Species-Resolved Diagnosis of Laser-Accelerated Heavy Ions Using a Thomson Parabola Spectrometer Coupled with a CR-39 Detector

Abstract: Species-resolved diagnosis of laser-accelerated heavy ions is crucial for understanding the underlying acceleration mechanisms and optimizing beam quality. However, conventional Thomson parabola spectrometers (TPS) coupled with image plates or scintillators cannot distinguish ions with similar charge-to-mass ratios, limiting the accuracy of heavy-ion characterization. In this work, a diagnostic method combining a TPS with a CR-39 detector is presented for species-resolved identification of ions in laser-driven heavy-ion acceleration experiments. By correlating track diameter with ion energy per nucleon, reference curves derived from $\mathrm{C^{5+}}$ and $\mathrm{O^{7+}}$ ions enable reliable distinction between $\mathrm{C^{6+}}$, $\mathrm{N^{7+}}$, and $\mathrm{O^{8+}}$ ions and reconstruction of their respective spectra. The method is experimentally validated at the Shanghai Superintense Ultrafast Laser Facility (SULF), where it further enables the identification of heavy ions such as $\mathrm{Zr^{30+}}$ and the determination of their energy distributions. Moreover, it mitigates signal overlap at the high-energy end of TPS measurements, preventing ambiguity arising from overlapping ion traces. This simple and self-consistent approach substantially extends the diagnostic capability of TPS–CR-39 systems, providing accurate and intuitive species-resolved spectroscopy for laser-driven heavy-ion acceleration studies.