This record reports ~ above the advancement of a magnetically thrust high-velocity implosion experiment conducted on the CQ-3 facility, a compact pulsed power generator v a load current of 2.1 MA. The existing generates a high Lorentz force in between inner and outer liner made indigenous 2024 aluminum. Equally positioned photonic Doppler velocimetry probes document the liner velocities. In experiment CQ3-Shot137, the inner liner imploded with a radial converging velocity that 6.57 km/s when the external liner expanded at a much lower velocity. One-dimensional magneto-hydrodynamics simulation with suitable material models detailed curves of velocity matches time that agree well with the experimental measurements. Simulation then shows that the inside liner underwent a shock-less compression to approximately 19 GPa and also reached one off-Hugoniot high-pressure state. Follow to the scaling legislation that the best loading pressure is proportional to the square that the load current amplitude, the results show that such a compact capacitor bank as CQ-3 has actually the potential come generate push as high as 100 GPa within the inner liner in such an implosion experiment. The is emphasized that the technique described in this record can be easily replicated at short cost.

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The quasi-isentropic compression experiment (ICE)1 compresses products to off-Hugoniot says in which the pressure and temperature space decoupled. In contrast, the product state in one adiabatic shock compression is limited to the Hugoniot state in i beg your pardon pressure and also temperature space coupled. In recent years, the ICE has received attention in the fields of material dynamics2,3,4,5,6, condensed matter physics7,8,9, laboratory astrophysics10, and also inertial fusion11,12,13. Over there are substantial platforms on which the ICE have the right to be conducted, including the gas gun, pulsed strength device, and laser facility. The gas gun have the right to only be offered for a planar ICE, conversely, a pulsed power or laser facility typically requires heavy investment and also an to work team. Examples of such framework are Z14 at the Sandia national Laboratory, Pegasus I/II15,16 and Atlas17,18 in ~ the Los Alamos nationwide Laboratory, Shiva Star19,20 at the Air pressure Research Laboratory, magnetic compression generators21,22 at the All-Russian Scientific research study Institute of speculative Physics and Los Alamos national Laboratory, NIF23 in ~ the Lawrence Livermore nationwide Laboratory, and also OMEGA24 at Rochester University. In this paper, we demonstrate ICE via cylindrical implosion at a fairly compact pulsed-power facility, CQ-3 in ~ the academy of fluid Physics in China25.

Pulsed power tools usually provide good current exceeding 1 MA with a rise time of 101 come 103 ns. This existing flows through a fill configuration to create high push in the sample. The current rises smoothly from zero to a peak, and it has thus to be widely accepted that materials undergo quasi-isentropic compression in such experiments. There space usually two varieties of load configuration because that ICEs performed on pulsed strength devices. The first uses a strip-line sample to establish a plane strain compression state26,27. The second uses a cylindrical liner sample to realize a converging implosion state2,28. Because that the very first configuration, the top pressure is much lower than expected because the dynamic inductance due to the two strip electrodes increases rapidly through the distance between the electrodes throughout loading. In contrast, the cylindrical implosion configuration realizes much higher pressure due to the fact that of the low and steady dynamic inductance and convergence effect. This configuration offers two cylindrical liners, namely an within liner and outer liner. The present flows from the inner liner to the external liner, generating a strong Lorentz force that drives the heavy inner liner come a rapid converging velocity and thus generates high push within the liner.

The pulsed power tools requiring big investment mentioned over typically realize push as high as > 100 GPa via current exceeding 10 MA in ICEs. There room technical and economic obstacles in emerging such big facilities. Meanwhile, some laboratories have actually developed fairly compact pulsed strength devices, such together Veloce29, Phelix30, GEPI31, CEPAGE32, and the CQ series25,33. These framework usually output existing of 1–10 MA and thus have a much reduced loading ability. However, lock have benefits relating come convenience, short cost, and also easy operation. Combining the finite experimental information (such as velocity) through simulation that gives insight into material states (such as pressure and temperature), has come to be a paradigm because that studying product properties under the excessive conditions.

In this paper, we demonstrate implosion quasi-isentropic compression top top CQ-3, i beg your pardon is a compact pulsed power machine at the institute of fluid Physics. A magnetically driven metal liner implosion experiment performed at high velocity ~ above the CQ-3 an equipment is described. As an integrated experiment, the product model and simulation algorithm can be studied and also validated comprehensively. The an equipment parameters of CQ-3 and also the details the the speculative assembly are defined in section 2. The experimental results of CQ3-Shot137, namely the liner velocity histories and load existing waveform, space presented in section 3. One-dimensional magnetohydrodynamics (MHD) calculations and data analyses the this shot are presented in ar 4. Section 5 summarizes the results of the study and also suggests future work.


