Errors in the field reconstruction using CR-39 proton radiographs with high fluence variation

Area of Science:

• Plasma physics
• Particle detection
• Image reconstruction

Background:

• CR-39 proton radiography images fields in plasmas using charged particles.
• Etch time critically affects signal-to-noise and detection efficiency.
• Single etch times lead to >15% error in high-fluence variation data.

Purpose of the Study:

• Quantify etch time impact on background-to-signal ratio (BSR) and efficiency.
• Assess how these factors affect electric and magnetic field reconstruction.
• Determine optimal etching strategies for CR-39 radiography.

Main Methods:

• Experiments at MIT Linear Electrostatic Ion Accelerator measured BSR and efficiency vs. fluence and etch time.
• Synthetic radiographs generated with known fields, modulated by empirical BSR/efficiency values.
• Field reconstruction performed using a Monge-Ampère code with modulated radiographs.

Main Results:

• Empirical data collected for BSR and efficiency losses across a wide fluence range (3 × 10³ to 7 × 10⁵ cm⁻²).
• Reconstruction errors quantified for single vs. combined etch times.
• Mean squared error of reconstructed fields decreased by factors of 1.2-7 with combined etches.

Conclusions:

• Combining short and long etches improves accuracy for CR-39 radiographs with high fluence variation.
• This optimized approach mitigates signal errors in low- and high-fluence regions.
• The findings enhance the reliability of electric and magnetic field measurements in plasma research.