A method for measuring dark current electron beams in an RF linac

X-ray fluorescence from thin foils inserted into the Naval Postgraduate School linac has been used to measure the integrated electron beam intensity when the accelerator is operating with dark current. The measured X-ray flux, the known inner shell ionization cross sections and radiative transition probabilities are used to obtain measurements of dark currents of the order of 10^-14 Amperes. The same arrangement allows continuous, in-situ energy calibration of our SiLi detector in the electromagnetic noise environment of the linac. This technique was originally developed to perform absolute production efficiency measurements of parametric X-ray generation in the 5-50 keV range