Fig. 1. (a) Schematic of liquid sheet generation. (b) Top view of liquid sheet generation. (c) Overview of the main modules of the diagnostic system.

Fig. 2. (a) Schematic diagram of reflectance spectroscopy. (b) Side view and front view of the LST; the light source is connected to the six cores here to clearly display the measurement point. (c) A typical reflected spectrum of the LST with the theoretical fitting curve. (d) Theoretical reflectivity of films with different thicknesses at different wave numbers.

Fig. 3. (a) Fourier transform of a measured spectrum in wave number space. (b) Reflected spectrum of an ultra-thin liquid sheet at 238 nm with the theoretical fitting. (c) Thickness of the LST at different flow rates and positions. (d) Thickness of the LST at different misalignments of the colliding jets.

Fig. 4. (a) Typical interference fringes of the LST. (b) Wrapped phase in the red box of (a). (c) Thickness distribution unwrapped from (b). (d) Interference fringes corresponding to the thickness distribution of Hasson’s model. (e) The change of interference fringes with the improvement of flow symmetry.

Fig. 5. (a) Schematic diagram of the tilt angle measurement. (b) The tilt angle change within 1 hour. (c) The intensity integral of CCD1 and CCD3 to calculate the absolute reflectivity of the LST. (d) The change of the spot collected by CCD2 with the improvement of flow symmetry.

Fig. 6. (a) Schematic diagram of position measurement. (b) Time domain of the LST’s position (distance to the confocal detector). (c) Frequency domain of the LST’s vibration in (b). (d) Histogram of the LST’s relative position within 10 minutes.