The initial design of the capture cavities for a continuous wave (CW) polarized positron beam for the Continuous Electron Beam Accelerator Facility (CEBAF) upgrade at Jefferson Lab is presented. A chain of standing wave multi-cell copper cavities inside a solenoid tunnel are selected to bunch/capture positrons in CW mode. The capture efficiency is studied with varying cavity gradients and phases. The heating load from the incoming particle radiation shower and RF field will limit the achievable gradients, especially the first cavity. The cooling method and results are shown. The beam loading cancellation from positrons and electrons are investigated.

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.

The quest for novel technologies in the ever-evolving landscape of scientific exploration has led to the investigation of plasma lensing as a potential solution for optical matching devices for all kinds of positron sources. This research becomes increasingly significant as the need for higher data output demands innovative concepts to increase positron yield and therefore luminosity. Instabilities were observed during the first test trials. This poster presents the results of high-temporal resolution imaging to analyse the discharge instabilities. Furthermore, the results show not expected but interesting insights and challenges. Overcoming these challenges is pivotal for a future application of plasma lenses as an integral part of high-performance positron sources.

The International Linear Collider (ILC) is a next-generation electron-positron collider designed to operate at center-of-mass energies ranging from 250 GeV to 1 TeV, providing opportunities for exploring physics beyond the Standard Model. A critical component of the ILC is the E-driven positron source, which requires sophisticated technology to produce large quantities of positrons. Traditional accelerator design methods involve sequential optimization, which is inefficient and challenging for achieving global optimization. This study introduced the use of the Tree-structured Parzen Estimator (TPE) algorithm, a black-box optimization method, to improve the design efficiency of the ILC E-driven positron source. By implementing the TPE algorithm using Optuna, we optimized up to 8 parameters, achieving a positron capture efficiency of 1.42, significantly higher than the 1.20 efficiency obtained through manual optimization. This substantial improvement is expected to meet the safety standards for target destruction. The optimization process was also expedited, reducing the time from about a week to approximately half a day. These results demonstrate the potential of machine learning techniques in accelerator design, offering a more comprehensive global optimization by exploring a broader parameter space and avoiding local minima.

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}.

The secondary beam production target at future positron sources at the Continuous Electron Beam Accelerator Facility (CEBAF), the International Linear Collider (ILC) or the Future Circular Collider (FCC), features unprecedented mechanical and thermal stresses which may compromise sustainable and reliable operation. Candidate materials are required to possess high melting temperature together with excellent thermal conductivity, elasticity and radiation hardness properties. In order to substantiate the material choice for the CEBAF and ILC positron sources, the response of candidate materials such as titanium alloys, tungsten, and tantalum to electron beam irradiation was experimentally investigated. CEBAF and ILC expected operating conditions were mimicked using the 3.5 MeV electron beam of the MAMI facility injector. The material degradations were precisely analyzed via high energy X-ray diffraction at the HEMS beamline operated by the Helmholtz-Zentrum Hereon at the PETRA III synchrotron facility. This work reports the results of these measurements and their interpretation.

An effective high-power positron converter for electron linear accelerators is not currently available from industry. A commercial source would allow research institutes to have ready access to high-brightness positrons for a wealth of material science, nuclear, particle, and accelerator physics projects. Xelera Research LLC has designed, built, and tested a prototype free-surface liquid-metal (GaInSn) jet converter. Free-surface liquid-metal jets allow for significantly greater electron beam power densities than are possible with solid targets. Higher power densities lead to greater positron production and, importantly, allow continuous wave (CW) operation. A modified version of the GaInSn converter prototype is planned to be constructed and tested at the Thomas Jefferson National Accelerator Facility.

The Shanghai Light Source has been operated since 2009 to provide synchrotron radiation to 40 beamlines of the electron storage ring at a fixed electron energy of 3.5 GeV. The Shanghai Laser Electron Gamma Source (SLEGS) is approved to produce energy-tunable gamma rays in the inverse Compton slant-scattering of 100 W CO2 laser on the 3.5 GeV electrons as well as in the back-scattering. SLEGS can produce gamma rays in the energy range of 0.66 – 21.7 MeV with flux of 1e+5 – 1e+7 photons/s*. A positron source based on SLEGS is designed to produce positron beams in the energy range of 3 – 16 MeV with a flux of 1e+5 /s and energy resolution of ~7% with an aperture of 10 mm collimator. The positron generated has been simulated by GEANT4, uses a SLEGS gamma injected into a single-layer target, and a dipole magnet deflect positrons. Based on the energy-tunable SLEGS gamma rays, the optimized parameters at each gamma energy were simulated to obtain an energy-tunable positron source. We have confirmed positron generation in the commissioning. We plan to construct the positron source in the summer of 2024. We present the positron source based on results of simulation and test measurements.

Photocathodes capable of producing spin polarized electrons beams are required for both high energy and nuclear physics experiments. In this work, we describe in detail the commissioning of a new apparatus for photocathode characterization which includes a retarding field Mott polarimeter for the measure of photoelectron spin polarization. We will illustrate the design of superlattice structures equipped with Distributed Bragg Reflector and present the measurements of spin polarization and quantum efficiency of emitted electrons from these structures.

The FCC-e+e- project foresees the realization of the most intense ever realized source of positrons providing a bunch charge of the order of 5 nC. This big number of positrons (≈3.12e+10) is produced by pair conversion following a 6 GeV electron beam bremsstrahlung on a target, and as a consequence has large divergence and energy spread. The actual design of the positron injector includes a damping ring and a bunch compressor to reduce the beam particle distributions in the longitudinal and transverse phase spaces to values appropriate for the injection in the common LINAC, which accelerates both electron and positron beams from 1.54 to 6 GeV. An energy compressor installed after the positron LINAC improves the positron acceptance in the damping ring. This contribution presents relevant aspects related to the damping of the positron beam including the evaluation of the damping ring transmission efficiency through the whole transfer line from the positron source to the common LINAC, the energy compressor, and the bunch compressor in the injection and extraction branches of the Damping Ring.

Beam motion during injections could be a serious problem to x-ray users and jeopardize their experiments. In the Cornell Electron Storage Ring (CESR) the particles are injected with pulsed elements such as pulsed bumpers and septum which could cause transient motion of the stored beam. By analyzing the turn-by-turn position data of the stored beam acquired during injection, we identify the source of beam motion in different time scales. A new corrector coil is then designed to compensate the beam motion with 0.15 msec duration at a 60 Hz repetition rate in the vertical plane. In addition to the new corrector we also use one of the existing magnet coils to correct 60 Hz kicks and DC offsets. Although, during the last summer down the 60 Hz source was identified and suppressed by an order of magnitude, this corrector is still in use to minimize the injection transient. The waveforms, used to drive the correctors, are extracted based on the beam turn-by-turn coordinates and orbit kick analyses using the 110 CESR Beam Position Monitors data. In this paper we discuss the requirements and parameters of the new corrector, as well as the correction technique, which is proven to be effective.