Recyclable transmission line (RTL) and linear transformer driver (LTD) development for Z-pinch inertial fusion energy (Z-IFE) and high yield.

Abstract

Z-Pinch Inertial Fusion Energy (Z-IFE) complements and extends the single-shot zpinch fusion program on Z to a repetitive, high-yield, power plant scenario that can be used for the production of electricity, transmutation of nuclear waste, and hydrogen production, all with no CO 2 production and no long-lived radioactive nuclear waste. The Z-IFE concept uses a Linear Transformer Driver (LTD) accelerator, and a Recyclable Transmission Line (RTL) to connect the LTD driver to a high-yield fusion target inside a thick-liquid-wall power plant chamber.Results of RTL and LTD research are reported here, that include: (1) The key physics issues for RTLs involve the power flow at the high linear current densities that occur near the target (up to 5 MA/cm). These issues include surface heating, melting, ablation, plasma formation, electron flow, magnetic insulation, conductivity changes, magnetic field diffusion changes, possible ion flow, and RTL mass motion. These issues are studied theoretically, computationally (with the ALEGRA and LSP codes), and 4 will work at 5 MA/cm or higher, with anode-cathode gaps as small as 2 mm. (2) An RTL misalignment sensitivity study has been performed using a 3D circuit model. Results show very small load current variations for significant RTL misalignments. (3) The key structural issues for RTLs involve optimizing the RTL strength (varying shape, ribs, etc.) while minimizing the RTL mass. Optimization studies show RTL mass reductions by factors of three or more. (4) Fabrication and pressure testing of Z-PoP (Proof-ofPrinciple) size RTLs are successfully reported here. (5) Modeling of the effect of initial RTL imperfections on the buckling pressure has been performed. Results show that the curved RTL offers a much greater buckling pressure as well as less sensitivity to imperfections than three other RTL designs. (6) Repetitive operation of a 0.5 MA, 100 kV, 100 ns, LTD cavity with gas purging between shots and automated operation is demonstrated at the SNL Z-IFE LTD laboratory with rep-rates up to 10.3 seconds between shots (this is essentially at the goal of 10 seconds for Z-IFE). (7) A single LTD switch at Tomsk was fired repetitively every 12 seconds for 36,000 shots with no failures. Present results from all of these power flow studies validate the whole LTD/RTL concept for single-shot ICF high yield, and for repetitive-shot IFE.

A trigger source for linear transformer driver

“…The stray capacitance, Cg, acting as a peaking capacitor is the key to achieve a fast rise-time pulse. It can be estimated by the formula Cg = L/R L 2 , where L is the total inductance of the loop and RL is the load of the generator [10]. An estimated inductance of the generator is about 1.36 μH which is the sum of the capacitor inductance (80 nH), the switch inductance (210 nH), the inductance of the connecting leads (700 nH) and the inductance of the coaxial structure (370 nH) [8].…”

“…In future linear transformer drivers (LTD) may be an optimal choice for Z-Pinch driven fusionfission hybrid reactor (Z-FFR) and inertial fusion energy (IFE) where the required repetition rate is estimated to be 0.1 Hz [1,2]. So the high voltage pulses used to trigger the switches in the LTD stage should be continuously generated with the same repetition rate.…”

Investigation on current loss of high-power vacuum transmission lines with coaxial-disk transitions by particle-in-cell simulations

“…Current loss caused by the coaxial-disk transitions of the MITLs is one of the most fundamental problems that must be addressed. Unlike the vacuum insulator stacks separating the MITLs from the water lines and drivers in conventional systems, coaxial-disk transitions connect the MITLs to the drivers and transfer the combined pulsed power from tens of drivers to the disk MITLs under vacuum [10]. However, the non-uniform structure of the coaxial-disk transitions can lead to non-uniform magnetic fields and abrupt variation of the MITL impedance, which results in disturbed electron flow and current loss [11,12].…”