The polarized pre-injector for the Electron-Ion Collider is intended to produce four bunches every second, each containing 7 nC, with 85% polarization along the longitudinal axis, for injection into the Rapid Cycling Synchrotron. The pre-injector consists of a polarized electron source, bunching section, longitudinal phase space manipulation, and SLC-Type LINAC. To reduce energy spread and increase bunch length, a compact zig-zag chicane and dechirp cavity rotate the bunch in longitudinal phase space. In this paper, we will discuss the progress of recent pre-injection design and RF frequency selection. Additionally, we will examine the effects of wakefield, as well as coherent and incoherent synchrotron radiation on beam quality.

The status of commissioning of the electron injector intended for the next phase of the proton driven wakefield experiment (AWAKE) is presented, showing first experimental results from operating the brazing-free electron gun. To provide a high-quality electron beam, the UV laser was centered on the copper cathode, and a novel simplex and beam-based alignment of the focusing solenoid was performed. Measurements of the beam parameters and working points are addressed. The electron gun is shown to provide a high quality, stable and reproducible beam.

The Round to Flat Beam Transformation (RFBT) is one of the emittance exchange techniques that can improve the Luminosity for the future accelerator project International Linear collider (ILC). RFBT experiment can be conducted in the KEK-STF, and the expected performance is 334 in emittance ratio. In December 2023, we performed a pilot experiment at STF to optimize the injector conditions. To improve the RF Gun of STF, we applied dry ice cleaning to reduce the field emission. The field enhancement factor was improved from 233 to 100.

The Electron Ion Collider design strategy for reaching unprecedented luminosities and detection capabilities involves collision of flat bunches at a relatively large crossing angle. Effective head-on collisions are restored using crab cavities, which introduce a correlation of the particles' transverse coordinates with their longitudinal positions in the bunch, or crab dispersion. The collision geometry is further complicated by a tilt of the Electron Storage Ring plane with respect to that of the Hadron Storage Ring. In addition, the interaction point is placed inside the field of a detector solenoid. Reaching the design luminosity requires precise control of the 6D bunch distribution at the IP accounting for all of the aforementioned design features. This paper describes correction of the detector solenoid effect on the beam optics of the Hadron Storage Ring using a combination of local and global skew quadrupoles.

The injector section of the SHINE device is currently in the debugging phase. The electron beam energy in the injector section is low and is significantly affected by the geomagnetic field, with an intensity of approximately 250 milligauss. Through theoretical optimization, adjustments to the positions and intensity parameters of helical coils and corrector magnets are being made to significantly reduce the growth of beam emittance under the influence of the geomagnetic field. The aim is to optimize the beam quality of the injector section of the SHINE device based on this model.

We present an initial capture concept for the continuous wave (CW) polarized positron beam at the Continuous Electron Beam Accelerator Facility (CEBAF) upgrade at Jefferson Lab. This two-step concept is based on (1) the generation of bremsstrahlung radiation by a longitudinally polarized electron beam (1 mA, 120 MeV, >90% polarization), passing through a tungsten target, and (2) the production of e+e- pairs by these bremsstrahlung photons in the same target. To provide highly-polarized positron beams (>60% polarization) or high-current positron beams (>1 μA) with low polarization for nuclear physics experiments, the positron source requires a flexible capture system with an adjustable energy selection band. The results of beam dynamics simulations and calculations of the power deposited in the positron capture section are presented.

An electron beam degrader is under development with the objective of measuring the transverse and longitudinal acceptance of the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab. This project is in support of the CE+BAF positron capability. Computational simulations of beam-target interactions and particle tracking were performed integrating the GEANT4 and Elegant toolkits. A solenoid was added to the setup to control the beam's divergence. Parameter optimization of the solenoid field and magnetic quadrupoles gradient was also performed to further reduce particle loss through the rest of the injector beamline.

We present an update on the design of the Interaction Region (IR) for the the Electron Ion Collider (EIC) being built at Brookhaven National Laboratory (BNL). The EIC will collide high energy and highly polarized hadron and electron beams with a center of mass energy up to 140 GeV with luminosities of up to 10^34 /cm^2/s. The IR, located at RHIC's IR6, is designed to meet the requirements of the nuclear physics community as outlined in [1]. A second IR is technically feasible but not part of the project. The magnet apertures are sufficiently large to allow desired collision products to reach the far-forward detectors; the electron magnet apertures in the rear direction are chosen to be large enough to pass the synchrotron radiation fan. In the forward direction the electron apertures are large enough for non-Gaussian tails. The paper discusses a number of recent recent changes to the design. The machine free region was recently increased from 9 to 9.5 m to allow for more space in the forward direction for the detector. The superconducting magnets on the forward side now operate at 1.9 K, which helps crosstalk and space issues.

