We present the design and initial characterization of a multi-mode cavity, a novel electromagnetic structure with potential benefits such as compactness, efficiency, and cost reduction. The 2nd Harmonic mode was chosen to linearize the fundamental mode for use as an accelerating and bunching cavity. The reduction in the number of cavities required to bunch and accelerate promises cost and space savings over conventional approaches. Superfish and COMSOL simulations were used to optimize the cavity's geometry with the goal of balancing various design parameters, such as quality factor (Q-factor), harmonic modes, and mode coupling. A 3D-printed copper-plated cavity was used to validate code predictions. The cavity's multi-mode nature positions it for use with other harmonic modes with small deviations in design. For example, a 3rd Harmonic can be used to decrease energy spread by widening the peak of the fundamental. This research lays the foundation for further exploration of the cavity's applications and optimization for specific use cases, with potential implications for a wide range of accelerator fields.

This study focuses on the beam source for the LCLS-II-HE Low Emittance Injector (LEI) design: a state-of-the-art superconducting radiofrequency (SRF) gun. The LEI is intended to enable extending the LCLS-II-HE’s useful photon energy to 20 keV without additional cryomodules. We consider a robust two-slit emittance measurement optimized for the LEI SRF gun, compatible with the current LEI gun-to-linac beamline design, and extensible to measuring photocathode mean transverse energy (MTE) with the cathode at or below 4 K. In-situ measurement of photocathode MTE, and evolution thereof, could help optimize the overall performance of the LEI. A two-slit method enables determination of the detailed phase-space distribution of the electron bunch, beyond the normal Twiss parameters and emittance provided by methods such as solenoid scans. Additionally, we investigate the RF emittance by recessing the cathode. This allows us to study the influence of the RF field on the bunch phase space. In summary, our work introduces a cutting-edge two-slit emittance measurement methodology that combines different emittance-dampening techniques to isolate intrinsic emittance from the photocathode. Detailed results will be presented at the workshop to highlight established trends, dependencies, and a summary/concept of the future photocathode characterization beamline implementation.

SLAC’s LCLS-II-HE upgrade will expand the energy regime of their XFEL at high repetition rates. Due to the low emittance requirement, a superconducting QWR based electron gun was proposed by SLAC and is being developed by FRIB in collaboration with ANL and HZDR. The emittance compensation solenoid consists of two main coils, along with horizontal and vertical dipoles as well as normal and skew quadrupole correctors. To validate the performance and characterize the field profile of the magnet, we developed a mapper system. We utilized a SENIS 3D Hall probe on a cantilevered rail driven by an Arduino controlled stepper motor. With high repeatability, we were able to measure peak field strengths and fall off. Further data analysis allowed us to determine their relative locations, in addition to confirming alignment and integrated field strengths. In accordance with design specifications, we measured the peak solenoid fields to be about 172mT and their centers to be less than 0.1mm apart transversely. The mapping design, assembly, process, analysis, and lessons learned are discussed herein.

We present the design and initial characterization of a multi-mode cavity, a novel electromagnetic structure with potential benefits such as compactness, efficiency, and cost reduction. The 2nd Harmonic mode was chosen to linearize the fundamental mode for use as an accelerating and bunching cavity. The reduction in the number of cavities required to bunch and accelerate promises cost and space savings over conventional approaches. Superfish and COMSOL simulations were used to optimize the cavity's geometry with the goal of balancing various design parameters, such as quality factor (Q-factor), harmonic modes, and mode coupling. A 3D-printed copper-plated cavity was used to validate code predictions. The cavity's multi-mode nature positions it for use with other harmonic modes with small deviations in design. For example, a 3rd Harmonic can be used to decrease energy spread by widening the peak of the fundamental. This research lays the foundation for further exploration of the cavity's applications and optimization for specific use cases, with potential implications for a wide range of accelerator fields.

