Measurements of magnetic and electric fields in high energy electron beam diodes

The RITS accelerator (5–11MV, 100–200kA) at Sandia National Laboratories is being used to evaluate the Self-Magnetic Pinch (SMP) diode as a potential flash x-ray radiography source. This diode consists of a small, hollowed metal cathode and a planar, high atomic mass anode, with a small vacuum gap of approximately one centimeter. The electron beam is focused, due to its self-field, to a few millimeters at the target, generating bremsstrahlung x-rays. During this process, plasmas form on the electrode surfaces and propagate into the vacuum gap, with a velocity of a 1–10 cm's/microseconds. These plasmas are measured spectroscopically using a Czerny-Turner spectrometer with a gated, ICCD detector, and input optical fiber array. Local magnetic and electric fields of several Tesla and several MV/cm were measured through Zeeman splitting and Stark shifting of spectral lines. Specific transitions, the shape of which is susceptible to magnetic and electric field effects, were utilized through the application of dopants. Data was analyzed using detailed, time-dependent, collisional-radiative (CR) and line-shape calculations. In addition to spectral line analyses, determinations of plasma properties were obtained from continua and line spectra as well. Recent results are presented.