In the framework of EuPRAXIA@SPARC_LAB project, we are studying possible solutions to upgrade and measure the amplitude and phase stability of the RF accelerating fields generated by a klystron. These studies concern the C- and X- band klystrons installed in the LNF infrastructures. In particular, we will present our work on a fast phase feedback around the C-band power station (50 MW klystron and solid state modulator) installed at SPARC_LAB. We are trying to push the timing jitter below the standard limit of such systems (few tens of fs RMS). A second topic is the study of the jitter of the X-band power station (50 MW klystron and solid state modulator) installed in the TEX facility. Precise measurements on amplitude and phase of this system will be reported at different positions both upstream (LLRF and pre-amp) and downstream (waveguides and prototype structure) the klystron.

In anticipation of the Eupraxia@SPARC_LAB project at the INFN Frascati National Laboratories, an intensive testing and validation activity for the X-band RF system has commenced at the TEX test facility. The Eupraxia@SPARC_LAB project entails the development of a Free-Electron Laser (FEL) radiation source with a 1 GeV Linac based on plasma acceleration and an X-band radiofrequency (RF) booster. The booster is composed of 16 high-gradient accelerating structures working at 11.994GHz. All radiofrequency components comprising the basic module of the booster, from the power source to the structure, must undergo testing at nominal parameters and power levels to verify their reliability. For this reason, since 2021, several experimental runs have been conducted to test various components in X-band technology at the TEX facility. This paper presents the results obtained thus far from the different experimental runs, and it also outlines the future upgrade of the facility, which will enhance testing capabilities and the future prospects of the facility itself.

The Advanced Photons Source (APS) storage ring (SR) underwent an upgrade to the multi-bend achromat (MBA) lattice recently. As part of the upgrade, four out of the sixteen Radio Frequency (RF) cavities were removed from the storage ring. The remaining twelve cavities were left in place during the entire upgrade process and restored to full operating power to support beam commissioning once the installation activities were completed. This paper provides details on the planning and preparations made to preserve the cavity integrity during the installation period, challenges faced while restoring the cavities and how the cavity power coupler beta values were determined.

The Normal-Conducting Radio-Frequency (NCRF) systems for the Electron-Ion Collider Hadron Storage Ring (EIC HSR) consist of 4 unique cavity resonators. The HSR NCRF systems are composed of a 24.6 MHz capture and acceleration system, a combined 49.2 MHz and 98.4 MHz bunch splitting system, and a 197 MHz storage system for collider operations. This paper presents the preliminary design of the HSR NCRF systems. We describe the unique approach taken to optimize HSR performance while limiting the total number NCRF systems, reducing the NCRF systems contributions to the total HSR impedance while reducing operating complexity.

For several years, significant effort has been spent at GSI to improve the time structure of the spill during slow extraction in SIS18. This led to the requirement to extend the possibilities to experimentally improve the micro-spill structure by partially or fully capturing the beam with an RF of more than 40 MHz. Therefore, a so-called spill-structure manipulation cavity was designed, realized and optimized which allows the mentioned experiments. In this contribution, the design of the cavity and the challenges of its realization are described, and measurement results concerning the first experimental operation in the SIS18 synchrotron are presented.

The Eupraxia@SPARC_LAB project involves the development of a 1 GeV normal conducting Linac with an S-band injector followed by an X-band booster. To achieve the final energy, the booster consists of 16 traveling wave accelerating structures operating at 11.994 GHz with a minimum working gradient of 60 MV/m. An intensive design activity, prototyping, and testing of these structures is underway at INFN-LNF. This paper comprehensively presents all the work conducted in the design and prototyping, along with preliminary test results obtained from the first RF prototype of the Eupraxia@SPARC_LAB X-band accelerating structure.

The attainable acceleration gradient in normal conducting RF accelerating structure is limited by RF breakdown, a major challenge in high gradient operation. Some of the recent experiments at the Argonne Wakefield Accelerator (AWA) facility suggest the possibility of breakdown mitigation by using short RF pulses (on the order of a few nanoseconds) to drive the accelerating structures. To understand the physics of RF breakdown on a nanosecond time scale, we simulated the dark current in few accelerating structures in both long-pulse and short-pulse regimes comparatively, and studied multiple potential breakdown initiators, including field emission and multipacting. Our simulations suggest the potential of a class of accelerators designed to work in the short-pulse regime.

For the future multi-TeV muon collider, ionization cooling is a critical step to achieve the required beam emittance for a proton-driven muon beam. Ionization cooling of intense muon beams requires the operation of high-gradient, normal-conducting RF structures in the presence of strong magnetic fields. The MAP modular cavity study at Fermilab has demonstrated the RF breakdown threshold at 13 MV/m for copper surface and 50 MV/m for beryllium surface in a 3 T solenoid B field. Based on these surface E field limits, we design a new 805 MHz copper cavity with thin curved beryllium windows that can achieve a gradient (without the transit time factor) of ~27 MV/m, which is comparable to the current 6D cooling lattice design. We also explore the distributed coupling for feeding the RF power to multiple cavities in the cooling lattice to accommodate the tight space in the superconducting solenoids. This cavity design study can be applied to the muon collider demonstrator program to experimentally evaluate the 6D muon emittance cooling.

High Q cavities are an essential component for RF pulse compression. We are interested in developing compact superconducting cavities that operate at high temperature (liquid nitrogen, 80 K). We are designing an RF cavity at 11.424 GHz operating in the TM011 mode using eight facets with flat inner faces. These flat faces will be covered with High Temperature Superconductor (HTS) tapes. The cavity fill time (one exponential step) must be 1 microsecond. That sets loaded Q at 143,558. The external Q was selected to provide this loaded Q given the high ohmic Q. Cavity beta is 39.6. The cavity is fed by a TE10 to TM01 mode converter. Wall current is completely axial, so wall current does not cross the gaps between HTS tapes. Cavity tuning is accomplished by changing the separation between cavity facets using wedges.

