WEPA
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Wednesday Poster Session: WEPA
10 May 2023, 16:30 -
18:30
WEPA002
Suppression of microbunching instability based on optimized velocity bunching in linac-driven FELs
2646
The microbunching instability (MBI) driven by beam collective effects can cause significant electron beam quality degradation in advanced x-ray free electron lasers. Typically, multiple stage magnetic bunch compressors used to generate high peak current electron beam will dramatically amplify the microbunching instability. In this paper, by redesigning the solenoid elaborately and adopting a dual-mode buncher cavity with the third harmonic mode used to correct the RF curvature, it is potential for the electron beam to be further compressed in VB process. Therefore, a VB plus one bunch compressor could be a promising alternative scheme to achieve moderate peak current beam for high-repetition-rate X-ray FELs to suppress the additional MBI gain due to multi-stage magnetic bunch compressors.
Paper: WEPA002
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA002
About: Received: 03 May 2023 — Revised: 06 May 2023 — Accepted: 15 Jun 2023 — Issue date: 26 Sep 2023
DFCSR: A Fast Calculation of 2D/3D Coherent Synchrotron Radiation in Relativistic Beams
Coherent Synchrotron Radiation (CSR) is regarded as one of the most important reasons that limits beam brightness in modern accelerators. Current numerical packages containing CSR wake fields generally use 1D models, which can become invalid in extreme compression regime. On the other hand, the existing 2D or 3D codes are often slow. Here we report a novel particle tracking codes --- DFCSR --- which can simulate 2D/3D CSR and space charge wakes in relativistic electron beams 2 or 3 order of magnitude faster than conventional models like CSRtrack. We performed benchmark simulations based on FACET-II beams, where electron beams are compressed to reach 300kA peak current. The tracking code is written in Python and C programming languages with human-friendly input styles and is open-sourced on Github. It can serve as a powerful simulation tool for the design of next-generation accelerators.
WEPA004
Beam-ion Instabilities and Their Mitigation for SOLEIL II
2650
Beam-ion instabilities belong to a broader class of two-beam instabilities caused by the interaction of a primary beam (electron or hadron bunches) with a secondary beam (ion or electron cloud). The transverse oscillations of these beams can couple with each other. Their amplitude will grow, leading to beam losses. These instabilities can limit the operation of fourth-generation light sources with low emittances and high intensity. Many existing light sources, including synchrotron SOLEIL, are conducting upgrade studies towards fourth-generation light source parameters. This contribution investigates beam-ion instability and potential mitigation measures in SOLEIL II. The instability threshold is determined with analytical estimations and particle tracking results. The trapping of ions in the primary electron beam is discussed for the current lattice design. Differences between different numerical models of this beam-ion interaction are briefly discussed.
Paper: WEPA004
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA004
About: Received: 03 May 2023 — Revised: 30 Jun 2023 — Accepted: 30 Jun 2023 — Issue date: 26 Sep 2023
WEPA005
Landau damping with a transversely gaussian pulsed electron lens
2654
A pulsed electron lens produces a betatron tune shift along a hadron bunch as a function of the longitudinal coordinates, which is a longitudinal detuning. An example of transverse detuning is the tune shifts due to octupole magnets. This paper considers a pulsed electron lens as a measure to mitigate the head-tail instabilities. A detailed analytical description within a Vlasov formalism presents the coherent properties of the longitudinal and transverse detuning. The analytical predictions are compared with the results of the particle tracking simulations. A pulsed electron lens is demonstrated to be a source of tune spread with two components: a static one, leading to Landau damping; and a dynamic one, leading to an effective impedance modification, which we demonstrate analytically and in our particle tracking simulations. The effective impedance modification can be important for beam stability due to devices causing longitudinal detuning, especially for nonzero head-tail modes. The Vlasov formalism is extended to include the combination of longitudinal and transverse detuning. As a possible application at the SIS100 heavy-ion synchrotron (FAIR at GSI Darmstadt, Germany), a combination of a pulsed electron lens with octupole magnets is considered.
Paper: WEPA005
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA005
About: Received: 03 May 2023 — Revised: 08 Jun 2023 — Accepted: 11 May 2023 — Issue date: 26 Sep 2023
WEPA009
Transient beam loading studies in view of the Elettra 2.0 upgrade project
2657
An upgrade project is ongoing at Elettra Sincrotrone Trieste for a 4th-generation storage ring light source called Elettra 2.0. The new machine poses new challenges in terms of performance of the accelerator and sub-systems. One concern, currently under investigation, is about the effects of the passive superconducting third harmonic cavity on the stored beam due to the presence of a dark gap in the beam filling pattern. A simulator based on an analytical frequency-domain model was developed to evaluate the variation of the synchronous phase and synchrotron frequency along the bunch train, as well as the distortion of the bunch profile. Experiments have been carried out in the present Elettra storage ring to characterize the harmonic cavity and to measure the ef-fect of transient beam loading by using the longitudinal multi-bunch feedback system. An ongoing benchmarking of the model and experimental results is reported.
Paper: WEPA009
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA009
About: Received: 03 May 2023 — Revised: 11 May 2023 — Accepted: 12 May 2023 — Issue date: 26 Sep 2023
WEPA011
Longitudinal microwave instability with long bunches in the CERN Proton Synchrotron
2661
Longitudinal microwave instabilities are driven by beam coupling impedance sources which have a very short wavelength compared to the bunch length. These instabilities can be a significant limitation to performance on an accelerator. In the CERN Proton Synchrotron (PS), microwave instability is mostly observed at transition crossing for ion and proton beams, when bunches are shortest. Vacuum equipment such as pumping manifolds and sector valves are suspected as a driving impedance. The method used to study the instability relies on measuring the longitudinal profile modulation of long bunches with a minimal momentum spread while debunching in the PS, with RF off and only induced voltage acting upon the beam. The low momentum spread minimises the variation in particle drift speeds and increases the duration in which the modulations are visible. The spectral analysis of the modulated beam, combined with modelling of long bunch instability growth aims to fully characterise this instability and its origin. The objective being to mitigate the instability and improve the performance and versatility of the PS beam production schemes.
Paper: WEPA011
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA011
About: Received: 02 May 2023 — Revised: 07 May 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
WEPA012
Measurements of longitudinal Loss of Landau damping in the CERN Proton Synchrotron
2665
Landau damping represents the most efficient stabilization mechanism in hadron synchrotron accelerators to mitigate coherent beam instabilities. Recent studies allowed expanding the novel analytical criteria of loss of Landau damping (LLD) to the double harmonic RF system case above transition energy, providing an analytical estimate of the longitudinal stability. The threshold has a strong dependence on the voltage ratio between the harmonic and the main RF systems. Based on that, measurements of single bunch oscillations after a rigid-dipole perturbation have been performed in the CERN Proton Synchrotron (PS). Several configurations have been tested thanks to the multi-harmonic RF systems available in the PS. Higher-harmonic RF systems at 20 MHz and 40 MHz, both in phase (bunch shortening mode) and in counter-phase (bunch lengthening mode) with respect to the principal one at 10 MHz, have been measured.
Paper: WEPA012
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA012
About: Received: 03 May 2023 — Revised: 10 May 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
WEPA013
Longitudinal loss of Landau damping in the CERN super proton synchrotron at 200 GeV
2669
Landau damping plays a crucial role in preserving single-bunch stability. In view of delivering the beam to the High-luminosity LHC (HL-LHC), the Super Proton Synchrotron (SPS) must double the intensity per bunch. In this intensity range, the loss of Landau damping (LLD) in the longitudinal plane can pose an important performance limitation. Observation of the beam response to a rigid-bunch dipole perturbation is a common technique to study the LLD. This contribution presents measurements for a single bunch at 200 GeV in a double-harmonic RF system with a higher harmonic voltage at four times the fundamental RF frequency are presented, showing the impact on Landau damping. Beyond the analytical estimates, the observations are moreover compared to the results from novel stability criteria implemented in the semi-analytical code MELODY, as well as with macroparticle simulation in BLonD.
Paper: WEPA013
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA013
About: Received: 03 May 2023 — Revised: 11 May 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
WEPA015
Instability mitigation using octupoles in bunches with space-charge
2673
Octupole magnets are a central mitigation method against the transverse collective instabilities expected for the high-intensity operation of the SIS18 and SIS100 synchrotrons in the FAIR project. For these beam parameters, the self-field space-charge effect dominates the betatron footprint, and strongly modifies the instability drive and the Landau damping properties. The space-charge tune shifts are related to all three incoherent amplitudes, and is an intrinsic interaction. We consider all these effects and study Landau damping of head-tail modes due to the combination of octupoles and space-charge. Using the data from experimental instability observations, and particle tracking simulations, we provide estimations for the expected high-intensity operation of the SIS synchrotrons.
Paper: WEPA015
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA015
About: Received: 03 May 2023 — Revised: 05 Jun 2023 — Accepted: 19 Jun 2023 — Issue date: 26 Sep 2023
WEPA017
Turn-by-turn measurements of the energy spread at negative momentum compaction factor at KARA
2677
The Karlsruhe Research Accelerator (KARA), the storage ring at KIT, allows short electron bunch operation with positive as well as negative momentum compaction factor. For both cases, the beam dynamics are studied. Using a line array camera KALYPSO (KArlsruhe Linear arraY detector for MHz rePetition rate SpectrOscopy), based on TI-LGAD, the horizontal intensity distribution of the emitted visible part of the synchrotron radiation is measured at a 5-degree port of a bending magnet on a turn-by-turn time scale. As the measurement is located at a dispersive section, the dynamics of the energy spread can be studied by measuring the horizontal bunch profile. The MHz acquisition rate and the low-light sensitivity of the line camera allow measurements at low bunch currents and the investigation of the microbunching instability. This contribution presents the results of the bunch profile measurements performed at positive and negative momentum compaction factor.
Paper: WEPA017
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA017
About: Received: 02 May 2023 — Revised: 25 May 2023 — Accepted: 25 May 2023 — Issue date: 26 Sep 2023
WEPA018
Systematic study of longitudinal excitations to influence the microbunching instability at KARA
2681
Radio-frequency (RF) modulations can influence the microbunching instability dynamics and serve to eventually control them with reinforcement learning (RL) methods. Implementing such a feedback system at the Karlsruhe Research Accelerator (KARA) will require that the action decided by the RL agent, in this case an RF modulation, is applied effectively to the electron beam. Such a modulation can be carried out at KARA by two different devices: the kicker cavity of the bunch-by-bunch feedback system and the accelerating cavities of the main RF system. The Low-Level RF (LLRF) feedback system would require hardware and firmware modifications to accept the continuous action signal given by the RL agent, so systematic measurements were performed to decide which system should be used in the future. Modulations around different harmonics of the synchrotron frequency were applied and the coherent synchrotron light emitted due to the microbunching dynamics analyzed. These measurements were also performed at negative momentum compaction optics, a regime in which the control of the microbunching instability could yield especially intense light.
Paper: WEPA018
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA018
About: Received: 03 May 2023 — Revised: 11 May 2023 — Accepted: 11 May 2023 — Issue date: 26 Sep 2023
WEPA020
Time-resolved measurement and simulation of a longitudinal single-bunch instability at the MAX IV 3 GeV ring
2685
The study and understanding of collective effects plays a vital role for fourth-generation light sources. These effects mostly need to be mitigated and controlled to achieve the design operational parameters. However, they can also be utilized to gain insights into the properties of the machine. While the 3 GeV storage ring at the MAX IV light source is running in multi-bunch mode during user operation. Single-bunch operation is available in dedicated machine study shifts, providing the possibility to study collective effects at higher bunch currents. In such a current range an instability has been observed in the longitudinal plane. Above the threshold current of the instability a dynamic deformation of the bunch profile and a strong increase in energy spread occurs. Dedicated measurements were conducted with multiple diagnostic tools such as time-resolved bunch profile measurements. First simulations of the observed effects were performed with a Vlasov-Fokker-Planck solver. This contribution presents measurement results and draws a comparison to the simulations.
Paper: WEPA020
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA020
About: Received: 03 May 2023 — Revised: 07 May 2023 — Accepted: 21 Jun 2023 — Issue date: 26 Sep 2023
WEPA021
Modelling the experimental data for long-range beam-beam wire compensators at the CERN LHC with diffusive models
2689
Current-carrying wires have long been proposed as measures to mitigate beam-beam effects. Dedicated hardware has been installed at CERN Large Hadron Collider (LHC) and experimental sessions have been organised to study the beam dynamics in the presence of the wire compensators. In this paper, a diffusive model is presented to model the collected experimental data and its performance is discussed in detail.
Paper: WEPA021
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA021
About: Received: 30 Apr 2023 — Revised: 08 May 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
WEPA022
Recent measurements and analyses of the beam-halo dynamics at the CERN LHC using collimator scans
2693
Controlling beam losses is of paramount importance in superconducting particle accelerators, mainly for ensuring optimal machine performance and an efficient operation. Models based on global diffusion processes, in which the form of the diffusion coefficient is the stability-time estimate of the Nekhoroshev theorem, have been studied and proposed to investigate the beam-halo dynamics. Recent measurements with collimator scans were carried out at the CERN Large Hadron Collider (LHC) with the aim of reconstructing the form of the diffusion coefficient. The results of the analyses performed are presented and discussed in detail.
Paper: WEPA022
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA022
About: Received: 30 Apr 2023 — Revised: 08 May 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
WEPA023
Impact of the neutral molecule trapping on beam lifetime and beam profile
2697
This proceeding addresses the effect of the neutral molecules trapped by the beam. It is in particular discussed the effect of a non-uniform neutral molecule distribution on the beam profile and the resulting beam lifetime. According to the trapping temperature it is discussed in a general framework how the beam profile is modified. and the consequent beam loss.
Paper: WEPA023
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA023
About: Received: 01 Apr 2023 — Revised: 26 Jun 2023 — Accepted: 26 Jun 2023 — Issue date: 26 Sep 2023
WEPA024
Study of high-intensity bunch merging and its experimental application on rapid cycling synchrotrons
2701
Longitudinal beam manipulation have been widely employed for various scientific and industrial applications in many hadron (heavy ion or proton) synchrotrons. One of the most important manipulations is the longitudinal bunch merging based on the dual rf system. For high-intensity hadron beams, longitudinal space-charge matching and cavity beam loading matching and compensation are of practical concern to minimize the emittance blow-up for merging of high-intensity beams. For rapid cycling synchrotrons, a trade off should be made between the limited bunch merging time and the high-intensity effects. This paper discusses the schemes for high-intensity hadron bunch merging and proposes a fast bunch merging scheme for rapid cycling synchrotrons. Some experimental preparations for the bunch merging in the CSNS/RCS are also introduced.
Paper: WEPA024
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA024
About: Received: 23 Apr 2023 — Revised: 25 May 2023 — Accepted: 25 May 2023 — Issue date: 26 Sep 2023
WEPA025
Space-charge limit in hadron synchrotrons induced by a gradient error
2705
The half-integer resonance is considered to be one of the strongest effects limiting the intensity of the FAIR SIS100 heavy-ion synchrotron which is currently under construction at GSI. Results of simulations under realistic synchrotron-operation conditions show that for bunched beams, a relatively small gradient error can result in a large half-integer stop-band width significantly reducing the maximum achievable bunch intensity. In addition to the results of simulations in SIS100, we characterize the half-integer stop band in SIS18 using experimental data.
Paper: WEPA025
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA025
About: Received: 03 May 2023 — Revised: 17 May 2023 — Accepted: 22 Jun 2023 — Issue date: 26 Sep 2023
WEPA026
Active deep learning for nonlinear optics design of a vertical FFA accelerator
2709
Vertical Fixed-Field Alternating Gradient (vFFA) accelerators exhibit particle orbits which move vertically during acceleration. This recently rediscovered circular accelerator type has several advantages over conventional ring accelerators, such as zero momentum compaction factor. At the same time, inherently non-planar orbits and a unique transverse coupling make controlling the beam dynamics a complex task. In general, betatron tune adjustment is crucial to avoid resonances, particularly when space charge effects are present. Due to highly nonlinear magnetic fields in the vFFA, it remains a challenging task to determine an optimal lattice design in terms of maximising the dynamic aperture. This contribution describes a deep learning based algorithm which strongly improves on regular grid scans and random search to find an optimal lattice: a surrogate model is built iteratively from simulations with varying lattice parameters to predict the dynamic aperture. The training of the model follows an active learning paradigm, which thus considerably reduces the number of samples needed from the computationally expensive simulations.
