRF photoinjector produces bunches with a few-MeV energies at up to MHz repetition rates, making it a suitable electron source also for MeV-UED experiments. The high repetition rate provides a significant advantage for the characterization of samples with low scattering cross-sections such as liquids and gases. In this paper, we outline the conceptual MeV-UED instrument program under development at HZDR. We also showcase the beam quality achieved in first simulations of the ELBE SRF gun operating at low bunch charge as an electron source for diffraction experiments.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-WEPC49
About: Received: 14 May 2024 — Revised: 21 May 2024 — Accepted: 21 May 2024 — Issue date: 01 Jul 2024
SUPC055
Development of new method of NEA Activation with Cs-Sb-O
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Negative Electron Affinity (NEA) activated GaAs photocathodes are the only one capable of generating spin-polarized electron beam larger than 90%. However, the NEA layer currently made from mainstream cesium (Cs) and oxygen (O) is chemically unstable, the NEA-GaAs photocathode has a rapid QE degradation over time or electron beam. As a result, it requires an operating vacuum pressure of 1e-9 Pa and has a short lifetime. Recently, a new NEA layer using heterojunctions with semiconductor thin film of alkali metals and antimony or tellurium has been proposed. The latest research shows that the NEA activation method using Cs-Sb-O is made by co-evaporation of Cs, O2 and Sb. However, the co-evaporation method has high demands on equipment. Therefore, in this work, we attempted to fabricate a Cs-Sb-O NEA layer using a separation evaporation method. Specifically, we attempted four recipes and successfully fabricated the NEA layer by Cs-Sb-O. We also evaluated the dependence of QE on Sb thickness and found that it is easy to form a NEA layer with 0.2 nm of Sb.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-WEPC62
About: Received: 09 May 2024 — Revised: 23 May 2024 — Accepted: 24 May 2024 — Issue date: 01 Jul 2024
SUPC056
Dark current reduction for NSRRC photoinjector system by collimator
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The coherent THz facility developed at NSRRC delivers superradiant radiation with wavelengths ranging from 100 – 500 um from a gap tuneable U100 planar undulator. An S-band laser-driven photocathode rf gun has been used in its 25 MeV linac system to generate a sub-picosecond high brightness relativistic electron beam via velocity bunching for emission of coherent THz radiations. However, the high accelerating field in the gun cavity is found to be the main cause of electron field emission that generates the non-negligible background current (dark current) in the system. A portion of the field emission (FE) electrons with launching conditions close to that of the main beam can be accelerated to high energies by the booster linac structure located downstream. The primary cause of excessive radiation dosage stems from the collision of these unwanted high-energy electrons with the system's vacuum vessel. In order to limit the transportation of FE electrons from rf gun to the booster linac, a collimation system will be implemented at upstream of the booster linac. In this work, the drive linac system has been modeled with 3D space charge tracking code – IMPACT-T for both main beam as well as dark current simulation. Particle transmission and energy distribution of dark current after collimation has been simulated. Trajectories of electrons at various initial positions and particle loss mechanism have also been analyzed.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-WEPC63
About: Received: 15 May 2024 — Revised: 19 May 2024 — Accepted: 19 May 2024 — Issue date: 01 Jul 2024
SUPC057
Towards operating low mean transverse energy alkali antimonide photocathodes at Argonne Cathode Test-stand
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The performance and scientific reach of advanced electron accelerator applications, such as particle colliders, x-ray free electron lasers, and ultrafast electron diffraction, are determined by beam brightness. The beam brightness is constrained by the quality of photocathodes and is associated with low Mean Transverse Energy (MTE) of photoemitted electrons. To meet the requirements for applications demanding a bright electron beam, photocathodes must exhibit ultrasmooth physical and chemical roughness, a long operational lifetime, and robustness under high applied electric fields and laser fluences. In this work, we present the development of an experimental setup for the growth and in-situ characterization of high-quality, low-MTE alkali antimonide photocathodes. Additionally, we describe the modifications made to the Argonne Cathode Test-stand (ACT) at the Argonne Wakefield Accelerator (AWA) Facility, necessary for studying the performance of alkali antimonide photocathodes under real photoinjector conditions.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-WEPC64
About: Received: 15 May 2024 — Revised: 24 May 2024 — Accepted: 24 May 2024 — Issue date: 01 Jul 2024
SUPC058
Monte Carlo modeling of spin-polarized photoemission from NEA GaAs with low-temperature and strained-lattice effects
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GaAs-based photocathodes activated to negative electron affinity (NEA) is the only existing technology that can deliver intense and highly spin-polarized electron beams for the forthcoming Electron-Ion Collider as well as enable spin-polarized scanning tunneling microscopy, ultrafast spin-polarized low-energy electron diffraction, and other cutting-edge experiments. The degree of spin-polarization of electrons photoemitted from unstrained GaAs is usually considerably less than the theoretical maximum of 50%. However, it has been experimentally observed that the degree of electron spin polarization can be increased and even exceed the theoretical maximum when the sample is cooled to low temperatures. Additionally, in strained lattice samples, the theoretical maximum of spin polarization increases to 100%. The previously developed Monte Carlo approach to spin-polarized photoemission from unstrained, room temperature NEA GaAs provides excellent agreement with experimental data in a wide range of doping densities and photoexcitation energies. This study aims to extend the model’s capabilities by incorporating both low-temperature and strained-lattice effects into the band structure and exploring their impact on spin and momentum relaxation mechanisms. Modeling of both low-temperature and strained NEA GaAs will provide a foundation for modeling photoemission from novel spin-polarized materials and complex layered structures.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-WEPC65
