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

Linear transformer drivers can be used as fast pulsed-power generators to produce and study matter under extreme conditions, with densities larger than 10 times that of solids. While its scientific investigations can start in a laboratory, it will eventually require a source of x rays that can be provided only by specialized light source facilities. When relocation becomes a necessity, a compact, modular design is clearly advantageous. This paper shows how nested transmission lines can reduce considerably the footprint of MA-class pulsed-power generators based on linear transformer driver technology.

Section: Introductionmentioning

confidence: 99%

Current adding transmission lines for compact MA-class linear transformer drivers

Gourdain

Adams

Evans

et al. 2020

“…The signal propagation delay between two consecutive bricks is 1 ns, and the four-branch trigger line allows for a maximum propagation delay of 5 ns between any two bricks. Each switch connects to the trigger line via a 990 Ω resistor (3x HVR APC C2654A331L, 330 Ω epoxy-coated ceramic composite resistors in series) to provide insulation between bricks on a timescale of ≳10 ns, which is necessary for reliable parallel operation [16].…”

Section: A Trigger Circuitmentioning

confidence: 99%

“…The LTD concept was pioneered by Koval'chuk et al [7] and has received increasing attention in recent years [8][9][10][11], including a recent review on the history of LTD development [12]. Several LTD machines are operational or under development in the USA [13][14][15][16], Europe [17,18], Russia [19,20], and Asia [21,22].…”

Section: Introductionmentioning

confidence: 99%

MA-class linear transformer driver for Z -pinch research

Conti

Valenzuela

Fadeev

et al. 2020

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.

“…The number of switches can considerably exceed 10 4 in the newly developed petawatt-class LTDs [6][7][8]. The parameters of the primary energy storage device and LTD depend on the parameters of the switch, and studies of the different types of gas spark switch are therefore given special attention [9][10][11][12][13][14].…”

Section: Introductionmentioning

confidence: 99%

Multichannel switching in a multigap gas switch at atmospheric pressure

Zherlitsyn

Kumpyak

2020

The multichannel switching mode of a controlled multigap switch is studied. The switch is designed for capacitive energy storage, with a charging voltage of up to 100 kV and an energy output time of about 100 ns. The interval between the high-voltage and low-voltage electrodes of this switch is divided into seven series-connected gaps using ball electrodes, and six parallel rows of these ball electrodes allow for multichannel switching. An optical system based on collimators and photodiodes was used to determine the number of channels in the switch gaps. Statistics on the number of channels were collected and the probability of ignition of parallel spark channels was calculated for each of the switch gaps under different operating conditions. We show that both the electrical isolation between the channels and the rate of rise of the triggering pulse significantly affect the number of parallel ignited channels and their distribution over consecutive gaps. At a high triggering voltage pulse rise rate (∼800 kV=μs), a larger number of spark channels are ignited in the switch with electrical isolation between the channels and the characteristics of this switch are better. At a low triggering voltage pulse rise rate (less than 250 kV μs), better characteristics are realized in the switch without electrical isolation between the channels.