Future colliders will require injector linacs to accelerate large electron bunches over a wide range of energies. For example the Electron Ion Collider requires a pre-injector linac from 4 MeV up to 400 MeV over 35 m*. Currently this linac is being designed with 3 m long traveling wave structures, which provide a gradient of 16 MV/m. We propose the use of a 1 m distributed coupling design as a potential alternative and future upgrade path to this design. Distributed coupling allows power to be fed into each cavity directly via a waveguide manifold, avoiding on-axis coupling**. A distributed coupling structure at S-band was designed to optimize for shunt impedance and large aperture size. This design provides greater efficiency, thereby lowering the number of klystrons required to power the full linac. In addition, particle tracking analysis shows that this linac maintains lower emittance as bunch charge increases to 14 nC and wakefields become more prevalent. We present the design and fabrication of this distributed coupling structure, as well as cold test data and plans for higher power tests to verify on the structure's real world performance.

The present storage ring of the Siam Photon Source is equipped with the new 118 MHz capacitive type RF cavity, adapted from MAX-IV laboratory. This cavity has been installed in the ring since 2016. The cavity is operated with the digital low level RF controller and the solid-state RF amplifier. The system is running fine with less downtime and maintenance. After the full four insertion devices were added in the ring, there are instabilities detected in the beam signals. Investigation on the cavity were carried out with the simulation and measurement to characterize the higher order modes that may causes beam instabilities, especially the longitudinal modes. Simulation of the higher order modes will be presented. The modes properties from the measurements with various temperatures will also be presented. The cavity has two ports on its body reserved for the higher order modes damping mechanism. This study will be served as the baseline of the modes for the future designing of the damping mechanism.

As compared to conventional travelling-wave (TW) structures, parallel-coupled accelerating structures eliminate the requirement for the coupling between cells, providing greater flexibility in optimizing the shape of cells. Each cell is independently fed by a periodic feeding network for this structure. In this case, it has a significantly short filling time which allows for ultrashort pulse length, thereby increasing the achievable gradient. In this paper, a design of an X-band parallel-coupled TW structure is presented in detail.

Pulse compressors have been widely used to generate very high peak RF power in exchange for a reduction in the RF pulse length for linear accelerators. A C-band spherical pulse compressor is numerically studied for the linac of Super Tau-Charm Facility in this paper. Utilizing a dual-mode coupler for producing two orthogonal polarized TE11 modes, TE114 mode is chose for storing energy in resonant cavity enabling a Q0 over 1.3×105. By modulating the coupling factor to 8.6, an optimum average power gain of 4.8 can be achieved in the case of combing with a 3π/4 travelling wave accelerator. This paper concludes the optimum RF parameters of the pulse compressor, as well as the geometry tolerance is given for the next step machining.

The non-evaporable getter (NEG) coatings provide conductance-free evenly distributed pumping, low thermal outgassing rates, second electron yield, and photon-and electron-stimulated desorption. NEG coatings are crucial for achieving ultrahigh vacuum in fourth-generation diffraction storage ring vacuum systems. TiZrV thin films were deposited onto elongated CuCrZr pipes for this investigation. The influence of various deposition parameters on the microstructure and vacuum properties of NEG coatings was investigated. The microstructure, surface topography, roughness, and phase composition were evaluated using Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), Atomic Force Microscope (AFM), and X-ray Diffraction (XRD), respectively. Furthermore, the activation performance of the TiZrV films was investigated in relation to deposition parameters.

Numerical optimizations on couplers of the traveling wave accelerating structures usually require lots of calculation resources. This paper proposes a new technique for matching couplers to an accelerating structure in a more efficient way. It combines conventional Kroll method with improved Kyhl method, thereby simplifying the tuning and simulation process. We will present the detailed design of a constant-gradient C-band accelerating structure based on this new method.

A 500 MHz normal-conducting (NC) cavity is being developed for Super Tau-Charm Main Rings which have a current of 2 A and a synchronous radiation energy loss of 410 keV per turn. This NC cavity operates in a higher order mode of TM020. Through optimizations, it results in a high quality factor and a low R/Q. This feature is beneficial to reduce the required detuning frequency so that the coupled bunch instabilities (CBIs) driven by the ac-celerating mode are greatly suppressed. It employs ferrite absorbers inside coaxial slots located at the node of the TM020 mode to heavily damp all of dangerous parasitic modes except from the TM020 mode.

The Advanced Photon Source at Argonne National Laboratory (ANL) is in the process of acquiring solid state amplifiers (SSA) from R&K Limited to replace four 1MW klystron rf systems that provide rf power to the storage ring cavities. This project is necessary primarily due to klystron obsolescence. Based on present needs for the APS Upgrade, twelve 160kW SS rf amplifier systems will be required to replace the legacy klystrons. Each of the 352-MHz SSA systems consist of a rack-mounted control unit, two 85kW amplifier cabinets, four 48-way coaxial combiners, and a single 4-way waveguide final combiner. The system is designed with particular attention to reliability and redundancy to help ensure high reliability metrics for the APS-U rf system.

The upcoming High-Luminosity Large Hadron Collider (HL-LHC) program requires a beam performance in the CERN Proton Synchrotron (PS) that is at the limits of the current RF systems. Following the discontinuation of the RF tube production of the driver amplifiers a new solid-state design has been developed using radiation-hard amplifier technology. In view that the current system architecture has reached its maximum achievable gain, the goal was to reduce the cavity impedance encountered by high-intensity circulating beams. This reduction is achieved by increasing the fast feedback gain around the 10 MHz cavities. A 400W modular driver amplifier based on GaN technology and its control system have been prototyped and are currently in the testing phase. The FETs have been qualified for radiation in J-PARC and they will undergo additional irradiation time in the PS tunnel at CERN to additionally qualify the amplifier in its entirety. The paper outlines the modeling phase, the challenges encountered during prototyping, and the achieved results.

Industrial accelerator applications require efficient, scalable, continuous wave (CW) microwave power systems. Magnetrons are inexpensive and efficient devices for converting electrical energy into microwave power; however, their power output is limited to approximately 100 kW. Cost effective power combining magnetron systems would serve the accelerator industry by providing practical and affordable RF power to accelerator applications. In a magic tee configuration, two oscillators can be power combined and locked to a common frequency. Researchers at General Atomics, in collaboration with Thomas Jefferson National Accelerator Facility, have constructed an experiment to demonstrate the power combining of magnetrons in a such a configuration. An analytic model is presented describing the power combining efficiency of a 4-port magic tee, accounting for two magnetron output signals, an injection signal, and a reactive load. The Adler-Chen model is solved numerically using robust computational geometry techniques*. These complete solutions provide insight to the phenomena of magnetron frequency locking and optimal combining efficiency, which are compared to experiment.