About: Received: 15 May 2024 — Revised: 20 May 2024 — Accepted: 23 May 2024 — Issue date: 01 Jul 2024
SUPC059
Dark current studies for a SW C-band electron gun with a deflector
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To generate the very high brightness beams in light sources, injectors based on radiofrequency photo-guns with very high peak electric fields on the cathode are used. However, this very high surface electric field on the surface of a radio frequency cavity leads to the generation of dark current due to the field emission effect which can damage the instrumentation and radio-activate components. Consequently, it is important to reduce the emission of these electrons and evaluate the subsequent transportation. In this paper, the deflector has been innovatively positioned at the exit of the photo-gun so as to reduce the dark current as much as possible. The dark current emission and spectrum of the dark current of the C-band electron gun have been evaluated by Particle-In-Cell simulations. The dark current before the accelerating sections has been captured and observed both with and without the deflector.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-WEPC74
About: Received: 15 May 2024 — Revised: 20 May 2024 — Accepted: 21 May 2024 — Issue date: 01 Jul 2024
SUPC060
Dark current in the LCLS Injector: characterization and mitigation strategies
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In addition to the desired electron beam, RF photoinjectors such as the one in LCLS-II produce dark current via field emission. Left unchecked, the dark current can cause various operational issues in the accelerator, such as increased radiation, damage to accelerator components and diagnostics, and desorption of gases from vacuum chamber surfaces. In this contribution, we present measurements of the dark current in the LCLS-II injector, including imaging, current, and energy distributions of the observed dark current emitters. These measurements allow us to characterize each emitter in terms of the Fowler-Nordheim model of field emission, which in turn enables us to more accurately model the behavior of the dark current in the accelerator. Taking these results into account, we also present potential active and passive mitigation strategies.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-WEPC75
About: Received: 15 May 2024 — Revised: 21 May 2024 — Accepted: 22 May 2024 — Issue date: 01 Jul 2024
SUPC062
Temporal profile shaping for a dispersive section using a multi-objective genetic algorithm
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The importance of shaping temporal profiles in accelerator physics is highlighted by a wide range of applications, such as plasma acceleration and improved performance in free electron laser applications. In our study, we focus on controlling the dispersion in a bunch compressor and the energy chirp of the beam entering the compressor to achieve diverse temporal profiles. The transmission of electron beams through dispersive regions, like bunch compressors and transport lines, can significantly impact the beam's temporal profile. Failure to rigorously control each component's parameters may result in deviation from the desired beam profile. we propose the application of a multi-objective genetic algorithm to address this one-to-many problem. After multiple optimization iterations, we obtained several feasible solutions for controlling the dispersion section and various energy chirps to achieve desired temporal profile.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-THPG03
About: Received: 15 May 2024 — Revised: 23 May 2024 — Accepted: 23 May 2024 — Issue date: 01 Jul 2024
SUPC063
Performance optimization design of photocathode injector based on multi-objective genetic algorithm
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Generating beam with nC-level charge is of great significance for particle colliders. In order to achieve lower emittance and length of bunch, based on the photocathode injector, we designed a L-band gun and L-band accelerating tube. However, with many coupled parameters, it is difficult to optimize its performance to the limit when optimizing them separately. Therefore, we employed a multi-objective genetic algorithm for searching in the multi-dimensional parameter space and utilized a deep Gaussian process as a surrogate model to solve the high-dimensional parameter optimization problem. Through optimization, we successfully obtained the normalized transverse emittance of 3.4 π mm·mrad and the bunch length of 1.0 mm for a fixed charge of 5 nC. This indicates that our method can effectively improve the performance of the photocathode injector.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-THPG02
About: Received: 15 May 2024 — Revised: 21 May 2024 — Accepted: 21 May 2024 — Issue date: 01 Jul 2024
SUPC065
Novel high-intensity X and Gamma-rays sources using crystals
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The research is focused on finding new ways to generate high-intensity, monochromatic X and gamma-rays, surpassing the capabilities of existing methods. While Free-Electron Lasers (FEL) have limitations on photon energy, and Inverse Compton Scattering relies on powerful lasers, the search for alternatives continues. TECHNO-CLS, a PATHFINDER project funded by the European Innovation Council, is dedicated to crafting innovative gamma-ray Light Sources (LSs), utilizing linear, bent, or periodically bent crystals. Similar to magnetic undulators, crystals leverage a strong interplanar electrostatic field to prompt particle oscillation, resulting in electromagnetic radiation. By reducing the oscillation period to sub-mm dimensions, these undulators can produce tens of MeV in photon energy when exposed to GeV electron beams*. As a passive and sustainable element, CLSs show great promise. In the initial phase of the project, we identified techniques to realize CLSs, using alternated pattern deposition on silicon, using simulation to optimize the pattern and conducted experiments at CERN PS with Tungsten and Iridium crystals.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-WEPC80
About: Received: 15 May 2024 — Revised: 21 May 2024 — Accepted: 21 May 2024 — Issue date: 01 Jul 2024
SUPC066
