Recent trends in power electronics indicate increasing demand for fast response switching networks with sub nanosecond switching speed at a variety of volt-ages. Gate driving networks meet the desired switching speeds using COTS (Commercial Off-The Shelf) parts. This work describes an IVA (Inductive Voltage Adder) system capable of switching in the single digits of ns with a projected voltage output of 2 kV, using a gate driving topology to drive GaN (Gallium Nitride) HEMTs (High Electron Mobility Transistor). These rapid switching systems are proposed to be used in the LAMP (LANSCE Accelerator Modernization Project) chopper to effectively produce clean beam to select target stations, producing the needed output.

When the closed-orbit spin tune is ramped linearly through an isolated spin-orbit resonance, the asymptotic polarization loss is well-approximated by the Froissart-Stora formula. However, it is often observed in accelerator simulations that the crossing speed, defined as the slope of the amplitude-dependent spin tune with respect to the machine azimuth, changes at the moment of resonance crossing. For example, the behavior of the amplitude-dependent spin tune in the vicinity of a higher-order spin-orbit resonance can often be reasonably approximated by such a piecewise-linear function. In this paper, we derive an extension to the Froissart-Stora formula which describes the asymptotic polarization loss in the case of changing crossing speed. We then demonstrate that this formula provides a good estimate of the polarization lost when crossing a higher-order spin-orbit resonance in both a toy model and simulations of RHIC.

A new method is formulated for calculating the invariant spin field (ISF) at a phase space point by leveraging the property that spins which are distributed along the ISF achieve maximum time-averaged polarization. To quantify this, we construct the time-average of spin rotation matrices beginning at a certain phase space point. It is recognized that the ISF vector at that point achieves the matrix-norm, meaning that the ISF corresponds to the first right-singular vector of that matrix. We show the relation of this method with traditional stroboscopic averaging, such that these methods are two sides of the same coin. This approach offers a new perspective in invariant spin field calculations.

Monte Carlo simulations are a powerful tool for modeling photoemission from photocathodes, enabling the prediction of key parameters such as quantum efficiency, mean transverse energy, electron spin polarization, and photocathode response time. However, these simulations require material band structure parameters, which are not always available from experiments. This work aims to establish a reliable framework for calculating electronic band structure parameters using Density Functional Theory (DFT). Specifically, we apply this framework to investigate the effects of lattice strain and temperature on the electronic band structure and electron transport in GaAs. This approach will be further extended to explore band structure modifications in heavily p-doped semiconductors and to calculate electronic band structures of novel spin-polarized photocathode materials.

Spin motion in particle accelerators obeys the Thomas-Bargmann-Michel-Telegdi (T-BMT) equation. Due to the structure of the T-BMT equation, the spin-transfer quaternion of a magnet is generally a nonlinear function of the entrance coordinates even if the phase-space motion is linear. This nonlinear function can be written as a Dyson expansion, for example as employed in the program SPRINT, which normalized the first-order expansion of the spin-transfer quaternion. Alternatively, this nonlinear function can be written as a Magnus expansion. This paper points out that in cases where the phase-space coordinates change little, as is generally the case for accelerator elements, the Magnus expansion is a much more appropriate method to describe the nonlinear spin motion because this expansion terminates after the first term when the phase-space coordinates are constant. We will demonstrate, with several examples, that an approximation based on the Magnus expansion leads to very good agreement with time-consuming numerical integration, and to significantly better agreement than obtained with historical codes like SPRINT.

The Hadron Storage Ring of the Electron-Ion Collider will feature 6 Siberian snakes placed at the start of each arc to coherently cancel spin precession from diametrically opposite arcs in the ring. To avoid spin-orbital resonances, the alternating sum of the rotation axes of all snakes is 90 degrees, ensuring the closed-orbit spin tune is ½ and sufficiently far away from betatron tunes and integer tunes. This choice does not account for amplitude-dependent spin tune (ADST) shift, which introduces high-order spin orbit resonances in the vicinity of strong first-order resonances. By varying betatron phase advances across each of the 6 arcs, we minimize the strength of first-order spin-orbit resonances as well as ADST shift. In the case of uncooled helium-3, we find it is necessary to minimally vary the vertical orbital tune as well but are able to completely avoid depolarization throughout the ramp with time-dependent phase advances.

