Electron flow in the SABRE linear induction adder in positive polarity

Abstract

In a positive polarity induction adder each of the induction cavities is a cathode, which emits electrons at a unique potential. These broad spectrum electrons strongly affect Magnetically Insulated Transmission Line (MITL) behavior. Electron flow decreases the cavity-to-MITL coupling efficiency, and reduces the power transport efficiency along the system. Also the operating impedance of the MITL is lowered, reducing the diode impedance required for good coupling and good total system power efficiency. It is therefore imperative to understand the details of MITL electron flow. In previous work, measurement of MITL electron flow for a twenty-stage linear induction adder (Hermes III), operated in positive polarity, was compared with simulations. There was qualitative agreement, but some differences were noted. For example, measured electron flow in the first cavities was greater than in the simulations. We have extended the work on this subject with detailed current measurements on a ten-stage linear induction adder (SABRE). Time resolved electron flow is determined from the difference between anode and cathode currents at several axial locations. A time-resolved mapping of electron flow versus adder length is constructed. Measurements of electron flow in the initial cavities agreed well with simulations. Electron flow for times near the current peak exhibits a monotonic increase with length, except at the adder end. >