An electron beam modulation laser for steady-state microbunching
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Steady-state microbunching (SSMB) represents an innovative scheme for generating high-power coherent radiation. This approach is expected to generate kilowatt-scale extreme ultraviolet (EUV) radiation for lithography in the semiconductor industry. During the second phase of the SSMB proof-of-principle experiment (SSMB PoP II), the creation of quasi-steady-state microbunches requires specific modulation of the electron beam. This modulation is achieved through a phase-locked laser with a high repetition rate, which enables the detection of continuous coherent radiation over multiple turns. To meet the requirements of SSMB PoP II, a high-power, high-repetition-rate, phase-stabilized pulsed laser has been developed. The single-frequency pulsed laser has been achieved using an electro-optic modulator stage, three amplification stages, and a phase-locked feedback system. Here we report on the development and test results of the electron beam modulation laser.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-TUPG72
About: Received: 15 May 2024 — Revised: 17 May 2024 — Accepted: 17 May 2024 — Issue date: 01 Jul 2024
SUPC067
Lattice design of a pulsed synchrotron for a muon collider fitting within the Fermilab site boundary
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A muon collider allows one to have a high energy reach for physics studies while having a relatively compact footprint. Ideally such a machine would accelerate muon beams to about 5 TeV. We present a preliminary lattice design for a pulsed synchrotron that will accelerate muon beams to their maximum collision energy and having a circumference of 16.5 km, which would allow it to fit just within the Fermilab site boundary. We wish to estimate the maximum energy that muons can be accelerated to on the Fermilab site based on a realistic lattice layout. To achieve a high average bend field, superconducting fixed field dipoles are interleaved with iron-dominated dipoles whose field is rapidly ramped from negative to positive field. Multiple RF stations are required to ensure that the beam energy and the dipole fields are reasonably well synchronized and to avoid longitudinal losses due to the large synchrotron tune. We use FODO arc cells with dispersion suppressed into the RF straights. We will discuss tradeoffs between maximum energy, energy range, and muon decays. We will consider whether to mix superconducting and iron quadrupoles like the dipoles.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-MOPR01
About: Received: 15 May 2024 — Revised: 22 May 2024 — Accepted: 22 May 2024 — Issue date: 01 Jul 2024
SUPC068
Design of prototype magnet for FETS-FFA
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Capable of achieving a high repetition rate with strong focusing, Fixed Field Alternating gradient (FFA) accelerators have the potential to be used for pulsed high intensity operations. With no pulsed high intensity FFA ever built so far, a prototype machine called FETS-FFA has been proposed to study the FFA option for the next generation spallation neutron source (ISIS-II). One of the essential components of this machine will be the main magnets which must satisfy the following conditions: zero chromaticity during acceleration, flexibility in operating tune point to test dynamics for high beam intensity and a large dynamic aperture to avoid uncontrolled loss. The chosen lattice design utilizes spiral magnets to provide edge focusing to focus in the vertical direction while also introducing a reverse bending magnet to better control the vertical tune. A three-dimensional study is being carried out in OPERA 3D software to investigate the parameters of the magnets to achieve the required field. The details on the design will be presented in this paper.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-MOPR05
About: Received: 15 May 2024 — Revised: 20 May 2024 — Accepted: 20 May 2024 — Issue date: 01 Jul 2024
SUPC069
Multicell dielectric disk acceleraing structure high power experiment results
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A Dielectric Disk Accelerator (DDA) is a metallic accelerating structure loaded with dielectric disks to increase its shunt impedance. These structures use short RF pulses of 9 ns to achieve accelerating gradients of more than 100 MV/m. Single cell and multicell clamped structures have been designed and high power tested at the Argonne Wakefield Accelerator. During testing, the single cell clamped DDA structure achieved an accelerating gradient of 102 MV/m with no visible damage in the RF volume region. The minimal damage that was seen outside the RF volume was likely due to RF leakage from uneven clamping during assembly. Based on the success of that experiment, a clamped multicell DDA structure has been designed and tested at high power. Simulation results for this new structure show a 108 MV/m accelerating gradient with 400 MW of input power with high shunt impedance and group velocity. Engineering designs were improved from the single cell structure for a more consistent clamping over the entire structure. Up to this point in the high power experiments, the results show a peak input power of 222 MW correlating to an accelerating gradient of 80 MV/m. Testing of this structure will continue January 2024.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-TUBN1
About: Received: 15 May 2024 — Revised: 23 May 2024 — Accepted: 23 May 2024 — Issue date: 01 Jul 2024
Experimental investigation of zero transverse force modes in sub-THz dielectric lined waveguide
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Dielectric-lined waveguides have been extensively studied for high-gradient acceleration in beam-driven dielectric wakefield acceleration (DWFA) and for beam manipulations, including the application of zero transverse force modes in the waveguides. In this paper, we investigate the zero transverse force modes excited by a relativistic electron bunch passing through a dielectric waveguide with a rectangular transverse cross section. Numerical simulations were performed to optimize the start-to-end beamline using Opal-t, ELEGANT, and WARPX. A Longitudinal Phase Space (LPS) measurement system is used to understand the interaction of the beam with the waveguide modes, and analysis of the resolution of the LPS system was conducted. We will discuss preliminary experimental data collected at the Argonne Wakefield Accelerator (AWA) benchmarked with the simulation results.
