The Electron-Ion Collider is gearing up for "Critical Decision 2", the project baseline with defined scope, cost and schedule. Lattice designs are being finalized, and preliminary component design is being carried out. Beam dynamics studies such as dynamic aperture optimization, instability and polarization studies, and beam-beam simulations are continuing in parallel. We report on the latest developments and the overall status of the project, and present the plans for future activities.

Polarization levels in the Electron Storage Ring (ESR) of the Electron-Ion Collider (EIC) must be maintained for a sufficient time before depolarized bunches are replaced. The depolarizing effects of synchrotron radiation can be minimized with spin matching, however the optics requirements for the ring must still be satisfied. Furthermore, the robustness of the polarization in the presence of misalignments, beam-beam effects, and the eventual insertion of a vertical emittance creator – necessary to match the electron and ion beam sizes at the interaction point – must be ensured. In this work, the results of various polarization analyses of the ESR lattices are presented, and their implications discussed; the necessity for a longitudinal spin match in the 18 GeV case is investigated, and vertical emittance creation schemes with minimal effects on polarization are analyzed.

This study is motivated by the search for the electric dipole moment (EDM) of elementary particles. The most promising idea in that regard is the “Frozen Spin” concept first proposed by the BNL. This concept, however, requires the building of a brand-new facility devoted to the EDM-search. NICA is not such a facility, hence the need for a modification compatible with the existing optics; one that wouldn’t disrupt the ring’s capability for parallel experiments. Such a modification is the “Quasi-Frozen Spin” idea, realized by adding transport channels, bypassing the ring’s straight sections. Wien-filters are placed in these channels in order to compensate spin-rotations caused by the ring’s arc dipoles, thus making its net spin-transfer matrix unitary. Even though, during its movement along the beam line, the beam’s polarization vector deviates from alignment with the momentum vector, this motion is regular and fits within one beam revolution, allowing for the buildup of the EDM-signal. The present study shows that the “Quasi-Frozen Spin”-specific optics is consistent with the existing NICA lattice and that the modified structure is capable of maintaining a requisite spin-coherence time.

NICA is mainly designed for experiments with heavy ions and polarized proton and deuteron beams at an energy of the former about 13 GeV. For these purposes, appropriate SPD and MPD detectors, as well as other necessary implements, are installed in the straight sections. EDM experiment supposes use deuterons at an energy of about 240 MeV. To ensure the «Quasi-Frozen Spin» mode, E+B elements (namely, Wien Filters) are required as well. Such elements can be placed in straight sections to compensate the arc spin rotations. For EDM measurement experiments, it is necessary to operate NICA in the storage ring, and not the collider mode. To do this, it is proposed to install ByPass channels. Thus, it is possible to create a completely new regular structure in a straight section. Creating ByPass channels will make possible to engage NICA in various experiments at once.

Modernization of the NESTOR hard X-ray generator storage ring for switching to the operating frequency of the accelerator of 2.856 GHz requires corresponding changes in the design of the high-frequency system, and this, in turn, leads to the need to modernize the laser-optical system. The necessary calculations were carried out to determine the new characteristics of the pulsed laser, the Fabry-Perot cavity, and the lens optical system matching the beam geometry. The obtained results confirm the possibility to use an already existing laser-optical system at a new operating frequency of the accelerator with some changes in the design.

Optimization and realistic estimates of the sensitivity of the measurement of charged particle Electric Dipole Moment (EDM) in storage rings require a good understanding of systematic errors that can contribute to a vertical spin build-up mimicking the EDM signal to be detected. A specific case of systematic effect due to offsets of electrostatic bendings and longitudinal magnetic fields is studied. Spin tracking simulations to investigate whether this special case generates spin rotations, which cannot be disentangled from the ones due a finite EDM by combining observations made with both counter-rotating beams as predicted by analytical derivations, will be presented.

A series of power outages during setup for RHIC Run 23 damaged two of the four helical dipole modules that comprised one of the full Siberian Snakes in RHIC’s Blue ring. The remaining two helical dipoles were reconfigured as a “partial” snake, one which rotates the spin by an angle less than 180 degrees. This partial snake configuration has a rotation angle and axis which both deviate from the ideal. We describe the compensatory measures taken to address the effects of these deviations. These include reconfiguring the other Blue snake to rematch the stable spin direction at injection and a change of the nominal store energy from 255 GeV to 254.2 GeV to improve the stable spin direction condition at store. Polarization transmission through RHIC acceleration was as good as with full snakes and we present some analytical and tracking results that corroborate the observed robustness with respect to deviations from ideal snakes.

