Compact High-current Repetitive Pulse Accelerators

Abstract

The appearance of high-current accelerators has offered ample possibilities for the creation of basically new devices to be used in various fields of science and technology. Despite an increasing demand for hlgh-current accelerators, most of them are now costly and unique devices, which are usually placed in special rooms and serviced by the developers themselves. This makes such devices almost unavailable for such fields as chemistry, biology, medicine, and the like, which possess no specialists in the field involved. Practice has shown that, in most of experiments, the stored energy of up to 5 J Isqulte sufficient. It is energetically profitable to increase average beam power by using a repetitively operatin~ device. High-current accelerators are direct-action devices, that is devices with the total accelerating voltage applied across the diode, which puts stringent requirements for the electric strength of the insulation. The most important unit in a device like this is the pulsed power source. Depending on the type of power source, accelerators are subdivided into three groups, namely, Marx generators, inductive energy stores with opening switches, and Tesla transformers. Some combined schemes are also used. Marx generators represent the most wide-spread type of high-current pulse generator producing pulses of microsecond or nanosecond duration [I]. Their obvious advantages are high energy-storage capacity and very short time of action of the total voltage on the insulation. Marx generators are not free from shortcomings, such as the difficulty of adjusting a large number of spark gaps involved in the generator circuit and the unreliable operation of capacitors in the nanosecond mode. The large losses and limited lifetimes of these elements hinder the device repetitive operation. Inductive energy stores are more compact and simpler in design as compared to capacitive energy stores, but for operating them on the nanosecond scale, fast opening switches are required. Most widely employed for this purpose are exploding thin wires, the use of which makes accelerators rather compact. Such opening switches are unsuitable for repetitive operation. The pulse repetition rate in repetitive pulse generators can be increased by using plasma opening switches [2, 3].