In a radiofrequency accelerating structure with ceramic insertion, high shunt impedance (162 megaohm/m) and high group velocity (3.1% of the speed of light) are achieved simultaneously. The ceramic insertion is in the form of a cylinder, sandwiched between copper endplates with the beam aperture opened at the center. We report our theoretical study on this novel type of traveling wave accelerating structure that operates with a 2pi/3-mode at 5.7 GHz. The high shunt impedance is realized by the low-loss, highly reflective ceramic insertion confining the accelerating mode at the center. The high group velocity, or fast filling time of the radiofrequency wave, is made possible by the side coupling slots designed with large dimensions. As a result, this novel traveling wave accelerating structure enhances the power efficiency significantly, by two means. The high shunt impedance allows providing a greater accelerating gradient with a given amount of radiofrequency power. The fast filling time allows an earlier start of the beam acceleration within each radiofrequency power pulse, thus leading to a higher duty factor of the accelerator beam production. This type of the structure design allows using metallic iris features, which minimizes the electric field magnitude witnessed by the ceramic component. We also discuss the scheme of using periodic permanent magnets to focus an electron beam in the accelerating structure. The unique radiofrequency coupler design is also addressed.

The Los Alamos Neutron Science Center (LANSCE) is one of the oldest operating high-power accelerators in the United States, having recently celebrated its 50th anniversary of operation. LANSCE is comprised of an 800-MeV linac capable of concurrently accelerating both H+ and H- ions, and can presently provide beam to six separate user stations. The proposed LANSCE Modernization Project (LAMP) is intended to revitalize and enhance the performance of two key areas in the LANSCE accelerator complex: the front end of the accelerator, from the sources to the end of the drift tube linac at 100 MeV; and the 800-MeV proton storage ring, or PSR. This paper provides a high-level overview of the proposed LAMP scope of work, timeline and performance goals.

The proton storage ring (PSR) upgrade for the LANSCE Modernization Project aims to minimize the yearly maintenance outage by minimizing beam loss. Several improvements could potentially impact the beam dynamics in the PSR, including a larger coated beam pipe and new buncher, injection, and extraction systems. The larger diameter, from 4” to 6”, will directly impact the beam dynamics due to an increased pole-to-pole gap height within the dipoles and quadrupoles, which would in turn increase their effective length and alter their fringe field profiles. In this work, a simulation model of the PSR ring was developed using the particle tracking code pyORBIT to study the effect of different beam pipe diameters on the beam optics. The parameters of the injected beam are derived from an existing model of the PSR injection system, and the resulting beam parameters will be used in a simulation model of the extraction system, to be presented separately at the conference. The pyORBIT results were benchmarked against beam optics simulations created using accelerator codes including MAD-X, etc. The pyORBIT simulation model of the PSR ring will be described, and the results will be presented at the conference.

The Los Alamos Neutron Science Center (LANSCE) is one of the oldest operating high-average-power accelerators in the United States, having recently celebrated its 50th anniversary of operation. LANSCE is comprised of an 800-MeV linac capable of concurrently accelerating both H+ and H- ions, and can presently provide beam to six separate user stations. The Proton Storage Ring (PSR) at LANSCE acts as a pulse-stacker, providing intense bunches of protons to the Lujan neutron scattering center target. Critical subsystems have become increasingly difficult to maintain due to spare parts availability; more generally, the PSR contributes significantly to our annual maintenance duration due to beam spill and component activation. The proposed LAMP project would extend the operating lifetime and improve the operational characteristics of the PSR via increasing the physical aperture by 50%; modernizing and improving the performance of the RF buncher system, extraction kickers and impedance inserts; and updating the injection line and stripper foil system for reduced injection losses and improved maintainability. This paper provides an overview of the PSR portion of LAMP.

The Los Alamos Neutron Science Center (LANSCE) is one of the oldest operating high-average-power accelerators in the United States, having recently celebrated its 50th anniversary of operation. LANSCE is comprised of an 800-MeV linac capable of concurrently accelerating both H+ and H- ions, and can presently provide beam to six separate user stations. The LANSCE accelerator operates with much of its original equipment, including the Cockcroft-Walton injectors and drift-tube linac. As part of the proposed LANSCE Modernization Project (LAMP), a refurbishment and upgrade effort would replace the initial portion of the LANSCE accelerator, from ion sources to the end of the 100-MeV drift-tube linac. This paper describes the overall approach taken to establish performance goals, downselect a preferred technology approach, and identify viable pathways towards implementation.

