Dynamics of supernova bounce in laboratory

We draw attention to recent high-explosive (HE) experiments which provide compression of macroscopic amount of matter to high, even record, values of pressure in comparison with other HE experiments. The observed bounce after the compression corresponds to processes in core-collapse supernova explosions after neutrino trapping. Conditions provided in the experiments resemble those in core-collapse supernovae, permitting their use for laboratory astrophysics. A unique feature of the experiments is compression at low entropy. The values of specific entropy are close to those obtained in numerical simulations during the process of collapse in supernova explosions, and much lower than those obtained at laser ignition facilities, another type of high-compression experiment. Both in supernovae and HE experiments the bounce occurs at low entropy, so the HE experiments provide a new platform to realize some supernova collapse effects in laboratory, especially to study hydrodynamics of collapsing flows and the bounce. Due to the good resolution of diagnostics in the compression of macroscopic amounts of material with essential effects of nonideal plasma in EOS, and observed development of 3D instabilities, these experiments may serve as a useful benchmark for astrophysical hydrodynamic codes.

Figure 1

Schematics of experiment. 1, sources of x-ray radiation (betatrons); 2, shielding; 3, registrators; 4–5, collimators (Pb); 6, cone (Al); 7, target experimental device (working gas, shells, high explosive). This design is for a two-cascade device with the central block shown in Fig. 3. In the case of a single-cascade device the central block is simpler, cf. Fig. 2.

Figure 2

(a) x-Ray images of spherical device with a single-cascade scheme [16]. The image shows both the initial state and the maximum compression state. (b) Schematics of the single-cascade device dynamics. Circles (green online) show the positions of internal shell boundary measured in the experiment. The square dot shows the shell position measured by electrocontact technique. DW, detonation wave; SW, shock wave; RW, reveberating wave; HE, high explosive.

Figure 3

(a) A schematic design of a two-cascade spherical experimental device: 1, shell 1 (Fe1); 2, shell 2 (Fe2); 3, explosive; 4, plexiglass. (b) x-Ray patterns (roentgenograms) of the shells in the initial state. (c) Initial and final states of the shell shown in one shot.

Figure 4

$R\left(t\right)$ diagrams for shells in the experimental device filled with deuterium which produced the record high compression. (a) x-Ray images of the shell 2 (see Fig. 3) as a function of time, where $t_0$ is the initial state, $t_1$ and $t_2$ are the compression phases, $t_3$ is the moment of maximum compression (“bounce”) and $t_4$ is the expansion phase; light and red circles are the outer and inner boundaries of the shell 2, respectively. (b) Experimental data and calculated $R\left(t\right)$ diagrams, symbol $\square$ denotes the results of electrocontact technique, symbols $+$ and $\times$ are used for x-ray data from the model experiment, and symbols $\diamond$ and $◯$– for the data of the basic experiment.

Figure 5

Hypothetical phase transition in quasi-isentropic HE-driven compression experiments (1972–2017) and in “cold” (low-entropy) theoretical models. Experiment: hollow circles, quasi-isentropic VNIIEF 1972 –1975 [17, 18]; rectangles, quasi-isentropic compression 2007–2017 [16, 26]; arrows, phase-transition-like discontinuities (1) in Refs. [17, 18] and (2) in Refs. [16, 26] supposed as “plasma” phase transitions (PPT). Calculation results: green, isotherm $T=0$ K from EOS SESAME [32]; red line, isotherm $T=300$ K from SAHA-EOS [31] (“chemical picture”); light blue and blue, isotherm $T=0$ K from two “wide-range” semiempirical EOSes: Refs. [33] and [34] correspondingly. Magenta circle, critical point of first-order liquid-liquid phase transition via ab initio QMD.

Figure 6

Two isentropes: 1 is the isentropic curve from the point M1 with the use of VNIIEF EOS for deuterium, and 2 is the isentrope based on SAHA-EOS from Fig. 15 in Ref. [26] above 150 GPa, which miraculously enters a new point MB5.

Figure 7

Evolution of radius coordinates during collapse and bounce for a protoneutron star at several fixed Lagrangean masses $m=0.3÷1.6M_{\odot }$ (with $0.1M_{\odot }$ step). A dashed line, which connects empty circles, shows the position of the shock. The lower-left corner of figure contains the zoomed-in part of the main image for the reduced time interval around the bounce and $m=0.3÷0.7M_{\odot }$.

Figure 8

Velocity of matter as a function of $r$. Zero time is the moment of bounce. Left and right panels show $v\left(r\right)$ for different moments before and after the bounce, correspondingly. The value of $t$ (in ms) is shown on each curve.

Figure 9

Entropy in the collapsing core. Left panel shows entropy profiles as a function of Lagrangean mass $m$ before the bounce and the right panel after. The moments of time are the same, as in Fig. 8.