An electron-beam-heating model for the gamble II rod pinch

The rod-pinch diode concentrates electron deposition onto the tip of a high-atomic-number, mm-dia. anode rod to create an ultra-bright x-ray source for multi-MV radiography. Here, a technique is presented whereby line-spread functions acquired on-axis and at 90° to the rod are used to determine the electron-deposition distribution. Results show that the smaller measured onaxis spot size for heated rods on Gamble II is due to pinching closer to the tapered tip. For a diode power of 6×l0¹⁰ W, peak electron heating of 1×10¹⁴ W/cm³ is calculated. MHD calculations of the e-beam-heated rod response agree with Schlieren measurements of plasma expansion.