The Los Alamos Neutron Science Center (LASNCE) is over 50 years old. Currently, Cockroft-Waltons are being used to accelerate H+ and H- beams to 750 keV. The LANSCE Modernization Project (LAMP) is proposing to replace the font-end of LANSCE with a Radio-Frequency Quadrupole (RFQ). A RFQ Test Stand is being commissioned at LANL for technical demonstration of simultaneous dual-beam species acceleration through a RFQ under the timing constraints required by the LANSCE users facilities. We will describe the status and present initial results of the 35keV H+ line on the RFQ Test Stand.

We present a beam-focusing architecture using electro- and permanent magnets for a novel compact electron beam buncher under development for space-borne electron accelerators. Developing compact and efficient accelerator components has become desirable with renewed interest in using space-borne electron beams for ionospheric aurora research and very low frequency wave generation for particle removal from the magnetosphere. An electron gun injects a direct current electron beam, and the buncher modulates the DC beam into periodic bunches at a frequency of 5.7 GHz. A 5.7 GHz linear accelerator in the downstream will capture the bunched beam with minimal acceptance mismatch. The beam modulation is done by three radiofrequency pillbox cavities. The buncher uses the electrostatic potential depression (EPD) method to shorten the structure length remarkably. The electron gun and a tunable solenoid provide the initial focusing of the beam. We then use a series of permanent magnets surrounding the buncher cavities clamped together by ferromagnetic steel plates to focus the beam through the buncher. Permanent magnets do not consume any power and weigh less than solenoid magnets, which provide equivalent focusing, making them ideal for use on a satellite or sounding rocket. We use the three-dimensional (3D) particle tracking solver from CST Studio Suite to simulate the beam-focusing.

THz (1e+12 Hz) radiation is very attractive for its non-ionizing penetrative nature and unique absorption in water, metals, and other chemicals. While THz has great potential for imaging and for diagnosing chemical traces, it has not been utilized extensively due to scarcity of high-power THz sources. Currently, compact THz sources deliver power in the range of 50 μW — 0.5 W, insufficient for most imaging and sensing applications. A compact THz sources is proposed to mitigate this gap of technology. FELs have been used for THz generation but have not been compact enough for most applications. The recent demonstration of waveguide THz FELs [1] has opened the door to more compact THz FELs. We propose a design of a seeded THz FEL with an overmoded waveguide. In addition, an efficient use of compact photoinjector to drive particles in energy of 2-4 MeV greatly reduces the overall footprint by 20%. We plan to use high-power GUNN diodes provides to efficiently seed THz power to the electron bunches, reducing the overall length of the device by 200%. An overmoded waveguide will allow for a larger waveguide to be used. The design has the potential to unleash full potential of THz spectrum.

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.

This poster will discuss the design of the photocathode vacuum suitcase that we currently design and construct for the Cathodes And Radiofrequency Interactions in Extremes (CARIE) test stand. The CARIE test stand is built to test behavior of the high quantum efficiency photocathodes at strong fields. The semiconductor photocathodes must be grown and delivered to the photoinjector under ultra-high-vacuum (UHV) conditions in order to maintain their properties. This is typically done using portable UHV vacuum systems called vacuum suitcases. We will discuss the vacuum and photocathode handling design of the CARIE vacuum suitcase and the status of the suitcase construction and testing.

We report simulation results showing the use of sacrificial bunch charge to achieve high brightness in photoinjector beamlines designed for Ultrafast Electron Diffraction (UED) and Inverse Compton Scattering (ICS). The beam undergoes nonlaminar focusing during which the tails dynamically linearize the core’s transverse phase space. An aperture then removes the resulting diffuse tails, leaving a beam with high brightness. We employ this scheme in C-band photoinjector guns, whose high gradients are attractive for both low (UED) and high charge (ICS) applications. In our simulations we use a 1.6 cell gun with a peak field at the cathode of 240 MV/m. We start with negligible intrinsic emittance and use a multi-objective genetic algorithm to obtain a Pareto front minimizing bunch length and emittance. For ICS applications, we obtain an extremely small minimum emittance of 80 nm at a final charge of 250 pC per bunch and 1.44 ps rms bunch length. For a final bunch charge of 1e+5 electrons, typical for UED experiments, we obtain an emittance of 1.2 nm at an rms bunch length of 50 fs. Both results far exceed the brightness state of the art for these applications.

The TopGun photoinjector is a 1.6-cell C-band gun developed by the University of California, Los Angeles team. Originally optimized for 100 pC operation, its low emittance design has been our starting point. However, the Los Alamos National Laboratory (LANL) needs to operate with a 250 pC bunch charge while maintaining an emittance below 100 nm. The initial optimization of the high charge TopGun-like photoinjector design, intended for construction at LANL, has been previously reported. That design had a single objective: achieving the lowest possible emittance, which was attained at significantly longer bunch length, thereby limiting improvements in beam brightness. Here, we present a multi-objective genetic optimization of the high charge TopGun-like photoinjector design to obtain a Pareto front minimizing bunch length and emittance. We have successfully reduced the bunch length from 8.18 ps to 5.67 ps while maintaining similar emittance values.

Higher-order mode (HOM) damping is essential for building large-scale facility linear accelerators, such as a linear collider, because of the need to reduce the wakefield strength inside the accelerating structure. We designed a C-band accelerator cavity with distributed coupling and thin HOM-damping waveguides oriented in the radial direction. It was proposed that nickel-chrome (NiCr) coating deposited on the surface of the thin waveguides will be used to increase the surface resistivity and to damp the HOMs. Recently, we designed a two-cell cavity to conduct a concise high power test that will help us understand the fabrication challenges for the cavity with NiCr HOM absorbers, and examine the performance of the NiCr coating under high-power conditioning. This presentation will report the detailed electromagnetic and engineering design of the cavity, the theoretical prediction of the cavity high-gradient performance, the status of fabrication, and plans for high-gradient testing.

