Experience with development of sealed linear waveguide electron accelerators

A sealed linear electron accelerator eliminates the need for vacuum pumps, valves, flanges and similar hardware, making it the only acceptable design for such geophysical applications as well as logging. A sealed accelerator tube used as a transportable gamma radiation source is described. Ten such tubes were built. The first models had vacuum gauges to monitor the internal pressure; it ranged between .00001 and .000001 n/sq m. The MTBF was more than 500 hours. The accelerator has an electron energy of 6 to 7 MeV with a pulsed current of 20 to 20 mA when driven by a 3 cm band transmitter with a pulse power of 500 KW; the accelerator weighs 9 kg, has an overall length of 2,300 mm and a maximum diameter of 88 mm. Because there are no external lines and pumps, the prestart time was reduced to 3 to 5 minutes. The high vacuum allows the use of an oxide cathode having a large current density which reduces the electron beam diameter and facilitates its focusing. A drawing of the sealed accelerator tube is shown along with a graph plotting the temperature, pressure and gas fow as a function of time during the thermal vacuum sealing of the accelerator tube.