The Mainz Energy recovering Superconducting Accelerator MESA is a multi-turn energy recovery linac with beam energies in the 100 MeV regime currently under construction at Institut für Kernphysik (KPH) of Johannes Gutenberg-Universität Mainz. The main accelerator consists of two superconducting Rossendorf type modules, while the injector MAMBO (MilliAMpere BOoster) relies on normal conducting technology. The high power RF system is relying completely an solid state technology. After some in-depth testing of a 15 kW prototype amplifier in 2017-2019 a modified version of the amplifier modules was developed. In 2020 series production has begun at JEMA France and first amplifiers, a 74 kW, a 56 kW and two 15 kW have been delivered to KPH lately. In this paper we will present the results of the performance measurements of the amplifiers.

Los Alamos Neutron Science Center (LANSCE) relies on 44 klystron modulator systems to feed the accelerating cavities and produce proton beam of 800 MeV. This paper focuses on the new VA-862A1 86kV 1.25 MW klystron units and aims to compare their performance with previously purchased units. Service hours for each klystron unit was used as the primary metric in the analysis and records from various sources cross-corroborated to confirm recorded information. Factors such as prior repair/rebuilds, factory acceptance tests and runtime notes were carefully inspected to provide a comprehensive view of the klystron performance during analysis. Klystron units currently being used in the LINAC were surveyed along with failed units and analysis performed to predict the next failure. The frequency and cause of failure was also compared with historical performance and failure data and results utilized for LANSCE SCCL performance optimization.

To meet phase stability requirements, a high peak power coaxial magnetron-based RF system with >70% efficiency would normally be injection locked to an RF source by using a circulator to send the locking signal into the magnetron through the antenna. This added requirement of a high-power circulator pushes the inherently low coaxial magnetron’s cost-per-watt to a high overall RF Power Source system cost-per- watt. For this project, the injected phase locking signal for the magnetron will use a novel input port that does not require a high- power circulator. The new input port uses the cathode stalk assembly to turn the filament-cathode into an antenna that couples to the resonant circuit of the magnetron. The coupling system between the cathode stalk, which runs at high voltage, and the RF input includes isolation for high voltage.

The National Synchrotron Radiation Research Center (NSRRC) has developed a 300 kW solid-state amplifier. This 300 kW solid-state amplifier RF transmitter has been operating continuously since August 2023, consistently delivering an output of 250 kW RF power during user beam time at 500 mA. This report describes the performance of the solid-state amplifier RF transmitter during this period, module failure rates, and specific instances of malfunction.

Efficient calculation of multi-dimensional derivatives of various performance metrics of RF sources with respect to different design parameters is a critical element of their optimization and sensitivity analysis. The direct approach is to change slightly the value of a design parameter of interest and compute the resulting change in the metric of interest; an example is a calculation of how a small change in klystron cavity spacing affect output power. The major problem with this approach is a number of required runs of a simulation code. For example, when there are many (N) design parameters of interest then (N+1) runs are required. N can be very large for detailed design of RF sources for accelerators [*, **]. By computing the solution of the adjoint of the perturbed equations for the beam-wave interaction, we have shown [***] that all N partial derivatives may be computed with only three runs of the simulation code, no matter how large (N) is. Once calculated, these partial derivatives may be used to specify manufacturing tolerances and/or used in a design optimization calculation. We will also present examples of applications of adjoint approach to klystron and TWT design.

Klystrons and Multiple-Beam Klystrons (MBKs) are widely used or proposed to be used in accelerators as high-power RF sources. Development and optimization of klystron and MBK’s designs is aided by the use of different simulation tools, including highly efficient large-signal codes. We present an overview of capabilities of the TESLA-family of 2.5D large-signal codes, which have been developed at the Naval Research Laboratory (NRL) and which are suitable for the accurate modeling of single-beam and multiple beam klystrons. TESLA algorithm does support proper treatment of ‘slow’ and ‘reflected’ particles, what enables accurate modeling of high-efficiency klystrons. Recently developed more general TESLA-Z algorithm is based on the impedance matrix approach and enabled accurate, geometry-driven large-signal modeling of devices with such challenging elements as multiple-gap cavities, filter-loading, couplers and windows. Finally, recent introduction of the reduced-order, 1.5D versions of the TESLA algorithms enabled much faster, but limited modeling options. Examples of applications of TESLA-family of codes to the modeling of advanced single-beam and MBKs will be presented.

We present new capabilities in the Neptune electromagnetic particle-in-cell (EM-PIC) simulation code and design environment created to support geometry-based design of high power RF sources. Neptune’s time-domain EM-PIC model to simulate high-voltage, high-current electron beam/RF interactions is a key component of the first-principles design codes created by NRL and Leidos, which provide a comprehensive, geometry-based approach to RF source design*. Neptune allows importing multi-part device geometry created by conventional CAD tools, which can simplify the design process for complex 3D devices. Imported CAD parts can be manipulated, modified and combined with other geometric elements as needed using a constructive solid geometry (CSG) model to create the device geometry to be used for simulation. New features of the EM-PIC model include an improved waveguide port model, with time-resolved waveguide mode diagnostics, and support for customized electron beam models. We will summarize the new capabilities and present examples of applications to high power RF sources.

Recent efforts at SLAC aim at developing high-power accelerators powered by compact, high-efficiency RF sources such as klystrons and Inductive output tubes (IOT). Stellant Systems (formerly L3Harris Electron Devices) has long pioneered the IOT design and recently leveraged its power toward various accelerator applications. In this talk, we show the progress of developing a 1.3 GHz HEIOT in terms of design, and manufacturing. We also show results of 3D space-charge beam dynamics simulation of an L-Band inductive output tube (IOT) RF electron gun using the accelerator code ACE3P as a transformative approach to HEIOT design. Based on the beam optics simulation we have designed an efficient output structure that results in >100 kW of average power with an upward of 80% power efficiency. We have designed the amplifier with special attention to cooling requirement at 100 kW including extensive thermal analysis of the anode, output structure and windows. We also commissioned a solid state driver for testing purposes. In this presentation we will discuss the progress of the amplifier build and the testing plans.

