Publications

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

The Saturn accelerator has historically lacked the capability to measure time-resolved spectra for its 3-ring bremsstrahlung x-ray source. This project aimed to create a spectrometer called AXIOM to provide this capability. The project had three major development pillars: hardware, simulation, and unfold code. The hardware consists of a ring of 24 detectors around an existing x-ray pinhole camera. The diagnostic was fielded on two shots at Saturn and over 100 shots at the TriMeV accelerator at Idaho Accelerator Center. A new Saturn x-ray environment simulation was created using measured data to validate. This simulation allows for timeresolved spectra computation to compare the experimental results. The AXIOM-Unfold code is a new parametric unfold code using modern global optimizers and uncertainty quantification. The code was written in Python, uses Gitlab version control and issue tracking, and has been developed with long term code support and maintenance in mind.

It is very difficult to measure the voltage of the load on the Saturn accelerator. Time-resolved measurements such as vacuum voltmeters and V-dot monitors are impractical at best and completely change the pulsed power behavior at the load at worst. We would like to know the load voltage of the machine so that we could correctly model the radiation transport and tune our x-ray unfold methodology and circuit simulations of the accelerator. Step wedges have been used for decades as a tool to measure the end - point energies of high energy particle beams. Typically, the technique is used for multi-megavolt accelerators, but we have adapted it to Saturn's modest <2 MV end-point energy and modified the standard bremsstrahlung x-ray source to extract the electron beam without changing the physics of the load region. We found clear evidence of high energy electrons >2 MV. We also attempted to unfold an electron energy spectrum using a machine learning algorithm and while these results come with large uncertainties, they qualitatively agree with PIC simulation results.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

HERMES III is a 20-MeV linear induction accelerator that was constructed at Sandia National Laboratories in the late 1980's and continues operation to this day. The accelerator utilizes 10 Marx banks for its initial energy storage and pulse formation. These Marx banks discharge their energy into 20 intermediate storage capacitors which, in turn, feed 80 pulse forming lines that further condition the pulse. Transmission line feeds from the pulse forming lines then deliver the electrical energy to 20 induction cavities arrayed along the axis of the machine to build the final output pulse along a central magnetically insulated transmission line (MITL). There are two triggering systems within the accelerator that work together in this energy discharge process. One simultaneously triggers the initial discharge of energy from each of the 10 Marx banks; the other staggers the triggering of the Rimfire gas switches following each intermediate storage capacitor so as to properly synchronize the energy delivery to the downstream cavities and the MITL with the pulse propagation along the MITL. Until recently, these triggering systems were the original systems dating back to the initial commissioning of the accelerator, however both have now been replaced with new and more modernized systems. Design details for both triggering systems will be presented, along with an overview of some of the initial operational data from the HERMES III accelerator using these new triggering systems.

Abstract not provided.

Abstract not provided.

Abstract not provided.

This paper describes the hardware changes made to the triggering system of the HERMES III accelerator at Sandia National Laboratories, New Mexico. The HERMES III accelerator is a gamma ray simulator producing 100 kRad dose per shot with a full width half max pulse duration of approximately 25 nanoseconds and averaging six shots per day. For each accelerator test, approximately 400 probe signals are recorded over approximately 65 digitizers. The original digitizer trigger system employed numerous independent legacy signal generators resulting in non-referenceable digitizer time bases. We detail our efforts to reference the digitizer time bases together using a modular and scalable approach with commercial-off-the-shelf components. This upgraded trigger system presently measures a maximum digitizer trigger time spread of less than two nanoseconds across the 65+ digitizers. This document details the hardware changes, provides a summary of the accelerator charging process, presents 'one-line' trigger system diagrams and summarizes the times of interest for a typical HERMES accelerator shot.

This paper describes the software changes made to the data processing and display system for HERMES III accelerator at the Simulation Technology Laboratory (STL) at Sandia National Laboratories, New Mexico. The HERMES III accelerator is a gamma ray simulator producing 100kRad[Si] dose per shot with a full width half max pulse duration of 25 nanoseconds averaging six shots per day. For each accelerator test approximately 400 probe signals are recorded over approximately 65 digitizers. The original data processing system provided the operator a report summarizing the start of probe signal timings for groups of probes located within the power flow conductors. This timing information is indicative of power flow symmetry allowing the operator to make necessary adjustments prior to the next test. The report also provided data overlays concerning laser trigger light output, x-ray diode currents and x-ray source output. Power flow in the HERMES III accelerator is comprised of many circuit paths and detailed current and voltage information within these paths could provide a more thorough understanding of accelerator operation and performance, however this information was either not quickly available to the operators or the display of the data was not optimum. We expanded our data processing abilities to determine the current and voltage amplitudes throughout the power flow conductors and improved the data display abilities so data plots can be presented in a more organized fashion. We detail our efforts creating a software program capable of processing the 400 probe signals together with an organized method for displaying the dozens of current and voltage probes. This process is implemented immediately after all digitizer data has been collected so the operator is provided timing and power flow information shortly after each accelerator shot.

The HERMES III accelerator at Sandia National Laboratories is a 20-cavity multi-stage linear induction voltage accelerator typically producing a 20-MV, 40-ns, 600-kA output pulse. Energy is initially stored in Marx banks that are each discharged into two intermediate store capacitors. Each of these capacitors are then switched with an SF6-insulated high voltage Rimfire gas switch into four parallel pulse forming lines that further condition the discharge pulse and deliver it to the induction cavities arrayed along the axis of the machine. Presently, a single 0.9-J KrF laser operating at 248 nm, the output of which is divided into twenty beams, is used to trigger the 20 rim-fire switches. As part of an upgrade to the accelerator, however, a new solid state laser triggering system is being designed to replace this system and provide additional capabilities for the accelerator. The laser triggering system will be made up of 10 discrete compact flash-lamp pumped, Q-switched Nd:YAG lasers (Tempest 300), each having an output energy of 40 mJ at a wavelength of 266 nm. As each laser will be responsible for triggering only two of the rim-fire switches, it becomes possible to shape the output pulse by varying the times at which the individual lasers fire. Overall reliability for the accelerator's operation with these new lasers will be increased, as well. The general layout of this new laser triggering system design will be presented, along with details pertaining to the triggering of the lasers and the optical beam paths.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.