Paper: WEPA026
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA026
About: Received: 03 May 2023 — Revised: 08 May 2023 — Accepted: 19 Jun 2023 — Issue date: 26 Sep 2023
WEPA027
Measurements at peak operational beam current in the SNS beam test facility
2713
Work at the SNS beam test facility has focused on high dimensional and high dynamic range measurements of the medium energy (2.5 Mev) beam distribution. This is motivated by the need to understand and predict beam losses down to one-part-per-million. The initial demonstration of full-and-direct 6D phase space measurement was done at a current of 40 mA transported through the RFQ. Since that demonstration, more detailed studies have been performed at lower transported currents (in the range 30 mA and below). This is due to a hardware change - recent runs utilize the original SNS RFQ, which after a decade of service in the SNS achieves transmission significantly below design (50-60%, vs >80%). A short run in 2023 with a newly-commissioned RFQ enables maximum transmission. Preliminary results from beam distribution measurements during this run are discussed.
Paper: WEPA027
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA027
About: Received: 01 May 2023 — Revised: 13 May 2023 — Accepted: 23 Jun 2023 — Issue date: 26 Sep 2023
WEPA028
Detailed characterization of a five-dimensional phase space distribution
2717
We image the five-dimensional phase space distribution of a hadron beam in unprecedented detail. The resolution and dynamic range of the measurement are sufficient to resolve sharp, high-dimensional features in low-density regions of phase space. We develop several visualization techniques, including non-planar slicing, to facilitate the identification and analysis of such features. We use these techniques to examine the transverse dependence of longitudinal hollowing and the longitudinal dependence of transverse hollowing in the distribution. Our results strengthen the claim that low-dimensional projections do not adequately characterize high-dimensional phase space distributions.
Paper: WEPA028
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA028
About: Received: 01 May 2023 — Revised: 18 May 2023 — Accepted: 20 Jun 2023 — Issue date: 26 Sep 2023
WEPA030
Current Status of the Beam Dynamics Simulations for the HBS Drift Tube Linac
2721
As various experimental reactors in Europe are already or will be decommissioned over the next years, new neutron sources will be necessary to meet the demand for neutrons in research and development. The High Brilliance Neutron Source is an accelerator driven neutron source planned at the Forschungszentrum Jülich. The accelerator will accelerate a proton beam up to an end energy of 70 MeV, using normal conducting CH-type cavities. Because of the high beam current of 100 mA, the beam dynamics concept requires special care. In this paper, the current status of the beam dynamics for the drift tube linac is dicsussed.
Paper: WEPA030
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA030
About: Received: 03 May 2023 — Revised: 10 May 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
Beam dynamics study of the high-power electron beam irradiator using niobium-tin superconducting cavity
At KEK a design of the compact 10 MeV, 50 mA accelerator for irradiation purpose was proposed. Current design includes a 100 kV thermionic DC electron gun with an RF grid, 1-cell normal-conducting buncher cavity, and Nb3Sn superconducting cavities to accelerate the beam to the final energy of 10 MeV. The goal of the present beam dynamics study is the beam loss suppression (to the ppm level), since it results in a thermal load on the cavity. Then the beam performance at the accelerator exit should be confirmed. The main issue was to transport the beam without loss, since the initial electron energy (100 keV) is low, and the beam parameters are intricately correlated. In addition, the space charge effect is considerable. For this reason, simultaneous optimization of multiple parameters was necessary. Here we report optimization results and their effect on the design of the machine.
WEPA034
Characterization of high dynamic range beam emittance
2724
Measurement of hadron beam emittances with very high dynamic range, one part-per-million and above, become available recently. This level of dynamic range is required for studying the origin and evolution of the halo in high intensity hadron linacs. There are no established or commonly known metrics to describe such distributions. Using data from the emittance measurements of 2.5Mev H- beam at the SNS Beam Test Facility we demonstrate that most common emittance metrics the RMS emittance and the Halo parameter H are totally insensitive to low level features of the distribution. We also suggest a new metric, which is unambiguously computable, invariant of linear simplectic transformations, and capturing features important for low loss beam transport.
Paper: WEPA034
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA034
About: Received: 04 May 2023 — Revised: 06 Jun 2023 — Accepted: 06 Jun 2023 — Issue date: 26 Sep 2023
WEPA035
Polarized electron injector for positron production at CEBAF
2727
As a part of the effort to expand the capabilities of CE-BAF 12 GeV (Continuous Electron Beam Accelerator Facility) at Jefferson Lab, the addition of a polarized positron source is considered. This capability would provide acceleration of high duty-cycle polarized posi-trons, with spin >60% polarization, through the same main CEBAF accelerator machine with appropriate mag-net field reversals and linac phasing to the four CEBAF experimental halls. To produce this positron beam, a high average current (3-10 mA) highly polarized electron beam with energy of 100 – 150 MeV is required at the positron source target. The focus of this paper is the de-sign of that polarized electron beam injector. We will describe the production and delivery of a >3 mA highly polarized electron beam. We will discuss different aspects of the design, the photocathode gun, beam dynamics simulation results, spin manipulation, bunching and accelerating process and final electron beam parameters.
Paper: WEPA035
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA035
About: Received: 03 May 2023 — Revised: 10 May 2023 — Accepted: 11 May 2023 — Issue date: 26 Sep 2023
WEPA036
CSR-induced projected emittance growth study for the beam switchyard at the European XFEL
2731
Minimizing projected emittance of high brightness electron beam is important for efficient overlap between electron beam and radiation pulse in an FEL facility. Coherent synchrotron radiation (CSR) emission in a single bending section in the beam transport system usually introduces different slice energy modulation hence different slice transverse kicks in the designed dispersion-free lattice, causing projected emittance growth. Here we present theoretical and simulation study of CSR effect on the projected emittance growth in the beam switchyard arc before SASE2 undulator beamline at the European XFEL. We analyze arc optics impact on CSR effect, as well as emittance degradation compensation by controlling beam properties upstream of the arc. With the projected emittance optimized, the overall FEL radiation pulse energy can be improved.
Paper: WEPA036
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA036
About: Received: 08 May 2023 — Revised: 10 May 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
WEPA037
Round-to-flat and flat-to-round beam transformations at the Argonne Wakefield Accelerator Facility
2735
In this paper, we present a study of the transformation of a magnetized electron beam from round to flat and back to round using a skew quadrupole triplet. Electron cooling of hadron beams requires a magnetized electron beam, which can be generated from an RF photoinjector. However, such a beam is coupled in four-dimensional phase space, making it difficult to transport through beamlines. To address this challenge, we use a skew quadrupole triplet to remove the coupling and form a flat beam with different emittance in the horizontal and vertical planes and a high aspect ratio. Likewise, we use an additional skew quadrupole triplet to restore the correlation to the beam. We use particle tracking simulations to identify the optimal positions and strengths of the skew quadrupole magnets for the beam transformation. Finally, we present experimental demonstrations of the beam transformation at the Argonne Wakefield Accelerator Facility.
Paper: WEPA037
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA037
About: Received: 04 May 2023 — Revised: 12 May 2023 — Accepted: 23 Jun 2023 — Issue date: 26 Sep 2023
The Optical Stochastic Cooling Program at Fermilab
Optical Stochastic Cooling (OSC) was recently demonstrated at Fermilab’s Integrable Optics Test Accelerator (IOTA) storage ring. This demonstration marked the first realization of the stochastic cooling (SC) principle in the optical regime and achieved a system bandwidth of approximately 20 THz, more than three orders of magnitude greater than state-of-the-art SC systems. The initial experiments, which used 100-MeV electrons and a radiation wavelength of 950 nm, included comprehensive measurements with both beams and individual electrons in one, two and three-dimensional configurations. Here we describe the results of these experiments, which did not include optical amplification, as well as our current development efforts at the Fermilab Accelerator Science and Technology (FAST) facility towards a high-gain, amplified-OSC demonstration in the near future.
WEPA040
Beam dynamics optimization of EuPRAXIA@SPARC_LAB RF injector
2739
At EuPRAXIA@SPARC_LAB an X-ray FEL user facility is driven by a plasma accelerator in the particle-driven configuration where an ultra-relativistic beam, the driver, through a plasma generates a wake of charge density useful for accelerate a witness beam. The electron bunches are generated through the so-called comb technique in an RF injector that consist of a 1.6 cell S-band gun followed by four S-band TW accelerating structures. The main working point foresees a 30pC witness and a 200pC driver longitudinally compressed in the first accelerating structure operated in the velocity-bunching regime, that allows to accelerate and manipulate the beam to reach proper transverse and longitudinal parameters. The optimization of the witness emittance is performed with additional magnetic field around the gun and the S-band structures and by shaping the laser pulse at the cathode. The paper reports on beam dynamics studies performed also for beams with higher charges to maximize the transformer ratio in the plasma and the beam brightness. In addition, the insertion of an X-band RF cavity after the gun is proposed aiming to shape the beam current distribution as needed and stabilize it with respect to RF jitters.
Paper: WEPA040
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA040
About: Received: 01 Apr 2023 — Revised: 12 May 2023 — Accepted: 21 Jun 2023 — Issue date: 26 Sep 2023
WEPA041
Simulation of shot noise effects in the EIC strong hadron cooling accelerator using real number of electrons
2743
The electron ion collider, the next generation nuclear physics collider is being actively studied. In order to achieve the designed luminosity 10^34/cm^2/s with a reasonable lifetime, an efficient coherent electron cooling scheme was proposed to reduce the hadron beam emittance and counter intrabeam scattering. Such a cooling scheme requires a good electron beam quality with a small energy spread. However, the shot noise in the electron beam through the accelerator might be amplified due to the microbunching instability and might degrade the electron beam quality in the modulator section of the strong hadron cooling channel and correspondingly cooling rate. In this study, we reported on a self-consistent simulation study of these effects using the real number of electrons. This captures the details of shot noise.
Paper: WEPA041
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA041
About: Received: 01 May 2023 — Revised: 07 May 2023 — Accepted: 11 May 2023 — Issue date: 26 Sep 2023
WEPA042
Emittance compensation in a high charge TOPGUN photoinjector
2747
A simple acceleration of a high charge, needle-shaped electron bunch from a cathode is affected by strong correlated emittance growth due to current-dependent transverse space-charge forces. It was shown that such emittance growth could be reversed by focusing the bunch soon after it emerges from the cathode, and that one can expect to retrieve the emittance the beam was born with – the intrinsic emittance. We present a space charge emittance compensation study for a 250 pC radiofrequency photoinjector based on a 100 pC design developed by the UCLA team. We expect that a bright electron beam with an order of magnitude improvement over currently operating photoinjectors can be achieved with 250 pC electron bunches that maintain their emittance below 100 nm-rad.
Paper: WEPA042
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA042
About: Received: 03 May 2023 — Revised: 02 Jun 2023 — Accepted: 22 Jun 2023 — Issue date: 26 Sep 2023
WEPA043
Modeling of the amplified optical stochastic cooling experiment at IOTA
2751
Optical Stochastic Cooling (OSC), a beam cooling technique based on Stochastic Cooling, is in the early stages of experimental development. It uses radiation produced by the beam in an undulator magnet (the pickup) to correct the momentum deviation of particles downstream in another undulator (the kicker). The OSC mechanism was recently demonstrated at Fermilab’s IOTA ring using a passive configuration. However, the cooling rate of OSC can be dramatically increased by first amplifying the undulator radiation before applying the corrective kick. In collaboration with the IOTA experiment, we developed a computational model of the OSC mechanism. This paper presents beam-dynamics simulations of the amplified-OSC configuration. We implement a model of intrabeam scattering and study the effects on beam equilibrium and diffusion rate as a function of bunch charge. Finally, we investigate the phase-space dynamics with various coupling configurations between the transverse and longitudinal planes.
Paper: WEPA043
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA043
About: Received: 12 May 2023 — Revised: 12 May 2023 — Accepted: 20 Jun 2023 — Issue date: 26 Sep 2023
WEPA044
Electron microbunching using amplified optical stochastic cooling
2755
Optical Stochastic Cooling (OSC) is a feedback beam cooling technique that uses radiation produced by a beam to correct particles' own momentum deviation. This system is made up of two undulator magnets, the pickup and kicker, separated by a bypass chicane that introduces a momentum-dependent path length. The beam produces radiation in the pickup and arrives in the kicker with a delay relative to its momentum, where it is coupled with the undulator radiation, receiving a corrective kick. The undulator radiation can be amplified to increase the strength of the corrective kick; this is done using an optical amplifier. The optical amplifier is driven by a pump laser which can be used to selectively amplify temporal slices of the undulator radiation. In this paper, we propose a method to use the amplified-OSC mechanism to create micro-bunches within the beam and study the performance of this multi-bunch-formation mechanism by considering diffusive effects and gain of the amplifier.
Paper: WEPA044
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA044
About: Received: 09 May 2023 — Revised: 11 May 2023 — Accepted: 20 Jun 2023 — Issue date: 26 Sep 2023
WEPA045
Arbitrary transverse and longitudinal correlation generation using transverse wiggler and wakefield structures
2759
Transverse wigglers and wakefield structures are promising candidates for imparting arbitrary correlation on transverse and longitudinal phase spaces respectively. They provide sinusoidal electromagnetic fields that become building blocks for Fourier synthesis. We present the progress of arbitrary correlation generation using transverse wiggler and wakefield structures.
Paper: WEPA045
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA045
About: Received: 13 Apr 2023 — Revised: 11 May 2023 — Accepted: 20 Jun 2023 — Issue date: 26 Sep 2023
WEPA046
Emittance exchange with periphery cut for high-brightness beam
2763
The exchange of transverse and longitudinal emittances is a unique feature of emittance exchange (EEX) beamline, but it is also a limitation of it at the same time. Most of the modern high-brightness injectors provide much smaller emittance in the transverse plane than the longitudinal plane. Thus, a beam passing through a single EEX beamline ends up with a large transverse emittance, which significantly limits EEX beamline’s use for its various applications. Here, we present a preliminary study for avoiding this issue by optimizing the beamline for longitudinal emittance, correcting nonlinearities, and cutting the periphery of the phase space.
Paper: WEPA046
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA046
About: Received: 13 Apr 2023 — Revised: 11 May 2023 — Accepted: 20 Jun 2023 — Issue date: 26 Sep 2023
WEPA049
Microwave driven space-charge compensation with optical diagnostics and feedback
2767
A system is being developed for the maintenance of a space-charge neutralising plasma from the residual gas within the LEBT of the Front End Test Stand (FETS) at UKRI-STFC Rutherford Appleton Laboratory. Space-charge neutralisation will occur when an ion beam is allowed to collide with and ionise a background gas with pressure greater than 10-4 Torr in the presence of a solenoid fringe field, neutralisation can mitigate excess beam loss and reduce the need for beam chopping. To maintain a low density plasma between pulses, S-Band (3.4 GHz) microwaves will be injected into a LEBT cavity situated between solenoids. In order to provide sufficient microwave power to the cavity a two stage amplification system will be employed, with each stage providing a gain of 10 dB. A novel high-speed, low light-level optical diagnostics system based on Silicon Photomultiplier MPPC’s will be used in combination with a directional coupler for forward and reverse RF power measurement to provide feedback about the state of the plasma within the cavity. An overview of the design of this system will be presented along with preliminary test results.
