Quantification of Proton Radiation Damage in Polyimide Aerogel by Cantilever-Enhanced Photoacoustic Spectroscopy

Charged particles radiation induces the performances degradation of space polyimide (PI) aerogel, which puts forward the requirement for the accurate quantification of the radiation-induced damage. Photoacoustic spectroscopy (PAS) was proposed with a cantilever for the sensitive resonance detection of the photoacoustic (PA) pressure based on the analysis of cantilever-air dynamic coupling theory and finite element simulation. Wavelength scan PAS inspection of the proton irradiated PI aerogel verified the sensitivity of PA signals to the radiation fluence. Dual-wavelength PAS was first theoretically investigated and performed by measuring the PA signals alternately induced by the 405- and 532-nm lasers. Based on the presented theoretical relation between the PA signals and the radiation characteristics, the derived normalized damage fraction ( $f_{a}$ ) revealed distinct reliance on the proton fluence ( $\phi$ ). The experimental results and the theoretical relations fit well on the goodness of $\chi ^{2} = 8.2 \times 10^{-4}$ , and the fit value of the single-proton damage area ( $\sigma$ ) was $1.4\times 10^{-16}$ cm ² . The relative error for the measurement of fluence ( $\phi$ ) was 5%. The research indicates that the presented cantilever-enhanced PAS method is an efficient tool for rapid and accurate quantification of the proton radiation-induced damage in PI aerogel.