The Electron Storage Ring (ESR) of the Electron-Ion Collider (EIC) to be built at Brookhaven National Laboratory will provide spin-polarized electron beams at 5, 10, and 18 GeV for collisions with polarized hadrons. Electron bunches with polarizations parallel and anti-parallel to the arc dipole fields will co-circulate in the ring at the same time, and each bunch must be replaced once it is sufficiently depolarized by synchrotron radiation. In this work, we detail the unique challenges posed by designing such a collider ring to operate at different energies, and their solutions. This includes satisfying spin matching conditions, calculating optimal energies for polarization, determining best figures-of-merit, maintaining high polarization without a traditional longitudinal spin match, restoring the spin match with random closed orbit distortions, and implementing global coupling compensation and vertical emittance creation schemes that preserve high polarization. Nonlinear tracking results are presented showing polarization requirements are exceeded.

We are researching the development of an ultra-high intensity heavy ion source based on laser ablation ion source (LIS) technology coupled with a unique beam injection technique called Direct Plasma Injection Scheme (DPIS). A metallic target is ablated using a Q-switched Nd:YAG laser to generate a pulsed high-density plasma, which is then injected and accelerated by a radio-frequency quadrupole (RFQ) linear accelerator. The ion source enables the production of rare isotopes, the use of particle beams in cancer treatment, and nuclear physics experiments. The exploration of multiple charge states for Mg production is currently underway. The measurement of beam current is conducted using a Faraday cup positioned at the end of the beam line. Following the RFQ acceleration, the beam is transported by multiple quadrupole magnets and a steerer, and a dipole magnet then directs the beamline into the Faraday cup. Notably, we have accomplished an ion beam current of about 20 mA for Mg10+ ions and a current exceeding 10 mA for fully stripped Mg12+ ions. In this presentation, I will discuss the operation of the LIS at Brookhaven National Laboratory (BNL) and the outcomes of Mg ion production.

The physical realization of integrable Hamiltonian dynamics provides promising avenues for investigations of new particle accelerators, best demonstrated by the Integrable Optics Test Accelerator (IOTA) at Fermilab. The core concept of IOTA centers around the results of the Danilov-Nagaitsev paper, where taking the paraxial approximation of the Hamiltonian for a charged particle can lead to a completely integrable system for a charged particle in the transverse plane. However, certain generalizations of that paper fail to provide similar results. We provide insights into some reasons for failure, as well as discuss a set-up for establishing a 6D integrable Hamiltonian system, in order to include the possibility of acceleration.

The utilization of laser modulation techniques shows potential in producing sub-femtosecond electron beams within photoinjector electron guns. The precise spatial alignment between the modulated laser and electron beam is crucial for the stable emission of sub-femtosecond electron beams. In practical applications, inevitable lateral positional fluctuations are present in both the modulated laser and electron beam pulses, resulting in uneven and suboptimal modulation effects of the laser on the electron beam. Photocathode electron guns commonly utilize solenoid focusing for transverse electron beam concentration, inducing transverse phase space coupling and causing the laser-induced transverse jitter in the electron gun to not accurately reflect the transverse jitter of the electron beam. This study seeks to employ coherent lasers and devise a solenoid coil to disentangle the transverse phase space of the electron beam, ensuring that the transverse jitter of the electron beam aligns with the jitter of the modulated laser at the focal point.

Muon colliders hold promise for high luminosity multi-TeV collisions, without synchrotron radiation challenges. However, this involves investigation into novel methods of muon production, acceleration, cooling, storage, and detection. Thus, a cooling demonstrator has been proposed to investigate 6D muon ionization cooling. The MICE experiment validated ionization cooling to reduce transverse emittance. The demonstrator will extend this to also cool longitudinal emittance. It would also use bunched beams instead of single particles from a muon source. The 6D cooling lattice comprises successive cells which consist of: solenoids for tight focusing, dipoles to introduce dispersion in the beam, wedge-shaped absorbers for differential beam absorption, and RF cavities for reacceleration. In this paper, the simulation and further optimization of the rectilinear cooling channel is discussed. This analysis extends existing theoretical and numerical work using BDSIM, a Geant4-based accelerator framework built to simulate the transport and interaction of particles. The study also incorporates beams from existing proton drivers, using output from targetry and capture designs for the same.