SUPC071
Design, fabrication, and testing of a W-band corrugated waveguide for Wakefield acceleration
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In the field of structure wakefield acceleration there is considerable interest in radiofrequency (RF) structures capable of producing high gradients. Structures in the sub-terahertz (sub-THz) regime are of note due to their high gradient and high efficiency, allowing for a low physical footprint. In the pursuit of this goal we have designed a metallic corrugated W-band structure using the CST Studio Suite. After optimizing for the maximum achievable gradient from a nominal Argonne Wakefield Accelerator (AWA) electron bunch at 65 MeV with a Gaussian distribution we attempted to achieve a higher transformer ratio using a shaped bunch. Shaped bunches such as these are achievable at the AWA emittance exchange (EEX) beamline. Preliminary results from the structure testing at AWA using shaped electron bunches will be presented. Further tests are planned, involving a comprehensive optimization of the beamline at AWA.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-MOPR25
About: Received: 24 May 2024 — Revised: 24 May 2024 — Accepted: 24 May 2024 — Issue date: 01 Jul 2024
SUPC072
Test of a metamaterial structure for structure-based wakefield acceleration
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Metamaterial accelerators driven by nanosecond-long RF pulses show promise to mitigate RF breakdown. Recent high-power tests at the Argonne Wakefield Accelerator (AWA) with an X-band metamaterial structure have demonstrated to achieve a gradient of 190 MV/m, while we also observed a new acceleration regime, the breakdown-insensitive acceleration regime (BIAR), where the RF breakdown may not interrupt acceleration of a main beam. Statistical analysis between different breakdown types reveals that the characteristics of the BIAR breakdown are beneficial to high-gradient acceleration at short pulse lengths.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-MOPR26
About: Received: 15 May 2024 — Revised: 23 May 2024 — Accepted: 23 May 2024 — Issue date: 01 Jul 2024
SUPC074
Novel positron beam generation based on Shanghai Laser Electron Gamma Source
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The Shanghai Light Source has been operated since 2009 to provide synchrotron radiation to 40 beamlines of the electron storage ring at a fixed electron energy of 3.5 GeV. The Shanghai Laser Electron Gamma Source (SLEGS) is approved to produce energy-tunable gamma rays in the inverse Compton slant-scattering of 100 W CO2 laser on the 3.5 GeV electrons as well as in the back-scattering. SLEGS can produce gamma rays in the energy range of 0.66 – 21.7 MeV with flux of 1e+5 – 1e+7 photons/s*. A positron source based on SLEGS is designed to produce positron beams in the energy range of 3 – 16 MeV with a flux of 1e+5 /s and energy resolution of ~7% with an aperture of 10 mm collimator. The positron generated has been simulated by GEANT4, uses a SLEGS gamma injected into a single-layer target, and a dipole magnet deflect positrons. Based on the energy-tunable SLEGS gamma rays, the optimized parameters at each gamma energy were simulated to obtain an energy-tunable positron source. We have confirmed positron generation in the commissioning. We plan to construct the positron source in the summer of 2024. We present the positron source based on results of simulation and test measurements.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-TUPC84
About: Received: 14 May 2024 — Revised: 20 May 2024 — Accepted: 21 May 2024 — Issue date: 01 Jul 2024
Optimization of laser coupling into optically field ionized plasma channels for laser-plasma acceleration
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Laser-plasma accelerators (LPAs) can have high acceleration gradients on the order of 100 GeV/m. The high acceleration gradients of LPAs offer the possibility of powering future colliders at the TeV range and reducing the size of particle accelerators at present energy levels. LPAs need tightly focused, high intensity laser pulses and require guiding structures to maintain the laser focus over the optimum acceleration length. It is necessary to match the parameters of the guiding structure and the laser pulse to couple the maximum laser energy into the guiding structure. Optically field ionized (OFI) plasma channels are a guiding structure capable of matching the parameters of the petawatt (PW) laser facility at the Berkeley Lab Laser Accelerator (BELLA) Center [1, 2]. We will present results on the optimization of laser coupling into OFI plasma channels on BELLA PW. We will also discuss how optimization of laser coupling relates to upcoming staging experiments on BELLA PW.
SUPC076
Instability of asymmetric electron drive beams in hollow plasma channels
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Using hollow plasma channels is one approach to compact positron acceleration, potentially reducing the cost and footprint of future linear colliders. However, it is prone to transverse instabilities since beams misaligned from the channel axis tend to get deflected into the channel boundary. In contrast, asymmetric electron drive beams can tolerate misalignment and propagate stably after the initial evolution, but this has only been reported for short distances. In this work, we use quasi-static particle-in-cell simulations to demonstrate the instability of asymmetric drivers even after splitting into two beamlets and reaching equilibrium. As the driver decelerates, its particles gradually return into the channel, making the driver susceptible to deflection by the transverse dipole mode. To understand this behavior, the transverse motion of an individual beam particle is modeled. Strategies to mitigate this instability are also proposed.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-MOPR53
About: Received: 15 May 2024 — Revised: 19 May 2024 — Accepted: 19 May 2024 — Issue date: 01 Jul 2024
SUPC077
Automated emittance and energy gain optimization for plasma wakefield acceleration
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At the Facility for Advanced Accelerator Experimental Tests (FACET-II) accelerator, a pair of 10 GeV high-current electron beams is used to investigate Plasma Wakefield Acceleration (PWFA) in plasmas of different lengths. While PWFA has achieved astonishingly high accelerating gradients of tens of GeV/m, matching the electron beam into the plasma wake is necessary to achieve a beam quality required for precise tuning of future high energy linear accelerators. The purpose of this study was to explore how start-to-end simulations could be used to optimize two important measures of beam quality, namely maximizing energy gain and minimizing transverse emittance growth in a 2 cm long plasma. These two beam parameters were investigated with an in-depth model of the FACET-II accelerator using numerical optimization. The results presented in the paper demonstrate the importance of utilizing beam-transport simulations in tandem with particle-in-cell simulations and provide insight into optimizing these two important beam parameters without the need to devote significant accelerator physics time tuning the FACET-II accelerator.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-MOPR57
About: Received: 14 May 2024 — Revised: 19 May 2024 — Accepted: 19 May 2024 — Issue date: 01 Jul 2024
SUPC078
UV-Soft X-ray betatron radiation characterization from laser-plasma wakefield acceleration
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The spontaneous emission of radiation from relativistic electrons within a plasma channel is called betatron radiation and has great potential to become a compact x-ray source in the future. We present an analysis of the performance of a broad secondary radiation source based on a high-gradient laser-plasma wakefield electron accelerator. The purpose of this study is to assess the possibility of having a new source for a non-destructive X-ray phase contrast imaging and tomography of heterogeneous materials. We report studies of compact and UV-soft X ray generation via betatron oscillations in plasma channel and in particular measurement of the radiation spectrum emitted from electron beam is analyzed from a grazing incident monochromator at Centro de Laseres Pulsados Ultraintensos (CLPU).
