Sandia National Labs FY20 LDRD Annual Report


Next-gen pulsed power machines benefit from research on diagnosing field strengths and plasma conditions in magnetically insulated transmission lines using active dopant spectroscopy. Accurate estimates of plasma parameters and field strengths in power flow regions using active dopant spectroscopy will inform theory and simulation efforts are needed to design next-generation pulsed-power machines, and improve optical spectroscopy efforts to diagnose load conditions, such as feed plasmas and magnetic and electric fields. The team developed and demonstrated a laser-activated dopant diagnostic on a Mykonos linear transformer driver, obtained spectral measurements of field strengths and electron densities within the anode-cathode gap, and showed that its implementation does not appreciably affect current delivery, as a precursor to similar measurements on the Z machine. Measurements on Mykonos showed that expansion

of the ablation plasma is the primary mechanism that drives loss, which can be controlled by timing the laser within 150 ns of peak current. Within this time frame, no noticeable current loss is measured, and the ablation plasma may be used to diagnose magnetically insulated transmission line conditions. As a result of this LDRD, Sandia is planning to implement this diagnostic on the Z machine to measure localized electric and magnetic fields. (PI: Sonal Patel)

Mykonos linear transformer driver hardware used during the active dopant project.

Developing inductively driven diagnostic X-ray sources to enable transformative radiography and diffraction capabilities on Z machine. Penetrating X-rays are one of the most effective tools for diagnosing high energy density experiments, whether through radiographic imaging or X-ray diffraction. To expand the X-ray diagnostic capabilities at the 26-MA Z Pulsed Power Facility, Sandia developed a new diagnostic X-ray source called the inductively driven X-pinch (IDXP). This X-ray source is powered by a miniature transmission line inductively coupled to fringe magnetic fields in the final power feed. During this LDRD, the team carried out a multistage development of the IDXP concept through experiments both on Z and in a surrogate setup on the 1-MA Mykonos facility.

The creation of a radiography-quality X-pinch hot spot was verified through a combination of X-ray diode traces, laser shadowgraphy, and source radiography. The success of the IDXP experiments on Mykonos recently enabled the first-ever diagnostic X-pinch to be fielded on Z. (PI: Clayton Myers) The line-of-sight diagnostic suite developed for inductively driven X-pinch experiments on the 1-MA Mykonos facility. These data are used to verify the formation of a radiography-quality X-ray hot spot in the IDXP.



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