Experimental maker and fill configuration

The CQ-3 an equipment has power storage the 78 kJ, a charging voltage that 60–90 kV, a maximum short-circuit discharge present of 3 MA, and also a rise time (10–90%) that 470 ns. The overall volume that the CQ-3 maker is 3.4 m × 3.4 m × 3.0 m. The main components are 32 capacitor/switch modules, four multi-channel triggers, hundreds of low-inductance coaxial cable infection lines with shift connectors, and also a sealed target room at the center of the device. The capacitor bank is split into four groups, all sharing an eight-channel pulsed voltage trigger. The waveform the the discharging present can be readjusted by editing the activity time of every trigger. The size of the target chamber room a diameter of 70 cm and also a elevation of 70 cm, and also the vacuum within the chamber have the right to reach 10−2 Pa. The conceptual design and also a photograph of the CQ-3 an equipment are shown in Fig. 1.


Figure 1

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(a) theoretical design and also (b) photograph of the CQ-3 device.


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Compared with various other compact devices, CQ-3 has actually its own distinctive advantages. Firstly, in comparison with Veloce, GEPI, CEPAGE and CQ-433, the is feasible for CQ-3 come conduct greater vacuum in the target chamber, due to the fact that the energy transfer mode of CQ-3 is coaxial cables fairly than parallel metallic plates. Therefore, that is perfect to carry out some experiments through high sealing requirements or toxic products on CQ-3. Secondly, besides the strip-line experiment, CQ-3 is additionally suitable because that cylindrical liner experiment due to the fact that its target chamber is situated in the geometric center of the power storage capacitors, which provides the current evenly distributed in the circumferential direction and the implosion symmetric. For both Phelix and also CQ3 devices, which use coaxial cable transmission lines, the distinction is the the current rise time the Phelix is around 10 μs, make it suitable for researching the implosion dynamics of larger liner. The current rise time of CQ-3 is much less than 500 ns, making it more suitable for little liner experiments through high implosion velocity and also compression.

The cylindrical load configuration comprises two coaxial cylindrical liners (Fig. 2). The lower ends that the inner and also outer liners are linked with the cathode and also anode flanges respectively. The top ends are connected through a short-circuit lid to type a series circuit. The room between the two liners is filled with high-density polyethylene as the insulating medium. An axial load present flows v both liners and also interacts with the linked azimuthal magnetic ar to create a radial Lorentz pressure that increases the convergent convulsion of the inside liner and the outward growth of the external liner (respectively referred to as the implosion and expansion below). The product of the within liner is compressed by ramp waves throughout its implosion vice versa, the external liner withstands a hoop tension.


Figure 2

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r–θ ar of the liner configuration.


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In experiment CQ3-Shot137, both inner and outer liner were written of 2024 aluminum. The liners had actually initial inner radii of 2.485 and 4.990 mm and also thicknesses the 515 and 495 μm, respectively. The efficient height the the liners was 10 mm, and the surface roughness was around 200 nm. Both the short-circuit lid (the upper electrode) and the infection flanges (the reduced electrodes) to be made native 304 stainless steel. The surface ar roughness of the upper and also lower electrodes was roughly 3.2 μm. The physical style of the liner configuration was based on the thin-shell model34 incorporating circuit equations and also one-dimensional MHD modeling, where optimum parameters that the liner and also its implosion for achieving greater velocities were considered.

Configuration layout and also diagnostic techniques

The environment layout the the pack configuration (liners) and photonic Doppler velocimetry (PDV) probes on the speculative platform (i.e., the flange plates) is shown in Fig. 3. The liner were correctly positioned relying on the precision machined flanges, and great electrical contacts to be ensured in the same way. The experiment through a charging voltage that 80 kV was carried out in ~ ambient temperature and also pressure. The load existing was measured using the Rogowski belt placed on the cathode flange.


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Installation layout of the load configuration in CQ3-Shot137. (1. Internal photonic Doppler velocimetry probes 2. Outside photonic Doppler velocimetry probe 3. Probe assistance 4. Anode flange 5. Cathode flange 6. High-density polyethylene insulation 7. Short-circuit cap 8. Within liner 9. Outer liner).

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Using the diagnostic an approach described in recommendation <2>, PDV probes were supplied to measure up the velocities that the cost-free surfaces that the inner and also outer liners, denoted here as V1 (the implosion velocity) and also V2 (the development velocity). Dimensions were produced each liner using three probes, which to be uniformly arranged on the circumference, such the the symmetry and also stability the the liner motion can be established by to compare the three comparable PDV measure up results. V1 was measured v endoscopic multiplex (three-point) PDV probes, such the there were three measured V1 histories. The radii of the internal probes were roughly 0.68 mm, and also the three multiplex probes (labeled N1 (0°), N2 (120°), and N3 (240°)) to be arranged in ~ intervals the 120°. Meanwhile, V2 to be measured with three straight inserted single-point PDV probes (labeled W1 (0°), W2 (120°), and W3 (240°)) the were evenly dispersed on a large circumference. The early distance between the external probes and outer liner was about 4 mm. The arrays of PDV probes to be located specifically at the mid-height of the liner as shown in Fig. 4. The skepticism in the PDV measure was much less than 1%35. The bandwidth that the oscilloscopes for PDV signal salvation was collection at 16 GHz and the acquisition price at 25 GS/s.