Paper: WEPA049
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA049
About: Received: 05 May 2023 — Revised: 22 May 2023 — Accepted: 22 May 2023 — Issue date: 26 Sep 2023
WEPA050
A modified round to flat beam transformation lattice for angular dispersion induced microbunching technique
2770
Due to the beam in the storage ring has a very low vertical emittance. The angular dispersion induced microbunching (ADM) scheme is used to generate high brightness coherent synchrotron radiation. To apply a similar scheme in a linear accelerator, it is necessary to reduce the vertical emittance of the beam in the linear accelerator. Generally, angular-momentum-dominated round beams can be generated by immersing the cathode into the axial solenoid magnetic field, the angular momentum is then removed by skew quadrupoles downstream of the solenoid, resulting in a flat beam with low vertical emittance. In this paper, on the basis of the existing basic structure, considering the chromatic effects in the round-to-flat beam transformation, we propose an achromatic scheme that uses chicane to generate dispersion segment, inserts skew quadrupoles in the dispersion segment for matching, and uses sextupole to correct chromatic aberration. The numerical simulation results of ASTRA and ELEGANT show that the transverse emittance ratio of the beam has been further improved.
Paper: WEPA050
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA050
About: Received: 08 May 2023 — Revised: 18 May 2023 — Accepted: 19 Jun 2023 — Issue date: 26 Sep 2023
WEPA051
Microbunching gain evaluation of bunch stretcher designs
2774
The planned Electron Ion Collider (EIC) has an Energy Recovery Linac (ERL) which provides Strong Hadron Cooling (SHC) in order to control the beam quality of the hadrons. This requires that the electron beam delivered to the cooling section be minimally perturbed by the preceding bunch stretcher necessary in the 100 GeV configuration. This paper evaluates different stretcher designs for the SHC ERL, based on current design requirements.
Paper: WEPA051
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA051
About: Received: 03 May 2023 — Revised: 22 May 2023 — Accepted: 22 May 2023 — Issue date: 26 Sep 2023
Demonstration of Flat/Round Transformations of Angular Momentum and Space Charge Dominated Electron Beams
We describe an experiment to demonstrate Derbenev’s flat-to-round (FTR) and round-to-flat (RTF) optical transformations*, designed to match electron beams from a high-energy storage ring into and out of a solenoidal cooling channel. We are using a linear transport system with a design optimized by a computationally-efficient adjoint moment equation technique developed by our group for general application to beam optical systems**. We will explore cases on FTR/FTR, first with low space charge, followed by further examples with significant space charge, comparing simulations to beam measurements and reoptimizing the design as needed to test alternative experimental configurations. Our goal is to experimentally and computationally test the Derbenev scheme, which has not been done in its entirety, and to carry out a rigorous, experimental validation of the adjoint moment equation techniques.
WEPA053
Impact of multiple beam-beam encounters on LHC absolute-luminosity calibrations by the van der Meer method
2777
The LHC particle-physics program requires that the delivered luminosity be measured to an absolute accuracy in the 1% range. To this effect, the absolute luminosity scale at each interaction point (IP) is calibrated by scanning the beams across each other according to the van der Meer method. During such scans, the orbit and the shape of the colliding bunches are significantly distorted by their mutual electromagnetic interaction; the resulting biases, if left uncorrected, would absorb a major fraction of the systematic-uncertainty budget on the luminosity calibration. The present report summarizes recent studies of such biases in the single-IP configuration, and generalizes it to the more typical case where bunches collide not only at the scanning IP, but also experience additional head-on encounters at up to 3 locations around the ring. Simulations carried out with the COherent-Multibunch Beam-beam Interaction multiparticle code (COMBI) are used to characterize the dependence of beam--beam-induced luminosity-calibration biases on the phase advance between IPs, and to derive scaling laws that relate the multi-IP case to the simpler and better understood single-IP configuration.
Paper: WEPA053
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA053
About: Received: 03 May 2023 — Revised: 19 May 2023 — Accepted: 19 May 2023 — Issue date: 26 Sep 2023
WEPA054
Beam dynamics study of a CW L-band SRF gun for the high duty cycle EuXFEL
2781
The upgrade of the European XFEL to support a future high duty cycle (HDC) operation mode requires new design concepts for the photoinjector. In particular, the electron gun is crucial for achieving high quality beams at high peak currents. Among other variants, a 1.6-cell TESLA-type RF-gun is the preferable solution for the HDC EuXFEL. The SRF gun design, however, requires the application of unconventional emittance compensation schemes. One alternative is embedded RF focusing by means of a retracted cathode. Such a scheme has been previously successfully tested, e.g., at the ELBE accelerator of the HZDR. However, the beam dynamics characterization and parameter optimization for this design remains a challenge. This is primarily due to the 3D geometry of the cathode region, which cannot be easily handled by available tracking codes. In this work, we present a simulation and optimization study of the EuXFEL injector line including the geometrical and space charge effects related to a retracted-cathode SRF gun design.
Paper: WEPA054
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA054
About: Received: 03 May 2023 — Revised: 08 Jun 2023 — Accepted: 08 Jun 2023 — Issue date: 26 Sep 2023
WEPA057
Analytic and numerical calculation of collider luminosity with CRAB dynamics
2785
For an integral part of electron-ion collider (EIC) de-sign, the crab crossing scheme provides a head-on collision for beams with a nonzero crossing angle. Recently we provided a framework for accurate numerical simulations of beam-beam effects with crabbing crossing dynamics. The framework was implemented in a simulation code package named “CASA BeamBeam”. We offer com-prehensive formulas for calculation of collider luminosity for various cases in the code package. The luminosity calculation module of CASA Beam-Beam now includes the hourglass effect, the beam-tilt effects and the beam offset effect. The benchmarking results show good agreement between the numerical calculation and analyt-ic solution.
Paper: WEPA057
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA057
About: Received: 11 May 2023 — Revised: 12 May 2023 — Accepted: 23 Jun 2023 — Issue date: 26 Sep 2023
A bead-pulling test stand for s-band cavities
Additive manufacturing is a promising approach to reduce production costs for high-frequency cavities while increasing design freedom. This potential will be evaluated through studies on several cavity prototypes and their performance. Especially for the evaluation of the field distribution in cm-sized S-band cavities and thus the shunt impedance, the development of a measurement setup for qualitative and fast measurements is useful. Therefore, we present a perturbation measurement (bead-pulling) test stand that allows a standardized and efficient measurement of the field distribution in cavities. It consists of a motorized linear translation stage, a microcontroller, and a vector network analyzer, all controlled via LabVIEW. The perturbation constant $\alpha$ ($\mathrm{Al_2O_3}$) was determined using a drift tube cavity previously characterized with a 16 MeV tandem Van de Graaff proton beam. In addition, the measurement accuracy with different step sizes and speeds of the linear translations stage was tested on this cavity. Subsequently, the first measurements on an additively manufactured 5-cell drift tube cavity were performed to determine its shunt impedance.
WEPA060
Beam-beam long-range wire compensators in LHC Run 3
2789
Beam-beam effects are known to undermine the performance of the LHC during proton-proton collisions. In order to enhance the luminosity production and increase the tolerance of the working point of the machine after the High Luminosity upgrade of the LHC, it is relevant to study the possibility of using current-carrying wires to compensate long-range beam-beam effects. Following proof of principle studies in LHC Run 2, beam-beam wire compensators embedded in the collimators of the LHC are used in standard operation since the start of Run 3. In this paper, a figure of merit quantifying the efficiency of luminosity production is introduced and measurements from LHC Run 3 are presented. Bunch-by-bunch data is used to demonstrate the successful compensation of beam-beam effects in the LHC.
Paper: WEPA060
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA060
About: Received: 03 May 2023 — Revised: 10 May 2023 — Accepted: 19 Jun 2023 — Issue date: 26 Sep 2023
Electron beam transport modeling in a linear induction accelerator for X-ray flash radiography
X-ray flash radiography is a powerful diagnostic used worldwide for investigating the structural response of matter under impulsive loading during hydrodynamic experiments. These experiments require a specific X-Ray source generated by a Linear Induction Accelerator (LIA). LIAs produce an intense electron pulsed beam, with a high-energy and providing a high dose at 1 m. Therefore, comprehension and prediction of the electron beam dynamic are essential to guarantee correct realization of the hydrodynamic experiments. At CEA DAM, X-Ray flash radiography experiments are performed on the UK/FR joint facility EPURE, a unique triple-axis radiographic facility with two LIAs and one Inductive Voltage Adder “MERLIN”. In this study, envelope and particle-in-cell codes simulate the electron beam transport from the production of the beam in the injector to its transport along the accelerator. Thanks to the developed models, parametric studies are made about the influence of beam parameters, as the initial emittance, on the transport. Moreover, the developed codes take into account some beam instabilities, as the beam breakup instability or corkscrew motion. Studies show that the initial beam centroid offset has a significant impact on the beam instabilities during the transport. In addition, simulation results are compared with experimental data acquired on the EPURE facility, notably comparisons about our method to center the beam for limiting beam instabilities.
WEPA064
Generalized gradient map tracking in the Siberian snakes of the AGS and RHIC
2793
Accurate and efficient particle tracking through Siberian Snakes is crucial to building comprehensive accelerator simulation model. At the Alternating Gradient Synchrotron (AGS) and Relativistic Heavy Ion Collider (RHIC), Siberian Snakes are traditionally modeled in MAD-X by Taylor map matrices generated at specific current and energy configurations. This method falls short during ramping due to the nonphysical jumps between matrices. Another common method is to use grid field maps for the Snakes, but field map files are usually very large and thus cumbersome to use. In this work, we apply a new method called the Generalized Gradient (GG) map formalism to model complex fields in Siberian Snakes. GG formalism provides an analytic function in x and y for which automatic differentiation, i.e. Differential Algebra or Truncated Power Series Algebra can find accurate high order maps. We present simulation results of the Siberian Snakes in both the AGS and RHIC using the Bmad toolkit for accelerator simulation, demonstrating that GG formalism provides accurate particle tracking results.
Paper: WEPA064
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA064
About: Received: 03 May 2023 — Revised: 06 May 2023 — Accepted: 15 Jun 2023 — Issue date: 26 Sep 2023
WEPA065
Towards fully differentiable accelerator modeling
2797
Optimization and design of particle accelerators is challenging due to the large number of free parameters and the corresponding lack of gradient information available to the optimizer. Thus, full optimization of large beamlines becomes infeasible due to the exponential growth of free parameter space the optimization algorithm must navigate. Providing exact or approximate gradient information to the optimizer can significantly improve convergence speed, enabling practical optimization of high-dimensional problems. To achieve this, we have leveraged state-of-the-art automatic differentiation techniques developed by the machine learning community to enable end-to-end differentiable particle tracking simulations. We demonstrate that even a simple tracking simulation with gradient information can be used to significantly improve beamline design optimization. Furthermore, we show the flexibility of our implementation with various applications that make use of different kinds of derivative information.
Paper: WEPA065
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA065
About: Received: 03 May 2023 — Revised: 18 May 2023 — Accepted: 22 Jun 2023 — Issue date: 26 Sep 2023
WEPA066
Tools for integrated simulation of collimation processes in Xsuite
2801
The existing code for particle scattering and tracking in collimation systems integrated in SixTrack, called K2, was migrated from the current software in FORTRAN, to a new Python/C interface integrated in the Xsuite tracking code that is being developed at CERN. This is an essential step towards a full integration of collimation studies using Xtrack, and will allow profiting from GPU computing advances and the BOINC volunteer computing network. Furthermore, several improvements to the functionality of the code were introduced, for example aperture interpolation for more precise longitudinal location of particle losses in a collimator. A thorough testing of the new implementation was performed, using as case studies various collimation layout configurations for the LHC Run 3 and HL-LHC. In this paper, the challenges are outlined and the first results are presented, including simulated loss maps which are compared to the reference results generated by SixTrack.
Paper: WEPA066
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA066
About: Received: 02 May 2023 — Revised: 12 May 2023 — Accepted: 20 Jun 2023 — Issue date: 26 Sep 2023
WEPA067
PLACET3: 6D tracking through PETS and accelerating structures wakefields
2805
We present the latest updates to the PLACET3 tracking package which focus on the impact of both transverse and longitudinal wakefields on a beam travelling through accelerating and decelerating structures. The main focus of this update was the first implementation of 6D tracking through Power Extraction and Transfer Structures (PETS) for the Compact Linear Collider (CLIC) which is described through short and long-range longitudinal wakefields. Additionally, we present the impact of different numerical schemes on the computation of wakefields in accelerating structures.
Paper: WEPA067
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA067
About: Received: 03 May 2023 — Revised: 05 Jun 2023 — Accepted: 21 Jun 2023 — Issue date: 26 Sep 2023
WEPA069
Macroparticle collisionality in PIC solver
2809
Traditionally PIC solver compute electric field created by the beam as a mean field. The effect of particle collisions is normally neglected by the algorithm. In this proceeding we address how to include the collisions between the macro particles, and discuss the computational challenges and strategies to include the collisionallity in PIC solvers as particle-particle interaction. We present simulations that benchmark our understanding and analyse potential artifacts as energy conservation or other effects.
Paper: WEPA069
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA069
About: Received: 01 Apr 2023 — Revised: 11 May 2023 — Accepted: 23 Jun 2023 — Issue date: 26 Sep 2023
WEPA070
Calculation of beam sizes in coupled electron storage rings
2813
The description of coupling phenomena in electron storage rings is extended beyond the very common formula based on the coupled Hamiltonian [1] into the region where the small coupling is in competition with damping and diffusion from synchrotron radiation. In the derivation, the moment mapping approach is used in combination with the simplified simulation of radiation effects introduced by Hirata and Ruggiero [2]. The results of this theoretical approach are compared to the predictions of well-established theories dealing with coupling in electron storage rings: The envelope mapping approach from Ohmi, et al. [3], and Chao’s SLIM approach [4]. [1] G. Guignard, “Betatron coupling and related impact of radiation”, Phys. Rev. E 51, 6104, June 1995, or his contributions to CERN Accelerator Schools [2] K. Hirata, F. Ruggiero in “Treatment of Radiation for Multiparticle Tracking in Electron Storage Rings”, Part. Acc. Vol. 28, pp. 137-142 (1990) [3] K. Ohmi, et al., in “From the Beam-Envelope Matrix to Synchrotron-Radiation Integrals”, Phys. Rev. E, Vol. 49, p. 751 [4] A. Chao, in ”Evaluation of Beam Distribution Parameters in an Electron Storage Ring”, J. Appl. Phys. 50, 595 (1979) or SLAC-PUB-2143, June 1978
Paper: WEPA070
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA070
About: Received: 02 May 2023 — Revised: 10 May 2023 — Accepted: 21 Jun 2023 — Issue date: 26 Sep 2023
WEPA071
Bloch equation for the description of linear coupling in storage rings
2817
Linear coupling in storage rings mixes horizontal and vertical beam motion. This is similar to the mixing of states in an atomic two-level system by a resonant laser interaction or the mixing of the two states of any spin-½ particle in static and dynamic external magnetic fields like, for example, in nuclear magnetic resonance, NMR, measurements. These coupled two-level systems are usually described by the Bloch equation [1] which is a set of coupled, first-order differential equations connecting the population of the states with some other parameters which contain in addition to the strength of the coupling and the detuning, some sort of phase information of the involved states. In linearly coupled storage rings horizontal and vertical emittance can be viewed as the population of ground and excited level and it will be shown that the Bloch equations can also model the time-dependent evolution of the transverse emittances of an ensemble of circulating particles. This is especially useful in cases where the emittance is exchanged by crossing the coupling resonance or where the coupling strength itself is a function of time. [1] F. Bloch, “Nuclear induction,” Physical Review, vol. 70, no. 7-8, pp. 460–474, 1946.