We describe methods for measuring the three-dimensional stable spin vector for RHIC stores at two locations in the ring, namely the proton-Carbon (pC) polarimeters and the interaction point at the STAR detector. Both the pC and STAR local polarimetry can only measure the two transverse components of the stable spin direction. Measuring the full spin vector requires making a local spin rotation at the measurement point. This is accomplished using the helical dipole spin rotators for STAR and a local horizontal orbit angle for the pC polarimeters, respectively. The stable spin direction at a third point, the hydrogen jet polarimeter is determined via spin tracking from the nearby pC polarimeter. We describe the measurement and analysis methods used and present results of the measurements made during RHIC Run 22.

The Electron Ion Collier (EIC) will utilize highly polarized electron and ion beams. To preserve polarization through numerous depolarizing resonances over the whole EIC hadron accelerator chain, harmonic orbit correction, partial snakes,horizontal tune jump system and full snakes have been used. A new scheme using skew quadrupoles to compensate horizontal intrinsic resonances is under development. In addition, close attentions have been paid to betatron tune control, orbit control and beam line alignment. The polarization of 60% at 255 GeV has been delivered to experiments with 1.8E11 bunch intensity. For the EIC era, the beam brightness has to be maintained to reach the desired luminosity.This will be achieved by electron cooling at injection of EIC hadron storage ring. Since we only have one hadron ring in the EIC era, existing spin rotator and snakes can be converted to six snake configuration for one hadron ring. The number of snakes can be increased. With properly arranged snakes in EIC and reduction of emittance, the polarization can reach 70% at 275 GeV. The general strategy of polarization preservation scheme in the injectors and hadron ring of the EIC is described in this paper.

To maintain polarization in a polarized proton collider, it is important to know the spin tune of the polarized proton beam, which is defined as the number of full spin precessions per revolution. A nine-magnet spin flipper has demonstrated high spin-flip efficiency in the presence of two Siberian snakes. The spin flipper drives a spin resonance with a given frequency (or tune) and strength. When the drive tune is close to the spin tune, the proton spin direction is not vertical anymore, but precesses around the vertical direction. By measuring the precession frequency of the horizontal component, the spin tune can be precisely measured. A driven coherent spin motion and fast turn-by-turn polarization measurement are keys to the measurement. The vertical spin direction is restored after turning the spin flipper off. The fact that this manipulation preserves the polarization makes it possible to measure the spin tune during the operation of a polarized collider such as RHIC and EIC.

Acceleration of polarized electron and positron beams to ultra-high beam energies is of interests for polarized beam applications in future 100km-scale e+e- circular colliders. However, it was widely envisaged that crossing hundreds of spin depolarization resonances would lead to severe depolarization during the energy ramp in the booster synchrotron. In this work, we have studied the spin resonance structure of a booster lattice for the Circular Electron Positron Collider (CEPC). The 100 km-scale booster lattice has a periodicity of 8 and each arc region contains hundreds of FODO cells. We show that the first super strong depolarization resonances only occur beyond 120 GeV, and other resonances are much weaker, due to the effectively very high periodicity of the lattice structure in terms of spin resonances. This finding is similar to the concept of ``Spin resonance free injector’’ for the Electron Ion Collider [V. Ranjbar, Phys. Rev. Accel. Beams, 20, 111003, 2018]. Spin tracking simulations verify that beam polarization can be mostly maintained in the fast ramping to 45.6 GeV and 80 GeV beam energies, without using special hardware like Siberian snakes. We also discuss possible measures to maintain beam polarization up to 120 GeV. This study opens the way for injection of highly polarized beams generated from the source into the collider rings, to enable resonant depolarization measurements as well as longitudinally polarized colliding beam experiments.

The high precision measurement of the centre-of-mass energy in the Future Circular Collider e+e- (FCC-ee) at Z and W energies can be realized through resonant spin depolarization utilizing transversely polarized beams. This requires a guaranteed sufficiently-high spin polarization in the presence of lattice imperfections. Investigations of the impact of misalignments on the equilibrium polarization are conducted using analytical and Monte-Carlo spin simulations with Bmad. Potential optimization schemes to ensure high polarization using orbit bumps have been explored.

The Future Circular electron-positron Collider, FCC- ee, is designed for unprecedented precision for particle physics experiments from the Z-pole up to above the top-pair-threshold, corresponding to a beam energy range from 45.6 to 182.5 GeV. Performing collisions at various particle-physics resonances requires precise knowledge of the centre-of-mass energy (ECM) and collision boosts at all four interaction points. Measurement of the ECM by resonant depolarization of transversely polarized pilot bunches in combination with a 3D polarimeter, aims to achieve a systematic uncertainty of 4 and 100 keV for the Z-pole and W-pair-threshold energies respectively. The ECM itself depends on the RF-cavity locations, beamstrahlung, longitudinal impedance, the Earth’s tides, opposite sign dispersion and possible collision offsets. Application of monochromatization schemes are envisaged at certain beam energies to reduce the energy spread. The latest results of studies of the energy calibration, polarization and monochromatization are reported here.