A superconducting radio frequency (SRF) cryomodule (CM) for the International Linear Collider (ILC) Technology Network (ITN) is being developed at KEK. In the scope of this, a waveguide system is being designed. Its main features are a low center of gravity, a reduced number of corners and waveguide elements, and a compact bellow for connecting it to the input power coupler. Furthermore, the waveguide layout was designed to stay within the CM. This will avoid interference between components in the case of a multi-CM assembly. It is planned to adapt both the waveguide system and the installation process for the ITN. Analytical calculations and simulations have shown that most of the reflected power is dissipated in the load of the variable hybrid on removing the circulator. Thus, in the initial layout of the waveguide, the circulator is strategically installed to allow a future replacement with an H-corner integrated with a directional coupler, without disrupting the other waveguide components. Furthermore, a low-power test on a similar waveguide system showed that analytical calculations and simulation matched the measured values well.

For achieving sufficient RF power from a solid state amplifier for accelerate particles applications usually many transistor stages need to be combined. Power levels of more than one kilowatt (kW) per transistor are state of the art for a variety of frequencies. Depending on the required total output power for multi ten kW systems a combining structure is needed. The approach of a sequential multi stage combining bears some advantages. As reflected power also plays a crucial role for the amplifies when used for particle acceleration in a cavity, we investigated the effect of a controlled short within a 6:1 smart combining structure and how it affects the reflected power into the loads in this design. The design we consider is a non-isolating combining with a circulator and load in each single transistor module so that no external customized circulators are needed for this system. Our findings illustrate that strong imbalances can occur, depending on the position of the different modules to each other. We will share experimental and simulation results on findings of a controlled short and the imbalances that can occur.

The magnetron as an efficient RF source for a compact industrial SRF accelerator has been proposed [1]. The performance of injection phase lock on two independent magnetron transmitters operated at 915 MHz, in CW mode with maximum power of 75 kW each has been demonstrated to satisfy for this application [2]. This industrial type magnetron has transformer and SCR rectifier on the DC anode power supply. Output power spectrum with phase locking can achieve noise reduction of -21 dBc at the 1st 60 Hz, -29 dBc at 1st 120 Hz with only -22.6 dBc injection power. Solenoid current increase of 16% can increase the magnetron relative natural frequency by 4e-4. Further solenoid current modulation with feedback control and the 2x75 kW power combining scheme with the WR975 magic-tee are to be further studied. We intend to use one 75 kW power station with InnoSys' switching DC power supplies to drive normal conducting and superconducting RF cavities for an industrial compact linac. We are also going to report on the 4x1.2 kW power combining experiment on the 2450 MHz magnetron system carried out at GA, including the control algorithm with modified magnetron heads with trim-coils and characterized at JLab.

The ALBA synchrotron light source is in the process of a significant upgrade, aiming to become a fourth-generation facility by reducing its emittance by at least 20 times. The initial phase of this project involves a comprehensive prototyping program designed to validate various critical technologies, such as magnets, vacuum systems, girders, etc., essential for facilitating the impending upgrade. This paper focuses on the development of the prototype magnets to implement the MBA lattice designed by our Beam Dynamics group. The lattice presents unique challenges, notably a remarkable degree of compactness necessitating magnet-to-magnet distances of just a few centimeters. Additionally, stringent strength requirements are imposed on both the quadrupolar (up to 110 T/m) and the sextupolar (up to 5000 T/m²) magnets. In this paper we will describe the design details of the initial set of resistive-type prototypes, as well as the preliminary efforts to develop alternative designs making use of permanent magnets. This dual-track approach reflects our dedication to both conventional methods and innovative solutions for the upgraded storage ring.

A quadruple wiggler consisting of a row of alternating polarity quadrupoles is used in a collinear wakefield accelerator under development at Argonne National Laboratory. We designed such a wiggler and fabricated a prototype consisting of four quadrupoles. The permanent magnet-excited quadrupole has a bore diameter of 3 mm, a length of 25 mm, and a peak magnetic field gradient of 0.94 T/mm. Fine translational and angular adjustment mechanisms were implemented in all quadrupoles to obtain better than one-micrometer alignment of the quadrupole wiggler assembly. The quadrupole wiggler prototype was measured and aligned employing the pulsed wire technique. We describe the design, fabrication, and alignment of this quadrupole wiggler prototype and describe the influence of the ambient temperature on the quadrupole wiggler alignment.

Particle accelerators use high field quality magnets to steer and focus beams. Normal conducting magnets commonly use soft iron for the yoke, which is subject to hysteresis effects. It is common practice to use an initialization procedure to accomplish a defined state of the magnet for which its hysteresis behavior must be known. In this article, a variation of the scalar Jiles-Atherton model with an improved physical basis called the Extended Jiles-Atherton (EJA) model is employed to predict the B-H trajectories in a Rapid Cycling Synchrotron (RCS) magnet. Simulations are conducted using COMSOL Multiphysics using the external material feature to integrate EJA model with the Finite Element Method (FEM). Results from the experimental studies conducted on a magnet prototype are also presented. Finally, potential improvements in the model and extension to the case of a two-dimensional anisotropic material are discussed.

The electron-ion collider (EIC) at Brookhaven National Laboratory (BNL) is designed to deliver a peak luminosity of 1e+34 1/cm2 1/sec. The EIC will take advantage of the existing Relativistic Heavy Ion Collider (RHIC) facility. Two additional rings will be installed: an electron storage ring (ESR) and a rapid cycling electron synchrotron ring (RCS). This paper presents an update on the normal conducting magnet designs required for both the ESR and RCS rings. The ESR will store polarized electron beams up to 18 GeV and utilizes a triplet of dipole magnets to increase the emittance at 5 GeV and generate excess bending to create additional radiation damping to allow a larger beam-beam tune shift. The RCS will accelerate single bunches of spin-polarized electrons at various energies from 5 GeV to 18 GeV, with a ramp rate of 100 ms and 1 Hz repetition rate. Both rings require dipole, quadrupole and sextupole magnets with different specifications.

