FRIB, East Lansing, Michigan, USA
LANL, Los Alamos, New Mexico, USA
The cathode test stand (CTS) at LANL is designed to hold off voltages of up to 500kV and can supply pulse durations up to 2.6 μs. Using this test stand, we are able to test both field emission and photocathodes with different geometries and materials at various pulse lengths and PFN voltages. Currently, the test stand is used to evaluate field emission using a velvet cathode over various pulse lengths. The CTS employs various diagnostic tools, including E-dots, B-dots, and a scintillator coupled with a pepperpot mask in order to measure the extracted voltage, current, beam distribution, and transverse emittance. Xenos [1] has been used to create and simulate diode geometries that permits study to optimize various beam parameters. These geometries include changing the size and recess of the cathode as well as implementing a Pierce geometry. Here, we will discuss comparisons for various simulated cathodes and how changes in geometry impact given beam parameters.
[1] See https://www.fieldp.com/xenos.html for information about the Xenos software.
LANL, Los Alamos, New Mexico, USA
The penetrating radiography provided by the Dual Axis Radiographic Hydrodynamic Test (DARHT) facility is a key capability in executing a core mission of the Los Alamos National Laboratory (LANL). A new suite of software is being developed in the Python programming language to support operations of the of two DARHT linear induction accelerators (LIAs). Historical data, built as hdf5 data structures for over a decade of operations, are being used to develop automated failure and anomaly detection software and train machine learning models to assist in beam tuning. Adaptive machine learning (AML) that incorporate physics-based models are being designed to use non-invasive diagnostic measurements to address the challenge of time variation in accelerator performance and target density evolution. AML methods are also being developed for experiments that use invasive diagnostics to understand the accelerator behavior at key locations, the results of which will be fed back into the accelerator models. The status and future outlook for these developments will be reported, including how Jupyter notebooks are being used to rapidly deploy these advances as highly-interactive web applications.
WEZD4
LANL, Los Alamos, New Mexico, USA
LBNL, Berkeley, California, USA
SLAC, Menlo Park, California, USA
University of Chicago, Chicago, Illinois, USA
A novel diagnostic has been developed that uses off-axis undulator radiation to characterize the longitudinal bunch profile of an electron beam. The diagnostic uses a small, ~0.1-m long undulator with mirrors that focus the undulator radiation onto an array of pyrometers. The mirrors both focus the radiation onto the pyrometer and remove the chirping effect that comes from the finite length of the undulator. Numerical and analytical models have been developed to calculate the radiation for a given bunch length, and a phase retrieval algorithm has been developed to extract the bunch profile from measured data. The diagnostic has been installed at the BELLA laser-plasma wakefield accelerator, and will be used to characterize the bunch length there. The concept and relevant results will be presented.
THYD2
LANL, Los Alamos, New Mexico, USA