The SuperKEKB accelerator is currently in operation in Tsukuba, Japan, with a planned long shutdown in 2026. Among the possible upgrades being considered during this period is the change to a polarized electron beam in the High Energy Ring. Such a change would require modifications in the source generation and transport, geometrical and lattice variations to provide spin rotation, and polarimetry. A Polarized SuperKEKB Working Group has been formed from members of the Belle II experiment and the SuperKEKB accelerator team to investigate the possibilities and challenges of these modifications. This talk lays out the goals of the proposed upgrade, considers the necessary changes to the existing accelerator and their feasibility and lays out the physics motivation behind such an effort.

In the future 100 km-scale Circular Electron Positron Collider (CEPC), beam polarization is an important design aspect. Transverse beam polarization for resonant depolarization is essential for precision measurements of the beam energies at Z-pol and WW threshold. Longitudinally polarized colliding beams are also beneficial for expanding the capability of the physics program. This paper reports the progress in the design studies of polarized beams for the CEPC. We focus on the approach of injection of polarized beams generated from the source into the collider rings for both applications. Our investigation into key issues in this approach is summarized, including polarized positron beam generation, beam polarization maintenance in the booster, and spin rotator design in the collider rings. Implications to resonant depolarization measurements are also discussed.

GaAs cathode is a unique device generating a spin-polarized electron beam by photo-electron effect with a circularly polarized laser illumination. Negative Electron Affinity (NEA) surface which is artificially made has an essential role in spin polarization, but the NEA surface has limited vitality. In this study, we activated GaAs as NEA cathode by evaporating Cs, K, and Sb metal on its cleaned surface. The experimental results including the quantum efficiency spectrum and the lifetime will be presented.

Positron beams would provide a new and meaningful probe for the experimental program at the Thomas Jefferson National Accelerator Facility (JLab). The JLab Positron Working Group, formed in 2018 and now with over 250 members from 75 institutions, continues to develop an experimental program with high duty-cycle positron beams including but not limited to future hadronic physics and dark matter experiments. Critical requirements involve generating positron beams with a high degree of spin polarization, sufficient intensity and a continuous-wave (CW) bunch train compatible with acceleration to 12 GeV at the Continuous Electron Beam Accelerator Facility (CEBAF). In this presentation we describe a start-to-end layout for positron beams at 12 GeV CEBAF utilizing the Low Energy Research Facility (LERF) at Jefferson Lab to build two new injectors. A GaAs dc high voltage photo-gun first generates >1 mA of polarized electrons which are then accelerated to 80-150 MeV and directed to a high-power spinning W target for polarized bremsstrahlung and positron pair creation. A second injector then collects, bunches and accelerates the positrons to 123 MeV. The positron beams are transported by a new beam line and injected into the CEBAF acceptance for acceleration to the end stations with energies up to 12 GeV. The layout is optimized to provide Users with positron spin polarization >60% and intensity greater than >100 nA, and with higher intensities when polarization is not required.

The High Energy Photon Source (HEPS) is a 4th generation synchrotron radiation source being built in China. An APPLE-Knot undulator with a new configuration is designed for the XCMD beamline of the HEPS. It is the first time to apply four-row APPLE-Knot undulator in storage ring based light sources. The main differences between the novel design and the conventional design of the APPLE-Knot undulators are discussed. Furthermore, the influences of the APPLE-Knot undulator on storage ring optics, as well as the dynamic effects during the process of gap variation at different polarization modes, are investigated and will be introduced in this paper.

SIRIUS is the 4th generation synchrotron light source built and operated by the Brazilian Synchrotron Light Laboratory (LNLS). SIRIUS is currently operating with six beamlines and eight others are at different stages of deployment. In this work we report on the development of simulation tools to analyze the impact of insertion devices (IDs) on SIRIUS beam orbit, optics and dynamic aperture (DA), aiming at defining their specifications for external suppliers and verifying the feasibility of installing existing IDs. In particular, we analyze the fields of two IDS used in the previous LNLS synchrotron light source (UVX), now decommissioned: one planar 2T hybrid wiggler and one EPU of the type Apple-II. These IDs were installed in SIRIUS in 2022 and are now temporarily serving as light sources for the commissioning of PAINEIRA and SABIÁ beamlines. Furthermore, we also analyze the effects of two new IDs that will be used as titular light sources for CARNAÚBA, CATERETÊ, EMA, and PAINEIRA beamlines. One is an In-Vaccum Undulator (IVU) and the other is a Vertically Polarizing Undulator (VPU). An undulator built In-house will be used as a temporary light source for the SAPUCAIA beamline commissioning and its effects on SIRIUS beam parameters are also reported.

