Fig. 1. Structural diagram of the RSNS type CR-39 dosimeter (a) (PP: Polypropylene; HDPE: High-density polyethylene; PA-6: Polyamide 6) and structure view of the 3D printed dosimeter (b)

Fig. 2. Irradiation geometry diagram including the ²⁵²Cf neutron source, the dosimeters and the ISO water slab phantom

Fig. 3. Diagram of Radosys etching holders (a), snapshots of the stainless steel vessel designed to withstand CO₂ pressures (b) and the RB4 etching equipment (c)

Fig. 4. Microscopic local views of CR-39 foils treated under 1.5 MPa of CO₂ for untreated detectors (a) and 6 h (b), 24 h (c), 72 h (d), 120 h (e), 168 h (f)

Fig. 5. Sensitivity variation with CO₂ pressure under different processing time (a), and sensitivity changes over time under different CO₂ pressures (b)

Fig. 6. 3D view of sensitivity and projection in CR-39 irradiated by ²⁵²Cf neutron source and treated under various CO₂ pressures and durations (a) (color online), and the intersecting curve of sensitivity (5.87 tracks·mm^-2·mSv^-1) (b)

Fig. 7. Track size distributions in CR-39 at irradiation by ²⁵²Cf and treated under various partial pressures of CO₂ and durations

Fig. 8. CR-39 track size distributions under various CO₂ pre-treatment pressures and durations (a~e), and track size distributions expose to ²⁵²Cf and ²⁴¹Am-Be neutron sources (f)^[26]

Fig. 9. Response curve function of a typical CR-39 dosimeter^[28] compared with the fluence to personal dose equivalent conversion coefficient H_p,slab(10,0°)^[29]