Our work addresses the challenge of estimating spin polarization in high-energy electron and positron storage rings, such as the Electron Storage Ring (ESR) of the Electron-Ion Collider (EIC) at Brookhaven National Lab (BNL) and those in the electron/positron Future Circular Collider (FCC-ee) at CERN. We model the spin and orbital motion of particle bunches using the recently introduced spin-orbit Fokker-Planck (SOFP) equation, a linear time-evolution partial differential equation (PDE). In this paper, we propose a novel machine learning (ML) approach leveraging a randomized Fourier neural network (rFNN) framework, specifically designed to solve linear PDEs. We will discuss the SOFP highlight its relevance to spin polarization studies, and share preliminary results demonstrating the network’s performance on the Poisson problem.

Wakefield accelerators have the potential to achieve accelerating fields in the GV/m range, offering a promising path to more compact and cost-effective acceleration compared to conventional methods. Structure-based wakefield accelerator (SWFA) technology provides a viable approach to implementing beam-driven wakefield acceleration. An experiment at the Argonne Wakefield Accelerator (AWA) will utilize dielectric-lined structures to explore multi-beam excitation of wakefields for wakefield-pulse shortening and mapping of the transverse wakefield topology. These structures were commercially sourced and require a thin metallic film deposited on their outer surface. The first part of this paper summarizes the preparation of these structures. In parallel, a two-bunch beam configuration is required to support the experimental investigation, where one bunch excites the wakefield and the second serves as a loading or probe bunch. The experimental generation and testing of this two-bunch scheme at AWA are presented in this work.

High quantum efficiency (QE) semiconductor photocathodes are essential for generating high average beam current and brightness. One class of semiconductor photocathodes considered for use in photoinjectors for unpolarized and polarized electron beams are III-nitride heterostructures. These materials can exhibit negative electron affinity at the surface, utilizing intrinsic polarization fields to engineer the band structure without the need for additional surface treatments. In this study, we investigate the effects of light exposure on the surface of III-nitride photocathodes and the resulting changes in QE and photoemission, using photoemission electron microscopy (PEEM) for characterization. We demonstrate that exposing a GaN photocathode to a 240 nm wavelength laser at 870 µW for 15 minutes increases the QE by two orders of magnitude, with a maximum QE of 2.34 × 10⁻⁴ observed. Although III-nitride photocathodes are known for their robustness, our findings indicate that laser exposure can significantly alter their QE. Our observations reveal the need for a detailed investigation of photo-induced effects on QE in III-Nitride photocathodes.

This paper deals with estimating spin depolarization in planned very high energy electron-positron storage rings like the FCC-ee. The paper covers three aspects of the work: 1) the putative so-called uncorrelated resonance crossing due to noise in the spin-rotation phase advance caused by photon emission in synchrotron radiation. This is expected to suppress the depolarization caused by synchrotron sideband resonances, 2) a study of the performance of our code on multiple high performance systems, and 3) the novel exploitation of a high order Magnus expansion applied to spin transport. The study uses Monte-Carlo spin-orbit tracking for a simple model of spin motion, the so-called single resonance model, augmented by the effects of radiation. The results presented here represent the first steps of a planned detailed large-scale exploration.

The OPPIS has undergone multiple upgrades since 2000, with the most recent completed in 2022. Improvements to the Rb and Na cells have reduced vapor dispersion in the beamline, significantly lowering consumption and improving source stability. Plasmatron modifications extended component lifetimes. These upgrades enabled reliable Run-24 operation, with a mean current of 350 μA, 300 μs pulse width, and ~80% polarization delivered at the 200 MeV linac exit. Development is also underway for a high-intensity (2×10¹¹ ions/pulse) polarized ³He⁺⁺ source for the future EIC. The approach uses metastability-exchange optical pumping of high-purity ³He gas in a strong magnetic field, followed by ionization in EBIS. In tests with an “open” cell, 80–85% polarization has been achieved. The final gas cell configuration is now being tested with a 5 T EBIS solenoid magnet.

The Argonne Wakefield Accelerator (AWA) facility operates a high-charge (100s of nC) electron beam in a bunch train, with eight electron bunches at a 769 ps spacing matching the linac operating frequency of 1.3 GHz. AWA’s electron beam is optimized for producing large wakefields in resonant structures to study structure wakefield acceleration. This is achieved by maximizing total beam charge, and by correct bunch train timing to enhance the wakefield via inter-bunch coherence. The properties of the bunch train are determined by a “multisplitter” in the photoinjector laser system, in which a series of beamsplitters splits one laser source into eight - ideally equal - pulses. However, AWA’s previous system did not split pulses evenly, with up to a 2:1 ratio between pulse energies within a train. Damaging electrical breakdown events within the electron gun, driven by high single bunch charge, occurred at lower total charge in this non-uniform set-up, limiting maximum charge. Thus, a new multisplitter using polarizing beamsplitters and half-wave plates (HWPs) was implemented. Unlike the previous fixed-ratio beam-splitter design, the new system enables tuning the splitting ratio for each beamsplitter, resulting in a more uniform pulse train. Large 2” optics and uncoated HWPs are also used to increase the laser intensity damage threshold (LIDT). This paper presents the design, characterization and lessons learned in early commissioning of AWA's upgraded laser pulse train generator.

