ASNT

cavities, it gains energy as it is accelerated across gaps in the evacuated cavities and comes out the other end of the cavity. When the RF power is phased properly, increased acceleration is achieved. Figure 9 shows the general arrangement of an electron linear accelerator system’s subsystem component parts with the elements associated with the RF/microwave excitation and linear accelerator beamline. Not shown in Figure 9 are all of the electronic power and control subsystems that are necessary to drive the RF source and electron gun, as well as optimize all system parameters. These subsystems have a significant effect on the output characteristics of the linear accelerator system. The most common RF excitation sources are high-peak power magnetrons and klystrons, with circuitry to tune their output to the optimal frequency of the linear accelerator with which they are paired. For research purposes, electron linear acceler- ators have been designed and built to accelerate electrons to gigaelectronvolt energies, or to acceler- ate heavier particles, such as protons. A famous example of this type of linear accelerator for physics research is the 3.1 km (2 mi) long Stanford linear accelerator (SLAC), which is a traveling wave structure. There are two general types of linear

Figure 8 Monobloc designed 6 MeV linear accelerator system with all drive and control electronics housed in a single cabinet to eliminate exposed high-voltage cables and minimize footprint and weight of X-ray system.

Radio frequency system

Laser

Radio frequency source

Accelerator

Pulse transformer

Electron gun

Collimator

Figure 9 General arrangement of subsystems of linear accelerator.

CHAPTER 3

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Part 2