Paper: WEPA071
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA071
About: Received: 02 May 2023 — Revised: 10 May 2023 — Accepted: 21 Jun 2023 — Issue date: 26 Sep 2023
WEPA074
BDSIM v1.7.0 developments for the modelling of accelerators and their environment
2821
Beam Delivery Simulation (BDSIM) is a program based on Geant4 that creates 3D radiation transport models of accelerators from a simple optical description in a vastly reduced time with great flexibility. It also uses ROOT and CLHEP to create a single simulation model that can accurately track all particles species in an accelerator to predict and understand beam losses, secondary radiation, dosimetric quantities and their origins. We present a broad overview of new features added to BDSIM in version 1.7. In particular, the ability to transform and reflect field maps as well as visualise the fields in Geant4 are presented. A new “CT” object is introduced to allow DICOM images to be used for simulations of Phantoms in proximity to a beamline. For experiments such as FASER, SHADOWS and NA62, a muon production biasing scheme has been added and is presented.
Paper: WEPA074
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA074
About: Received: 05 May 2023 — Revised: 22 May 2023 — Accepted: 22 May 2023 — Issue date: 26 Sep 2023
WEPA078
Symplectic neural surrogate models for beam dynamics
2825
The self-consistent nonlinear dynamics of a relativistic charged particle beam interacting with its complete self-fields is a fundamental problem underpinning many of the accelerator design issues in high brightness beam applications, as well as the development of advanced accelerators. A novel self-consistent code is developed based on a Lagrangian method for the calculation of the particles’ radiation near-fields using wavefront/wavelet meshes via the Green’s function of the Maxwell equations. These fields are then interpolated onto a moving mesh for dynamic update of the beam. This method allows radiation co-propagation and self-consistent interaction with the beam in 2D/3D simulations at greatly reduced numerical errors. Multiple levels of parallelisms are inherent in this method and implemented in our code CoSyR [1] to enable at-scale simulations of nonlinear beam dynamics on modern computing platforms using MPI, multi-threading, and GPUs. Our simulations reveal the slice emittance growth in a bend and the interplay between the longitudinal and transverse dynamics that occurs in a complex manner not captured in the 1D longitudinal static-state coherent synchrotron radiation model. Finally, we show that surrogate models with symplectic neural networks can be trained from simulations with significant time-savings for the modeling of nonlinear beam dynamics effects.
Paper: WEPA078
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA078
About: Received: 10 May 2023 — Revised: 23 May 2023 — Accepted: 23 May 2023 — Issue date: 26 Sep 2023
WEPA079
Simulations of radiation reaction in inverse Compton scattering
2829
The effect of radiation reaction is often negligible in inverse Compton scattering. However, in the nonlinear Compton regime, at high laser fields and high electron beam energies where electron recoil must be properly accounted for, there is experimental data which demonstrates the onset of radiation reaction * . We model the radiation reaction as a series of emissions from individual electrons with decreasing energy. This allows us to use the code we previously developed for simulating single-emission inverse Compton scattering events ** . We use the new code to simulate the experiment reported in Cole et al. 2018, and to compare it to other models of radiation reaction.
Paper: WEPA079
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA079
About: Received: 03 May 2023 — Revised: 06 Jun 2023 — Accepted: 06 Jun 2023 — Issue date: 26 Sep 2023
WEPA080
Numerical simulations of radiation reaction using Lorentz-Abraham-Dirac formalism
2831
An accelerating charged particle emits electromagnetic radiation. The motion of the particle is further damped via self-interaction with its own radiation. For relativistic particles, the subsequent motion is described via a correction to the Lorentz force, known as the Lorentz-Abraham-Dirac force. The aim of this research is to use the Lorentz-Abraham-Dirac force to computationally simulate the radiation damping that occurs during nonlinear inverse Compton scattering. We build on our previous work and the code which simulates single-emission inverse Compton scattering to incorporate the effect of multiple emissions, thereby modeling the radiation reaction.
Paper: WEPA080
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA080
About: Received: 03 May 2023 — Revised: 11 May 2023 — Accepted: 20 Jun 2023 — Issue date: 26 Sep 2023
OPAL and Future Directions Towards the Exascale Area
OPAL (Object Oriented Parallel Accelerator Library) is a C++ based massively parallel open-source program for tracking charged particles in large scale accelerator structures and beam lines, including 3D space charge, collisions, particle-matter-gas interaction, and 3D undulator radiation. The meticulous parallel architecture allows large and difficult problems, including one-to-one simulations with high resolution and no macro particles, to be tackled in a reasonable amount of time. The current code state as well as the most recent physics advancements and upgrades are discussed, including the unique feature of a sampler for creating massive, labeled data sets with tens of thousands of cores for machine learning. We also demonstrate scalability of our core algorithms up to 4600 GPUs and 32'000 CPUs, as part of our effort to make OPAL exascale ready.
WEPA085
Hellweg improvements for 3D traveling wave linac design with beam loading
2834
The industrial, medical and homeland security markets for low-to-moderate energy electron linacs are growing rapidly, often requiring beam currents that strongly load the accelerating fields. The two-beam accelerator (TBA) is one concept for the structure wakefield acceleration approach to an electron-positron collider. Transient beam loading effects are a significant challenge for the drive beam in a TBA structure, where energy droop in high-charge bunch trains must be understood and compensated. The Hellweg code accurately models steady state beam loading for traveling wave RF structures with a fast reduced model. The Hellweg equations of motion have recently been generalized to include arbitrary charge-to-mass ratio and to use momentum as the dynamical variable. These and other recent developments are discussed, including a new browser-based GUI. Proposed future developments include support of standing wave RF structures and transient beam loading effects.
Paper: WEPA085
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA085
About: Received: 03 May 2023 — Revised: 11 May 2023 — Accepted: 23 Jun 2023 — Issue date: 26 Sep 2023
WEPA086
PyTao: the Python interface to Tao
2838
PyTao is a Python interface to the Bmad based Tao program for accelerator design and simulation. This enables advanced design and optimization beyond the normal capabilities of Tao as well as simplifying the use of Tao as an online model for an operating accelerator. Here we will describe this interface and some of its applications, including online models for the the LCLS and LCLS-II at SLAC National Accelerator Laboratory.
Paper: WEPA086
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA086
About: Received: 11 May 2023 — Revised: 11 May 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
WEPA088
Scattered field formulation for wakefield and space charge calculations
2842
In the injector section of electron linacs, both internal space charge forces and wakefield effects influence the beam dynamics. To account for both effects, full electromagnetic PIC simulations are usually required. Unfortunately, PIC solvers require large computational resources. On the other hand, particle-tracking codes in the bunch reference frame describe the beam dynamics under space-charge fields. These codes, however, often fail to include the effect of geometric wakefields especially for low energy beams. As an alternative modeling approach, we propose to decouple the wakefield scattered by the geometry from the space-charge field. Then, we use for each of the contributions the simulation approach that is more appropriate for the respective interaction. We decompose the total electromagnetic field into an incident and a scattered part. The incident field is computed by a space-charge solver in the rest frame of the bunch assuming that particles are in free space. Since this field does not fulfill the boundary conditions at the chamber walls, it acts as an excitation for the scattered part. The latter can be efficiently computed using a particle-free wakefield code. In the full paper, we will present beam dynamics simulations for the injector section of the European XFEL. The aim of these simulations is the quantification of the uncorrelated energy spread induced by geometric wakefields at low energies, which so far is not considered in existing wakefield models.
Paper: WEPA088
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA088
About: Received: 03 May 2023 — Revised: 10 May 2023 — Accepted: 19 Jun 2023 — Issue date: 26 Sep 2023
WEPA090
Study of LHC e-cloud instabilities using the linearised Vlasov method
2846
Modelling electron cloud driven instabilities using a Vlasov approach enables studying the beam stability on time scales not accessible to conventional Particle In Cell simulation methods. A linear description of electron cloud forces, including the betatron tune modulation along the bunch, is used in the Vlasov approach. This method is benchmarked against macroparticle simulations based on the same linear description of electron cloud forces. Applying high chromaticity settings is the main mitigation strategy for these instabilities. The effect of chromaticity can be taken into account using the Vlasov method. The Vlasov approach agrees with macroparticle simulations for strong electron clouds, and a stabilizing effect from positive chromaticity can be seen in both approaches. For positive chromaticity, the Vlasov approach shows the existence of weak instabilities which are not observed in the macroparticle simulations. This feature suggests the existence of damping mechanisms that are not captured by the linearized Vlasov equation.
Paper: WEPA090
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA090
About: Received: 03 May 2023 — Revised: 06 May 2023 — Accepted: 15 Jun 2023 — Issue date: 26 Sep 2023
WEPA091
Electron cloud observations and mitigation for the LHC Run 3
2850
When operated with the nominal bunch spacing of 25 ns, the Large Hadron Collider (LHC) suffers from significant electron cloud effects. During the second operational run (Run 2) of the LHC, beam-induced conditioning allowed a satisfactory exploitation of 25 ns beams for luminosity production but could not fully suppress electron cloud formation. It has since been understood that this limitation was due to a degradation of some of the beam screen surfaces that occurred with beam operation after air exposure during the first long shutdown period. In the LHC Run 3, several electron cloud effects are expected to become even more important due to the increase in bunch intensity foreseen during the run. In addition, the beam screens have again been exposed to air during the preceding shutdown period, leading to a reset of most of the conditioning acquired in Run 2 and opening the possibility for further degradation. In this contribution, we describe the experimental observations of electron cloud effects during operation with beam after the start of Run 3 in 2022 and discuss their implications for future operation and mitigation strategies for the remainder of the run.
Paper: WEPA091
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA091
About: Received: 02 May 2023 — Revised: 22 Jun 2023 — Accepted: 22 Jun 2023 — Issue date: 26 Sep 2023
WEPA092
Electron cloud build-up studies for FCC-ee
2854
The Future Circular Collider (FCC) study is developing designs for a new research infrastructure to host the next generation of higher performance particle colliders to extend the research currently being conducted at CERN. In particular, FCC-ee is an electron-positron collider, which is the first stage towards a 100 TeV proton-proton collider FCC-hh. FCC-ee may be affected by electron cloud (e-cloud) and the strongest effects are foreseen for the Z configuration, due to the highest number of bunches, which corresponds to the smallest bunch spacing. The presence of a large electron density in the beam pipe can limit the achievable performance of the accelerator through different effects like transverse instabilities, transverse emittance growth, particle losses, vacuum degradation and additional heat loads of the inner surface of the vacuum chambers. In the design phase, the goal is to suppress the e-cloud effects in FCC-ee and, therefore, a preliminary study to identify the parameters, which play a significant role in the e-cloud formation has been performed. In this paper, an extensive e-cloud simulation study is presented. In particular, the impact of the e-cloud is studied for different configurations, for example: for the electron and the positron beam; in the different elements of the particle accelerator; changing the beam chamber geometry; for different values of the Secondary Emission Yield (SEY); and for different beam parameters.
Paper: WEPA092
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA092
About: Received: 11 May 2023 — Revised: 11 May 2023 — Accepted: 15 Jun 2023 — Issue date: 26 Sep 2023
WEPA093
Electron cloud measurements in Fermilab booster
2858
Fermilab Booster synchrotron requires an intensity upgrade from 4.5×1012 to 6.5×1012 protons per pulse as a part of Fermilab’s Proton Improvement Plan-II (PIP-II). One of the factors which may limit the high-intensity performance is the fast transverse instabilities caused by electron cloud effects. According to the experience in the Recycler, the electron cloud gradually builds up over multiple turns inside the combined function magnets and can reach final intensities orders of magnitude greater than in a pure dipole. Since the Booster synchrotron also incorporates combined function magnets, it is important to measure the presence of electron cloud. The effect of the electron cloud was investigated using two different methods: measuring bunch-by-bunch tune shift by changing the bunch train structure at different intensities and propagating a microwave carrier signal through the beampipe and analyzing the phase modulation of the signal. This paper presents the results of the two methods and corresponding simulation results conducted using PyECLOUD software.
Paper: WEPA093
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA093
About: Received: 04 May 2023 — Revised: 08 Jun 2023 — Accepted: 08 Jun 2023 — Issue date: 26 Sep 2023
WEPA094
Model of a dynamic orbit correction system based on neural network in CLS
2862
In CLS, Deep Learning was applied to make a dynamic model for the Orbit Correction System (OCS). The OCS consists of 48 sets of BPMs BERGOZ (96 data sheets with 900 Hz recording) that measure the beam position and use the SVD matrix to calculate the strength of the orbit correctors (48 sets of Orbit Correctors 'OC'). The Neural Network was built, trained, and tested using 96 BPM signals. Five layers of the network (Input Layer, Three Hidden Layers, and Output Layer) provide the time evolution of OC's signals (18 Hz), which can be achieved with high accuracy (Mean Square Error = 10e-7). The results are based on data collected during all challenging situations of the CLS storage ring’s current beam position. An Arduino Board was used to test this methodology in real-time, and the time of operation was within the range of system timing (30 - 40 microseconds).
Paper: WEPA094
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA094
About: Received: 03 May 2023 — Revised: 05 Jun 2023 — Accepted: 19 Jun 2023 — Issue date: 26 Sep 2023
WEPA095
Neural networks for ID gap orbit distortion compensation in PETRA III
2866
In recent years, the use of machine learning methods has proved to be capable of considerably speeding up both fundamental and applied research. Accelerator physics applications have also profited from the power of these tools. This includes a wide spectrum of applications from beam measurements to machine performance optimisation. PETRA III is one of the world's brightest storage-ring-based X-ray radiation sources. The beamlines are supplied with light from various undulators tailored to the specific needs of the experiments. In the ideal case, a perfectly tuned undulator always has a first and second field integrals equal to zero. But, in practice, field integral changes during gap movements can never be avoided for real-life devices. Deep Neural Networks can be used to predict the distortion in the closed orbit induced by the undulator gap variations on the circulating electron beam. In this contribution a few current state-of-the-art deep learning algorithms were trained on measurements from PETRA III. The different architecture performances are then compared to identify the best model for the gap-induced distortion compensation.
Paper: WEPA095
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA095
About: Received: 02 May 2023 — Revised: 06 May 2023 — Accepted: 11 May 2023 — Issue date: 26 Sep 2023
WEPA097
Accelerating dynamic aperture evaluation using deep neural networks
2870
The Dynamic Aperture (DA) is an important concept for the study of non-linear beam dynamics in a circular accelerator. The DA is defined as the extent of the phase-space region in which the particle's motion remains bounded over a finite number of turns. Such a region is shaped by the imperfections in the magnetic fields, beam-beam effects, electron lens, electron clouds, and other nonlinear effects. The study of the DA provides insight into the mechanisms driving the time evolution of beam losses, which is essential for the operation of existing circular accelerators, such as the CERN Large Hadron Collider (LHC), as well as for the design of future ones. The standard approach for the numerical evaluation of the DA relies on the ability to accurately track initial conditions, distributed in phase space, for a realistic time scale, and this is computationally demanding. In order to accelerate the DA calculation, we propose the use of a Machine Learning (ML) technique for the DA regression based on simulated HL-LHC data. We demonstrate the implementation of a Deep Neural Network (DNN) model by measuring the time and assessing the performance of the DA regressor, as well as carrying out studies with various hardware architectures including CPU, GPU, and TPU.
Paper: WEPA097
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA097
About: Received: 11 May 2023 — Revised: 11 May 2023 — Accepted: 19 Jun 2023 — Issue date: 26 Sep 2023
WEPA098
Injection optimization via reinforcement learning at the cooler synchrotron COSY
2874
It is crucial to have a particle beam with high intensity and small emittance in a timely manner. The main challenges restraining the availability of the beam to the user and limiting the beam intensity in storage rings are a lengthy optimization process, and the injection losses. The setup of the Injection Beam Line (IBL) depends on a large number of configurations in a complex, non-linear, and time-dependent way. Reinforcement Learning (RL) methods have shown great potential in optimizing various complex systems. However, unlike other optimization methods, RL agents are sample inefficient and have to be to be trained in simulation before running them on the real IBL. In this research, we train RL agents to learn the optimal injection strategy of the IBL for the Cooler Synchrotron (COSY) at Forschungszentrum Jülich. We address the challenge of sim-to-real transfer, where the RL agent trained in simulation does not perform well in the real world, by incorporating domain randomization. The goal is to increase the beam intensity inside COSY while decreasing the setup time required. This method has the potential to be applied in future accelerators like the FAIR facility.
