We report on adding a muti-wavelength emission and absorption diagnostic to the Los Alamos Neutron Science Center (LANSCE) H− ion source, a filament/arc driven, multi-cusp, surface conversion system. In this work we are better quantifying our runtime and source recycle processes. The LANSCE source is used in repeated four-week run cycles during the annual six-month run period. Here, we test the hypothesis that real-time monitoring of the plasma temperature and cesium density will provide feedback information to increase run cycle time, optimize H− current, and monitor the source’s health. We have installed system with fiber transport for monitoring the Hα Balmer line absorption strength of excited state hydrogen at 656 nm and the D2 absorption line of cesium at 852 nm. Our measurement and fiber transport to/from the active source provides a nonintrusive method for extracting data from the source’s 750 kV high voltage environment. Collection of TLDS absorption and emission lines from excited states are incorporated into the data collection scheme with a series of narrow-band dichroic mirrors. Our design of a sweeping TLDS allows for collection of emission and absorption data within the same sub-millisecond plasma arc pulse, and the combination of these measurements allows us to monitor the generating hydrogen plasma temperature and cesium density during ion source conditioning and operations.

The LANSCE proton storage ring (PSR) accumulates 795 MeV protons into a short, 290 ns pulse over 625 μs, or about 1745 turns. One of the primary limitations for maximum proton pulse intensity is beam loss between the H⁻ stripper foil and the first dipole magnet downstream of the foil. One of the major beam losses in this region, referred to as “first-turn losses,” are due to incomplete stripping of the injected H⁻ beam into H⁺ during the injection process. First-turn losses not only result in a lower extracted proton pulse intensity but can also result in longer maintenance periods following beam runs due to the activation of PSR components, which require “cooling down” prior to any hands-on maintenance. In this work, a detailed particle-tracking model of the PSR injection system was created using the simulation package General Particle Tracer (GPT) using three C++ custom elements created to simulate foil scattering, foil stripping, and Lorentz stripping. The model was used to study the effect of different stripper foil parameters and different injection offsets on first-turn losses and emittance growth. The simulation model will be described, and the simulation results will be presented at the conference.

At the Los Alamos Neutron Science Center (LANSCE), the injection system of the Proton Storage Ring (PSR) utilizes charge exchange via a stripping foil to convert H⁻ ions into H⁺. While beam losses caused by partially stripped neutral hydrogen atoms are a primary concern, interactions between the circulating beam and the injection foil also play a significant role in overall beam loss. Each stored proton interacts with the foil 30 times on average. As a result, large-angle scattering is a dominant cause of beam losses in beam dynamics simulations. To mitigate these effects, a set of bump magnets is employed to gradually move the closed orbit away from the foil during the accumulation process. In this work, we first compare various foil scattering algorithms used in ring simulations against results from Monte Carlo (MC) codes. We then quantify the impacts of different bumping schemes, assess uncertainties related to injection offsets, generate interaction 2d-distribution on the foil for heat load simulations, and evaluate the effects of different injected beam distributions.

We discuss selection of ion sources for the LANSCE Accelerator Modernization Project (LAMP). LANSCE currently operates both an H+ and H− ion source, providing beams to five independent user facilities. The H+ source is a duoplasmatron that provides protons for the Isotope Production Facility (IPF). The H- source is a surface-converter ion source configured with two tungsten hot filaments that provides beam to the other four LANSCE user facilities. To meet beam delivery requirements, the LAMP conceptual design has one H+ ion source and two H− ion sources. The upgraded sources in the LAMP conceptual design are two SNS (Spallation Neutron Source) style RF H− ion sources and an upgraded duoplasmatron for the H+ source.

Beam brightness can be enhanced with high gradient operation in photocathode guns. Such high gradient guns, such as the L-band gun at the Argonne Wakefield Accelerator (AWA) facility and the C-band high gradient gun being commissioned in the CARIE project at Los Alamos National Laboratory, are also typically equipped with semiconductor photocathodes due to their high quantum efficiency. To investigate the photoemission process in semiconductor thin-film photocathode under such conditions, we developed Monte-Carlo transport and photoemission models employing electronic, phonon, dielectric and optical properties directly from Density Functional Theory (DFT) calculation, as well as the photo excitation model based on the light interference effect in thin films. This photoemission model is further employed in photocathode gun simulation and used to investigate a recent high-gradient experiment conducted at the AWA photo injector. We will discuss the effects of the high field gradient on photoemission through a comparison of the measurement and the simulated beam dynamics.

LANSCE uses a duoplasmatron ion source to produce H+ ion beams for the Isotope Production Facility, which uses 100 MeV proton beams to produce a variety of therapeutic and diagnostic isotopes for research purposes and also supports a variety of other experiments for materials and nuclear physics. We have recently begun work to improve the reliability, peak current, and lifetime of the ion source, while restoring existing capabilities to build new ion sources and filaments. This poster will cover these efforts, with a particular focus on the work to re-establish and improve the filament production capability and production of higher peak current beams.

At Los Alamos National Laboratory, we finalized the design of a 1.6-cell C-band RF photoinjector cavity for the Cathodes And Radiofrequency Interactions in Extremes (CARIE) project. The photoinjector cavity is intended to operate at 5.712 GHz, with an intense electric field on the photocathode up to 240 MV/m, producing 250-pC electron bunches at room temperature. The photoinjector cavity design focused on minimizing the peak electric and magnetic fields. The distributed RF coupling waveguide network design was optimized for achieving minimized vacuum pressure at the photocathode plug emitting surface. We report the RF simulation and vacuum simulation results of the photoinjector cavity. We also discuss the mechanical design considerations related to photocathode plug alignment, laser pipes, and baking out. The designed photoinjector cavity is currently under fabrication.

This poster will discuss the performance of CsTe photocathodes recently grown for the CARIE (Cathodes and Radiofrequency Interactions in Extremes) project at LANL. CARIE requires a low emittance, high quantum efficiency (QE) photocathode, capable of withstanding challenging vacuum conditions and high fields. CsTe is a natural fit. We will describe recent efforts to optimize the co-deposition process after our growth chamber was rebuilt from contamination. We will also show our study of QE from CsTe on different substrates.