Fig. 1. Physical image of the DEPU in operation at BL09U (Dream Line) of SSRF

Fig. 2. Flux simulation of the DEPU emitting from the white slit

Fig. 3. The layout of the beamline BL09U

Fig. 4. Total transmission efficiency from beamline to ARPES sample position

Fig. 5. Ar 3s3p⁶np double ionization excitation spectra(a) Full spectrum, (b) Fine spectrum of partially scan

Fig. 6. Ar 2p ionization excitation spectra

Fig. 7. Nitrogen 1s ionization excitation spectra

Fig. 8. Neon 1s→np Rydberg transition ionization excitation spectra

Fig. 9. White slit aperture sizes (X-horizontal, Y-vertical) corresponding to 4σ emission angles of LEID/HEID fundamentals

Fig. 10. Comparison of measured and simulated gap-energy relationship for LEID

Fig. 11. Measured 4σ fluxes of LEID as a function of fundamental energy, using LEG and MEG gratings respectively

Fig. 12. Comparison of the measured and the simulated correspondence between GAP values against energy positions of fundamentals for HEID

Fig. 13. The measured 4σ fluxes of HEID as a function of fundamental energy, using HEG/VEG grating respectively