The layout of Elettra 2.0 preserves the useful length of the long straight sections so that all the existing insertion devices (IDs) could in principle be maintained in the upgraded machine. However, new high-performance beamlines are planned that will take advantage of the much lower electron beam emittance. Therefore new undulators are being designed and constructed for these beamlines. Space is also available in some of the short straight sections, and we’re developing compact undulators and wigglers to make optimal use of them. In this contribution the parameters and characteristics of the new IDs will be presented.

The Advanced Light Source (ALS) at the Lawrence Berkeley National Laboratory (LBL) is going through an upgrade (ALS-U), where the ALS triple-bend achromat is replaced by a nine-bend achromat storage ring (SR) with on-axis injection using beam swapping from a triple-bend achromat accumulator ring (AR). The small beam size at the straight sections of the ALS-U has opened the possibility to use small-diameter circular vacuum chambers for insertion devices. An elliptically polarizing X-type undulator with a small circular vacuum chamber and symmetric placement of the magnet rows around the vacuum chambers is being developed at LBL. This type of undulator is suitable for the ALS-U and other fourth generation light sources. Salient features of the X-type undulator include the mechanical construction with compact crossed roller bearings and fully hydraulic motion control system. These are described together with a status report of the progress of the prototyping work.

Hefei Advance Light Facility (HALF) is a 2.2 GeV diffraction-limited storage ring, which is developed by National Synchrotron Radiation Laboratory in China. It has 20 long straight sections and 20 middle straight sections. All the experimental stations in the first stage will employ undulator as the light source. In this paper, we introduce the preliminary design of insertion devices of HALF, which includes 11 undulators and 2 wigglers. The undulator design is carefully optimized based on the current undulator technology and experiment user demands. The photon flux of these undulators can cover the photon energy from 5 eV to 10 keV with the flux greater than $10^{14}$ phs/s/0.1\% B.W. It can reach an ultra-high brilliance at the soft X-ray wavelength region. Most of the insertion devices are the elliptically polarized undulators and the in-vacuum undulators, therefore the light source of HALF will be charactered by a flexible tunability on polarization state and a broad range of photon energy from VUV to X-ray wavelength region.

Polarization control of undulator radiation attracts a great attention due to its application prospects in material and biology. Various undulators have been developed to obtain radiation of specific polarization states. In the electron storage ring light source, different methods have been proposed to realize a specific polarization switching. However, there is still a strong demanding to improving the switching speed and/or increasing the available polarization state in a single beam line. This paper gives systematic analysis of simple schemes to obtain the polarization switching by using the segmentation of the undulators with the phase shifter placed between each adjacent undulators. Through switching the polarization state of each undulator and the phase shifts, the polarization state can be fast switched between different polarization states in a same undulator line. The theoretical analysis for the radiation characteristics under different undulator configurations are demonstrated to reveal the basic principle of this simple method.

For the first time, photoemission of spin-polarized electron beams from gallium nitride (GaN) photocathodes are observed and characterized. The spin polarizations of the emitted electrons from epitaxially grown hexagonal and cubic GaN photocathodes activated to Negative Electron Affinity (NEA) via cesium deposition are measured in a retarding-field Mott polarimeter.

​A novel technique, called a spin transparency mode, for preservation and control of electron and ion spin polarization in colliders and storage rings has been proposed. The beam polarization can then be fully controlled by small adjustments of the snake axis orientations and snake strengths. An experiment has been carried out recently to test the concept. One of the RHIC rings is set to be “transparent” to the spin by making the axes of its two Siberian snakes nearly parallel. The polarization was rotated from vertical to radial and from up to down by varying the snake currents. This paper summarizes the recent experiment results and discusses the comparison with simulations.