We report on the implementation of the rocking curve imaging setup with a silicon (111) channel-cut crystal beam expander at Stanford Synchrotron Radiation Light source (SSRL) B17-2. B17-2 is a high-brightness, in-vacuum undulator (IVU) hard X-ray (~5 – 18 keV) beamline optimized for material scattering applications. Recently, we utilized it to perform rocking curve imaging (RCI) of diamond and silicon crystals. The expander is installed in addition to the previously existing RCI optics setup. We achieved horizontal beam magnifications of up to 1.38x at 6.951 keV and 2.25x at 9.831 keV. This work presents the updated RCI setup and experimental results to validate the performance of the Si (111) expander. Future improvements to the setup are also mentioned.

Spin-polarized electron sources find application in both high-energy and nuclear physics experiments. We describe in detail the design and characterization of different photocathodes based on GaAs/GaAsP superlattice structures. These structures are fabricated with a Distributed Bragg Reflector (DBR) aimed at achieving a high quantum efficiency (QE)~ 20% in addition to a high electron spin polarization (ESP) ~85% at the desired wavelength of 780 nm. We present the QE and ESP measurements of photoemitted electrons as a function of wavelength of incident light, along with morphological and photoluminescence measurements.

Jefferson Lab (JLab) is developing a concept to upgrade the Continuous Electron Beam Accelerator Facility (CEBAF) to additionally deliver spin-polarized continuous-wave positron beams for its nuclear physics program users (Ce+BAF 12 GeV). The concept involves repurposing the Low Energy Recirculator Facility (LERF) at JLab as a dual injector, first producing 100-300 MeV spin-polarized electron beams which are subsequently used for the generation and formation of 123 MeV continuous-wave positron beams. The positron beams are transported to CEBAF and injected for acceleration up to 12 GeV, tailored to the requirements of its four experimental halls. Given the higher emittance of the secondary positron beams, the CEBAF optics are optimized for low dispersion and low beta functions to enhance transmission within the Ce+BAF acceptance limits and with an R56 to manage the positron beams bunch length and energy spread. Potential bottlenecks are being investigated through both optical modeling and measurements using an electron beam, as well as degraded electron beams, to map the 6d acceptance of CEBAF as it is today. This presentation shares preliminary results from multi-particle tracking simulations of the positron beam up to 12 GeV, including spatial, momentum, and spin characteristics, and explores the feasibility of delivering beams simultaneously to multiple experimental halls via extraction optics.

A baseline concept for a continuous wave (CW) polarized positron injector was developed for the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab. This concept is based on the generation of CW longitudinally polarized positrons by a high-current, polarized electron beam (1 mA, 130‑370 MeV, and 90% longitudinal polarization) that passes through a rotating, water-cooled, tungsten target. The simulation results for the Ce+BAF injector at the Low Energy Recirculator Facility (LERF) are presented, including positron beam generation, capture, energy selection, and acceleration to 123 MeV. The positron yield (or positron current) and longitudinal polarization are calculated considering the longitudinal and transverse CEBAF acceptances (<1% energy spread, <1 mm bunch length and normalized emittance of <100 mm mrad). The impact of target thickness, drive electron beam energy, and transverse size on positron yield within the required emittance limit is evaluated.

Spin-transparent storage rings, where any spin direction repeats after one full turn, can be used in conjunction with ion traps as a new quantum computing platform [1]. Advantages of spin-transparent rings for quantum computing include: large numbers of stored qubits; long quantum coherence times of up to several hours; long storage lifetimes; and room temperature operation. These exceptional qualities mean rings could provide a scalable way to implement algorithms with deep complexity requiring many quantum operations while simultaneously providing a large number of qubits. This new platform where the qubit has long quantum coherence time can also be used as a quantum sensor or a part of a quantum memory.

We present a hybrid permanent magnet-based adjustable phase undulator, featuring a period length of 17.2 mm, a gap of 8.5 mm, and a total length of 2.4 m. This planar polarized undulator adjusts field intensity through longitudinal jaw movement, with mechanically linked magnet arrays ensuring smooth motion. Building on previous work, this report focuses on newly developed tuning techniques for trajectory and phase error correction. Our engineering experience demonstrates the effectiveness of these methods in optimizing undulator performance.