Paper: WEPA098
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA098
About: Received: 29 Apr 2023 — Revised: 12 May 2023 — Accepted: 20 Jun 2023 — Issue date: 26 Sep 2023
WEPA099
Reinforcement control for LEBT and RFQ of linear accelerators
2877
As a scientific system with many subsystems, particle accelerator system is getting more complex， due to rising demands on accelerator performance. Meanwhile, it is increasingly difficult to study such complex systems using traditional research methods based on physical models. At present, machine learning (ML) is mature enough to be applied in accelerator science such as beam diagnostics and equipment control. Compared with traditional research methods, machine learning has strong generality and high computational efficiency. However, problems such as incomplete database or insufficient test time often hinder the application of ML in accelerator operation control and optimization. To further explore the application of ML in accelerator science, in this paper, we demonstrate the feasibility of reinforcement learning in accelerator control using: 1) replacement model of linear accelerator components based on neural network; and 2) reinforcement control and fast matching of the LEBT and RFQ of the linear accelerator, which is based on reinforcement learning. These methods will be experimentally verified on a linear accelerator.
Paper: WEPA099
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA099
About: Received: 10 May 2023 — Revised: 28 May 2023 — Accepted: 21 Jun 2023 — Issue date: 26 Sep 2023
WEPA100
Demonstration of Beam Emittance Optimization using Reinforcement Learning
2881
In Particle accelerators, commissioning of a complex beam line requires extensive use of computer models. When the as-built beam line cannot be exactly modeled by the simulation (due for example to mechanical errors or to the extensive usage of the non-linear focusing forces), the solution found in the simulations needs to be adjusted. Thus, it is often required to modify the settings by exploring different parameters ranges on the real accelerator. Given the high parameter space, this is a demanding task both in term of beam time and in term of required expertise. Furthermore, there is no guarantee to reach the optimal solution. This paper proposes a Reinforcement Learning approach to develop a model able to efficiently explore the parameter space of a beam line and iteratively move towards the optimal solution. The approach is first applied for the ADIGE Medium Resolution Mass Separator (MRMS) at INFN Legnaro National Laboratories (LNL), where the potentials of an electrostatic multipole must be correctly tuned to minimize the output beam emittance after the separation stage.
Paper: WEPA100
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA100
About: Received: 02 May 2023 — Revised: 09 May 2023 — Accepted: 19 Jun 2023 — Issue date: 26 Sep 2023
WEPA101
Hybrid beamline element ML-training for surrogates in the impactX beam-dynamics code
2885
The modeling of current and next-generation particle accelerators is a complex endeavour, ranging from the simulation-guided exploration of advanced lattice elements, over design, to commissioning and operations. This paper explores hybrid beamline modeling, towards coupling s-based particle-in-cell beam dynamics with machine-learning (ML) surrogate models. As a first example, we train a surrogate model of an advanced accelerator element, a laser-wakefield accelerator stage, via the time-based particle-in-cell code WarpX [1]. A second example trains trains a model for the IOTA nonlinear lens via the s-based code ImpactX [2].
Paper: WEPA101
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA101
About: Received: 04 May 2023 — Revised: 18 May 2023 — Accepted: 23 Jun 2023 — Issue date: 26 Sep 2023
WEPA104
Prediction of superconducting magnet quenches with machine learning
2889
Superconducting magnet technology is one of the foundations of large particle accelerator facilities. A challenge with operating these systems is the possibility for the magnets to quench. The ability to predict quenches and take precautionary action in advance would reduce the likelihood of a catastrophic failure and increase the lifetime operability of particle accelerators. We are developing a machine learning workflow for prediction and detection of superconducting magnet quenches. In collaboration with Brookhaven National Laboratory (BNL), our methods for algorithm development will utilize magnet data from test stands and the Relativistic Heavy Ion Collider ring magnets to allow for a robust identification of magnet quenches. Our methods divide the problem into two different aspects. First, we are developing machine learning algorithms for binary and multi-classification of the various types of quench events. Second, our prototype machine learning model will be used to predict a quench event using precursor identification. We plan to integrate and test our monitoring system at the BNL facility to perform quench identification and prediction.
Paper: WEPA104
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA104
About: Received: 03 May 2023 — Revised: 22 May 2023 — Accepted: 22 May 2023 — Issue date: 26 Sep 2023
WEPA105
Efficient computation of two-dimensional coherent synchrotron radiation with neural networks
2892
The design and tuning of accelerators are both complicated processes involving many physical effects. Of these, the modeling of coherent synchrotron radiation has long been one of the most complicated and time consuming. This is especially true when modeling two and three-dimensional CSR, which is often neglected in state-of-the-art accelerator modeling due to its time consuming nature. We present a neural network designed to model 2D CSR, demonstrating both faithful accuracy to the physics and a dramatic speedup over even the fastest existing codes. We study its performance in the context of the last bunch compressor of the FACET-II facility, where the intense short pulse demands at least a 2D treatment, and find that we can reproduce the results of more standard tracking codes in a fraction of the time.
Paper: WEPA105
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA105
About: Received: 04 May 2023 — Revised: 10 May 2023 — Accepted: 11 May 2023 — Issue date: 26 Sep 2023
WEPA106
Machine learning-based optimization of storage ring injection efficiency
2896
The electron injection chain of the DELTA accelerator facility starts with a 90 keV electron gun, followed by a linear accelerator (70 MeV), a first transfer line (T1) between linac and booster, a booster synchrotron (70 MeV to 1.5 GeV) and a second the transfer line (T2) connecting the booster and the storage ring (1.5 GeV). Since DELTA does not use a fast topping-up injection mode, each software-driven injection ramp cycle takes about 7 seconds. Depending on the injection efficiency, 250 to 400 ramp cycles are required to reach the maximum beam current of 130 mA in the storage ring. Therefore, for fast post-injection a high electron transfer rate is crucial. During the injection, a large number of parameters (e.g., magnet settings, timings of pulsed elements) have to be adjusted manually. The injection efficiency depends mainly on the settings of the booster extraction elements, the transfer line magnets, and the storage ring injection components. In order to automate the injection procedure and to improve the electron transfer efficiency, the application of innovative machine learning concepts (e.g., neural networks, Gaussian processes and decision trees) was studied.
Paper: WEPA106
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA106
About: Received: 27 Mar 2023 — Revised: 07 Jun 2023 — Accepted: 21 Jun 2023 — Issue date: 26 Sep 2023
WEPA107
A machine learning approach to shaping magnetic fringe fields for beam dynamics control
2900
Fringe fields at the entrance and exit of multipole magnets can adversely affect the dynamics of particles in the beam, but there is also the possibility that fringe fields of the right form could be used to enhance the accelerator performance. Accelerator design work could benefit from efficient and realistic models of multipole fringe fields at an early stage in the design process. We explore novel techniques based upon analytical solutions of multipole fringe fields to produce magnets that satisfy specific requirements for the beam dynamics. Machine learning techniques are used in the design process currently being developed, to link properties of the beam dynamics to the magnet geometry in an efficient way.
Paper: WEPA107
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA107
About: Received: 13 Apr 2023 — Revised: 07 May 2023 — Accepted: 12 May 2023 — Issue date: 26 Sep 2023
WEPA108
Data intensive science and particle accelerators: driving science and innovation
2904
Particle accelerators and light sources are some of the largest, most data intensive, and most complex scientific systems. The connections and relations between machine subsystems are complicated and often nonlinear with system dynamics involving large parameter spaces that evolve over multiple relevant time scales and accelerator systems. Data Intensive Science offers exciting prospects for accelerator design and operation. This includes the optimization of machine design and the reconstruction of transverse beam distributions using machine learning, as well as data analysis in high data rate monitors. This contribution presents the new Liverpool Center for Doctoral Training for Innovation in Data Intensive Science (LIV.INNO) and its exciting research and training program.
Paper: WEPA108
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA108
About: Received: 29 Apr 2023 — Revised: 05 Jun 2023 — Accepted: 05 Jun 2023 — Issue date: 26 Sep 2023
WEPA109
Parallel prediction of beam spot with neural networks and PCA at TTX
2908
At TTX, we try to use machine learning to give the virtual detection of the beam spot. The prediction of beam spot is difficult when the dimension becomes larger. We try to use PCA to make it smaller and use Neural networks to predict it. However, the weight of different dimension varies widely. We predict them parallel and get good results with easy neural networks.
Paper: WEPA109
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA109
About: Received: 19 Apr 2023 — Revised: 11 May 2023 — Accepted: 22 Jun 2023 — Issue date: 26 Sep 2023
WEPA111
A low energy linac solution for 3D scanning applications
2912
Due to a recent interest in scanning thinner containers such as cars or aviation unit load devices (ULDs), lower energy linac solutions are required in order to obtain sufficient image contrast. In this work, we present the complete design of a C-band, bi-periodic, 2 MeV electron linac to fulfil this need. Multi-objective optimisation techniques are employed to optimise the RF cavities for maximum shunt impedance and to optimise the cell lengths/amplitudes of the bunching cavities to achieve a 90% capture efficiency. A full thermal analysis of the system, including the X-ray target, has been performed to explore the thermal management of the system, including a CFD analysis to estimate the effectiveness of typical thermal approximations made during the design process. Finally, a novel RF system for connecting and firing multiple linacs sequentially to generate quasi-3D images is described.
Paper: WEPA111
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA111
About: Received: 01 May 2023 — Revised: 10 May 2023 — Accepted: 19 Jun 2023 — Issue date: 26 Sep 2023
WEPA113
Numerical design of a compact TE11-to-TM01 mode converter for THz-driven electron acceleration
2916
In recent years the generation of high power millimeter wave and Terahertz radiation has progressed substantially, enabling electron beam manipulation and acceleration in structures with a footprint of several centimeters. However, in many experiments the external driving pulse is coupled collinearly into the waveguide structure which increases the coupling footprint relative to the wavelength tremendously (≈30 𝜆 or more) in comparison to conventional structures (≈1 𝜆 or less). Here, the design of a double-bend mode converter for 300 GHz is presented which converts the fundamental TE11 mode quasi-instantaneously to the TM01 mode for the accelerating structure. In comparison to an s-shaped converter, the present design makes an additional waveguide bend obsolete. The structure length along the beam axis is only 4 mm (4 𝜆), showing a major advance in compactness. Combined with a horn antenna for free-space to waveguide coupling, the maximum power coupled into the structure reaches 83%, while the collinear scheme does not exceed 74%.
Paper: WEPA113
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA113
About: Received: 03 May 2023 — Revised: 11 May 2023 — Accepted: 20 Jun 2023 — Issue date: 26 Sep 2023
WEPA114
RF design of the waveguide network for the klystron-based CLIC module
2920
A new RF Module was designed for the Klystron-based CLIC main linac. The new module deploys two X-band klystrons to feed eight CLIC-K accelerating structures giving a beam energy increase of 156 MeV. This module will use a double-height waveguide distribution network which can reduce the RF power loss in the network by about 37%. All the RF components were redesigned to match the double-height requirement, mainly including the 3 dB hybrid, the RF vacuum flange, the bending waveguide, correction cavies and the BOC pulse compressor. A CLIC-K accelerating structure with bended damping waveguides was designed for the new module. The result of RF design work for the klystron based CLIC module is summarized.
Paper: WEPA114
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA114
About: Received: 28 Apr 2023 — Revised: 11 May 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
WEPA115
RF design of the pulse compression system for the klystron-based CLIC main linac
2924
A pulse compression system based on double-height waveguides was designed for the Klystron-based CLIC main linac. The optimized power gain of the system is 3.81 with the particular pulse shape required for the CLIC-K accelerating structure. This pulse compression system consists of a main Barrel Open Cavity (BOC)-type pulse compressor and 4 novel correction cavities. The BOC pulse compressor has the Q0 of 2.36e5 with working mode TM1,1,32 and the β of 6.6. A novel coupling waveguide network which can ease the machining procedure was designed for the BOC pulse compressor. For the correction cavities, a new method based on a single cylinder cavity and a 3-dB hybrid was studied. Each of the correction cavities has the Q0 of 5e4 and the β of about 1.3.
Paper: WEPA115
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA115
About: Received: 28 Apr 2023 — Revised: 11 May 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
WEPA117
Improved waveforms for barrier-bucket systems
2928
Barrier-Bucket (BB) systems provide a method to apply a short gap to a coasting beam. This is utilized for different applications, like ion cleaning, or to compensate the medium energy loss caused by internal experiments. BB-cavities are broadband cavities, and the applied signal is commonly a short sine burst, followed by a flat section at zero voltage. Since the transfer function of the BB-system is usually neither flat nor linear, it is common to predistort the signal to obtain the desired shape at the rf gap. Nevertheless, the resulting waveform still has a ripple in the flat section. This is due to the lowpass characteristic of the amplifier and the sharp edges at the ends of the sine, which lead to an infinite number of harmonics. This paper provides better suited BB-waveforms, which are designed with a finite number of harmonics from the beginning. It is shown that a much better flatness can be achieved than for a conventional BB-waveform, without sacrificing any performance. These advanced waveforms are currently used at the hadron synchrotron COSY at Forschungszentrum Jülich, leading to improved BB-bunch shapes, in particular for electron-cooled beams.
Paper: WEPA117
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA117
About: Received: 01 May 2023 — Revised: 01 Jun 2023 — Accepted: 21 Jun 2023 — Issue date: 26 Sep 2023
WEPA118
Upgrades of S-band Accelerating Structures and Pulse Compressors in the Electron and Positron Injector Linac of KEK
2932
New S-band disk-loaded TM01-2pi/3-travelling-wave structures and pulse compressors have been developed for upgrades of the injector linac for SuperKEKB and Photon-factory storage rings in KEK. The structures 2-m long have ingenious disk irises with oval fillets reducing discharge in high-power operation and modulations in radius suppressing beam break-up instabilities arising from HEM11 wakefields. The pulse compressors are of compact spherical-cavity-type resonating at the degenerate TE112 dipole modes with a high Q-value of 98,000 and yield a peak power gain of 6.2. The structures generate an acceleration gradient of 25.9 MV/m in power operation of 40 MW by using the pulse compressor and stably accelerate a two-bunch beam with a bunch charge of 4 nC.
Paper: WEPA118
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA118
About: Received: 02 May 2023 — Revised: 10 May 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
WEPA119
Low-power model tests of the wide-band cavity to compensate the transient beam loading in the next generation light sources
2936
In the next-generation light sources, the bunch lengthening using the combination of the fundamental and harmonic cavities is a key technology to generate ultra-low emittance beam. Since the performance of the above bunch lengthening is limited by the transient beam loading (TBL) effect on the cavities, we proposed a TBL compensation technique using a wide-band longitudinal kicker cavity [1]. Then, we considered the kicker design based on the KEK-LS storage ring as an example of the next-generation light sources [2]. We employed a frequency of 1.5 GHz (third-harmonic) and the single mode (SM) cavity concept where harmful HOMs are damped by rf absorbers on the beam pipes. The SM-type concept has two advantages. One is its simple structure where it has no HOM dumper on the cavity and another is its low R/Q which reduces the TBL effect in the kicker itself significantly. The RF power is supplied with two large coupling holes whose total external Q is 300. The small external Q is essential to provide a voltage of 50 kV with a -3dB bandwidth (BW) of about 5 MHz which is needed to compensate for the TBL effects sufficiently. To verify the small external Q and damping of HOMs, we fabricated the low-power model of the kicker and measured its performance. In this presentation, we introduced the kicker's design and the performance tests' results.
Paper: WEPA119
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA119
About: Received: 28 Apr 2023 — Revised: 24 May 2023 — Accepted: 24 May 2023 — Issue date: 26 Sep 2023
WEPA120
Design of a parallel-feeding deflecting cavity with variable polarization
2940
Transverse deflecting cavity (TDC) providing time-dependent kick with fixed polarization is an important tool for beam diagnostics and manipulation. Recently, several types of novel TDC with variable polarization have been developed to fulfill the requirements of multi-dimensional phase space measurement of high-quality electron beam as well as fast scanning in proton therapy. Based on the parallel feeding technology, we propose a new design with alternating racetrack cells where the two chains are fed by waveguide networks independently. Each chain provides fixed polarization in either horizontal or vertical plane and variable polarization can be achieved by adjusting the amplitude and phase of the input power to the networks. The structure has several advantages, such as compactness, tunability, high shunt impedance, etc. In this manuscript, physical and mechanical design of this TDC will be presented in detail.