Brookhaven National Laboratory (BNL) was recently chosen to host the Electron Ion Collider (EIC), which will collide high energy and highly polarized hadron and electron beams with a center of mass energy up to 140 GeV and a luminosity of up to 1e+34 1/cm^2/s. Part of the accelerator complex is a Rapid Cycling Synchrotron (RCS), which is planned to accelerate electrons from 400 MeV to 18 GeV. Due to the large energy range and the given circumference of the ring, the magnetic fields of the RCS magnets at injection are very low (~mT). A test dipole magnet was constructed to study differences in field quality from 5-50 mT. The paper discusses the design of the test magnet and first measurement results.

The EIC will collide high energy and highly polarized hadron and electron beams with luminosities up to 1e+34 /cm^2/s. Bremsstrahlung photons from the Bethe-Heitler process at the interaction point (IP) need to be counted to determine the delivered luminosities. The pair spectrometer luminosity detector utilizes photon conversions (e+ and e- pairs) in the far-backward region. A sweeper dipole magnet was designed to sweep away the photon conversions that occur at the thick exit window. An analyzer dipole magnet was designed with an integrated field of 1.13 T*m to deflect the electrons and positrons that will be analyzed by the tracker and calorimeter detectors. Both magnets were designed and simulated using the 3-dimensional (3D) finite element method (FEM). The effects of notch size and locations on the iron yoke to the magnetic field quality were studied. The tracker performance, including tracker position resolutions and tracker energy resolutions, were analyzed based on the field map of the designed dipole magnets.

The ESRF-EBS injection is performed with a standard off-axis injection scheme consisting of two in-air septa S1/2, one in vacuum septum S3 and four kicker magnets K1 to K4 to generate the injection bump. We can achieve 80% efficiency with this scheme. Despite many modifications and adjustments which allow the reduction of the perturbation, some beamlines are still affected. The Non-Linear Kicker could be a solution to this problem because it acts only on the injected beam. This paper reports on the magnetic design of the Non-Linear Kicker, including the octupole like Magnetic field simulations, magnetic forces calculations and mechanical tolerance optimizations.

The nonlinear integrable optics studies at the integrable optics test accelerator (IOTA) demand fine control of the chromaticity using sextupole magnets. During the last experimental run undesirable misalignments and multipole composition in some sextupole magnets impacted operations. This report outlines the beam-based methods used to identify the nature of the misalignments and defects, and the subsequent magnetic measurements and remediation of the magnets for future runs.

The Rapid Cyclotron Synchrotron (RCS) is an acceleration ring designed for boosting the electron energy from 400 MeV after the LINAC to 1 GeV prepared for injection into the Electron Storage Ring (ESR). Operating in a pulsed mode at 1 Hz, the RCS accelerates four consecutive bunches with dipole magnet ramping rapidly at each injection. Rapid ramping of the magnetic field induces eddy currents, causing delays and high harmonic effects which are detrimental to low-energy electron bunches. To mitigate this, cost-effective multi-turn coils with specific patterns are proposed. These coils, powered by eddy currents from main dipole field ramping, generate counter fields to cancel selected high harmonic components. This paper explores the coil pattern selection process.

In the framework of the SABINA project (Source of Advanced Beam Imaging for Novel Applications), a new Free Electron Laser line will be realized at the Laboratori Nazionali di Frascati (LNF). It will be based in the SPARC_LAB laboratory with the purpose to supply radiation in the Thz/MIR range to external user. The line layout foresees two correctors between the three APPLE-X undulators devoted to providing angular and position offset correction to the beam aiming to maximize the efficiency of the FEL process. They will steer the electron beam both in the X and Y axis at the mrad level, and they will be integrated with Beam Position Monitors to perform the trajectory correction and the position monitoring at the same point. This paper presents the magnetic design of the two correctors performed by OPERA 3D software, the mechanical design, the manufacturing together with the magnetic measurement performed at the magnetic laboratory facility in LNF using a Hall probe system.

To reduce the electric power consumption and advance the magnetic stability, a prototype of BTS dipole magnet in TPS transfer line between booster and storage ring came into sight. An 1 m long, high current dipole will be replaced by a permanent magnet with Sm2Co17. The new permanent dipole magnet will decrease total volume compared with original electric one, and the homogeneity of integral field is promoted as well. With simulation, the assembly deviation was also discussed. This article presents the magnet circuit design status of prototype to upgrade the transport line in TPS.

A 4th generation storage ring based light source is being developed in Korea since 2021. It features <100 pm rad emittance, about 800 m circumference, 4 GeV e-beam energy, full energy booster injection, and more than 40 beamlines which includes more than 24 insertion device (ID) beamlines. For extraction/injection to the booster and storage ring, it needs 4 septums, and 6 kickers. Particularly, for SR injection needs an eddy current septum with 1 mm septum thickness for 10 mrad bending, and a thick septum with 5 degree direct current driven septum. In this report, the design of the injection magnets (kickers, septums) for Korea-4GSR will be discussed.

Fourth-generation synchrotron radiation sources, which are currently being planned in several accelerator laboratories, require fast orbit feedback systems to correct distortions in the particle orbit in order to meet stringent stability requirements. Such feedback systems feature corrector magnets powered at frequencies up to the kilohertz range, giving rise to strong eddy currents. To understand the eddy current effects and the characteristics of these fast corrector magnets, elaborate finite element simulations must be conducted. This paper gives an overview of the most important findings of our simulation studies for the fast corrector magnets of the future synchrotron radiation source PETRA IV at DESY, Hamburg, Germany. Using a homogenization technique for the laminated yokes, we simulate the magnets over a wide frequency range.

