Off-line measurement experiments of far-field intensity caused by large-aperture continuous phase plates

In order to measure and evaluate the far-field intensity caused by large-aperture continuous phase plates, off-line measurement system with 351 nm laser for the far-field intensity was built according to the physical demand parameters of the laser system in ICF equipment. The experiment for CPP with 330 mm330 mm aperture was carried out. The measurement reproducibility and accuracy were analyzed according to the calculated result with scale diffraction theory. The diameter of dispersion focus is about 2.9 times diffraction-limited diameter and the maximal size that the system can measure is f600 mm or 430 mm430 mm. The reproducibility for measuring encircled energy fraction in defocusing amount 2 mm is better than 0.2%. The shape and distribution from experiment accord with the calculated result, the measured encircled energy percentage is 0.85% less than the calculated result and the measured radius is 13 m larger than the calculated result, the difference is caused by temporal smoothing of the measurement system, so the measurement accuracy could be enhanced through shortening time of exposure of CCD and reducing the optical aberration of the measurement system.