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 on‐axis spot size for heated rods on Gamble II is due to pinching closer to the tapered tip. For a diode power of 6×10¹⁰ 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.