Adjustable collimation for dark-field proton radiography contrast enhancement.

Area of Science:

• Physics
• Materials Science
• Imaging Technology

Background:

• Proton radiography (pRad) at Los Alamos National Laboratory uses 800 MeV protons.
• High-energy protons struggle to image thin samples with small density variations.
• Existing imaging methods lack sufficient contrast for certain materials.

Purpose of the Study:

• To test a dark-field imaging condition using pre- and post-object beam collimation.
• To optimize contrast for imaging thin samples with minimal areal density changes.
• To evaluate the impact of collimator size combinations on image quality.

Main Methods:

• Established a dark-field imaging condition via beam collimation before and after the sample.
• Utilized an inverse collimator to remove unscattered protons and define a scattering angle range.
• Systematically varied collimator sizes and assessed contrast-to-noise ratio, spatial resolution, and proton transmission.

Main Results:

• Substantial enhancement in contrast-to-noise ratio was achieved for thin samples.
• Objects with low areal density variations, previously nearly transparent, became visible.
• Different collimator combinations were compared for optimal imaging performance.

Conclusions:

• The developed dark-field imaging technique significantly improves the detectability of subtle material variations.
• This method opens new possibilities for imaging previously invisible objects using high-energy protons.
• Optimized collimation strategies are key to maximizing contrast in proton radiography.