MA-class linear transformer driver for Z -pinch research

Abstract

A linear transformer driver (LTD) generator capable of delivering up to 0.9 MA current pulses with 160 ns rise time has been assembled and commissioned at University of California San Diego. The machine is an upgrade of the LTD-III pulser from Sandia National Laboratories, consisting of 40 capacitors and 20 spark gap switches, arranged in a 20-brick configuration. The driver was modified with the addition of a new trigger system, active premagnetization of the inductive cores, a vacuum chamber with multiple diagnostic ports, and a vacuum power feed to couple the driver to plasma loads. The new machine is called compact experimental system for Z-pinch and ablation research (CESZAR). The driver has a maximum bipolar charge voltage of AE100 kV, but for reliability and testing, and to reduce the risk of damage to components, the machine was operated at AE60 kV, producing 550 kA peak currents with a rise time of 170 ns on a 3.5 nH short circuit. While the peak current is scaled down due to the reduced charge voltage, the pulse shape and circuit parameters are close to the results of the cavity and power feed models but suggest a slightly higher inductance than predicted. The machine was then used to drive wire array Z-pinch and gas puff Z-pinch experiments as initial dynamic plasma loads. The evolution of the wire array Z pinch is consistent with the general knowledge of this kind of experiment, featuring wire ablation and stagnation of the precursor plasma on axis. The gas puff Z pinches were configured as a single, hollow argon gas shell, in preparation for more structured gas puff targets such as multispecies, multishell implosions. The implosion dynamics agree generally with 1D magnetohydrodynamics simulation results, but large zippering and magneto-Rayleigh-Taylor instabilities are observed. The CESZAR load region was designed to accommodate many load types to be driven by the machine, which makes it a versatile platform for studying Z-pinch plasmas. The completion of the CESZAR driver allows plasma experiments on energy coupling from LTD machines to plasma loads, instability mitigation techniques and magnetic field distributions in Z pinches, and interface dynamics in multispecies implosions.

Experimental results of a 330 GW impedance-matched Marx generator

“…The CESZAR trigger circuit is equipped with an 80-nF capacitor bank that is used to trigger twenty FDGSs within a single LTD cavity. A 990-Ω resistive coupling is applied between trigger busbars and trigger pins 40 . Alternatively, an extendable triggering system was introduced for the M-50 testbed LTD module and achieved less than 2-ns jitter.…”

“…Over the past few decades, there have been several design iterations of LTDs with published experimental results 12,[37][38][39][40] . However, based on the concept presented by Stygar et al 1 in 2017 and prior to this paper, scientific publications have yet to exist for a successfully engineered and tested IMG.…”

Численная Модель Единичного Зазора ЛТД Разрядника

“…Т. 5, № 2(12) Введение ЛТД ступень -это базовый элемент ЛТД генератора, который является перспективным направлением развития импульсной техники [1][2][3][4][5]. Одним из главных достоинств ЛТД ступеней является субмикросекундная длительность выходного импульса, достигаемая без использования дополнительных схем укорочения и/или обострения импульса [1].…”

“…До недавнего времени в ЛТД ступенях использовалась система запуска, разработанная на начальном этапе разработки ЛТД генераторов на основе экспериментальных исследований [1,6]. В настоящее время появилось много работ, посвященных способам модернизации системы запуска ЛТД ступени [3,[7][8][9]. Однако в данных работах в основном описываются экспериментальные исследования.…”

Coreless Fast Pulsed-Power Drivers

“…In many applications, designers turn to capacitive isolation when inductive isolation cannot be used. This approach is especially attractive for MA-class machines [5]- [7]. By removing the magnetic cores, we can de facto reduce maintenance, footprint, cost and simplify experimental operation.…”