Development of a hybrid mode linear transformer driver stage

At present, the mainstream technologies of primary power sources of large pulse power devices adopt Marx or linear transformer driver (LTD) designs. Based on the analysis of the characteristics of these two types of circuit topologies, the concept of a hybrid mode LTD stage based on Marx branches is proposed. The analysis shows that the hybrid mode LTD stage can realize the following goals: (a) to reduce the energy and power handled by the basic components (switch and capacitor) to lengthen their lifetime; (b) to reduce the requirements of the multipath synchronous trigger system; and (c) to improve the maintainability of the LTD stage by using independent Marx generators instead of “traditional LTD bricks.” To verify the technique, a hybrid mode LTD stage consisting of 50 branches (four-stage compact Marx generators) was designed, manufactured and tested. The stage has a radius of about 3.3 m and a height of 0.6 m. The single Marx circuit’s load current is about 21 kA, with a rise time of $\sim 90\mathrm{ns}$ (10%–90%), under the conditions of capacitors charged to $\pm 40\mathrm{kV}$ and a $6.9\mathrm{\Omega }$ matched load. The whole stage’s load current is $\sim 1\mathrm{MA}$, with a rise time of $\sim 112\mathrm{ns}$ (10%–90%), when the capacitors are charged to $\pm 45\mathrm{kV}$ and the matched load is $0.14\mathrm{\Omega }$.

Figure 1

Inverse relationship of different circuit topologies.

Figure 2

Simplified basic discharge circuit.

Figure 3

Construction of hybrid mode LTD stage.

Figure 4

The design of the hybrid mode LTD stage based on the Marx.

Figure 5

The circuit model of a hybrid mode LTD stage.

Figure 6

Load current simulation result of a hybrid mode LTD stage.

Figure 7

The configuration of long-life gas spark-gap switch.

Figure 8

Electric fields distribution of charging and triggering time.

Figure 9

Electrode ablation result.

Figure 10

The system block diagram of four-stage coaxial Marx.

Figure 11

Picture of the four-stage coaxial Marx.

Figure 12

50 consecutive discharge waveforms of the four-stage Marx.

Figure 13

Diagram of the repetitive multipath trigger system.

Figure 14

Configuration of the former-trigger unit.

Figure 15

Configuration of the latter-trigger unit.

Figure 16

Practical pictures of the whole trigger system (left: former-trigger unit; right: latter-trigger unit).

Figure 17

Experimental output waveforms of the trigger system (ten consecutive shots).

Figure 18

Reset circuit topology and schematic diagram of the stage.

Figure 19

The installed hybrid mode LTD stage.

Figure 20

Load output voltage waveforms of the hybrid mode LTD stage.