Design of a 5-MA 100-ns linear-transformer-driver accelerator for wire array Z-pinch experiments

Abstract

The linear-transformer-driver (LTD) is a recently developed pulsed-power technology that shows great promise for a number of applications. These include a Z-pinch-driven fission-fusion-hybrid reactor that is being developed by the Chinese Academy of Engineering Physics. In support of the reactor development effort, we are planning to build an LTD-based accelerator that is optimized for driving wire-array Z-pinch loads. The accelerator comprises six modules in parallel, each of which has eight series 0.8-MA LTD cavities in a voltage-adder configuration. Vacuum transmission lines are used from the interior of the adder to the central vacuum chamber where the load is placed. Thus the traditional stack-flashover problem is eliminated. The machine is 3.2 m tall and 12 m in outer diameter including supports. A prototype cavity was built and tested for more than 6000 shots intermittently at a repetition rate of 0.1 Hz. A novel trigger, in which only one input trigger pulse is needed by utilizing an internal trigger brick, was developed and successfully verified in these shots. A full circuit modeling was conducted for the accelerator. The simulation result shows that a current pulse rising to 5.2 MA in 91 ns (10%-90%) can be delivered to the wire-array load, which is 1.5 cm in height, 1.2 cm in initial radius, and 1 mg in mass. The maximum implosion velocity of the load is 32 cm=μs when compressed to 0.1 of the initial radius. The maximum kinetic energy is 78 kJ, which is 11.7% of the electric energy stored in the capacitors. This accelerator is supposed to enable a radiation energy efficiency of 20%-30%, providing a high efficient facility for research on the fast Z pinch and technologies for repetition-rate-operated accelerators.

100 GW linear transformer driver cavity: Design, simulations, and performance

“…The composition of these charging resistors has not been reported previously. This type of resistor, patented by Stoltzfus et al [45], was invented to provide highimpedance with long-term stability and to avoid the problems that arise when using aqueous resistors, such as copper sulfate, in high-power LTDs [16,34,42,46]. Aqueous resistors are known to permeate water through their plastic housings contaminating the cavity and at the same time creating air bubbles inside the resistor that can dramatically change the impedance of the resistor and even create breakdowns inside the resistor.…”

“…Previous work exists where monolithic solid resistors were used in place of conventional aqueous resistors but it was found that these would occasionally disintegrate or degrade [34,46]. Recent work has also been done by Zhou et al [16] that uses wirecoil "spring" inductors instead of aqueous resistors for charging and triggering.…”

“…Descriptions of other LTD trigger configurations are given in Refs. [16,28,31,34,36,37,42,[46][47][48][49], all of which, with the exception of Zhou et al, use aqueous resistors in their trigger circuits for switch-to-switch isolation and circuit protection. An example of this circuit including typical component values is shown in Fig.…”

“…The prime power source of such a machine may consist of a system of linear transformer drivers (LTDs) [7][8][9][10][11][12][13][14][15][16][17][18] fast Marx generators (FMGs) [7,9,[19][20][21][22] or impedance-matched Marx generators (IMGs) [18,23,24]. The pulsed power community has been developing LTD technology for 20 years on various single-cavity experiments [16,[25][26][27][28][29][30][31][32][33][34][35][36][37], multicavity (single "module") experiments [14,27,32,35,[38][39][40][41][42][43][44] and a few multimodule experiments [11,14]. The work presented here describes the design and performance of the first two meter...…”

Modeling power flow in the induction cavity with a two dimensional circuit simulation

“…Circuit simulation tools are usually used to estimate the operating parameters such as peak voltage, pulse duration and amplitude of conduction current for each component in the induction cavity [21,22]. They provide the designing criteria for each component.…”