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-MOPR58
About: Received: 22 May 2024 — Revised: 23 May 2024 — Accepted: 23 May 2024 — Issue date: 01 Jul 2024
Simulating the transverse probing of laser-driven plasma wakefields using ultrarelativistic electrons
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Laser wakefield accelerators (LWFAs) are capable of supporting accelerating and focusing forces on the order of 10–100 GeV/m, about three orders of magnitude greater than conventional RF accelerators. While theoretical solutions for the electromagnetic (EM) focusing fields have been developed, the field structures have yet to be verified experimentally. In this poster, we present simulation results for transverse probing of laser wakefields using ultrarelativistic electrons. We study the behavior of the probing electrons by implementing filtering masks to investigate focusing characteristics of thin electron "bands". The deflection of these bands after propagating through the wakefield is then used to characterize the EM forces. The simulated focusing behavior of these electron bands is in reasonable agreement with a theoretical model developed based on a thin lens model of the wakefield. Simulation results show the focusing of the bands to be an effective experimental diagnostic for verifying the EM field structure. This provides an analytic framework needed for the first direct measurements of focusing forces in an LWFA at the Accelerator Test Facility at Brookhaven National Lab.
SUPC080
Flat beam transport for a PWFA experiment at AWA
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Particle beams with asymmetric transverse emittances and profiles have been utilized in facilities for driving wakefields in dielectric waveguides and to drive plasma wakefields in plasma. The asymmetric plasma structures created by the beam produce focusing forces that are transversely asymmetric. We utilize the ellipticity of the plasma ion cavity to model the beam evolution of the flat beam driver.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-MOPR64
About: Received: 17 May 2024 — Revised: 21 May 2024 — Accepted: 21 May 2024 — Issue date: 01 Jul 2024
SUPC081
Comparison of flat beam PWFA analytic model with PIC simulations
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This paper explores the phenomenon of asymmetric blowout in plasma wakefield acceleration (PWFA), where the transversely asymmetric beam creates a transversely asymmetric blowout cavity in plasma. This deviation from the traditional axisymmetric models leads to unique focusing effects in the transverse plane and accelerating gradient depending on the transverse coordinates. We extend our series of studies on plasma wakefield acceleration (PWFA) by comparing our recently developed analytic model on the blowout cavity shape created by transversely asymmetric long beams, with Particle-in-Cell (PIC) simulations. The analysis focuses on validating the model's ability to predict the behaviors of different beam profiles in this regime.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-MOPR65
About: Received: 17 May 2024 — Revised: 23 May 2024 — Accepted: 23 May 2024 — Issue date: 01 Jul 2024
SUPC082
An ultimate single-ion source using a Coulomb crystal in a Paul trap
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An ion cloud confined in a Paul trap eventually reaches a Coulomb crystalline state when strongly cooled toward absolute zero. The normalized emittance of the Coulomb crystal can be in the sub-femtometer range. The trap is thus usable as a unique ion source for nano-beam production, though the available beam intensity is limited. This new concept was first discussed nearly 20 years ago* and later experimentally demonstrated by several research groups (**, ***). In this paper, we report on the result of a recent experiment where an attempt was made to extract Ca+ or N2+ ions one by one from a compact linear Paul trap. In addition to the regular extraction scheme based on a string Coulomb crystal, the possibility of using a multi-shell crystalline structure is explored in detail.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-MOPR71
About: Received: 15 May 2024 — Revised: 18 May 2024 — Accepted: 21 May 2024 — Issue date: 01 Jul 2024
SUPC083
Transport and dosimetry of laser-driven proton beams for radiobiology at the BELLA center
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Laser-driven ion accelerators (LDIAs) are well-suited for radiobiological research on ultra-high dose rate effects due to their high intensity. For this application, a transport system is required to deliver the desired beam intensity and dose distribution while online dosimetry is required due to the inherent shot-to-shot variability of LDIAs. At the BELLA Center's iP2 beamline, we implemented two compact, permanent magnet-based beam transport configurations for delivering 10 or 30 MeV protons to a biological sample, along with a suite of diagnostics used for dosimetry. These diagnostics include multiple integrating current transformers (ICTs) for indirect online dose measurements and calibrated radiochromic films (RCFs) to measure the dose profile and calibrate the ICT dosimetry. Benchmarked Monte-Carlo (MC) simulations of the beamline allow us to predict the dose received by the sample and correct the linear energy transfer (LET)-dependent response of the RCFs. This work not only further establishes the practicality of utilizing LDIAs for radiobiological research but also highlights the BELLA Center's capacity to accommodate further experiments in this domain.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-MOPR72
About: Received: 17 May 2024 — Revised: 20 May 2024 — Accepted: 20 May 2024 — Issue date: 01 Jul 2024
SUPC085
Demonstration of enhanced quantum efficiency from optical interference in alkali antimonide photocathodes