Conceptual studies for a muon collider identify fast-ramping magnets as a major design challenge. Rise rates of more than 1 T/ms are attainable with normal-conducting magnets, incorporating iron yokes to make sure that stored magnetic energies and inductances stay below reasonable thresholds. Moreover, for energy efficiency, the magnets need to exchange energy with capacitors, such that the electric grid only needs to compensate for the losses. The design of such magnet systems is based on two- and three-dimensional finite element models of the magnets coupled to circuit models of the power-electronics equipment. The occurring phenomena necessitate nonlinear and transient simulation schemes. This contribution presents the analysis of a two-dimensional, nonlinear and time transient analysis of a bending magnet, energized by a symmetrical current pulse of a few ms.The magnet yoke is represented by a homogenized material refraining from the spatial discretization of the individual laminates, but nevertheless representing the true eddy-current and hysteresis losses.

Research on a novel permanent quadrpole magnet (PQM) design is introduced in this paper. It can make the quadrupole magnetic field gradient continuously adjustable by modulating several permanent magnet blocks. Four poles of the magnet inform an integral whole to ensure good structural symmetry, which is essential to obtain high-quality quadrupole magnetic field permanent quadrupole magnet. Series of simula-tion calculations have been done to study the effects of four distinct types of pole position coordinate errors on the central magnetic field. By juxtaposing these results with those derived from optimal design scenario of PQM, the study underscores the critical role that pole symmetry plays in this context. Two integrated design methodologies were proposed, with one of the designs undergoing processing and coordinate detection. The results indicate that this design, is capable of meeting the specified requirements. This design effectively ad-dresses the issue of asymmetrical pole installation, thereby ensuring to a certain extent that well-machined pole can generate a high-quality magnetic field.

A failure of the RHIC powering system occurred at the end of run 23 and led to the discovery of ruptured con-ductors on the 12x150A current leads used to feed cur-rent to the superconducting (SC) magnet circuits. These ruptured conductors are thought to have led to an electri-cal breakdown, first within the solder joint, and then across adjacent conductors of the same current lead assembly. A fatigue experiment has been set up to study the behavior of Sn96Ag4 solder joints under cycling load at cryogenic temperature. Mitigation measures to mini-mize further fatigue cycling have been implemented for the next RHIC run and will be discussed. This paper aims to describe our understanding of the solder joint cracking issue encountered and present the mitigation measures for future RHIC operation.

The stress-strain state of the titanium foils of the accelerator output windows at various thicknesses was studied with the choice of first-grade titanium foil as a brand. The latter is more affordable and accessible compared to a second-grade titanium foil. The deformation diagram, density, Young's modulus, and Poisson's ratio of the first-grade titanium were selected as initial data. Atmospheric pressure was used as an external pressure, and the pressure from the vacuum side was taken as zero. The latter is acceptable in simulations of ultrahigh vacuum assemblies since it does not affect the overall picture of the stress-strain state. In addition to studying the central nodes of the metal foil, the sealing nodes were also considered as an object of research, with the study of stress intensity, meridional and circumferential stresses, and maximum displacements of the center. Based on the results, a function was obtained that allows us to accurately calculate the displacements of the center of the first-grade titanium foil depending on its thickness. The analysis of the received data was carried out.

This study examines Laser Engineered Surface Structures (LESS) in the context of their potential application within particle accelerators. These structures are investigated due to their efficient reduction of secondary electron yield to counteract the formation of electron clouds, a phenomenon detrimental to accelerator performance. A critical aspect of their evaluation involves understanding their radio-frequency characteristics to determine their influence on beam impedance. LESS involves intricate surface modifications, integrating etched grooves and deposited particulates, resulting in a complex surface topology. Measurements are conducted on two distinct surface patterns, from which particulates are then removed with incremental cleaning. Acquired data form the basis for mathematical models elucidating observed results. Novel approaches are investigated in addition to several established surface roughness models, including analysis of geometrical attributes of the surface topology and the associated electric currents. The aim is to develop a framework that describes roughness's influence across varying scales to assist in selecting appropriate treatment parameters.

As part of the Electron-Ion Collide (EIC) upgrade at Brookhaven National Laboratory (BNL), the development of new beam screens for the vacuum system is underway. The mechanical design of the beam screens received support from CERN, particularly in addressing the mechanical response during a magnet quench, i.e. a resistive transitions in the superconducting magnets. Maintaining an overall elastic behavior in this component is crucial for the efficient functioning of the collider. The mechanical behavior of the EIC beam screen during a quench was initially analyzed using analytical methods and subsequently validated through a Multiphysics FEM model developed for the High-Luminosity LHC (HL-LHC) beam screen. The FEM model underwent an initial verification against analytical formulations in its simpler 2D magnetic-based version. Following this, thermal and mechanical physics were fully coupled with the magnetic model in a 3D framework. Various features, including partial weld penetration, pumping holes, and guiding rings, were then taken into consideration. Additionally, the plastic behavior of the beam screen materials was considered too. The assessment included an analysis of the maximum deformation and stress experienced by the EIC beam screen during a magnet quench, resulting in an overall elastic response for the proposed design.

A new accelerator facility (FAIR) is currently being built at GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany. The FAIR accelerator facility will consist of various beam lines, which provide different functions and experiments using various particle beams (ions, proton and anti-protons). Due to unprecedented circumstances, the FAIR project is currently divided into several design phases. The first priority of the design phase (referred to as “Early Science”) is focused on the high energy beam transfer (HEBT) and Super Fragment Separator (SRFS) beamlines. To ensure the vacuum compatibility of these beam lines, vacuum acceptance tests of various prototypes and first of series of vacuum components are carried out before installation to the accelerator. This work will present some of the latest results of the vacuum acceptance tests for HEBT vacuum tubes produced in-house at GSI, the first of series of SFRS Slit vacuum parts and SFRS multiplet vacuum tubes.

Modification of an arc-cell vacuum system (length 14 m) for the cell SR18 in the TPS storage ring is described, which includes (a) replacement of a new bending chamber (B1) with an increased vertical aperture from 9 to 18 mm to prevent the B1 chamber from being exposed to synchronous radiation from the upstream elliptically polarized undulator (EPU), and (b) incensement of three pairs of flanges to separate the old arc-cell vacuum system into four subsystems (S3, B1, S4, B2). In this paper, we will report the manufacturing processes, measurement data and vacuum tests of these vacuum chambers.