The PSI Positron Production experiment, known as P\textsuperscript{3} or \textit{P-cubed}, is a proof-of-principle positron source and capture system that can greatly improve the state-of-the-art positron yield. The P\textsuperscript{3} project is led by the Paul Scherrer Institute in Switzerland, and addresses the long-standing challenge faced by conventional injector facilities to generate, capture, and damp the emittance of high-current positron beam, which is a major limiting factor for the feasibility of future electron-positron colliders. P\textsuperscript{3} follows the same basic principles as its predecessors, utilizing a positron source driven by pair-production and an RF linac with a high-field solenoid focusing system. However, it incorporates pioneering technology, such as high-temperature superconducting solenoids, that can outperform significantly the present positron capture efficiency rates. The P\textsuperscript{3} experiment will be hosted at PSI's SwissFEL, and will serve as the positron source test facility of CERN's FCC-ee. This paper outlines the concept, technology, infrastructure, physics studies and diagnostics of P\textsuperscript{3}.

We present the optics design of the solenoid compensation scheme at the FCC-ee. The 2T solenoids from the experiments induce coupling on the beams, generating an increase on vertical emittance. This compensation scheme minimizes emittance growth, with a final value of approximately 5% of the nominal.
 A screening solenoid is placed around the Final Focus Quadrupoles to protect them from the experiment’s field. 
A skew quadrupole component is added to the Final Doublet, aligning the magnet axis to the rotated reference frame of the beam. 
Two anti-solenoids placed approximately ±20 m from the IP are used to cancel the field integral. The vertical orbit generated by the horizontal crossing angle in the detector field is compensated by vertical correctors placed right after the beam pipe separation and next to the final focus quadrupoles.
 We describe the IR optics in this scheme, including the detector solenoid and the magnetic elements used for compensation.

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.

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.

In the final cooling stages for a muon collider, the transverse emittances are reduced while the longitudinal emittance is allowed to increase. In previous studies, Final 4-D cooling used absorbers within very high field solenoids to cool low-momentum muons. Simulations of the systems did not reach the desired cooling design goals. In this study, we develop and optimize a different conceptual design for the final 4D cooling channel, which is based on using dense wedge absorbers. We used G4Beamline to simulate the channel and Python to generate and analyze particle distributions. We optimized the design parameters of the cooling channel and produced conceptual designs (corresponding to possible starting points for the input beam) which achieve transverse cooling in both x and y by a factor of ~3.5. These channels achieve a lower transverse and longitudinal emittance than the best design previously published.

The storage ring from the SLS is currently in the process of a significant upgrade to a new multi-bend achromat that aims to improve the performance of the machine by allowing it to deliver even brighter beams to the beamlines. The linear accelerator of the SLS is an ageing piece of infrastructure that needs to continue to run for the few decades to continue to feed SLS 2.0 reliably. In this work, we investigate potential upgrades to the linac with the aim of reducing the overall complexity of the system.

The Micro Electron Diffraction for Ultrafast Structural Analysis (MEDUSA) beamline is a 140 keV ultrafast electron diffraction (UED) beamline currently operational at Cornell. The MEDUSA beamline specializes in the study of small samples, with electron beam probe sizes down to the single micron scale. These samples can be pumped by lasers with wavelengths ranging from IR to UV. In this proceeding, we discuss the upgrades made to MEDUSA, with a focus on a pair of foil wound solenoids we built for post sample magnification of the resulting diffraction patterns, and a measurement of their aberrations. Additionally, we detail the cryogenic compatibility changes made to allow the study of samples down to liquid nitrogen temperatures.

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

Muon production in the multi-TeV muon collider studied by the International Muon Collider Collaboration is planned to be performed with a high-power proton beam interacting with a fixed target. The design of the target area comes with a set of challenges related to the radiation load to front-end equipment. The confinement of the emerging pions and muons requires very strong magnetic fields achievable only by superconducting solenoids, which are sensitive to heat load and long-term radiation damage. The latter concerns the ionizing dose in insulation, as well as the displacement damage in the superconductor. The magnet shielding design has to limit the heat deposition and ensure that the induced radiation damage is compatible with the operational lifetime of the muon production complex. Finally, the fraction of the primary beam passing through the target unimpeded poses a need for an extraction channel. In this study, we use the FLUKA Monte Carlo code to assess the radiation load to the solenoids, and we explore the possible spent proton beam extraction scenarios taking into account the constraints stemming from the beam characteristics and the required magnetic field strength.