State-of-the-art spin-polarized photo-electron sources use GaAs-based photocathodes to provide electron beams with high degrees of spin-polarization. Such photo-guns are required to operate with both quantum efficiency and cathode lifetime as high as possible in order to meet the requirements of high-current applications such as energy-recovery linacs and colliders. Both quantum efficiency and lifetime are determined by the quality of the thin surface layer, typically consisting of Cs in combination with an oxidant, required for GaAs photocathodes to achieve negative electron affinity. This layer is applied during a so-called activation process. It is therefore of great interest to optimize and standardize this procedure in order to provide the best possible conditions for reliable photo-gun operation. This contribution presents the analysis of bulk-GaAs activations using Cs and O conducted at the Photo-CATCH test stand. The effects of Cs and O partial pressures on final quantum efficiency and lifetime, as well as the duration of the activation process were scrutinized in order to find an optimal partial pressure ratio at a reasonable duration of the procedure.

A Structured Laser Beam (SLB) is a type of optical beam with spatially inhomogeneous 3D polarisation structures. Generating SLBs from vector beams allows the creation of Hollow Structured Laser Beams (HSLB) with a dark central core. In this way, atypical electric and magnetic field vectors, which are purely longitudinally polarized in the dark zones of the beam, are obtained. The SLB spatial distribution can also include regions with both the electric and magnetic fields longitudinally polarized and oriented in the same or opposite directions. The SLB has a transverse distribution similar to that of a Bessel beam but can theoretically propagate to infinity, therefore giving the potential to generate strong, longitudinally oriented electric fields over long distances, which could possibly allow the acceleration of charged particles. The results of the study of this phenomenon, including simulations of the spatial distribution of the electromagnetic field components, are presented in this paper.

Spin is one of the intrinsic properties of particles. However, there are many incomprehensible problems about it. High energy polarized electron-ion collisions will provide unprecedented conditions for the study of spin physics and lead us to the study on the inner structure of matter and fundamental laws of interactions, and other forefronts of natural science. As the Phase II of the HIAF (High Intensity heavy ion Accelerator Facility) project, Electron-Ion Collider in China (EicC)* is under conceptual design phase. The production, acceleration and collision of polarized ions and electrons are essential for EicC accelerator facility. Therefore, R&D work such as key technologies prototyping has already been initiated. A spin polarized ion source for the production of intense proton and deuterium ion beams with high polarization is under development at the Institute of Modern Physics (IMP). Polarization is one of the key characteristics for polarized ion beams. To make the polarization measurement more precise, faster and more convenient, a polarimeter based on nuclear spin filter (SFP for short) is under design, which measures the polarization directly behind the ion source. Scheme of the SFP will be presented, the measurement process, simulations for crucial physical questions and design of theSFP will be discussed.

Polarized beam is an effective tool in basic research. An Electron-ion collider in China (EicC)*, as a future high energy nuclear physics project, has been proposed. Eicc can provide good research conditions for precision measurements of the partonic structure of nucleon or nuclei and the study on the interactions between nucleons and so on. High quality polarized beam is helpful to the accurate measurement of the relevant experiment date. Polarized proton and deuterium (H&D) beam source is one of the key technologies for EicC. Based on the atomic beam polarized ion source (ABPIS) scheme, a polarized H&D ion source with polarization more than 0.8 and beam current more than 1mA is under construction at the Institute of Modern Physics (IMP), providing theoretical and technical support for the design and construction of Eicc polarized source. In the ABPIS, the separating magnet ensures the electron polarization and the effective transmission of the atomic beam; the radiofrequency transition(RFT) unit ensures that the electronic polarization is converted into deserved nuclear polarization. In order to generate high intensity and high polarization H&D atomic beam, these assemblies need to be precisely designed and optimized. In the paper, an effective method for obtaining the optimal sextupole separating magnet structure will be described in detail; the numerical simulation of the method of adiabatic passage, the design and testing of the RFT units will also be discussed.

The high-intensity, polarized electron source is a critical component for the electron-ion collider which requires a polarized electron gun with higher voltage and higher bunch charge compared to any existing polarized electron source. At Brookhaven National Laboratory, we have built and successfully conditioned the inverted HVDC photoemission gun up to 350 kV. We report on the performance of GaAs photocathode to generate 70 µA average current and up to 16 nC bunch charge with a long lifetime using a circularly polarized laser at 780 nm wavelength. We discuss the Distributed Bragg Reflector GaAs/GaAsP Super Lattice photocathode performance in the DC gun and the anode bias and voltage impact on the lifetime. The gun also integrated a cathode cooling system for potential application on high-current electron sources. The various novel features are implemented and demonstrated in this polarized HVDC.

The magnetic and mechanical designs of a force-neutral adjustable phase undulator (FNAPU) are pre-sented. The FNAPU combines two magnetic assemblies with equal periods, one with an undulator magnetic structure and one with a force compensation magnet structure. The latter is used to neutralize the magnetic force affecting the undulator magnetic structure and vice versa in all undulator phases. Assembling in prox-imity a group of different FNAPUs is discussed.