This paper will describe efforts to simulate and test materials for the LANSCE PSR stripper foils. Stripper foils convert H- beams to H+ as part of the charge-exchange injection process in the LANSCE PSR that produces high intensity proton beams. The foil properties directly affect the total current and activation in the ring, and their overall robustness also determines the types of experiments that can be done, as the number of available foils is limited and some modes are particularly destructive to the foils. We will describe a preliminary approach to modelling, characterizing, testing and optimizing PSR foils performance and lifetime given the extreme heat and radiation conditions which can heavily constrain both characterization and testing, and note potential opportunities for a PSR upgrade as part of LAMP.

In late 2023 (6-8 November), Los Alamos National Laboratory hosted the “UED Opportunities for Dynamical Imaging of Materials” workshop in Santa Fe, New Mexico. The workshop was divided into two sections. The first part (1.5 days) was dedicated to material science and needs for UED imaging, and the second part (1 day) to discuss accelerator science driving next generation ultra-fast diffraction systems. In this workshop, emphasis was placed on identifying current and future scientific problems that will utilize compact MeV-UED machines, discussing state-of-the-art technological advances, and exploring future opportunities for MeV-UED machine developments. This paper will present an overview of the workshop’s goals and summarize discussions and conclusions.

It is desirable to decrease the dimensions and power loss of accelerator components as much as possible when using accelerated charged particle beams on a rocket or satellite for ionospheric and magnetospheric research applications. We present the experimental results of a radiofrequency (RF) pillbox cavity loaded with a low-loss, high-permittivity ceramic placed concentrically within the cavity. We use high-electron mobility transistors (HEMTs) to power the RF at a frequency of 5.712 GHz. At this frequency, the cavity operates at a TM020 mode. The ceramic enhances the cavity's accelerating field confined within the scope of the ceramic insertion, increasing the shunt impedance, and improving the power coupling from the RF to the electron beam with the same gradient as a conventional TM010 mode cavity. Moreover, because the power coupling to the beam is improved, we were able to reduce the longitudinal dimension of the cavity compared to the conventional cavity. We show that the cavity accelerated the beam by approximately 12 keV. We also show that the cavity and ceramic can survive a flight to space by conducting vibration and shock tests that replicate the rocket launch environment.

There is increasing interest in developing accelerator technologies for space missions, particularly for fundamental science. In order to meet these mission needs, key accelerator technologies must be redesigned to be able to function more reliably and efficiently in a remote and harsh environment. In this work we focus on a modest electron injector system, specifically the traditional thermionic cathode. Typically such cathodes are resistively heated by a power supply that is floated at the cathode accelerating negative high voltage. This can increase engineering complexity and add a significant load to the accelerating voltage supply. We pursue laser heating a thermionic cathode in order to remove the heater power supply from the injector system, allowing for reduced engineering complexity and power requirements for the injector. To date we have shown that a simple tantalum disk cathode can be heated by a laser with similar emission performance to the same disk resistively heated.

Ultrafast electron diffraction and microscopy (UED/UEM) has advanced beyond proof-of-concept stage into the realm of instrumentation. To date, most UED/UEMs have been constructed around high-gradient RF-driven electron guns designed as X-FEL beam sources. A UED/UEM system driven by a CW beam, either normal- or superconducting, offers several potential performance benefits over high-gradient pulsed beam sources. These include the ability to operate at much higher average repetition rates, and the ability to extend measurement times beyond O(1 μs). If a quarterwave-type beam source is used, there is an additional possibility to vary the time between probe pulses by other than an RF period. In this paper we present the basis for this claim, discuss implications for detectors, and consider also utilization of probe electron beams at different beam energies.