The Taiwan photon source (TPS), a synchrotron accelerator at the National Synchrotron Radiation Research Center in Taiwan, is a third-generation accelerator operating at 3 GeV that was designed to create a high energy photon source. The TPS front-end (FE) systems are located between the storage ring and beamline, which was designed to protect the safety of users as well as control experimental requirements. As the FE vacuum pressure influences the storage ring and beamline vacuum pressures, the FE vacuum systems must maintain a low dynamic pressure. Therefore, at the beginning of FE system construction, each FE vacuum system is baked at 200°C for 24 hours. Next, when the FE systems need to be upgraded or maintained lead to vacuum interventions, it must also be baked for 24 hours to recover a low dynamic pressure. However, the 24 hour baking process requires manpower support on-site owing to facility safety in the TPS tunnel. The maintenance of the FE systems takes two duty days. Therefore, reducing baking time is necessary in the TPS facility. The beam cleaning efficiency after reduced baking time has been described in this paper.

A setup of in-house made Goubau (G-) Line system for measuring the broadband impedance of vacuum components has been developed at the NSRRC for improving the beam-stability of the Taiwan Photon Source (TPS). A thin copper wire of 0.287 mm in diameter with polyimide-coating ~0.02 mm in thickness connects two horn-shape aluminum launchers face-to-face at a distance ~1.2 m far in between via two impedance-matching copper tapers welded on both ends of the wire that transports the surface waves through the vacuum duct under test (DUT) allocated at the middle of wire. Measurement of time domain reflection (TDR) for the G-Line has verified the systematic performance of matching the impedance of 50 ohms. A vector network analyzer measures the transmission parameters of S21 of the DUT from the G-Line that the longitudinal impedance of DUT can be obtained. Various DUTs of vacuum components e.g. flanges without gasket were measured for inspecting the G-Line performance, besides, the special designed aluminum gaskets with rf-shielding property sealed flanges were also inspected that must feature with ultra-low impedance. The detail design and the test results of the G-Line will be described.

A new charge selector is currently under development at FRIB to intercept unwanted charge states of higher-power 17 - 20 MeV/u stripped heavy ion beams. The charge selector is located in the first bending segment of the FRIB linac, where high dispersion separates charge states to allow for their selection. The design concept is based on rotating graphite cylinders that act as an intermediate heat transfer medium, efficiently absorbing beam power and radiating it to a water-cooled heat exchanger. The power in the beam spot of up to 5 kW and the rms spot width as small as 0.7 mm present significant design challenges. Beyond thermal stress, the proposed design addresses the effects of radiation damage and implantation of the intercepted ions. The challenges of the engineering design associated with high temperatures, thermal expansion, rotation and linear actuation feedthrough into vacuum, as well as radiation shielding and remote handling, will be discussed. A comprehensive exploration of these challenges aims to contribute to the broader field of beam interception technology.

Generating low emittance electron bunches from the photocathodes backing free-electron lasers (FEL) is a potential source of significant improvement in achievable X-ray peak powers. Temporally shaping the photoexcitation lasers with intensity profiles that are perfectly flattop or ellipsoidal has been demonstrated to improve the emittance of the emitted electron bunch. However, experimental techniques to achieve these profiles have not been demonstrated at the high-energy, high-repetition rate conditions required by next-generation XFELs, such as LCLS-II(HE). We present an experimental demonstration of the dispersion controlled nonlinear synthesis (DCNS) technique* which has been shown in theory to produce emittance-reducing laser profiles under these conditions. Our implementation generates 20 picosecond pulses in the ultraviolet with a flattop intensity profile. We compare the simulated emission of electron bunches to the currently implemented Gaussian temporal profiles and the performance of LCLS-II XFEL with electrons generated from both laser profiles. Finally, we suggest methods to adapt DCNS to non-uniform shaping and for lasers using other nonlinear conversion processes.

Transparent off-axis injection in a storage ring by means of a non-linear kicker requires tight field tolerances at the limit of modern technique. To characterize the field profile of the non-linear kicker under development for the ALBA-II storage ring, a dedicated measurement bench based on a variant of the vibrating wire technique was developed. The small size and limited weight of the kicker magnet under study allows for some unusual solution which substantially simplify the set-up. Field mapping is obtained by scanning the magnet aperture, while keeping the wire steady, simplifying considerably the wire tensioning system. The wire is suspended vertically in a pendulum configuration eliminating the wire sagging problem and resulting in an inherently stable wire tension. Furthermore we investigate the possibility to characterize time dependent phenomena, such as the effect of eddy currents induced in the titanium coating of the magnet vacuum chamber, by using using an etherodyne approach where the magnet and the wire are excited by a continuous wave signal with period close to the characteristic kicker pulse period and differing in frequency by the wire resonance frequency

The European LEAPS-INNOV project has launched a Research and Development program dedicated to the design of a new generation of germanium detectors for X-ray spectroscopy applications. The present article shows the results of the thermomechanical simulations of this design, based on finite element analysis (FEA) studies, under vacuum and cryogenic conditions. The first results of these simulations were published at IPAC'23*. In this new work, the final results are presented, which includes the thermal optimization of the detector with respect to the previous study, as well as new numerical simulations to investigate the effects of vibration transmission from the cryocooler to the head detector.

Within the field of Particle Accelerators engineering, the design of cooling channels for its components has heavily relied on experimental correlations to compute convective heat transfer coefficients. These coefficients are believed to have a conservative factor which end up in oversized designs. The following study assesses this conservative factor for fully developed flows, in the laminar, turbulent and transition regimes. It will also focus on different geometries to do so. With this objective in mind, simulation models have been developed and correlated with experiments carried out at ALBA synchrotron. In the course of this research, various turbulence models and meshes have been examined for the development of the simulations. Heat transfer coefficients were derived from the Computational Fluid Dynamics (CFD) simulations and juxtaposed with empirical correlations. The specific geometries under investigation encompass a circular channel with a 10mm inner diameter, a rectangular section channel, and a pinhole geometry, the latter being frequently employed in accelerator technology.