Cavity based X-ray free-electron lasers (CBXFEL) are next generation X-ray sources promising radiation with full three-dimensional coherence, nearly constant pulse to pulse stability and more than an order of magnitude higher spectral flux compared to SASE FELs. However, especially for the low gain X-ray free-electron laser oscillator (XFELO), the outcoupling of the radiation stored inside the cavity remains an issue, as only small outcoupling coefficients are tolerable. In this contribution, a scheme is proposed which exploits the polarization dependence of the crystal based X-ray diffraction, which poses the main reflection mechanism for forming the X-ray cavity. Especially for reflections close to a 45° Bragg-angle, as is proposed for the proof of concept experiment at the *Linac Coherent Light Source* (LCLS) at the *Stanford Linear Accelerator* (SLAC)"*", the polarization dependence of the reflection coefficient becomes very strong. By properly setting up the polarization of the FEL radiation with respect to the reflection direction, a very simple, yet potent and tunable outcoupling mechanism can be realized.

The Mainz Energy-recovering Superconducting Accelerator (MESA), currently under construction at the Johannes Gutenberg University (JGU) in Mainz, will offer two modes of operation, one of which is an energy-recovering (ER) mode in order to deliver electron beams of up to 155 MeV to two experiments. As an ERL, MESA, with it's high brightness electron beam, is a promising accelerator for supplying a Thomson back scattering based Gamma source. Furthermore, at MESA, the polarization of the electron beam can be set by the injector. The aim of this work is to provide a concept and comprehensive analysis of the merit and practical feasibility of a Thomson backscattering source at MESA under consideration of beam polarization and transversal effects. In this paper, the first results of our semi analytical approach to calculate various Thomson back scattering light source scenarios including polarization effects at MESA will be presented.

A beam cooler device has been constructed by the Laboratories de physique corpusculaire (LPC) of Caen (France) in collaboration with Laboratori Nazionali di Legnaro (INFN) for the SPES project. The design phase started in 2018 and the construction was carried out in 2021. In 2022 the functionality test have been done at LPC and the beam commissioning started. The Beam Cooler is capable to improve the quality of ion beams at low energy in terms of reduction of the transversal emittance and decreasing the energy spread. The description of the device will be done and the result of beam test done at LPC will be reported.

The matter-antimatter asymmetry might be understood by investigating the EDM (Electric Dipole Moment) of elementary charged particles. A permanent EDM of a subatomic particle violates time reversal and parity symmetry at the same time and would be, with the currently achievable experimental accuracy, an indication for further CP violation than established in the Standard Model. The JEDI-Collaboration (Juelich Electric Dipole moment Investigations) in Juelich has performed a direct EDM measurement for deuterons with the so called precurser experiments at the storage ring COSY (COoler SYnchrotron) by measuring the invariant spin axis. In order to interpret the measured data and to disentangle a potential EDM signal from systematic effects in the radial part of the invariant spin axis, spin tracking simulations in an accurate simulation model of COSY are needed. Therefore a model of COSY has been implemented using the software library Bmad. Systematic effects were considered by including element misalignments, effective dipole shortening, longitudinal fields and steerer kicks. These effects rotate the invariant spin axis in addition to the EDM and have to be analyzed and understood. The most recent spin tracking results as well as the methods to find the invariant spin axis will be presented.

The search for the Electric Dipole Moments (EDM) of charged particles in storage rings necessitates polarized beams with long Spin Coherence Time (SCT) of the circulating beam. The SCT is the time during which the RMS spread of the orientation of spins of all particles in the bunch reaches one radian. A long SCT is needed to observe the coherent effect of a polarization build-up induced by the EDM. For deuterons a SCT of 1000 s has been achieved at the COoler SYnchrotron COSY (Jülich, Germany). Accomplishing such long SCT for protons is far more challenging due to their higher anomalous magnetic moment, but essential for the planned EDM experiments. It has been shown that for protons, the SCT is strongly influenced by nearby intrinsic and integer spin resonances. The strengths of the latter have been calculated for a typical optics setting of COSY and the overall influence on the SCT was predicted. In addition, the efficiency of proton spin flipping with an RF-solenoid from initially vertical direction into the ring plane is also investigated.

The JEDI experiment is dedicated to the search for the electric dipole moment (EDM) of charged particles using storage rings, which can be a very sensitive probe of physics beyond the Standard Model. In order to reach the highest possible sensitivity, a fundamental parameter to be optimized is the Spin Coherence Time (SCT), i.e., the time interval within which the particles of the stored beam maintain a net polarization greater than 1/e. To identify the working conditions that maximize SCT, accurate spin-dynamics simulations with the code BMAD have been performed on the lattice of a "prototype" storage ring which uses a combination of electric and magnetic fields for bending. This contribution presents an analysis of the mechanisms behind the decoherence, and a technique to maximize SCT through the optimization of second-order optical parameters.