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We present measurements of enhanced quantum efficiency (QE) in thin film photocathodes due to optical interference in the cathode-substrate multilayer. Modulations in the quantum efficiency of Cs$_{3}$Sb films grown on multilayer 3C-SiC substrates are observed over a range of visible wavelengths, and are shown to increase the QE by more than a factor of two at certain wavelengths. We derive a model to describe the modulations in QE based on a three step photoemission process incorporating cases of both constant density of states and density functional theory (DFT) derived density of states, which is shown to be in good agreement with the measurements. Predictions from the model show that the QE can be enhanced by more than a factor of four by optimizing the cathode and substrate layer thicknesses. We also find that by optimizing layer thicknesses of the cathode-substrate system in the calculation, optical interference can enhance the QE beyond optically dense films. Advantages of this interference effect for electron accelerator sources are discussed.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-MOPR79
About: Received: 17 May 2024 — Revised: 23 May 2024 — Accepted: 23 May 2024 — Issue date: 01 Jul 2024
Optimizations for ultrafast electron diffraction with a cryogenic C-band gun
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Ultrafast electron diffraction (UED) is a growing accelerator application that enables the study of transient material processes at sub-picosecond timescales with nanometer spatial resolution. In this proceeding, we present simulations of the Cryogenic Brightness-Optimized Radiofrequency Gun (CYBORG) beamline using the General Particle Tracer (GPT) code that are optimized for the application of UED. We explore advantages of performing UED with a beamline equipped with a low intrinsic emittance photocathode, extraction fields approaching 200 MV/m, and a cathode temperature below 77 K. The electron beam bunch length and the 4D transverse emittance are critical metrics for achieving high spatial and temporal resolution in UED, and are minimized at the sample location in our optimization using a Non-Dominated Sorting Genetic Algorithm II (NSGA II).
SUPC087
Chemical robustness enhancement of negative electron affinity photocathodes through cesium-iodide deposition
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Photocathodes at Negative Electron Affinity (NEA), like GaAs and GaN, allow for efficient production of spin-polarized electrons. When activated to NEA with cesium and an oxidant, they are characterized by an extreme sensitivity to chemical poisoning, resulting in a short operational lifetime. In this work, we demonstrate that deposition of a cesium iodide (CsI) layer can be used to enhance the dark lifetime of both GaN and GaAs photocathodes activated with cesium. The mechanism behind this improvement is investigated using X-ray Photoelectron Spectroscopy (XPS) and Atomic Force Microscopy (AFM) techniques.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-MOPR82
About: Received: 17 May 2024 — Revised: 21 May 2024 — Accepted: 21 May 2024 — Issue date: 01 Jul 2024
SUPC089
Framework for a multiphysics model of optical field emission from extended nanostructures
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Laser-field emission, or optical field emission, is a process that can produce electron beams with high charge density and high brightness with ultrafast response times. Using an extended nanostructure, such as a nanoblade, permits plasmonic field enhancement up to 80 V/nm with an incident ultrafast laser of wavelength 800 nm. Stronger ionizing fields lead to higher current densities, so understanding how this field is attained will aid in further increasing brightness. In this paper we lay the framework to study the nanoblade system thermomechanically and plasmonically. We show that, in the moving frame following the laser driver, a steady state is reached, allowing us to reduce the computational complexity of the multiphysics calculation. We derive Maxwell's equations and the current dynamical equation for the steady state in such a moving frame. We also derive the eigenproblem for finding plasmonic modes in the structure with a nonlinear dielectric. The planned calculations to come will allow us to predict peak attainable fields and optimal experimental parameters. We leave off with a discussion of directions for numerical implementation.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-MOPR89
About: Received: 15 May 2024 — Revised: 23 May 2024 — Accepted: 24 May 2024 — Issue date: 01 Jul 2024
SUPC090
High gradient operation of cryogenic C-band RF photogun at UCLA
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Future electron accelerator applications such as x-ray free electron lasers and ultrafast electron diffraction are dependent on significantly increasing beam brightness. We have designed and produced a new CrYogenic Brightness-Optimized Radiofrequency Gun (CYBORG) for use in a new beamline at UCLA to study the brightness improvements achievable in this novel low temperature high gradient accelerating environment. We are currently in the process of commissioning the photogun for operation with peak cathode fields in excess of 120 MV/m. We report here on the status of conditioning the photogun and report on dark current measurements and maximum field achieved thus far.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-MOPR32
About: Received: 15 May 2024 — Revised: 24 May 2024 — Accepted: 24 May 2024 — Issue date: 01 Jul 2024
SUPC091
Evaluation of ultrafast THz near-fields for electron streaking