The Cool Copper Collider (C3) is a novel accelerator concept for a linear collider utilizing a cryogenically-cooled copper linear accelerator (linac) with a distributed coupling architecture. The C3 main linac is designed to accelerate electron/positron from 10 GeV to 125 GeV while preserving the beam emittance. Here we present the analysis of the multi-bunch beam dynamics for the C3 main linac. We show the beam dynamics simulation results of the C3 main linac to identify the frequency bands that cause emittance growth and the amount of frequency detuning required to suppress it. Results presented will be used to guide the future design of the accelerating structure.

A very high electron peak current is needed in many applications of modern electron accelerators. To achieve this high current, a large energy chirp must be imposed on the bunch so that the electrons will compress when they pass through a chicane. In existing linear accelerators (LINACs), this energy chirp is imposed by accelerating the beam off-crest from the peak fields of the RF cavities, which increases the total length and power requirements of the LINAC. A novel concept known as the Transverse Deflecting Cavity Based Chirper (TCBC) [1] can be used to actively impose a large energy chirp onto an electron beam in an accelerator, without the need for off-crest acceleration. The TCBC consists of 3 transverse deflecting cavities, which together impose an energy chirp while cancelling out the transverse deflection. An experiment is being developed to demonstrate this concept at the Argonne Wakefield Accelerator (AWA) facility. Here we explain the concept, show preliminary simulations of the experiment, and report on progress related to implementation of the experiment at AWA.

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.

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.

The C-band (5.712 GHz) accelerating structure with distributed coupling and four waveguide manifolds for HOM damping has been studied at Los Alamos National Laboratory to evaluate suppression of the higher-order-modes (HOMs). The HOM damping manifolds were covered by Nickel Chrome (NiCr) and had rounded edges at the interface of the waveguide with accelerating cavities. In this design study, we modeled a 20-cell accelerating structures and calculated the Q-factors and the transverse kick factors for the wakefields in the frequency range up to 40 GHz. Simulations were performed with the Omega3p code. The goal of the study was to bring all Q-factors below 10000 and kick-factors x Q-factors below 1000 V/pC/mm/m for all major HOMs. This presentation will summarize the results of the study.

This presentation will report on the status of assembling and commissioning of the Cathodes And Radio-frequency Interactions in Extremes (CARIE) C-band high gradient photoinjector test facility at Los Alamos National Laboratory (LANL). The construction of CARIE began in October of 2022. CARIE will house a high gradient copper RF photoinjector with a high quantum-efficiency cathode and produce an ultra-bright 250 pC electron beam accelerated to the energy of 7 MeV. The 50 MW 5.712 GHz Canon klystron will power the facility. The klystron was received and installed in fall of 2023. The WR187 waveguide line brings the power from the klystron into a concrete vault that is rated to provide radiation protection for an electron beam powers up to 20 kW. The first RF injector that was fabricated is made of copper and does not have cathode plugs. This injector will be commissioned to validate operation of the CARIE facility. The second injector that will accommodate cathode plugs and novel photocathodes was designed and will be fabricated. The status of the facility, the designs of the photoinjector and the beamline, and plans for photocathode testing will be presented.

High frequency RF guns cryogenically cooled to liquid nitrogen temperatures or lower offer potential for extreme accelerating electric fields exceeding 250 MV/m at the cathode. This can result in enormous increase in the brightness of electron beams obtained from RF guns but can be challenging to integrate high QE photocathodes. This talk will detail the efforts at LANL towards the realization of such a gun and possibly the first field and beam results from a C band room temperature gun.

The Los Alamos Neutron Science Center (LANSCE) accelerator produces high intensity H+ and H- beams for multiple experiments in fundamental and national security science. The proposed LANSCE Modernization Project (LAMP) is evaluating necessary upgrades to enable continuous LANSCE operations in years to come. LAMP seeks to upgrade the H+ and H- 750 kV Cockcroft-Walton (CW) generators with a dual-beam, 3-MeV Radiofrequency Quadrupole (RFQ). For technology maturation and know-how associated with this concept, an RFQ test stand with LAMP-like layout is being set-up to demonstrate dual-beam operation in an RFQ with all beam patterns required by experiments. The RFQ test stand will have 35-keV H+ and H- beamlines that simultaneously inject into a 750 keV RFQ. Assembly and initial characterization of the H+ beam is under way. The H- beamline has stringent requirements and will also demonstrate systems like a beam chopper and a low frequency buncher to produce required beam patterns. We describe the design of the H- beamline based on accelerator codes Warp and Impact.

At Los Alamos National Laboratory (LANL), we developed a 1.6-cell C-band RF photoinjector for the Cathodes And Radiofrequency Interactions in Extremes (CARIE) project. The injector will be used to study the behavior of advanced photocathode materials under very high RF gradients. The photocathodes will be prepared with an INFN-style photocathode plug, compatible with the plugs used by other institutions. This presentation will report the RF design of the photoinjector with distributed coupling and RF field symmetrization. Beam physics simulations show that symmetrized RF fields in the vicinity of the beam axis are essential for minimizing the normalized emittances for a 250-pC electron bunch. We will also present the design for the photocathode insertion and the analysis of the challenges related to reducing the peak electric fields, multipactor suppression, and resonant frequency tuning by fine adjustment of the plug position.