Ionization cooling stands as the only cooling technique capable of efficiently reducing the phase space of a muon beam within a short time frame. The optimal cooling parameters of a muon collider aim to minimize transverse emittance while simultaneously limiting longitudinal emittance growth, resulting in optimal luminosities within the collider ring. This study shows that achieving efficient cooling performance requires selecting the best initial muon beam parameters. Because for every transvere emittance there exist an optimal beam energy for ionization cooling. We present a technique that enables the determination of these optimal initial parameters through simulations and compare them with an improved analytical scattering model.

Achieving the low emittances necessary for a muon collider requires ionization cooling. Much of that cooling occurs in compact cooling cells where superconducting coils and conventional RF cavities are closely interleaved [1]. The real challenges for these cooling cells reside in their engineering challenges: high field solenoids, RF cavities, and absorbers, often designed near technological limits, placed in close proximity to each other. We thus propose to build a prototype ionization cooling cell to demonstrate the capability of constructing an ionization cooling channel reaching the lowest emittances and to provide engineering input for the design of such beamlines. The magnets and cavities will be powered at their design values, and an absorber will be included along with a mechanism for heating the absorber similarly to how a beam would.

Beam Delivery Simulation (BDSIM), is a C++ program that seamlessly models particle beam transport within an accelerator model that can encompass the beam line, the accelerator's environment, and any accompanying detectors. Based on a suite of high-energy physics software including Geant4, CLHEP, and ROOT, BDSIM transforms the optical design of an accelerator into a detailed 3D model. This facilitates the simulation of particle interactions with matter and the subsequent production of secondary particles. Widely utilized across diverse accelerators worldwide, BDSIM is ideal for simulating energy deposition and assessing charged particle backgrounds. Here, the latest BDSIM developments are shown, including python bindings & interfacing with external tracking tools such as Xsuite.

The SuperKEKB IR is designed to achieve extremely small vertical and horizontal beta functions at the IP. Superconducting magnets provide the focusing magnetic field required to squeeze down the beta functions. The Belle II detector solenoid field is fully compensated with the superconducting anti-solenoids on each side of the IP. For further luminosity improvement, an upgrade of the superconducting final focus quadrupole magnets is required; a new canceling scheme for the Belle-II solenoid field, based on new anti-solenoids, is to be implemented. The design concept of the new IR is to make the beam trajectory as parallel to the QC1 magnet axis as possible to cancel the X-Y coupling and chromaticity between the IP and QC1s and minimize vertical emittance by redesigning the anti-solenoid profile. Moving QC1P closer to the IP results in an increase in the required field strength and current density. Nb3Sn is selected as the cable material instead of the present NbTi. While superconducting properties are better, Nb3Sn magnet fabrication is quite difficult because of the brittleness of the material. New IR design idea and the technical challenges of the new IR magnets are described.

Magnets have been identified as one of the critical technologies for a proton-driven Muon Collider. Within the scope of the International Muon Collider Collaboration we have progressed in the review of requirements, and the development of concepts towards the initial engineering of several of the most critical magnets identified from our previous work. In this paper we present an update of the accelerator magnet configuration for all the parts of the Muon Collider complex, from muon production to collision. We then give details on the specific technologies that have been selected as baseline. Overall, it is clear that a Muon Collider requires very significant innovation in accelerator magnet technology, mostly relying on the success of HTS magnet development. We include in our description a list of options and development staging steps intended to mitigate technical, cost and schedule risk.

In this paper, we present a concise measurement of the Second-Order Transit Time Factor(TTF) of the relativistic electron beams within the bunching cavity of the Coherent Electron Cooling (CeC) Pop Experiment. Our study outlines a specialized measurement methodology that tackles the unique challenges posed by the CeC accelerator environment. The results not only provide significant insights into controlling CeC beam dynamics but also critically validate the theoretical prediction of the Second-Order TTF for relativistic electron beams. This work advances our understanding of beam dynamics and enhances the efficiency and control of CeC-based systems.

In this paper the beam-based alignment for solenoid and quadrupole magnets in the AREAL linear accelerator is presented. The AREAL accelerator, at this stage, operates with one solenoid, one quadrupole, corrector, and dipole magnets. The adjustment of solenoid and quadrupole magnets is crucial for the stable operation of the accelerator and for forming the desired beam required for the AREAL upgrade program. This work also takes into account the influence of the RF field radial component on the off-axis beam parameters and trajectory due to laser spot misalignment on the cathode. The study involves theoretical, simulation, and experimental comparisons.