The Electron Ion Collider is preparing now the design for the project baseline, to provide the high luminosity, polarization and flexibility for the EIC. This talk outlines the accelerator physics challenges including complex interaction region, flat hadron beams, beam cooling, high beam currents leading possibly to electron clouds and instabilities, and high beam polarization.

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.

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.

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)

Current and historic tracking studies of the RHIC accelerator lattice find difficulty in explaining the transmission efficiency of spin polarization from the AGS extraction to RHIC storage energies. In this paper, we discuss mechanisms that result in resonant depolarizing behavior, beyond the usual intrinsic and imperfection resonance structures. In particular, the focus of this paper will be on higher-order resonances that become apparent in the presence of snakes. The set of conditions that identify higher-order spin-orbit resonances are 𝜈 = 𝑗0 + 𝑗 ⃗ ⋅𝑄⃗for integers (𝑗0, 𝑗) ∈ ℤ^4, where 𝜈 is the spin tune and 𝑄⃗ contains the orbit tunes. Note that we do not use the closed-orbit spin tune 𝜈0 but rather the amplitude-dependent spin tune 𝜈(𝐽𝑥, 𝐽𝑦, 𝐽𝑧) that depends on the phase-space amplitudes. While Sibrian snakes keep 𝜈0 at 1/2, the amplitude-dependent spin tune can deviate from 1/2 and can cross resonances during acceleration.

The effect of both existing and the planned insertion devices on linear optics, dynamic and momentum aperture was modeled using the kick map approach. Cross check for some IDs have been done with different tracking codes. Mitigation strategy for avoiding the crossing of a 4th order resonance line, excited by some of the IDs, is proposed.

The potential in the Radio Frequency Quadrupole (RFQ) can be expressed as a sum of a transverse multipolar expansion: $\sum_{m=1}^\infty{A_{0m}}\left(\frac{r}{r_0}\right)^{2m}\cos(2m\theta)$, and a longitudinal term expressed as sum of Bessel functions: $\sum_{m=0}^\infty\sum_{n=1}^\infty A_{nm}I_{2m}(nkr)\cos(2m\theta)\cos(nkz)$. Since the paper of Kapchinskii and Teplyakov \cite{osti_4032849} this potential is used considering only the first term in transversal and longitudinal components, unfortunately such approximation does not reproduce properly a realistic RFQ as the one installed at the European Spallation Source (ESS). In this paper we evaluate the potential when more terms are considered and we compare it with the field map obtained from a numerical Poisson solver used at ESS.

The Insertion device development and measurement laboratory of Devi Ahilya University, Indore, India has ongoing activities on undulator design, development and measurements. A new type of undulator known as Asymmetric magnet pole with upper and lower structure having different period lengths will be designed and fabricated. Asymmetric magnet pole undulator has a special demanding field quality for suppressing the higher harmonic components of radiation and reducing on axis heat load from radiation. The undulator will be a variable gap undulator with upper structure consist of 25mm period having NdFeB magnets of rectangular cross section 6.25 mm, 6.25 mm and 50mm and lower structure will be with 50mm period length with the same magnet material but having rectangular cross section of 12.5mm, 12.5mm and 50mm. In this paper the design details for an asymmetric magnet pole undulator will be presented.

A source for polarized positron beams at the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab is being designed. The Polarized Electrons for Polarized Positrons (PEPPo) concept is used to produce polarized e$^+$e$^-$-pairs from the bremsstrahlung radiation of a longitudinally polarized electron beam interacting within a high-Z conversion target. The scheme under consideration includes a 4 mm thick tungsten target that absorbs 17 kW deposited by a 1 mA continuous-wave electron beam with an energy of 120 MeV. The concept of a rotating tungsten rim mounted on a water-cooled copper disk was explored. The results of ANSYS thermal and mechanical analyses are discussed together with FLUKA evaluations of the radiation damages.

