https://aip.scitation.org/doi/pdf/10.1016/j.mre.2016.01.004

From concept to reality - A review to the primary test stand and its preliminary application in high energy density physics

https://aip.scitation.org/doi/pdf/10.1016/j.mre.2016.06.001

Theoretical and numerical research of wire array Z-pinch and dynamic hohlraum at IAPCM

The Primary Test Stand (PTS) developed at the China Academy of Engineering Physics is a 20 TW pulsed power driver, which can deliver a ∼10 MA, 70 ns rise-time (10%–90%) current to a short-circuit load and has important applications in Z-pinch driven inertial confinement fusion and high energy density physics. Preliminary results of tungsten wire-array Z-pinch experiments on PTS are presented. The load geometries investigated include 15-mm-tall cylindrical single and nested arrays with diameter ranging from 13 mm to 30 mm, consisting of 132–300 tungsten wires with 5–10 μm in diameter. Multiple diagnostics were fielded to characterize the x-ray radiation from wire-array Z pinches. The x-ray peak power (∼50 TW) and total radiated energy (∼500 kJ) were obtained from a single 20-mm-diam array with 80-ns stagnation time. The highest x-ray peak power up to 80 TW with 2.4 ns FWHM was achieved by using a nested array with 20-mm outer diameter, and the total x-ray energy from the nested array is comparable to that of single array. Implosion velocity estimated from the time-resolved image measurement exceeds 30 cm/μs. The detailed experimental results and other findings are presented and discussed.

Preliminary experimental results of tungsten wire-array Z-pinches on primary test stand

A challenge for the TW-class accelerators driving $Z$-pinch experiments, such as Sandia National Laboratories' $Z$ machine, is to efficiently couple power from multiple storage banks into a single multi-MA transmission line. The physical processes that lead to current loss are identified in new large-scale, multidimensional simulations of the $Z$ machine. Kinetic models follow the range of physics occurring during a pulse, from vacuum pulse propagation to charged-particle emission and magnetically-insulated current flow to electrode plasma expansion. Simulations demonstrate that current is diverted from the load through a combination of standard transport (uninsulated charged-particle flows) and anomalous transport. Standard transport occurs in regions where the electrode current density is a few $1{0}^{4}\ensuremath{-}{10}^{5}\text{ }\text{ }\mathrm{A}/{\mathrm{cm}}^{2}$ and current is diverted from the load via transport without magnetic insulation. In regions with electrode current density $g{10}^{6}\text{ }\text{ }\mathrm{A}/{\mathrm{cm}}^{2}$, electrode surface plasmas develop velocity-shear instabilities and a Hall-field-related transport which scales with electron density and may, therefore, lead to increased current loss.

https://link.aps.org/pdf/10.1103/PhysRevAccelBeams.22.120401

Current transport and loss mechanisms in the Z accelerator

Current transmission efficiency in a conical transition magnetically insulated transmission line (MITL) has been studied experimentally on a 1.0-MV linear transformer driver system, which has 10 identical cavities connected in series with MITL. Transmission efficiencies of anode current as high as 98.4% and 93.1% could be achieved when the MITL operates at load-limited and self-limited flows, respectively. As for the cathode current, because of the sufficient length of conical transition MITL, cathode current is also able to sustain high transmission efficiency. But as long as the diode gap is too large, many of the electrons will be launched into the anode–cathode gap and the cathode current near the diode drastically decreases. Particle-in-cell simulations were conducted to validate the conclusions. The simulation results agree with experiments.

Current Transmission Efficiency for Conical Magnetically Insulated Transmission Line on a 1.0-MV Linear Transformer Driver System

The primary test stand (PTS) is a multiterawatt facility with a current of 8-10 MA and rise time of 90 ns, which is being built for Z-pinch studies at the Institute of Fluid Physics, China Academy of Engineering Physics The PTS consists of 24 modules that are connected in parallel Each module is based on the Marx generator and water pulse forming line as well as laser-triggered spark gap switch working at 5-MV level The nominal total stored energy of the PTS is 72 MJ All the Marx generators and laser-triggered spark gap switches had been tested at full voltage level before the PTS was assembled The design and installation of the PTS are described In this paper, the most recent results of the PTS commissioning will be introduced

Initial Performance of the Primary Test Stand

Pulsed power research for military and civil applications has been conducted at the China Academy of Engineering Physics (CAEP) for more than 50 years. The pulsed power research activities include development of pulsed power components, such as different kinds of high-voltage switches, series of pulsed power sources and pulsed X-ray machines, high-current accelerators for $Z$ -pinch and flash X-ray radiography, as well as medical application and electromagnetic launch. The most recent progress of pulsed power research at CAEP will be presented.

Overview of Pulsed Power Research at CAEP

Based on the principle of electromagnetic railgun launch, a circuit model was developed and validated, the pulse forming units (PFU) and the progress of the railgun launch were included. The corresponding Pspice circuit code was developed to simulate the current of each pulse forming unit. Acceleration properties of the armature were also simulated by the Pspice analog behavioral modeling tools. The simulated railgun current and the armature velocity were 2.6% and 9.8% higher than the experiment results, i.e., the simulation and the experiment results were roughly consistent with each other. The model has provided valuable data which can directly benefit the design and operation of the series augmented railgun systems.

Guan Yongchao

Papers

Initial Performance of the Primary Test Stand

Overview of Pulsed Power Research at CAEP

Circuit simulation of the electromagnetic railgun system