The high gradient of the photocathode radio-frequency electron gun (RF gun) increases the potential for field emission from the metal surface. Consequently, emitted electrons escaping from the RF gun result in the generation of a dark current, thereby degrading the gun's performance. A thorough investigation into the dark current phenomenon within the accelerator structure plays a crucial role in assessing the performance of the RF cavity and cathode, ensuring the accelerator operates under normal conditions. This paper focuses on establishing a transport matrix for off-axis particles in the RF gun and solenoid. This matrix predicates that field-emitted electrons tend to deviate from the center of the cathode. The study delves into both transverse and longitudinal dynamics characteristics of particles. By numerically tracking the path of dark electrons, we achieved a notable alignment between theoretical prediction and simulation results.

Generating beam with nC-level charge is of great significance for particle colliders. In order to achieve lower emittance and length of bunch, based on the photocathode injector, we designed a L-band gun and L-band accelerating tube. However, with many coupled parameters, it is difficult to optimize its performance to the limit when optimizing them separately. Therefore, we employed a multi-objective genetic algorithm for searching in the multi-dimensional parameter space and utilized a deep Gaussian process as a surrogate model to solve the high-dimensional parameter optimization problem. Through optimization, we successfully obtained the normalized transverse emittance of 3.4 π mm·mrad and the bunch length of 1.0 mm for a fixed charge of 5 nC. This indicates that our method can effectively improve the performance of the photocathode injector.

The stretched-wire alignment technique is one method of magnet alignment for linear induction accelerators. The applications of the Stretched-Wire Alignment Technique (SWAT) have been implemented for aligning magnets/solenoids on the Scorpius linear induction accelerator which will be sited at the Nevada National Security Site and the Flash X-Ray (FXR) linear induction accelerator at Lawrence Livermore National Laboratory’s Contained Firing Facility. This article describes both systematic (repeatable) and random sources of background/noise as well as practical ways to either eliminate or mitigate them to acceptable levels. Systematic sources include reflections from wire ends, rapid sag due to ohmic heating of the wire, magnetic materials, and shot rate. Random sources include air currents, vibration of nearby equipment, mechanical stability of test equipment, and the instruments used to measure the wire motion. Mitigations include curve fitting and adaptive noise signal cancellation, and mechanical damping. Finite Element Analysis (FEA) was used to interpret results.

LhARA, the Laser-hybrid Accelerator for Radiobiological Applications, is a proposed facility designed to advance radiobiological research by delivering high-intensity beams of protons and ions in unprecedented ways. Designed to serve the Ion Therapy Research Facility (ITRF), LhARA will be a two-stage facility that will employ laser-target acceleration in the first stage, generating proton bunches with energies around 15 MeV via the TNSA mechanism. A series of Gabor plasma lenses will efficiently capture the beam, directing it to an in-vitro end station. In the second stage, protons will be accelerated in a fixed-field alternating gradient ring, reaching up to 127 MeV, while ions can achieve up to 33.4 MeV/u. The resulting beams will be directed to either an in-vivo end station or a second in-vitro end station. The demonstrated technologies have the potential to shape the future of hadron therapy accelerators, offering versatility in time structures and spatial configurations, with instantaneous dose rates surpassing the ultra-high dose rates required for studies into the FLASH effect. Here, we present a status update of the LhARA accelerator as we approach a full conceptual design.

Ultrafast high-energy pulsed electron beams can provide deep penetration and variable linear energy transfers for testing microelectronics for radiation-induced single-event effects. Early experiments at the UCLA PEGASUS beamline (3 MeV) with 1 ps electron bunches and a 50 $\mu$m spot size yielded charge collection transients that are compared with reference heavy ion data. Sub-micron focusing of the beam would allow for the electron bunch to better mimic ion tracks by saturating the charge collection in a small cross-sectional area while simultaneously providing high spatial resolution to allow for the targeted testing of microelectronic components. Using micron-scale collimators and strong lenses, current experiments are planned at UCLA to achieve smaller spot sizes in pursuit of stronger correlations with heavy-ion data.

Permanent magnets are attractive options for nano focusing and $q$-magnification in MeV ultrafast electron diffraction (MeV-UED) due to their high field strengths and compact footprints. In this work, we present field characterization of axially and radially magnetized neodymium rings. Such rings can produce strong axisymmetric focusing and naturally fulfill the requirement of stigmatic imaging for post-sample optical systems. Field qualities of the rings and their application in MeV-UED are studied and presented.