## 2 Experimental Devices and Methods  
### Experimental Devices  
The experiments were carried out in a horizontal shock tube (Institute of Fluid Physics of China Academy of Engineering Physics, Mianyang, China). The system diagram is shown in Figure 1. The system is characterized by the following main features: (1) the cross section area of the inner cavity of the horizontal shock tube is 60 mm \(\times\) 60 mm, and the total length is 4000 mm; (2) a high-pressure chamber (length 1280 mm) and a low-pressure channel (length 2220 mm) are separated by a film in the initial state; (3) a measuring section (length 500 mm) equipped with quartz windows 60 mm \(\times\) 140 mm in size to carry out visualization, as well as a pneumatic droplet generator; (4) the pneumatic droplet generator is shown in Figure 2a, which consists of an end cover, generator base, gas nozzle, electric oscillator, sealing platen, fluid storage column and nozzle; (5) to prevent the influence of serial and parallel droplets on adjacent, we arranged the holes according to the pattern depicted in Figure 2b, with a spacing of 10 mm between adjacent holes, which equates to approximately 50 times the droplet diameter; (6) In the rapid recording process, dynamic spatial and temporal resolution is one of the main factors that determine the choice of recording equipment and its operation method. High-speed schlieren/shadowgraph systems cannot capture micron-level high-resolution and high-frame rate images. Moreover, these systems are subject to the defocusing phenomenon when attempting to capture the deformation and breakup of even a hundred-micron droplet, Therefore, we utilized the double-pulse laser holographic test technique to accurately record the droplets' deformation and breakup process.  
In our experiment, we employed a Beamtech dual-pulse Q-switched nanosecond laser system (Vilte-200) to generate laser light. For imaging purposes, we selected Apogee's CCD camera (RMV-50100), possessing a resolution of 8176 \(\times\) 6132 with a pixel size of 6.0 \(\upmu\)m \(\times\) 6.0 \(\upmu\)m, and a maximum shooting frequency of 27 Hz. Static pressure signal data was collected using pressure transducers (PCB 113B26) and an oscilloscope, while shock wave speed was determined via signal interval calculations.  
Figure 1: Schematic diagram of the experimental system.  
Figure 2: (**a**) The structure of the droplet generator, (**b**) top view of the droplet generator base.  
A high-pressure cylinder was utilized to pressurize the drive section with nitrogen gas to the desired experimental conditions. An input electrical signal triggered the digital delay generator, which then output signals A, B, C, and D. Signal A was connected to the CCD camera, which began recording upon signal reception. Signal B was connected to a double-pulse laser, releasing a first pulse to capture the initial position of the droplet and shock wave, and a second pulse to capture images of droplet deformation and breakup under the shock wave and high-speed gas flow. Signal C triggered the solenoid valve of the pneumatic droplet generator, generating droplets. Signal D activated the film-broken device, resulting in the rapid heating of the resistive wire in close contact with the film, burning off the diaphragm, and generating a shock wave. To ensure the smooth propagation of the after-shock gas flow in the shock tube, 0.02 mm, and 0.05 mm thick polypropylene films were chosen as the diaphragm material under low _We_ and high _We_ conditions, respectively.