Measurement of electron energy deposition necessary to form an anode plasma in Ta, Ti, and C for coaxial bremsstrahlung diodes

Measurements are made of surface doses necessary to initiate an anode plasma by electron bombardment of Ta, Ti, and C anodes for coaxial geometries characteristic of high-power electron-beam diodes. Measured lower and upper bounds of doses necessary to form an anode plasma are 54±7–139±16 J/g in Ta, 214±23–294±71 J/g in Ti, and 316±33–494±52 J/g in C. Within these bounds, probable values for the threshold are given under specific assumptions. The measurements are consistent with a thermal desorption model for plasma formation.