Paper: WEPA120
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA120
About: Received: 03 May 2023 — Revised: 08 May 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
WEPA121
Magnetic alloy core loaded 2nd harmonic cavity design and testing for CSNS-II RCS
2944
In this report, we present our recent progress in the de-sign and high-power testing of the 2nd harmonic cavity for the China Spallation Neutron Source upgrade project. To achieve optimal performance, high-performance mag-netic alloy (MA) cores with dimensions of Ф850mm × Ф316mm × 25mm were meticulously developed and fabricated to serve as the load material for the radio-frequency (RF) cavity. Through rigorous testing, we were able to achieve a remarkable cavity accelerating gradient of over 40 kV/m under 15% duty cycle. To ensure opti-mal cooling efficiency, we conducted a comprehensive fluid dynamics simulation analysis and verified our re-sults through experiments. Finally, to assess the long-term stability and performance of the cavity, we conduct-ed a series of extended operation tests. These experiments successfully confirmed the high-performance capabilities and exceptional stability of the 2nd harmonic cavity.
Paper: WEPA121
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA121
About: Received: 29 Apr 2023 — Revised: 12 May 2023 — Accepted: 20 Jun 2023 — Issue date: 26 Sep 2023
WEPA122
Dielectric Assist Accelerating structures for compact linear accelerators of low energy particles in hadrontherapy treatments
2947
Dielectric Assist Accelerating (DAA) structures based on ultralow-loss ceramic are being studied as an alternative to conventional disk-loaded copper cavities. This accelerating structure consists of dielectric disks with irises arranged periodically in metallic structures working under the TM02-π mode. Here, the numerical design of an S-band DAA structure for low beta particles, such as protons or carbon ions used for hadrontherapy treatments, is shown. Three dielectrics with different permittivity and loss tangent are studied as well as different particle velocities depending on the energy range. Through optimization, most of the RF power is stored in the vacuum space near the beam axis, leading to a significant reduction of power loss on the metallic walls. This allows to realize cavities with extremely high quality factor over 100 000 and shunt impedance over 300 MΩ/m at room temperature. The design optimization has been improved to reduce the peak electric field in certain locations of the cavity. In addition, first multipactor simulations are being carried out, using several coatings to reduce SEY, which has also been taken into account in the electromagnetic result.
Paper: WEPA122
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA122
About: Received: 02 May 2023 — Revised: 07 May 2023 — Accepted: 15 Jun 2023 — Issue date: 26 Sep 2023
WEPA124
RF design of a compact C-band RF pulse compressor for a VHEE linac for flash radiotherapy
2951
In this paper, the design of a compact C-band SLED RF Pulse Compressor for a Very High Electron Energy (VHEE) FLASH machine is presented. A spherical cavity RF pulse compressor - selected because of its compactness and relative ease of fabrication - is adopted to compress the 50 MW 3 µs RF pulse, down to 1 µs obtaining a peak power gain greater than 3. The main parameters – operating resonant mode, unloaded quality factor, coupling factor, peak power gain, geometry, peak surface fields - and S-parameters of the full RF design (spherical storage cavity + mode converter/polarizer) are computed and analyzed. Moreover, the pulse-compression effect on the acceleration performances is analyzed through the evaluation of the main figures of merit (charge per pulse, energy gain, accelerating gradient and efficiency)
Paper: WEPA124
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA124
About: Received: 01 May 2023 — Revised: 14 Jun 2023 — Accepted: 14 Jun 2023 — Issue date: 26 Sep 2023
WEPA125
Irradiation tests of a cavity core material and GaN devices in J-PARC Main Ring
2955
Magnetic alloy cavities have been used in many accelerators. We have irradiated small magnetic alloy rings in J-PARC to evaluate radiation effects on magnetic properties. Complex permeabilities and hysteresis curves were measured before and after the irradiation. No significant variation was observed by the total ionization dose of 18 kGy and neutron flux of 2.3$\times10^{14}$ n/cm$^2$. The doses were measured by RadMON ver.6 developed by CERN. The test will be continued to higher dose. High neutron irradiation caused radio activities and radioactive nuclei in the cores were identified in this work. We also tried to use RadMON with low gain mode. It suggested that RadMON can be used beyond 16 kGy. Gallium nitride devices were also tested for future applications in accelerator tunnels. They showed excellent radiation hardness.
Paper: WEPA125
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA125
About: Received: 27 Apr 2023 — Revised: 08 May 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
WEPA126
HOM dampers design for the MAX IV 100 MHz RF cavities
2958
The MAX IV 100 MHz RF cavities are the main contributors for the 3 GeV storage ring longitudinal coupled bunch instabilities. With the knowledge of strong higher order modes (HOMs) since the design stage of the cavities, extra ports are present for the future HOM dampers. This contribution presents the electromagnetic and mechanical designs and the thermal simulation for the HOM damper prototypes. They are planned to be installed during the summer 2023 shutdown in one of the 6 cavities of the 3 GeV ring.
Paper: WEPA126
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA126
About: Received: 03 May 2023 — Revised: 10 May 2023 — Accepted: 12 May 2023 — Issue date: 26 Sep 2023
WEPA127
Multipacting analysis of the SNS drift tube linac (DTL) RF vacuum window using Spark3d
2962
An ongoing study at the Spallation Neutron Source (SNS) seeks to better understand and address potential multipacting issues associated with the Drift Tube Linac (DTL) RF vacuum windows. An analysis of several failed operational windows showed indications of excessive RF heating on the TiN-coated alumina ceramics. Coupled with vacuum bursts and arcing during conditioning and/or operational periods, these problems have been attributed to electron activity likely caused by multipacting. The status of the study, 3-D electromagnetic simulation results, mitigating techniques and a future experimental plan for studying multipacting in the SNS DTL vacuum windows are presented.
Paper: WEPA127
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA127
About: Received: 01 May 2023 — Revised: 07 May 2023 — Accepted: 11 May 2023 — Issue date: 26 Sep 2023
WEPA130
Bimodal design of 500 MHz and 1.5 GHz normal conducting RF cavity for advanced synchrotron radiation facilities
2966
The advanced storage ring light source needs to realize ultra-low emissivity beam operation, and improving the Touschek lifetime puts forward higher requirements for the performance of RF cavity. In this paper, a novel bimodal normal conducting RF cavity is proposed. In one cavity, two power sources will be connected at the same time to realize the simultaneous operation of the two frequencies. The TM010 mode with the frequency of 500MHz is used for acceleration, and the TM020 mode with the frequency of 1.5GHz is used as the third harmonic to improve the height of the RF bucket and achieve the purpose of lengthening the beam bunch. Two couplers are designed to adapt to the working characteristics of bimodal RF cavity.
Paper: WEPA130
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA130
About: Received: 21 Mar 2023 — Revised: 06 Jun 2023 — Accepted: 06 Jun 2023 — Issue date: 26 Sep 2023
WEPA132
Basic high-power design of a 1.5-GHz TM020-type harmonic cavity for the KEK future light source
2969
In ultralow-emittance synchrotron light sources, harmonic RF cavities are very useful to lengthen the beam bunches by which the adverse effects due to intrabeam scattering can be mitigated. We are developing a 1.5-GHz TM020-type normal-conducting harmonic cavity which is to be used for the KEK future light source project. The harmonic cavity using the TM020 resonant mode has distinct advantages such as: 1) small RF-voltage fluctuation under the transient beam loading, and 2) sophisticated parasitic-mode damping structure which locates at the node of the accelerating field. In our design, we optimized* the inner shape of the cavity so that the coupling impedances due to parasitic modes were minimized. To minimize the losses of accelerating field in the parasitic-mode damping structure, we arranged three frequency-tuners symmetrically and devised an optimum loop of an input coupler, by which an axial symmetry of the cavity was almost maintained. Based on these concepts, we conducted a basic design of high-power cavity including thermal-structural analysis, which will be presented in this paper.
Paper: WEPA132
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA132
About: Received: 01 May 2023 — Revised: 08 May 2023 — Accepted: 19 Jun 2023 — Issue date: 26 Sep 2023
WEPA133
Test stand for conditioning high power tetrodes at TRIUMF
2973
A major part of the 520 MeV Cyclotron's RF system is the high-power RF amplifier. The amplifier is based on eight 4CW250,000B tetrodes. A new high-power tetrode or a high-power tetrode that underwent refurbishing could trip the RF system through inner sparks. The likelihood of those sparks should be reduced prior to applying nominal power to the new and refurbished tetrodes. This could be achieved by RF conditioning of these tetrodes on a test stand. The test stand represents a 150 kW RF amplifier loaded by a dummy load. The amplifier is built using common grid schematics. The test stand's output stage incorporates the 4CW250,000B tetrode that is under test. This paper describes the mechanical and electrical designs of the test stand, procedures of testing and conditioning for 4CW250,000B tetrodes, and the results of test stand's commissioning.
Paper: WEPA133
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA133
About: Received: 01 Apr 2023 — Revised: 11 May 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
WEPA134
Design, fabrication and mechanical tests of TIG-welded Ka-band accelerating structures for ultra-high gradient applications
2976
The investigation of the processes, materials, technology and welding procedures used to manufacture accelerating components for maximum accelerating gradient (>100 MV/m) and minimum RF breakdown probability has led us to the proposal of hard-copper structures in Ka-Band made of multiple parts. In this paper, we illustrate the TIG welding tests, including visual inspection and temperature monitoring, of Ka-band metallic RF cavities for the cases of two-half and four-quadrant models. The RF cavities made of multiple parts operate at ultra-high accelerating gradients (well above >100 MV/m). Therefore, the following aspects of the welding procedure were used as references for the positive outcome of the process: 1) Successful execution of each weld bead/seam in order to assure vacuum tightness of the cavity. 2) The cleanliness of the inside surfaces of the cavities: visual inspection for absence of oxidation after cutting the cavity samples; 3) The temperature of the cavity surfaces always below the annealing one (mechanical properties significantly change after heating above 590 ◦C), in order to keep the hardness of the copper.
Paper: WEPA134
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA134
About: Received: 01 May 2023 — Revised: 08 Jun 2023 — Accepted: 08 Jun 2023 — Issue date: 26 Sep 2023
WEPA135
Development of an S-band accelerating structure for Hefei Advanced Light Source facility
2980
The injector of Hefei Advanced Light source Facility (HALF) will choose the full energy injection method with beam energy up to 2.2 GeV by a LINAC, which will contain 40 S-band normal conducting traveling wave tubes. Quasi-symmetric single-feed racetrack couplers were used in design of TW tube utilized for reduction the field asymmetry inside the coupler cavity. The design and test result of prototype tube are discribed in this paper.
Paper: WEPA135
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA135
About: Received: 03 May 2023 — Revised: 11 May 2023 — Accepted: 20 Jun 2023 — Issue date: 26 Sep 2023
WEPA141
Characterisation facilities for evaluating superconducting thin films for SRF cavities
2983
Over recent years four dedicated facilities have been built at Daresbury Laboratory by a team working on thin film SRF cavities. Firstly, a conventional DC resistance facility allows measurements of critical temperature and residual resistance ratio. In addition, three other facilities were designed in house to address superconducting thin film (STF) characterisation specific to cavities. In a magnetic field penetration facility, a DC parallel magnetic field is applied locally from one side of the sample similar to the field within an RF cavity. The STF behaviour under RF conditions is tested with planar samples using a 7.8 GHz choke cavity with the main advantage of a quick turnaround. The final facility uses a novel idea of split single cell 6 GHz cavities. Such a cavity can be deposited with both planar and cylindrical magnetrons allowing for both deposition techniques to be tested in the same cavity. Also, the results can be compared to choke cavity measurements for planar samples. They can also be inspected easily both visually and with surface analysis instrumentation. All facilities are based on liquid helium free cryocoolers to simplify operation, safety and maintenance.
Paper: WEPA141
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA141
About: Received: 03 May 2023 — Revised: 22 Jun 2023 — Accepted: 22 Jun 2023 — Issue date: 26 Sep 2023
WEPA143
Design and commissioning of a new SRF cavity for a conduction-cooled system
2987
Cornell is designing a standalone superconducting radio-frequency (SRF) accelerating cryomodule which utilizes a conduction cooling scheme in place of liquid helium. A key component of this system is a new single-cell 1.3 GHz Nb$_3$Sn-coated SRF cavity. This cavity was designed based on Cornell’s ERL injector cavities in order to replicate their RF properties, such as being able to operate at high current (> 100 mA) and high average power (> 100 kW). Thermal modelling of the cavity was then used in order to optimize the design and placement of heat intercept rings to enable the use of conduction cooling. The cavity has since been fabricated and welded, and is currently undergoing chemical treatment before baseline RF tests are performed.
Paper: WEPA143
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA143
About: Received: 09 May 2023 — Revised: 10 May 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
WEPA144
RF and beam dynamics considerations for the cavity end group of the all superconducting DESY gun
2991
Future high duty cycle (HDC) operating modes are under development for the European XFEL. A L-band superconducting RF (SRF) gun is foreseen as the injector operating continuous wave (CW). To preserve the small beam emittance distracting effects like RF kicks from the power coupler, trapped higher order modes (HOMs) in the cavity end group and RF field asymmetries need to be considered and countermeasures to be taken. Apart from the beam dynamics, the feasibility and effort of the manufacturing and surface treatment, the later assembly and operation needs likewise consideration. In our contribution we present the outcome of our studies and the cavity end group which will be realized at our next prototype cavities.
Paper: WEPA144
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA144
About: Received: 03 May 2023 — Revised: 09 May 2023 — Accepted: 19 Jun 2023 — Issue date: 26 Sep 2023
WEPA145
Surface treatment experience of the all superconducting gun cavities
2995
The performance of superconducting cavities depends extremely on the material and surface properties. In the last decades processes have been developed for the successful series production of accelerating cavities needed for large scale facilities like the European XFEL. A main feature of these cavities are relatively large beam ports on both sides which can be used for the surface treatment processes. In contrast, superconducting gun cavities have only one beam port and a half-cell with a back-wall acting as mirror plate with some small space for the cathode in the center. Being apparently only a small feature, this fact tuns out requiring special attention for the surface treatment. This is in particular the case, if the target are similar high gradients like in the accelerating cavities. In our contribution we present the experience made within the last years and how we finally achieved high gradients.
Paper: WEPA145
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA145
About: Received: 02 May 2023 — Revised: 06 Jun 2023 — Accepted: 06 Jun 2023 — Issue date: 26 Sep 2023
WEPA148
Overview of material choices for HL-LHC collimators
2999
In view of the High-Luminosity (HL-LHC) upgrade of the LHC collimation system, different materials were investigated to determine how the jaws of the new collimators could be manufactured to meet the demanding requirements of HL-LHC, such as thermomechanical robustness and stability, RF impedance, UHV, etc. During the Long-Shutdown 2 (LS2), five primary and 10 secondary low-impedance collimators were already produced using novel material. For LS3, in addition to more secondary collimators, the production and installation of other types of collimators, including tertiaries and physics debris units, is planned. This paper details the final material choices and rationale for each collimator family.
