A material discrimination based on X-Ray systems is typically achieved by alternating photon pulses of two different energies. A new approach relies on the ability to generate X-ray pulses with an end-point energy that varies in a controlled fashion during the duration of the pulse. An intra-pulse multi-energy X-ray beam device will greatly enhance current cargo screening capabilities. This method originally was described in the AS&E patents [1]. This paper addresses a linac concept for the proposed scan and describes some proof of concept experiments carried out at SLAC. Show Partial Abstract