Radiation Induced Currents in Subminiature Coaxial Cables

Subminiature coaxial cables smaller than RG-58 were exposed to intense pulsed irradiation from a plasma focus device, and the currents induced on the center conductors were measured in a vacuum environment. The incident photons had energies mostly below 70 keV, and filters were used to vary the average hardness of the irradiation. The measured cable responses in units of Coulomb/rad(Si)-cm were compared to values calculated on the basis of photoemission from metal surfaces and electron ranges in insulators. It was found that the currents induced on the center conductors were several times larger than predicted for an ideal coaxial geometry because of small gaps between the dielectric surface and overlapping braid wires. For a given cable type, such as RG-174/U, large variations in cable responses were found according to each manufacturer´s construction techniques.