Ultrafast Microscopy using MeV beam has made significant progress in the past 5 years. However, in order to push to atomic level resolution, other than the requirements of beam source, there are also high demands in high strength focusing elements. In comparison of commercial 100s KeV level electron microscopes, an MeV imaging beamline requires Tesla level lenses, preferably round solenoid lens. Tesla class DC solenoids are prohibitively bulky and heavy, and superconducting solenoids are not cost effective. We have developed a novel miniature flux concentrator based solenoid lens system for MeV UED/UEM applications. It can reach 2-Tesla with 1e-5 level stability (depending on the pulsed current source). Here we will present detailed development process and experimental results.

The LHC Abort Gap Monitor (AGM) is part of the LHC machine protection system (MPS) and is designed to measure the particle population in a 3us wide region known as the "abort gap." This region needs to be kept empty to ensure safe beam dumps. The AGM captures the synchrotron light generated in the visible part of the spectra and converts it into an electric signal. This signal is then processed by an acquisition system and can trigger the ‘abort gap cleaning’ process. The current AGM, which has been in operation since 2010, uses an analogue integrator ASIC and a 40 MHz analogue-to-digital (ADC) converter to provide the particle population information. However, this solution is now considered obsolete and is being replaced by a digital signal processing approach. Working directly in the digital domain not only offers more scalability but also better determinism and reliability. This work presents the new technical solution for the acquisition chain, compares the characteristics of both implementations, and showcases recent measurements conducted on the LHC ion beams.

An 820 mA CW positive ion source is being developed to produce Mo-99 using the fusion of deuterium and tritium ion beams on a rotating target to produce neutrons for use in the production of radiopharmaceuticals. The ion source consists of an RF plasma source, a multi-aperture extractor, and 300 kV accelerating column. This paper will describe a simulation study of the beam through the extractor grid and the accelerator to the target. The uniformity of beam distribution on the target is an important aspect of the simulation.

NanoSonic has demonstrated advanced high radiation durable composite and polymeric materials for applications in radio frequency devices, cryomodule gate valves, and seals for beam dumps. Through additive and scalable manufacturing techniques, the novel radiation tolerant polymers for use within accelerator components and subsystems have shown potential to replace current state of the art materials which degrade through radiation induced brittle failure and other failure mechanisms. NanoSonic’s composites have undergone both shielding and exposure radiation testing at low doses of proton, iron, and electron irradiation (up to 27 Gy) and are currently being tested for ultra-high radiation exposure (up to 20.0 MGy). No remarkable mechanical changes have been observed after low dose testing for NanoSonic’s materials. These novel composite materials will reduce maintenance and replacement frequency offering the potential for significant cost reductions and operational downtime.

Paul Scherrer Institute (PSI) has led significant advancements in accelerator electronics development, leveraging Field Programmable Gate Arrays (FPGA) based Digital Signal Processing (DSP) across various critical systems, including Low Level RF (LLRF), Longitudinal Beam Loss Monitoring (LBLM), charge particle measurement via Integrating Current Transformers (ICT), Timing, Filling Pattern Monitor (FPM), Beam Position Monitor (BPM) and other essential beam instruments. Over the past decade, PSI’s approach to develop in-house control system platform (e.g. CPCI-S.0), has encouraged innovation. The strategic reorganization within PSI, fostering collaboration among FPGA firmware engineers, led to the inception of Open-Source FPGA DSP libraries hosted on GitHub. Serving as a comprehensive repository, these libraries empower developers by providing common FPGA IPs, fundamental DSP algorithms and Fixed-Point (FP) arithmetic units. Their presence advances prototype development by enabling rapid assembly of several measurement and or control concepts. In this contribution, we present the features and the transformative impact of the PSI Open-source FPGA libraries with a focus on LLRF. This initiative has not only empowered our team to provide valuable insights, but has also streamlined the integration of new recruits and students, enabling the seamless continuation of FPGA design frameworks.

The accelerator network of the Pohang Accelerator Laboratory (PAL) was initially designed and installed in 2015. It consists of three types of networks: a Public Network for external internet access, an Operation Network for accelerator operation and overall control, and a Control Network for device control and monitoring. From a hardware perspective, it comprises 2 firewalls, 1 intrusion prevention system, 4 backbones, 36 office network switches, and 77 switches for gallery and tunnel networks. Each network is physically or logically separated, and the backbone, serving as the main equipment, is configured in a redundant manner to prepare for failures

In this work, we will present some recent analysis of the reliability statistics of the CEBAF SRF linac systems. Based on the data collected by the existing Down Time Manager (DTM), the year-to-year downtime evolution trend of linac zones over the six-year period from FY18 to FY23 is established. An in-depth downtime analysis at a resolution beyond the linac zone level was carried out, by introducing an alternative system hierarchy consisting of the SRF linac sub-systems and components. This new paradigm was implemented in a pilot downtime study over the two-month period of CEBAF operation from 9/13/23 to 11/13/23, enabling localization of the responsible sub-systems (SRF, HPRF, LLRF, Beamline vacuum, Cryogenics, etc.) and hardware components (cavity, tuner, RF coupler, etc.) in the CEBAF SRF linac systems. Pinpointing downtime sources at the sub-systems and component levels holds the key to improving the CEBAF SRF systems reliability. It also helps identify areas of SRF technology development needed by future high-power high-reliability CW SRF linacs.

Field emission (FE) and vacuum arcs limit the maximum achievable accelerating field of both normal and superconducting cavities. The performance of accelerating cavities can be improved after a long conditioning process. Understanding this process and the formation of vacuum arcs is important for all technologies where vacuum arcs cause device failure. The understanding could be more complete with novel diagnostic tools and tests in variable environments. The cryogenic HV system in FREIA laboratory is used to study different aspects of conditioning using DC pulses at a wide range of temperatures, down to 4K. We are currently measuring FE currents during conditioning for Cu, Nb and Ti electrodes in function of temperature and breakdown rate. We are also developing a new characterization method, evaluating the surface resistivity of the electrodes during conditioning. Changes in the surface resistivity could indicate the formation of dislocations below the surface, which has been speculated to be a very important process behind conditioning. We will present the results of conditioning with the FE measurements and the surface resistivity measurements.