Design of 3.95 MeV X-band linac for future nondestructive inspection at nuclear plant

We are developing the portable non-destructive testing (NDT) X-ray sources with X-band linacs and low power magnetrons. Now, we start the experiment of electron acceleration and X-ray generation using by 950 keV X-band linac NDT system. The 950 keV X-band linac X-ray generator is under development for corrosion wastage of tubes and condition based maintenance of impeller pumps. However, about 1 MeV X-ray source can be only used for thin tubes of about 20 mm thickness. Therefore, we start to design about 4 MeV X-band linac X-ray NDT systems. By more high energy, the range of application is broader. We think that this X-ray NDT system will be used for corrosion wastage and cracking in thicker tubes at nuclear plants and larger impeller pumps. This system consists of X-band linac, thermionic cathode electron gun, magnetron and waveguide components etc. For higher electric field works out, the 3.95 MeV X-band linac structure is adopted side-coupled structure. This structure is more effective acceleration than 950 keV linac with alternating periodic structure (APS). We adopt 1.3 MW magnetron for RF source. This accelerator system is about 30 cm long. The beam current is about 150 mA, and X-ray dose rate is 10 Gy(a)1m/500 pps. In this paper, the detail of the whole system concept and the electromagnetic field of designed linac structure will be reported. (author)