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THz-frequency accelerating structures could provide the accelerating gradients needed for compact next generation particle accelerators. One of the most promising THz generation techniques for accelerator applications is optical rectification in lithium niobate using the tilted pulse front method. However, accelerator applications are limited by losses during transport and coupling of THz radiation to the acceleration structure. Applying the near-field of the lithium niobate source directly to the electron bunch removes losses due to transport and coupling, yielding a simplified and efficient system. Using electro-optic sampling we have reconstructed the full temporal 3D THz near-field close to the lithium niobate emission face and shown that it can be controlled by manipulating the generation setup. Analysis of the results of this measurement shows an estimated peak field strength of 86 MV/m. A future THz near-field electron streaking experiment is currently planned as a first test of manipulating an electron bunch with the THz near field. Analysis for this planned experiment has yielded an estimated THz near-field kick strength of 23 keV.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-MOPR92
About: Received: 15 May 2024 — Revised: 28 May 2024 — Accepted: 28 May 2024 — Issue date: 01 Jul 2024
SUPC092
Magnetic field modelling and symplectic integration of magnetic fields on curved reference frames for improved synchrotron design: first steps
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Compact synchrotrons, such as those proposed for cancer therapy, use short and highly bent dipoles. Large curvature drives non-linear effects in both body and fringe fields, which may be critical to control to obtain the desired dynamic aperture. Similarly to current practice, for straight magnet, our long-term goal is to aim at finding a parametrization of the field map that requires few terms to capture the relevant long term dynamical effects. This parametrization will then be used to optimize the performance of the synchrotron by long-term tracking simulations and, at the same time, drive the development of the magnet design by providing measurable quantities that can be computed from field maps. This paper presents the first steps towards the goal of representing the field with a few key parameters.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-TUPS09
About: Received: 15 May 2024 — Revised: 21 May 2024 — Accepted: 22 May 2024 — Issue date: 01 Jul 2024
SUPC093
ELISA: a compact linear accelerator for societal applications
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The experience gained at CERN by the R&D for LINAC4 has been exported to medical and societal applications. With an innovative design of the Radio Frequecy Quadrupole (RFQ) at high frequencies, it is possible to build very com- pact structures, reproducible in industry and with the po- tential of full portability. ELISA (Experimental LInac for Surface Analysis) is a linear proton accelerator installed in the Science Gateway exhibition at CERN since October 2023. With a footprint of only 2×1 square meters, ELISA consists of an ion source, a one-meter-long RFQ working at 750 MHz and an analysing line dedicated to Particle Induced X-ray Emission (PIXE). The system can accelerate a proton beam (extracted from the source at 20 keV) up to an energy of 2 MeV. In this paper the ELISA source commissioning is presented, with a multi-parameter optimization performed both computationally and experimentally and the ultimate optimization of beam emittance at 20 keV, finally achieving the required brilliance of the source. High energy beam com- missioning will also be discussed, including RFQ voltage scan to study the transmission and characterize the ELISA RFQ.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-THPR01
About: Received: 12 May 2024 — Revised: 21 May 2024 — Accepted: 23 May 2024 — Issue date: 01 Jul 2024
SUPC094
Improvements to 4-rod RFQs with additive manufacturing processes
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The institute of applied physics (IAP), university of Frankfurt, has been working for years on the development of increasingly powerful 4-Rod RFQ accelerators for hadron acceleration. The need for such accelerators has increased significantly in the recent past, as accelerator-driven neutron sources are becoming increasingly important following the closure of various test reactors. High beam currents, particle energies and operational stability are often required from those LINACs. In order to meet these requirements, the copper structure of the RFQ is to be manufactured using a new type of pure copper 3D printing in order to be able to introduce optimized cooling channels inside the copper parts. Comprehensive multiphysics simulations with ansys, cst and autodesk CFD will first be carried out to evaluate the operational stability and performance. In addition, it will be clarified whether the printed copper fulfills the necessary vacuum and conductivity requirements after CNC processing, or whether galvanic copper plating should be carried out.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-THPR08
About: Received: 15 May 2024 — Revised: 24 May 2024 — Accepted: 24 May 2024 — Issue date: 01 Jul 2024
Magnetic field study for air-cored HTS skeleton cyclotron
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Skeleton cyclotron is a compact size air-cored cyclotron with a high temperature superconducting (HTS) coil system. HTS coils’ high critical current density and high heat stability allow magnetic field induction without using any iron core. With this advantage, the magnetic field configuration can be adjusted quickly without consideration for the hysteresis from iron. The purpose of skeleton cyclotron is to change the beam type quickly between proton, deuteron and alpha particle for the needs of various RI production. In order to achieve this goal, the coil system has to be designed with superconductors’ properties taken into account, such as critical current density under strong external magnetic field etc. In this work, the coil system and magnetic field designed for the skeleton cyclotron will be presented. The capability of accelerating various beam type will also be discussed.