Paper: WEPA148
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA148
About: Received: 10 May 2023 — Revised: 11 May 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
WEPA149
Numerical calculation of the Lorentz force detuning and the pressure sensitivity for the HL-LHC crab cavity
3003
Crab cavities are fundamental components of the LHC upgrade in the framework of the HL-LHC project. These Radio Frequency cavities, operated at the appropriate frequency, ‘tilt’ the proton bunches to increase the luminosity at the collision points IP1 (ATLAS) and IP5 (CMS). During operation, the walls of the cavities are deformed due to the loading conditions. This deformation changes the electro-magnetic field inside the cavity and thus its RF frequency. Two different superconducting crab cavities have been developed: RF Dipole (RFD) and Double Quarter Wave (DQW). In the present study, the numerical evaluation of the Lorentz Force Detuning (LFD) and the Pressure Sensitivity (PS) of the DQW cavity, using COMSOL Multiphysics, is presented. The LFD analyses the change in fundamental frequency of the cavity due to the electro-magnetic forces acting on its walls, while the PS investigates the frequency shift when the cavity is subjected to pressure fluctuations of the Helium bath. Finally, a comparison is presented with the results measured during the cold test of the manufactured cavities.
Paper: WEPA149
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA149
About: Received: 11 May 2023 — Revised: 11 May 2023 — Accepted: 15 Jun 2023 — Issue date: 26 Sep 2023
WEPA150
Development and characterisation of advanced coatings for high energy physics applications
3006
The Future Circular Collider (FCC) study develops the technologies for next generation high performance particle colliders and accelerating structures. It places high requirements on the performance of Superconducting Radio Frequency (SRF) cavities used to accelerate the particle beam. While niobium-coated copper cavities are being considered for FCC-ee, alternative superconducting materials are investigated in view of reducing considerably the energy consumption of such a large machine. Nb3Sn, an A-15 intermetallic type II superconductor, is one of those potential candidates. However, due to its brittle nature, the only way to produce an Nb3Sn SRF cavity consists of elaborating it as a thin film using, for example, magnetron sputtering to coat copper-based cavities. The latest developments at CERN on Nb3Sn films production by DC-Magnetron Sputtering (DC-MS) and bipolar High Power Impulse Magnetron Sputtering (HiPIMS) are presented, together with a comprehensive microstructural and mechanical characterisation of the films. Special attention is paid to the role of interlayers to avoid Cu diffusion during the high temperature reaction and to the influence of the deposition method and parameters on the film superconducting performance.
Paper: WEPA150
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA150
About: Received: 30 Apr 2023 — Revised: 20 Jun 2023 — Accepted: 20 Jun 2023 — Issue date: 26 Sep 2023
WEPA151
RF CM Test Program at ESS TS2
3010
We present here the RF test program of the ESS TS2. Several tools have been prepared at TS2 for the later stages of the technical commissioning in the linac. Automated tools for tuning the cavities to resonance using spectral analysis or cavity gradient calibration have been deployed and tested to assist the later stages of facility commissioning.
Paper: WEPA151
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA151
About: Received: 11 May 2023 — Revised: 23 Jun 2023 — Accepted: 23 Jun 2023 — Issue date: 26 Sep 2023
WEPA152
Results of the elliptical cryomodule qualification at the ESS TS2
3014
The cryomodule qualification test stand (TS2) at Lund has been commissioned fully in 2021 and is delivering the components for the installation in the linac, which started in Q1 2023 after the end of the cryogenic distribution system commissioning. All the available medium beta cryomodules have been tested and the facility is now delivering the high beta cryomodules for the full scope of the linac. Statistics of the tests and operational experience of the facility is reported here.
Paper: WEPA152
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA152
About: Received: 03 May 2023 — Revised: 06 May 2023 — Accepted: 23 Jun 2023 — Issue date: 26 Sep 2023
Plasma cleaning efforts at Fermilab
Plasma processing can be used to mitigate hydrocarbon-related field emission in SRF cavities in situ in cryomodules. At Fermilab we developed plasma cleaning for LCLS-II 1.3GHz N-doped cavities and we successfully applied to the LCLS-II High Energy verification cryomodule (vCM). This test demonstrated that plasma processing can be a valuable tool to mitigate both field emission and multipacting in situ in cryomodules. This would result in a significant decrease of the CM testing time, of the linac commissioning time and cost, and in an increase in the accelerator reliability. Building upon this successful experience, we are now working on developing plasma processing for different cavity geometries, focusing both on the ignition method and on the gas mixture recipe.
Review of SRF technology developed for accelerators applied to searches for dark matter and other beyond the standard model physics
Recent efforts have shown that the SRF technology developed for accelerators can be successfully applied to new applications, including quantum computing, dark matter searches and beyond the standard model physics. The ultra-high quality factor of SRF cavities can allow to achieve unprecedented sensitivity in fields outside of the usual accelerator applications, for examples in dark photon and axion searches (both as dark matter candidates and lab-produced particles), to study the superconductor nonlinear behavior and could also allow to set a limit on photon-photon scattering. Applications of SRF cavities for gravitational waves searches are also being investigated. In this work we propose an overview of the applications of SRF technology originally developed for accelerators to new frontiers. The SQMS Physics and Sensing thrust is working on this effort as it strives to combine SRF cavities with the quantum technology, with a focus on new particle and BSM physics.
WEPA157
Flux expulsion and material properties of Niobium explored in 644-650 MHz cavities
3018
Upcoming projects requiring ~650 MHz medium-to-high-beta elliptical cavities such as Michigan State University’s Facility for Rare Isotope Beams’ energy upgrade and Fermilab’s Proton Improvement Project-II drive a need to understand magnetic RF loss mechanisms in greater detail. It remains to be seen whether flux trapping mitigation techniques used in 1.3 GHz cavities are as effective at ~650 MHz, given differences in cavity geometry, material of manufacture vendor, and frequency-dependent superconducting RF dynamics. We explore the fast-cooldown method, and high-temperature annealing (900°C), which promote flux-expulsion efficiency, but are more difficult to implement in ~650 MHz cavities. In high-power RF testing, we measure the cool-down temperature gradient vs flux expulsion efficiency, the cavity’s residual resistance sensitivity to trapped flux as a function of cavity treatment. We further used the Physical Property Measurement System available at Fermilab to directly measure the flux pinning force in bulk niobium samples, and correlate changes in the flux pinning force with different niobium vendors, heat treatments, and cavity flux expulsion performance.
Paper: WEPA157
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA157
About: Received: 12 May 2023 — Revised: 12 May 2023 — Accepted: 19 Jun 2023 — Issue date: 26 Sep 2023
WEPA160
Production of the 1.5 GHz fundamental power couplers for VSR demo
3022
Research Instruments (RI) and Thales have been producing the first two prototype 1.5 GHz fundamental power couplers for the VSR (Variable pulse length Storage Ring) DEMO since early 2021 and delivered these prototypes in late March 2023. These couplers are designed to provide up to 16 kW power to two 1.5 GHz superconducting cavities of the VSR DEMO module and provide variable coupling with a Qext range from 6x10^6 to 6x10^7. The paper describes the challenges in fabricating a scaled coupler and provides details on the modifications to the design as a result of these challenges. The impact of the late-stage design modification is discussed along with how this affects future conditioning plans.
Paper: WEPA160
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA160
About: Received: 28 Apr 2023 — Revised: 15 May 2023 — Accepted: 19 Jun 2023 — Issue date: 26 Sep 2023
WEPA161
Electrodeposition of copper on Niobium for cryocooler application
3026
The electrodeposition of copper onto niobium using commercial acidic and alkaline electrolytes was tested. The continuous dense polycrystalline copper films were successfully obtained in aqueous alkaline-type bath containing copper sulphate, sodium hydroxide and sodium gluconate. The effect of benzotriazole and sodi-um lauryl sulphate additives on the morphology and crystal structure of the deposited copper was investigat-ed by optical and scanning electron microscopy, and X-ray diffraction. No copper oxides were found in the grown films. Copper films had moderate adhesion properties that would be insufficient for cryocooler application. We are currently exploring different com-positions of electrolyte baths for obtaining the coatings on niobium with improved adhesion.
Paper: WEPA161
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA161
About: Received: 14 May 2023 — Revised: 17 May 2023 — Accepted: 22 Jun 2023 — Issue date: 26 Sep 2023
WEPA164
Thin films on HOM antennas to push the limits for higher beam currents at MESA
3029
The Mainz Energy-Recovering Superconducting Accelerator (MESA), an energy-recovering (ER) LINAC, is currently under construction at the Institute for Nuclear physics at the Johannes Gutenberg-Universität Mainz, Germany. In the ER mode continues wave (CW) beam is accelerated from 5 MeV up to 105 MeV. The energy gain of the beam is provided through 2 enhanced ELBE-type cryomodules containing two 1.3 GHz 9-cell TESLA cavities each. By pushing the limits of the beam current up to 10 mA, a quench can occur at the HOM Antennas. This is caused by an extensive power deposition within the antenna. Calculations have shown that a power transfer of 1 W must be assumed. However, tests of the 1.5 GHz version of the TESLA HOM coupler have shown a quench limit of 43 mW in CW. To prevent a quench of the HOM antennas by high beam currents without mayor modification of the design of the HOM antenna and F-part it is necessary to find suitable materials. Nb3Sn and NbTiN can be applied as a coating to the HOM antennas and have higher critical parameters than pure Nb which will lead to a higher power limit. As a further approach to improve the power transfer the material for the HOM antenna will be changed to oxygen-free high thermal conductive (OFHC) Copper. The antennas with a Cu core will be coated first with Nb. The limit of the coated antennas will be tested with the cavities of a cryomodule from the decommissioned ALICE accelerator from STFC Daresbury.
Paper: WEPA164
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA164
About: Received: 02 May 2023 — Revised: 18 May 2023 — Accepted: 19 Jun 2023 — Issue date: 26 Sep 2023
Development of RF Fundamental Coupler for 325 MHz Superconducting Single Spoke Resonator
An RF Fundamental Power Coupler(FPC) designed to operate under 7 kW CW for 325 MHz superconducting(SC) single spoke resonator(SSR) in the high energy SC Linac of the RAON. A prototype FPC has a coaxial shape with an impedance of 98 ohm and an outer radius of 36 mm. It is checked that the MP exists within the SSR operating range. Reduction or elimination of the MP is estimated applying DC voltage at the center conductor of the FPC. Detailed test setup and test results are presented.
WEPA166
RF preparation of QWR cavities for beam commissioning
3033
QWR cavities are prepared for beam commissioning. RF conditioning is performed for each QWR cavity. The total heat load including static and dynamic heat loads are measured for each cavity. The helium pressure fluctuation is reduced by changing the flow rate, supply pressure, return pressure, liquid helium level in reservoir, cryogenic valve control, etc. The cavity pressure is monitored during RF preparation. The amplitude and phase of the QWR cavity are stably controlled for beam commissioning.
Paper: WEPA166
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA166
About: Received: 25 Apr 2023 — Revised: 07 May 2023 — Accepted: 12 May 2023 — Issue date: 26 Sep 2023
WEPA167
RF superconducting cavity and zero-temperature physical phenomena
3036
What happens when the temperature reaches absolute zero? Physical phenomena at the zero-temperature limit are studied in accelerator physics. The background temperature of the universe goes down as long as expansion goes on. The BCS resistance of a superconducting cavity is shown as a function of temperature at different frequencies. The surface resistance of the Nb superconducting cavity is reduced to residual resistance and flux-trapped resistance at 0 K. Blackbody radiation is stopped by heat radiation at 0 K. Thermal expansion and thermal diffu-sion become zero at 0 K. Black holes evaporate at 0 K.
Paper: WEPA167
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA167
About: Received: 01 May 2023 — Revised: 11 May 2023 — Accepted: 23 Jun 2023 — Issue date: 26 Sep 2023
WEPA168
Removal of BCP defects for the 166.6 MHz HOM-damped quarter-wave srf cavities
3039
The compact 166 MHz HOM-damped quarter-wave superconducting cavities for HEPS have complex geometries, resulting in streak defects on the inner surface of the cavity after BCP etching. Surface areas with low flow velocity from fluid dynamics simulations coincide with defects observed on the cavity inner surface. Based on the 166 MHz cavity structure, an improved BCP setup with holes and discs was designed. The flow velocity at the defect locations was greatly increased, and defects did not reappear. An excellent cryogenic performance has been achieved in the subsequent vertical tests, indicating that the post processing of the cavity was successful. This paper presents the analysis, solution, and final results of BCP etching defects in the chemical processing of the 166.6 MHz srf cavity.
Paper: WEPA168
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA168
About: Received: 29 Apr 2023 — Revised: 11 May 2023 — Accepted: 19 Jun 2023 — Issue date: 26 Sep 2023
WEPA170
The mechanism of non-uniform distribution of tin sites on the surface of niobium during the nucleation process
3043
A uniform distribution of nucleation tin sites is essential to the growth of high quality Nb3Sn thin film by vapor diffusion method. The less-nuclear zones were commonly observed in previous nucleation experiments. However, a fully understanding of the occurrence of less-nuclear zones has not yet been achieved. Here, the adsorption energy of nuclear agent SnCl2 on different crystal planes of niobium (Nb) including Nb (110), Nb (100), Nb (211) are studied through density functional theory (DFT) calculations and several types of adsorption configurations are optimized. The large differences of calculated adsorption energy of SnCl2 on three different crystal planes reveal strong crystal direction selectivity during nucleation stage. In addition, the phenomenon of nucleation experiment on large grain samples further consolidates the accuracy of the calculation results. The calculation results explain the presence of less-nuclear zones during nucleation process and provide guidance for the subsequent suppression of these regions.
Paper: WEPA170
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA170
About: Received: 09 May 2023 — Revised: 23 Jun 2023 — Accepted: 08 Jun 2023 — Issue date: 26 Sep 2023
WEPA171
The optimization of the bronze-method Nb3Sn coatings on Cu substrates
3046
Nb3Sn thin films are mainly used on superconducting radio frequency (SRF) cavities, single-photon detectors and RF logic circuits. Copper-based Nb3Sn thin-film SRF (TFSRF) cavities are promising for particle accelerators because they may combine the advantages of high thermal conductivity and high gradient. In this paper, a bronze method, including multi-layer deposition and heat treatment, was used to generate Nb3Sn thin film on copper substrates. We first made a precursor by sputtering a niobium layer on the copper substrate and then electroplating a thicker bronze layer. Then we annealed the precursor in a vacuum tube furnace to synthesize Nb3Sn film. Considering the morphology and superconductivity of the Nb3Sn films, we compared the effects of various annealing temperatures and optimized the preparing conditions. The samples characterization of the morphology and superconductivity showed that high-quality Nb3Sn thin films had been successfully deposited on copper substrates. The superconducting transition temperature Tc can reach higher than 17.0 K. This synthesis route provides a new approach towards high-stability Nb3Sn TFSRF copper cavities.
Paper: WEPA171
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA171
About: Received: 10 May 2023 — Revised: 23 May 2023 — Accepted: 19 Jun 2023 — Issue date: 26 Sep 2023
Nb3Sn on Cu Coating By Magnetron Sputtering From Target Synthesized via Liquid Tin Diffusion
Nb3Sn on Nb thin films cavities by Tin Vapor Diffusion already show performance at 4.2 K comparable to Nb bulk cavities at 2 K, but a real breakthrough would be the use of copper (instead of Nb) as substrate, to enhance the thermal conductivity, opening up the possibility to cool down the cavity using cryocoolers instead of the more expensive helium bath. Magnetron sputtering is the most studied technology for this purpose, however coating substrates with complex geometry (such as elliptical cavities) may require targets with non-planar shape, difficult to achieve with classic powder sintering techniques due to the brittleness of Nb3Sn. In this work, carried out within the iFAST collaboration, the possibility of using the Liquid Tin Diffusion (LTD) technique to produce sputtering targets for 6 GHz elliptical cavities is explored. The LTD technique is a wire fabrication technology, already developed in the past at LNL for SRF applications, that allows the deposition of very thick and uniform coating on Nb substrates even with complex geometry. Improvements in LTD process, proof of concept of a single use LTD target production, and characterization of the Nb3Sn film coated by DC magnetron sputtering with these innovative targets are reported in this work.
WEPA175
INFN-LASA R&D on high-Q cavities for the PIP-II project
3049
As the series production of PIP-II 650 MHz low beta cavities approaches, INFN-LASA R&D activities on cavity prototypes are ongoing. Different surface treatments have been exploited in a joint effort between INFN and FNAL, to establish the series cavity recipe. Meanwhile, the vertical test facility has been upgraded for the test of high-Q cavities, by increasing its capability to reduce the trapped magnetic flux and by developing of a magnetic mapping system suitable in the cryostat environment. Here, we report the latest experimental results.
