Engineering topics
Publications and source records attributed to Bender III, Howard Albert.
Project Y laid the foundation for all work currently performed at LANL. LANL is responsible for the stewardship of most of the U.S. nuclear weapons, facilitates global security and nonproliferation, and has been a Federally Funded Research and Development Center (FFRDC) for more than 75 years.
As previously described, we have built a non-interceptive beam radius monitor that employs a diamagnetic loop. This device has been installed and tested with beam on the DARHT-I downstream transport. Installation details and sample test results are given in this report.
Diamagnetic-loop (DML) measurements can inform efforts to improve radiographic resolution. DML is non-invasive, so time-resolved data is available on every shot while tuning or executing a hydrotest. The time-resolved beam size can be deduced from the DML data. LIA beam-transport dynamics affecting beam size can be monitored while testing mitigation measures (e.g., beam halo suppression). Time-resolved beam size at final focus provides immediate information about spot size enlargement due to blur, and effectiveness of mitigation efforts. DML measures magnetic flux produced by a rotating beam, so it also enables monitoring of Larmor emittance that can enlarge the spot size. Beam rotation adds in quadrature with emittance, hence “Larmor emittance." Observing zero bias-field DML flux monitors beam rotation resulting from imperfect nulling of flux linking the cathode, and/or broken LIA transport symmetry (e.g., steering, quads, etc.).
Diamagnetic loops (DML) can be used as a noninvasive method for measurements of beam size in electron beam accelerators that use solenoidal magnetic transport. The loop fundamentally measures the magnetic flux excluded by a diamagnetic object. A comprehensive theory relates the rms beam radius to the excluded flux measured by the DML. We have built, and calibrated a DML apparatus. Recently, this DML has been used to measure the size of the electron beam near the final focus of the DARHT-I flash-radiography accelerator. Results are in agreement with beam transport code predictions. In this article, we review and summarize the construction, calibration, and electron-beam testing of this DML.