The production of high-current and intense spin polarized electron beams is of great importance in electron-based facilities. Tests are planned to produce such beams in 2023 using GaAs-based photocathodes installed in the Brookhaven National Lab RHIC Coherent electron Cooling superconducting radiofrequency (SRF) photogun [1]. A fast and efficient electron polarimeter operating in the MeV energy range is required to measure the beam spin polarization.  While Mott polarimeters provide larger measured asymmetries, a Compton Transmission polarimeter is well suited in the few MeV energy range. In this work, we report on a relatively compact and cost-effective Compton transmission polarimeter which has been built and calibrated at Jefferson Lab (JLab). First, we present the design of the polarimeter radiator, polarized target analyzing magnet, BGO detector assembly and data acquisition system. Next, results of a two-week commissioning study performed at the JLab Upgraded Injector Test Facility will be described. Here, a well-known polarized electron beam produced from a bulk GaAs photocathode in a dc high-voltage photogun was first measured in a 180 keV Mott scattering polarimeter, then used to characterize and calibrate the Compton transmission polarimeter as a function of the polarized target magnetization and beam properties. Finally, we report an effective analyzing power of the Compton polarimeter and compare experimental results with those produced via Geant4 simulations.

The Structured Laser Beam (SLB) is a type of optical beam characterized by an intense, sharply defined, low divergence core at its center, similar in its transverse intensity distribution to a Bessel beam. The SLB can propagate over a theoretically infinite distance, and has recently been tested up to a distance of 900 m. This test confirmed the low divergence of the SLB core, of about 0.01 mrad in this case. Furthermore, a hollow SLB (HSLB) can be created by feeding the generator with vector beams. These properties open the possibility of creating new types of optical alignment systems that could be used over long distances, for example for particle accelerators. Investigations are on-going to optimize the SLB and fully evaluate its alignment potential. Methods are under development to accurately detect the center of the SLB, based either on the beam intensity distribution or on the measurement of particular polarization states of the HSLB. Moreover, in order to deal with alignment in harsh environment, systems based on passive elements are also of interest. This paper summarize these studies and includes a discussion of phenomena such as the straightness of the SLB.

We present an approach for detection of anomalous behavior of magnet power supplies (PSs) in storage rings, which may serve as an early indication of an impending PS trip. In this new method, we train a Long Short-Term Memory (LSTM) neural network to predict the temperature of several components of a PS (transistors, capacitors) based on the PS current, PS voltage, room temperature, and cooling water temperature. For training and testing, years of historical data are used from the Advanced Photon Source (APS). The neural network is trained on the data corresponding to the normal operation of the PSs. Anomalous behavior of a PS can be detected when the observed PS temperature starts to deviate significantly from the LSTM prediction. This may allow for preemptive action by the operators or PS group.

NHa and IBA are collaborating to develop a new cyclotron dedicated to hadron therapy. The manufacturing of the magnet is in an advanced stage. In parallel, extensive studies are carried out to develop an accurate field mapping system. It is required to perform the high precision magnetic field measurement (75 ppm) that will provide the final isochronous field after the well-known shimming procedure. Due to the wide pole diameter (1.8 m), the large magnetic field amplitude and the numerous shims, a technology based solely on Hall probe would request too much time of operation and a mismatch to perform a full mapping of the magnetic field in what is considered a reasonable time. For this reason, a new system based on a dual search coil is under design. The two coil geometries will enable to match the different gradient regimes and granularity requirements present over the pole surfaces. In addition to the moving coils, an NMR probe will be included to provide the reference absolute measurement together with a Hall probe to confirm the data recorded through the search coils. In this report, the status of the new mechanical system providing the probe motion will be presented but the article focuses on the modelling of the search coil response as a function of its geometrical form factor. The aim is to evaluate and control the potential errors induced by the measurement of such averaged flux over the coil inner volume in case of very inhomogeneous fields.

In EUV lithography, high volume manufacturing already started using a laser-produced plasma (LPP) source of 250-W power at 13.5 nm. However, development of a high-power EUV light source is still very important to overcome the stochastic effects for a higher throughput and higher numerical aperture (NA) in future. The required EUV power for the 3-nm node and beyond at the maximum throughput of future scanners is estimated to be more than 1 kW. We have designed and studied an EUV-FEL light source based on ERL for future lithography [1,2]. This light source offers many advantages such as high EUV power (> 10 kW), upgradability to a Beyond EUV (BEUV) FEL for finer patterning, polarization controllability for high-NA lithography, low electricity consumption and cost per scanner, as compared to the LPP source. Excellent high-power performance of the EUV-FEL light source was newly demonstrated by a start-to-end simulation with new optimization and more accurate calculation and conceptual schemes of upgrade to a BEUV-FEL, polarization control of the FEL light and an optical beamline to the scanners were proposed. Proof of concept (PoC) of the EUV-FEL light source using an IR-FEL constructed in the Compact ERL (cERL) at KEK is also in progress. In this presentation, we will present the EUV-FEL light source for future lithography including the PoC using the cERL IR-FEL.