This study focuses on the beam source for the LCLS-II-HE Low Emittance Injector (LEI) design: a state-of-the-art superconducting radiofrequency (SRF) gun. The LEI is intended to enable extending the LCLS-II-HE’s useful photon energy to 20 keV without additional cryomodules. We consider a robust two-slit emittance measurement optimized for the LEI SRF gun, compatible with the current LEI gun-to-linac beamline design, and extensible to measuring photocathode mean transverse energy (MTE) with the cathode at or below 4 K. In-situ measurement of photocathode MTE, and evolution thereof, could help optimize the overall performance of the LEI. A two-slit method enables determination of the detailed phase-space distribution of the electron bunch, beyond the normal Twiss parameters and emittance provided by methods such as solenoid scans. Additionally, we investigate the RF emittance by recessing the cathode. This allows us to study the influence of the RF field on the bunch phase space. In summary, our work introduces a cutting-edge two-slit emittance measurement methodology that combines different emittance-dampening techniques to isolate intrinsic emittance from the photocathode. Detailed results will be presented at the workshop to highlight established trends, dependencies, and a summary/concept of the future photocathode characterization beamline implementation.

The core components of the LANSCE accelerator complex – the beam source area, drift-tube and cavity-coupled linear accelerators – are more than 50 years old; a critical subsystem for beam delivery to the Lujan Center, the proton storage ring (PSR), is more than 20 years old. The proposed LAMP project is intended to begin a revitalization and update of the LANSCE accelerator complex, starting with the beam source region, drift-tube linac, and PSR. To help assure we have selected an optimal candidate design for the source region, an internal workshop was held in August 2023 to consider options for providing two beam species at the peak and average currents, and beam macropulse formats, required by the various LANSCE user stations. This document describes the workshop goals and processes, presents the various configurations considered, and lists the results of the downselect process and potential paths forward.

The Los Alamos Neutron Science Center (LANSCE) accelerator delivers high intensity proton beams for fundamental science and national security experiments since 1972. The Proton Storage Ring (PSR) accumulates a full 625-us macro-pulse of proton beam and compresses it into a 290-ns long pulse, delivering an intense beam pulse to the Lujan Neutron Science target. The proposed LANSCE Modernization Project (LAMP) is evaluating necessary upgrades to the accelerator that will guarantee continuous beam operations in the next decades. Upgrades to the PSR and its high-energy injection and extraction beamlines are being considered to handle the higher beam intensity enabled by the LAMP upgrades in the front-end. For the PSR upgrades studies, we are building models of the PSR injection and extraction lines in codes which include space charge calculations like Elegant and Impact. These better illustrate the beam dispersion and the beam halo in the high-energy transport. This work describes the LANSCE PSR injection and extraction lines and the corresponding simulation models. The models are compared to available beam diagnostics data where available.

The Los Alamos Neutron Science Center (LANSCE) accelerator delivers high intensity proton beams for fundamental science and national security applications since 1972. LANSCE is capable of simultaneous H+ and H- beam operations to multiple experiments requiring different time structures. This is achieved upstream in the facility with a combination of two 750 kV Cockcroft-Walton (CW) generators, a chopper and radiofrequency cavities, before going into the 800-MeV linac. The proposed LANSCE Modernization Project (LAMP) is evaluating critical machine upgrades necessary to continuous beam operations in decades to come. A significant component of LAMP is replacing the two CW with a dual-species 3-MeV Radiofrequency Quadrupole (RFQ). This change requires a full re-design of the LAMP front-end accelerator to deliver the existing and expanded capabilities of the facility. This contribution will discuss the LAMP front-end accelerator layout based on the general beam requirements and on standard accelerator codes, showcasing the start-to-end propagation of H+ and H- beams from the source to the linac entrance.

The Los Alamos Neutron Science Center (LANSCE) accelerator uses charge exchange injection to accumulate a high-intensity proton beam in the Proton Storage Ring (PSR). H- ions are accelerated to 800 MeV and then stripped of their electrons by a thin foil at the ring injection site. The Monte Carlo N-Particle (MCNP) radiation transport code has been used to estimate the effect foil thickness has on the emittance growth of the ion beam. Results for the scattering angle of individual particles and emittance growth of the injected beam are presented for a range of foil thicknesses.