SUPC097
Towards mitigation of challenges in development of high power ISOL targets
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Worldwide Isotope Separation On-Line (ISOL) facilities face growing demand for producing and extracting high-purity exotic radioactive ion beams to serve nuclear physics, astrophysics and medical applications. In this technique, a particle beam interacts with a suitable target material to produce the desired isotopes through a combination of mechanisms like spallation, fragmentation and fission. TRIUMF has the world's highest-power ISOL facility—ISAC, handling 50 kW of proton beam power. The formidable challenge is to suitably handle the power deposited within the target material and maintain it at 2000°C to optimize the diffusion and effusion of the radioactive products. The intricacy of this design requires precise knowledge of the thermal properties of the target material. Typically, a blend of metallic carbide and graphite, these targets exhibit varying porosity and morphology and have effective thermal properties differing from individual constituent elements. To investigate these properties, a combined numerical-experimental approach is employed. This contribution discusses the optimization of target material sample size using numerical tools and outlines the exploration of thermal properties using an experimental apparatus, the Chamber for Heating Investigations (CHI), developed at TRIUMF.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-THPR23
About: Received: 15 May 2024 — Revised: 23 May 2024 — Accepted: 23 May 2024 — Issue date: 01 Jul 2024
SUPC098
Particles and photon attenuating behavior of lead free Eu3+ doped barium phosphate glass system
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The study investigates the radiation attenuation performance of five ternary glass systems with varying chemical compositions: 50P$_2$O$_5$-(50-x)BaO-xEu$_2$O$_3$, where x = 0, 1, 2, 4, and 6 mol%. It utilizes theoretical and Monte Carlo methods to determine shielding parameters such as attenuation coefficients, mean free path, value layers, electron densities, conductivity and neutron removal cross-sections across an energy range from 1 keV to 100 GeV. In addition to these analyses, the study explores kinetic energy stopping potentials and projected ranges of ions (H$^{+}$, He$^{+}$, and C$^{+}$) through the Stopping and Range of Ions in Matter database. Furthermore, research evaluates the dose rate attenuation behavior and trajectories of photons bombarded from $^{137}$Cs and $^{60}$Co sources using Particle and Heavy Ion Transport code System. Obtained results show that sample: 50P$_2$O$_5$-44BaO-6Eu$_2$O$_3$ with higher Eu$^{3+}$-doped glass has a potential for radiation shielding application among selected samples and is comparable with previously recommended, tested polymer and glass samples.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-WEPS07
About: Received: 15 May 2024 — Revised: 18 May 2024 — Accepted: 21 May 2024 — Issue date: 01 Jul 2024
SUPC099
High fidelity numerical modelling and condition monitoring applied to septum magnets at CERN
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The CERN Accelerator Beam Transfer group has recently launched a study to investigate the life cycles of pulsed septum magnets. The development is aiming to enhance the prediction of anomalies, leading to reduced life cycles of these beam transfer equipment. For this reason, the standard vacuum operated, direct drive septa magnet has been chosen to investigate critical design features. In the initial project phase, a so called High-Fidelity (HF) numerical simulation has been carried out, providing insight on critical components, like brazed joints, reducing the fatigue life. In parallel a dedicated test setup with state-of-the-art instrumentation has been developed, allowing to confirm the predicted system response. The novel approach for the beam transfer equipment will allow to review presently established design criteria. In a further iteration, the project is now aiming to demonstrate an anomaly detection and their prediction based on novel machine learning techniques. This paper presents the initial phase of developing the HF model, as well as the results of the instrumented magnet tests which will be compared to results from the numerical simulations.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-THPR29
About: Received: 14 May 2024 — Revised: 17 May 2024 — Accepted: 18 May 2024 — Issue date: 01 Jul 2024
SUPC100
First implementation of RF-KO slow extraction at COSY
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Radio Frequency Knock Out (RF-KO) resonant slow extraction is commissioned at the Cooler Synchrotron (COSY) Jülich for the first time to extract the stored beam and deliver spills with constant particle rates to the experiments. Therefore, transverse RF excitation generated with a software-defined radio is applied to control the extraction rate. A built-in feedback system adjusts the excitation amplitude to maintain the desired extraction rate. To suppress fluctuations of the particle rate on timescales of milliseconds and below, an optimization algorithm is used to tune the RF excitation signals. The method was used extensively during the final run of COSY in 2023, reliably delivering stable beams to various users.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-THPR34
About: Received: 13 May 2024 — Revised: 17 May 2024 — Accepted: 17 May 2024 — Issue date: 01 Jul 2024
SUPC101
The design of the proton-EDM injection line, from BNL AGS booster
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The proton Electric Dipole Moment (pEDM) storage ring to measure the electric dipole moment of the proton [1] is proposed to be built in the tunnel of the Alternating Gradient Synchrotron (AGS) at Brookhaven National Laboratory (BNL) by storage ring EDM (srEDM) Collaboration. We proposed that the AGS Booster to pEDM ring transfer and injection line (BtP) would use the partial portions of the existing BtA (AGS Booster to AGS) transfer line optics. In this practice, both of BtP Clockwise orientation (CW) and Counter-clockwise orientation (CCW) injection line are designed and matched in the hypothesis of a single turn injection scheme. The injecting beam-properties are matched to pEDM ring Twiss functions.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-THPR40
About: Received: 15 May 2024 — Revised: 19 May 2024 — Accepted: 19 May 2024 — Issue date: 01 Jul 2024
SUPC102
Crystal collimation for the HL-LHC upgrade using MERLIN++ accelerator physics library
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This paper details the implementation and benchmarking of crystal collimation within MERLIN++ accelerator physics library and demonstrates its application in simulating crystal collimation process for the High Luminosity(HL) upgrade of Large Hadron Collider(LHC) at CERN. Crystal collimation is one of the key technologies suggested to enhance the current collimation system according to the requirements of HL-LHC upgrade due to its increased beam energy and luminosity. This paper outlines the proposed methodology for this study which includes implementing the demonstrated physics of particle crystal interaction in MERLIN++, benchmarking it with the existing experimental data for simulating the HL-LHC operational scenarios with the crystals as primary collimators. MERLIN++ has already been efficiently used for multiple LHC collimation studies which highlights its importance , making it an essential simulation tool for comparative analysis with other simulation tools, as relying on a single tool for concluding the HL-LHC collimation system is often insufficient. As collimation systems are fundamental for machine protection , accurately predicting the crystal collimation performance is of utmost importance to know how they will perform in HL-LHC to guarantee that the HL-LHC meets its intended objectives with crystal collimators.
DOI: reference for this paper: 10.18429/JACoW-IPAC2024-TUPS41
About: Received: 15 May 2024 — Revised: 18 May 2024 — Accepted: 23 May 2024 — Issue date: 01 Jul 2024