SLAC, Menlo Park, California, USA
A specific feature of RF linacs based on the pulsed traveling wave (TW) mode of operation is that only a portion of the RF energy is used for the beam acceleration. The residual RF energy has to be terminated into an RF load. Higher accelerating gradients require higher RF sources and RF loads, which can stably terminate the residual RF power. This overview will outline vacuumed RF loads only. A common method to terminate multi-MW RF power is to use circulated water (or other liquid) as an absorbing medium. A solid dielectric interface (a high quality ceramic) is required to separate vacuum and liquid RF absorber mediums. Using such RF load approaches in TW linacs is troubling because there is a fragile ceramic window barrier and a failure could become catastrophic for linac vacuum and RF systems. Traditional loads comprising of a ceramic disk have limited peak and average power handling capability and are therefore not suitable for high gradient TW linacs. This overview will focus on 'vacuum dry' or 'all-metal' loads that do not employ any dielectric interface between vacuum and absorber. The first prototype is an original design of RF loads for the Stanford Two-Mile Accelerator.
SLAC, Menlo Park, California, USA
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*. This paper addresses a linac concept for the proposed scan and describes some proof of concept experiments carried out at SLAC.
* A. Arodzero et al., 'System and methods for intra-pulse multi-energy and adaptive multi-energy X-ray cargo inspection', US Patent 8,457, 274, 2013
SLAC, Menlo Park, California, USA
Overview of modern methods, circuits, and practical realizations for multi MW peak power pulsers will be presented. All used pulser components are manufactured by the US national industry and they are available for design and pulser fabrication. Two concepts will be discussed: (1) an approach is based on assistance of a nonlinear transmission line with ferromagnetic media and (2) an approach is based on assistance of special diodes which are working in a specific mode of operation. In both approaches the nonlinear characteristic of switching media (ferromagnetic and solid state plasma) are employed in final stage of the pulser to form the multi MW level nanosecond pulses.