Paper: WEPA175
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA175
About: Received: 05 May 2023 — Revised: 12 May 2023 — Accepted: 19 Jun 2023 — Issue date: 26 Sep 2023
WEPA176
Investigation of the fabrication method for the 3rd harmonic superconducting double-cell cavity
3053
The 3rd harmonic cavity is a key component for the 4th generation storage ring. A bunch lengthening by the harmonic cavity increases the Touschek lifetime, which can reduce the emittance in the storage ring. The resonant frequency is selected as 1500 MHz due to the resonant frequency of the main RF cavities being 500 MHz. The prototype cavity is an elliptical double-cell geometry to reduce power losses. Based on this design, three niobium cavities are fabricated. Deep drowned half-cells are welded by the electron beam welding machine after trimming at the edge of the equator and iris. The surface treatments are performed to increase the quality factor such as buffered chemical polishing, high-pressure rinsing, and annealing. In this paper, we presented the fabrication method of the 3rd harmonic superconducting cavity from niobium sheets to an elliptical double-cell cavity.
Paper: WEPA176
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA176
About: Received: 02 May 2023 — Revised: 09 May 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
WEPA178
Updates of high-density temperature and X-ray mapping
3056
A high-density temperature and X-ray mapping system has been developed. The X-ray mapping system, which uses strips with 32 channels of X-ray sensors, is now ready for use. The current sensor chip was selected about 10 years ago for Nb cavities operating at 2K, but recent advances in SRF cavities have required detection at higher temperatures, such as 20K for Nb3Sn materials. The current sensor chip was selected about 10 years ago for Nb cavities operating at 2K, but recent advances in SRF cavities have required detection at higher temperatures, such as 20K for Nb3Sn materials. Therefore, we are searching for a new temperature sensing element. These are reported.
Paper: WEPA178
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA178
About: Received: 10 May 2023 — Revised: 12 May 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
WEPA179
Multipactor studies for the FCC–ee superconducting swell cavities
3059
The Future Circular Collider (FCC) is a project of high performance particle collider. Several accelerating cavity technologies may equip it and are currently under study. One of them is the Slotted Waveguide ELLiptical (SWELL) superconducting (SC) cavity. It is a good candidate for nearly all the range of electron-positron interaction energies. It is made up of four independent quadrants clamped together, allowing for a seamless and very stiff structure. One of the important issues that remain to be addressed is the position of the multipactor barriers. In this study, we focus on the SWELL 1.3 GHz mono-cell prototype, which is very close to the well-known TESLA cavity. We calculated the position of its multipactor barriers using the simulation tools CST Microwave Studio and SPARK3D. These calculations were backed by electron emission measurements led on a Nb sample representative of the cavity’s coating. These are focused on the impact energy range between 0 and 80 eV. As a matter of a fact, we found it to be very important for the multipactor apparition while often being overlooked.
Paper: WEPA179
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA179
About: Received: 01 May 2023 — Revised: 08 Jun 2023 — Accepted: 08 Jun 2023 — Issue date: 26 Sep 2023
Mechanical Polishing of Nb3Sn Thin-Film Cavities
Nb3Sn superconducting radiofrequency (SRF) cavities have been an ongoing research topic for many years motivated by the potential for higher accelerating gradients and quality factors compared to niobium SRF cavities. The highest performing Nb3Sn cavities are manufactured using tin vapor-diffusion coating, which creates a Nb3Sn film with a surface roughness of around 100-200 nm. This is thought to be one of the limiting factors for the accelerating gradient of Nb3Sn cavities due to enhancement of magnetic field near sharp surface features. To smooth Nb3Sn SRF cavities, we have developed a mechanical polishing procedure which uses centrifugal barrel polishing to smooth the surface followed by a secondary tin coating step to repair the surface. We show that the accelerating field of a Nb3Sn SRF cavity is improved by applying this procedure. We also investigate the quench mechanism of the polished cavity by utilizing temperature mapping to measure which regions of the cavity experience heating during RF operation. We then cut samples from these regions and analyze the film microstructure and chemical composition in 3D using EDS and EBSD measurements together with a focused ion-beam (FIB) tomography technique.
WEPA182
Multi-physics simulation of quadrupole resonators in the time domain under uncertainties
3063
Exploring the fundamental properties of materials, including niobium or Nb3Sn, in high-precision surface resistance measurements is relevant to superconducting radio-frequency (RF) technology. For the precise determination of the RF properties of such materials, the calorimetric measurement is carried out with a quadrupole resonator (QPR). Mathematically, a QPR model is governed by a set of electromagnetic-stress-heat (EM-S-T) equations in the time domain under geometric and material uncertainties. It allows for profound insight into the QPR physics phenomena, such as dynamic Lorentz force detuning and microphonics, potentially resulting in measurement bias observed for the third operating mode of the given HZB-QPR (1.3 GHz). On top of the coupled EM-S-T problem, due to manufacturing imperfections, the stochasticity of input parameters substantially affects the performance of QPRs. Thus, uncertainty quantification (UQ) becomes necessary to provide reliable and predictable simulations of QPRs. The generalized polynomial chaos (gPC) expansion technique with the stochastic collocation method is proposed to find the UQ propagation by the QPR model. This methodology offers a more realistic mathematical model of the QPR, providing statistical moments, local and variance-based sensitivity, and cumulative/probabilistic density functions. Based on that information, a physically-based approach can be proposed to re-design the QPR and improve the measurement accuracy.
Paper: WEPA182
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA182
About: Received: 04 May 2023 — Revised: 06 Jun 2023 — Accepted: 06 Jun 2023 — Issue date: 26 Sep 2023
WEPA183
REBCO sample testing for a HTS high Q cavity
3067
Superconducting materials such as niobium have been extremely useful for rf accelerator technology but require low temperatures for operation ~2-4 K. The development of high temperature superconductors (HTS) is promising due to their transition temperature in excess of 80 K. In this work we are exploring the high-power RF performance of such materials at X-band (11.424 GHz). We are testing two kinds of REBCO coatings, deposition and tapes, on a copper substrate. Testing was done in a hemispherical cavity with a TE mode due to its ability to maximize the magnetic field on the sample and minimize electric field. We will report on the performance in terms of conductivity vs temperature at low and high power. These measurements will then be compared to the design performance of a full 3D cavity that is coated with REBCO. This cavity will utilize the TM010 mode, and we are targeting a Q of ~1 10^6 at 80 K. Such a cavity could be useful for high power rf accelerator applications. In one example, a cryogenic copper linac operating at liquid nitrogen temperature (77 K) could utilize such a high-Q cavity in its superconducting state for pulse compression.
Paper: WEPA183
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA183
About: Received: 03 May 2023 — Revised: 05 Jun 2023 — Accepted: 20 Jun 2023 — Issue date: 26 Sep 2023
WEPA184
V3Si Thin Films for SRF Applications
3071
The relatively high transition temperature of A15 superconducting materials makes them a potential alternative to Nb for radio-frequency applications. We present PVD deposition of one A15 material, V$_3$Si, on Cu and sapphire substrates. The surface structure and composition of the films were characterised via SEM and EDX. The superconducting properties were investigated using a field penetration facilty, four point probe and SQUID magnetrometry. Analysis showed that the composition was slightly Si rich by a few percent with a granular suface structure. Despite this superconductivity was observed on both Cu and sapphire substrates with critical temperatures of 12.8\,K and 14\,K. Field penetration measurements were conducted through two different facilities.
Paper: WEPA184
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA184
About: Received: 02 May 2023 — Revised: 07 May 2023 — Accepted: 19 Jun 2023 — Issue date: 26 Sep 2023
WEPA185
Split 6GHz SRF thin film cavities
3074
Many current accelerators use cavities that are manufactured as two half cells that are electron beam welded together, across the peak surface current of the cavity. This weld can limit the performance of Thin Film (TF) coated cavities by causing an increase in the surface resistance. Many problems with the coating process for TF Superconducting Radio Frequency (SRF) cavities are also due to this weld. TF SRF cavities can perform as well as bulk niobium cavities if the cavity is manufactured seamlessly, without any weld, however, they are much more difficult and expensive to manufacture. A cavity with a split parallel to the direction of the electric field, would not need to be welded. These cavities are easier to manufacture and coat. Thus, different coating techniques may be used leading to new materials and multilayer coating options which may allow SRF cavities to operate at better parameters than current state of the art cavities. TF SRF cavities have been developed for use in particle accelerators, as they have many advantages over normal conducting and bulk niobium cavities. One such advantage is that SRF TF cavities have a lower surface resistance, below the critical temperature, than NC cavities and a higher thermal conductivity than bulk niobium cavities leading to a more uniform temperature of the superconductor. This work discusses development and testing of longitudinally split seamless TF SRF cavities at Daresbury Laboratory
Paper: WEPA185
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA185
About: Received: 03 May 2023 — Revised: 10 May 2023 — Accepted: 19 Jun 2023 — Issue date: 26 Sep 2023
WEPA189
The collaborative effects of intrinsic and extrinsic impurities in low RRR SRF cavities
3078
The superconducting radio-frequency (SRF) community has shown that introducing certain impurities into high-purity niobium can improve quality factors and accelerating gradients. We question why some impurities improve RF performance while others hinder it. The purpose of this study is to characterize the impurity profile of niobium with a low residual resistance ratio (RRR) and correlate these impurities with the RF performance of low RRR cavities so that the mechanism of impurity-based improvements can be better understood and improved upon. The combination of RF testing and material analysis reveals a microscopic picture of why low RRR cavities experience low temperature-dependent BCS resistance behavior more prominently than their high RRR counterparts. We performed surface treatments, low temperature baking and nitrogen-doping, on low RRR cavities to evaluate how the intentional addition of oxygen and nitrogen to the RF layer further improves performance through changes in the mean free path and impurity profile. The results of this study have the potential to unlock a new understanding on SRF materials and enable the next generation of SRF surface treatments.
Paper: WEPA189
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA189
About: Received: 04 May 2023 — Revised: 12 May 2023 — Accepted: 19 Jun 2023 — Issue date: 26 Sep 2023
WEPA190
Origins of quench in buffered chemical polished and low temperature baked SRF cavities
3082
Electropolishing (EP) and buffered chemical polishing (BCP) are conventional surface preparation techniques for superconducting radiofrequency (SRF) cavities that remove damaged material from the cavity surface. One main issue with EP and BCP treated SRF cavities is high field Q-slope (HFQS), a drop in quality factor at high gradients that limits quench field. High gradient performance in EP cavities can be improved by applying a low temperature bake (LTB), but LTB does not consistently remove HFQS in BCP cavities. There is no consensus as to the why LTB is not effective on BCP prepared cavities, and the cause of HFQS in BCP cavities is not well understood. We examine the origins of quench in EP, BCP, EP+LTB, and BCP+LTB treated SRF cavities. We also show the effect of these treatments on the onset of HFQS, heating within the cavity up to quench, concentration of free hydrogen, and surface roughness.
Paper: WEPA190
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA190
About: Received: 03 May 2023 — Revised: 23 May 2023 — Accepted: 23 May 2023 — Issue date: 26 Sep 2023
WEPA191
Vertical tests of the 166.6 MHz HOM-damped Prototype SRF Cavities for HEPS
3086
The storage ring of the High Energy Photon Source will be driven by five higher-order-mode-damped 166.6 MHz beta=1 quarter-wave superconducting cavities operating at 4 K. Three prototype cavities were manufactured in Beijing and the surface preparations were conducted in Ningxia and Beijing. The cavities were subsequently vertical tested at PAPS in Huairou (Beijing). The cavity Q<sub>0</sub> at design voltage of 1.5 MV reached 3.8×10<sup>9</sup> at 4 K, exceeding the design goal of 1×10<sup>9</sup>. One cavity was subsequently welded with a helium jacket and vertical tested at 2 K achieving an RF performance comparable to the undressed cavities. No chemical polishing was conducted for the jacketed cavity.
Paper: WEPA191
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA191
About: Received: 01 May 2023 — Revised: 11 May 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
WEPA192
Frequency pre-tuning of the 166.6 MHz hom-damped srf cavities for HEPS
3090
A higher-order-mode-damped 166.6 MHz beta=1 quarter-wave superconducting cavity is being developed for the High Energy Photon Source. The frequency variation of the cavity in all the processes comprising of manufacturing, post-processing and cooldown to 4.2 K, should be strictly controlled due to the relatively small coarse tuning range. The step-by-step evolution of the cavity frequency was determined and the target frequency after fabrication was given. The pre-tuning scheme during fabrication was made in which the length of the inner conductor and the outer conductors are the free parameters for frequency pre-tuning while the cavity length is kept constant. The environment of the cavity in the cryomodule was considered in the analysis. Three bare cavities and one jacketed cavity were fabricated, post-processed and vertical tested with careful frequency monitoring. The measured frequencies were consistent with the predictions in each process.
Paper: WEPA192
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA192
About: Received: 01 May 2023 — Revised: 09 May 2023 — Accepted: 11 May 2023 — Issue date: 26 Sep 2023
Successful Al2O3 coating of superconducting niobium cavities by thermal ALD
Al2O3 is one of the potential insulator materials in the superconductor-insulator-superconductor (SIS) multilayer coatings of superconducting radio-frequency (SRF) cavities for pushing their performance limits. We report on the successful coating of two 1.3 GHz Tesla- shaped SRF cavities with 18 nm and 36 nm layers of Al2O3 deposited by thermal atomic layer deposition (ALD). The coating recipe was developed by thermal atomic layer deposition (ALD). The coating recipe was optimized with respect to different the applied process parameters such as exposure and purge times, substrate temperature and flow rates. After a proof-of-principle Al2O3 coating of a cavity, second the cavity maintained its maximum achievable accelerating field of more than 40 MV/m and no deterioration was observed [1]. On the contrary, an improvement of the surface resistance above 10 MV/m has been observed, which is now further under investigation.
WEPA194
Surface characterization of mid-T heat treated Nb samples to investigate the origin of residual resistance
3094
Annealing of niobium (Nb) cavities in UHV is crucial for the performance in the later cryogenic tests and operation. Recently, a so-called “mid-T bake” treatment has exhibited very high-quality factors for Nb cavities. In this way, the first set of mid-T treated samples were produced with cavities at Zanon Research & Innovation Srl. The cavity performances have been improved with lower BCS and residual resistances, however the residual resistances were varied very different between 3-12 nΩ and didn’t achieve the low values as we expected. Thus, the characterization of these samples is discussed, and the source of residual resistance mitigation has been studied here in detail. We present our investigation on potential origins. For this, we used XPS, MOKE and Auger measurements to study the surface magnetic domains and stoichiometry of structures.
Paper: WEPA194
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-WEPA194
About: Received: 12 May 2023 — Revised: 08 Jun 2023 — Accepted: 08 Jun 2023 — Issue date: 26 Sep 2023
XRR Analysis of Al2O3 coated and mid-T heat treated niobium for future implementation in SIS-based SRF cavities
Superconducting radio-frequency cavities made out of niobium form the fundamental block of modern particle accelerators. A model proposed by Gurevich [1] suggests the use of a superconductor-insulator-superconductor (SIS) structure to achieve higher accelerating fields and a reduced surface resistance beyond the thermodynamic limits of Nb. As a first step to pursue this approach, a single-cell cavity was coated with a thin Al2O3 film via atomic layer deposition (ALD) to create an insulating layer [2] and baked for 3h at 300°C (mid-T heat treatment) [3]. In parallel, a mechanically polished two-grain-Nb sample was treated and coated analogically to the cavity. To further understand the RF performance of the coated and annealed cavity, an XRR analysis of the sample was carried out at each processing step to follow the changes in the niobium native oxides at process conditions (120°C) and throughout the chemical deposition and show that the coating technique and the resulting structure form a viable way for a further tailoring of cavity properties.